3.5.1: Blotting
Blotting provides a means of identifying specific molecules out of a mixture. It employs three main steps. First, the mixture of molecules is separated by gel electrophoresis. The mixture could be DNA ( Southern Blot ), RNA ( Northern Blot ), or protein ( Western Blot ) and the gel could be agarose (for DNA/RNA) or polyacrylamide (for protein). Second, after the gel run is complete, the proteins or nucleic acids in the gel are transferred out of the gel onto a membrane/paper that physically binds to the molecules. This “blot", as it is called, has an imprint of the bands of nucleic acid or protein that were in the gel (see figure at left). The transfer can be accomplished by diffusion or by using an electrical current to move the molecules from the gel onto the membrane. The membrane may be treated to covalently link the bands to the surface of the blot. Last, a visualizing agent specific for the molecule of interest in the mixture is added to the membrane. For DNA/RNA, that might be a complementary nucleic acid sequence that is labeled in some fashion (radioactivity or dye). For a protein, it would typically involve an antibody that specifically binds to the protein of interest. The bound antibody can then be targeted by another antibody specific for the first antibody. The secondary antibody is usually linked to an enzyme which, in the presence of the right reagent, catalyzes a reaction that produces a signal (color or light) indicating where the antibody is bound. If the molecule of interest is in the original mixture, it will “light" up and reveal itself.
Western Blots
In a western blot procedure, proteins are first separated on an SDS-PAGE gel and then transferred to a membrane. This membrane replica is treated with antibodies that specifically recognize a protein or epitope of interest. Additional processing steps generate a signal at the position of the bound antibody. Between the steps, various washes are done to increase the signal-to-noise ratio on the final, developed blot. The major steps involved in a typical western blot are as follows:
-
Electrophoretic transfer of proteins from an SDS-PAGE gel to a membrane
-
Blocking of nonspecific protein binding sites on transfer membranes
-
Incubation of the membrane with a primary antibody specific for the epitope of interest
-
Incubation with a secondary antibody that recognizes primary antibodies
-
Visualization of bound antibodies
Electrophoretic transfer of proteins from an SDS-PAGE gel to a membrane
The first step in a western blot is to generate a replica of the SDS-PAGE gel by transferring proteins electrophoretically to a synthetic membrane with a high protein binding capacity. The membranes made of polyvinylidine fluoride (PVDF), a kind of plastic, are hydrophobic and the dry membranes do not wet properly with water. Therefore, PVDF membranes are first wet with methanol, then rinsed with deionized water, and finally rinsed with transfer buffer. They must not be allowed to dry out during the transfer and immunoblot procedures. If they do dry out, they must be re-wet with methanol and rinsed with water before proceeding.
During the transfer process, the gel and membrane are placed directly against each other within a “sandwich” of pre-wet filter papers and foam pads. During the electrophoretic transfer, current should flow evenly across the entire surface area of the gel. It is important, therefore, that air bubbles are not trapped between the gel and membrane. After the electrophoretic transfer, which can be done in a few hours or overnight with reduced voltage, the membrane replica with the transferred proteins can be allowed to dry out and stored for later visualization with antibodies.
Blocking of non-specific protein binding sites on membranes
The transfer membranes used in western blots bind proteins nonspecifically. Before the membranes are incubated with specific (and expensive) antibodies, they must be pretreated with blocking solutions that contain high concentrations of abundant (and cheap) proteins to saturate non-specific binding sites. If the transfer membranes are not adequately blocked before the antibody is applied, the nonspecific sites on the membranes will absorb some of the antibodies, reducing the amount of antibody available to bind the
Primary antibody binding
Either polyclonal or monoclonal antibodies can be used as the primary antibody on western blots. Antibodies can be directed toward a naturally-occurring protein or toward an epitope attached to an overexpressed protein (as we are doing). Increasingly, researchers are using epitope-tagged proteins in their experiments, because antibodies against naturally- occurring proteins are expensive and time-consuming to prepare.
Secondary antibody binding
The secondary antibodies used in western blots are designed to bind the FC fragments of primary antibodies, taking advantage of cross-species differences in antibody sequences. Secondary antisera are generally prepared by injecting an animal with FC fragments of IgGs from a second species. The first animal recognizes the FC fragments as foreign antigens and produces antibodies that bind the FC fragments.
Visualization of bound antibody
In this final step, the western blot is incubated with substrates for the enzyme that has been conjugated to the secondary antibody.
Contributors
Dr. Kevin Ahern and Dr. Indira Rajagopal (Oregon State University)
Contributed by Clare M. O’Connor , Associate Professor Emeritus (Biology) at Boston College


2.4: The Art of Rhetoric
What is Rhetoric?
In its simplest form, RHETORIC is the art of persuasion. Every time we write, we engage in debate or argument. Through writing and speaking, we try to persuade and influence our readers, either directly or indirectly. We work to get them to change their minds, to do something, or to begin thinking in new ways. Put simply, to be effective, every writer needs to know, and be able to use, principles of rhetoric.
Writing is about making choices, and knowing the principles of rhetoric allows a writer to make informed choices about various aspects of the writing process. Every act of writing takes place in a specific RHETORICAL SITUATION, which is a situation or circumstance in which someone (a writer or speaker) must persuade an audience to do something, to change their minds, to influence them, etc. This "rhetorical situation" is the same concept that L. Lennie Erwin terms "the writing situation" in his discussion on how writing is different from speaking (see " The Difference between Speaking and Writing ").
The three most basic, yet important components of a rhetorical situation are:
- The purpose of writing or rhetorical aim (the goal the writer is trying to achieve or argument the writer is trying to make)
- The intended audience
- The writer/speaker
These three elements of the rhetorical situation are in a constant and dynamic interrelation. All three are also necessary for communication through writing (or speaking) to take place. For example, if the writer is taken out of this equation, the text will not be created. Similarly, eliminating the text itself will leave the reader and writer, but without any means of conveying ideas between them, and so on.
Other components of the rhetorical situation include:
- the medium (the form of communication)
- the allotted time for the message (how much time does writer have? appropriate time to persuade?)
- the political, social, or cultural implications, place, etc.
All writing (or speaking) that is persuasive comes from a source of urgency or EXIGENCE –– a need to communicate the message.
NOTE
Please note that the term “rhetoric” also is used to mean someone speaking bombastic thoughts that are empty of meaning. The online Oxford dictionary defines rhetoric also as “language designed to have a persuasive or impressive effect on its audience, but often regarded as lacking in sincerity or meaningful content” and the example they give is, “all we have from the Opposition is empty rhetoric.” Such a meaning is unfortunately derived from the emphasis of rhetoric on presentation and delivery. In this course, we will focus on rhetoric as a means of effective communication as we aspire to become skilled rhetoricians ourselves.
The following video focuses on the use of rhetoric from the viewpoint as a writer. As you watch, consider how the same elements hold true from the viewpoint of a reader.
The Rhetorical Situation
When composing an essay, every writer must take into account the conditions under which the writing is produced and will be read. It is customary to represent the three key elements of the rhetorical situation as a triangle of writer, reader, and text, or, as they are represented on this image, as "communicator," "audience," and "message."
Figure 2.4.1: The Rhetorical Triangle
Source:
St. Edward's University
Changing the characteristics of any of the elements depicted in the figure above will change the other elements as well. For example, with a change in the beliefs and values of the audience, the message will also change to accommodate those new beliefs.
What does this understanding of rhetoric have to do with academic and research writing? Everything, really. If you have ever had trouble with a writing assignment, chances are it was because you could not figure out the assignment’s purpose. Or perhaps you did not understand very well who was your reader. It is hard to commit to purposeless writing done for no one in particular, which is how many students incorrectly approach academic writing.
Rhetorical Appeals
In order to persuade their readers, writers must use three types of proofs, or rhetorical appeals. They are logos , or logical appeal; pathos , or emotional appeal; and ethos , or ethical appeal, or appeal based on the character and credibility of the author. An additional appeal, called kairos, refers to whether a message is "of its time period." It is easy to notice that modern words “logical,” “pathetic,” and “ethical” are derived from those Greek words. In his work Rhetoric , Aristotle writes that the three appeals must be used together in every piece of persuasive discourse. An argument based on the appeal to logic, or emotions alone will not be an effective one.
Pathos
Pathos can best be described as the use of emotional appeal to sway another's opinion in a rhetorical argument. Emotion itself should require no definition, but it should be noted that effective 'pathetic' appeal (the use of pathos) is often used in ways that can cause anger or sorrow in the minds and hearts of the audience.
Pathos is often the rhetorical vehicle of public service announcements. A number of anti-smoking and passive smoking related commercials use pathos heavily. One of the more memorable videos shows an elderly man rising from the couch to meet his young grandson who, followed by his mother, is taking his first steps toward the grandfather. As the old man coaxes the young child forward, the grandfather begins to disappear. As the child walks through him the mother says "I wish your grandpa could see you now." The audience is left to assume that the grandfather has died, as the voice-over informs us that cigarette smoke kills so many people a year, with a closing statement, "be there for the ones you love." This commercial uses powerful words (like "love") and images to get at the emotions of the viewer, encouraging them to quit smoking. The goal is for the audience to become so "enlightened" and emotionally moved that the smoking viewers will never touch another cigarette.
Ethos
Ethos can be seen as the credibility that authors, writers, and speakers have when they present themselves in front of an audience. If, on the first day of class, your professor walked in, kind of bent over and looking like they had been out all night and picking their nose, how would you perceive that instructor? What would your view of the class he takes be? How confident would you be that this person knows what they are talking about?
Ethos encompasses a large number of different things which can include what a person wears, says, the words they use, their tone of voice, their credentials, their experience, their relationship with the audience, verbal and nonverbal behavior, criminal records, etc. At times, it can be as important to know who the person presenting the material is, as what they are saying about a topic.
Many companies, especially those big enough to afford famous spokespeople, will use celebrities in their ad campaigns to promote the sale of their products. Certain soft drink companies have used the likes of Ray Charles, Madonna, and Britney Spears to sell their products, and have been successful in doing so. The thing you need to ask yourself is: what do these celebrities add to the product other than their fame? Or is it their relationship with the audience that is the selling point?
Often times ads for medical products or even chewing gum might say that four out of five doctors/dentists recommend a certain product. Some commercials may even show a doctor in a white lab coat approving whatever is for sale. Now, provided that the person you are viewing is an actual doctor, this might be an example of a good ethos argument. On the other hand, if an automotive company uses a famous sports figure to endorse a product, we might wonder what that person knows about this product. The campaign and celebrity are not being used to inform the consumer, but rather to catch their attention with what is actually a faulty example of ethos.
How does this apply to writing? To begin, if you are going to cite an article about racial equality published by the Ku Klux Klan, or a Neo-Nazi organization, this might send up a red flag that this particular article might be written from a biased viewpoint. You need to research an author's background to re-assure yourself that what they are writing is unbiased. Also, if you are trying to present a formal project, you may want to increase your positive ethos by using appropriate terminology. Writing that "abortions are all whack and stuff" is probably not the best way to convince your audience of your point of view. It may happen that you as a writer adopt different voices for different assignments, but your word choice and your approach to the assignment should reflect what it is you want to say.
Logos
Logos is most easily defined as the logical appeal of an argument. Say that you are writing a paper on COVID-19 and you say "COVID-19 is just like the flu, so we should take the same measures as the flu." This statement is illogical because the virus itself, it's characteristics, and the overall situation is not like that of the flu. The statement has an illogical comparison. The COVID-19 virus is in a different family of viruses (corona viruses) than are the various influenza viruses, such as H1N1. COVID-19 displays a wide variety of symptoms (or no symptoms) and is much more contagious precisely because it can be transmitted without any symptoms. In addition, we have immunizations against the flu virus, which we do not yet have for the COVID-19 virus.
Kairos
"Kairos" is an important, but sometimes illusive, rhetorical term. The word itself means "time," and time is central to the concept, which means the "right time" or the "ideal moment" for communicating. Kairos is basically about the context of the moment: what's relevant to the audience at any particular time? Some rhetoricians describe kairos as a fourth " appeal " because rhetors frequently appeal to the urgency of a particular time or moment to engage an audience.
Timing, as they sometimes say, is everything. Rhetoric is about finding the best "available means" of persuasion "at any given moment" or "in any given case." Past, present, and future ("forensic," "epideictic," and "demonstrative" as the video, below, on labels them) are definitely part of the picture here, as well.
Video: How to use rhetoric to get what you want by Camille A. Langston. All Rights Reserved. Standard YouTube license.
Summary: Chart
The chart below summarizes the key points relating to the rhetorical appeals:
Rhetorical Appeal |
Abbreviated Definition |
Reflective Questions |
|
Appeal to credibility You may want to think of ethos as related to "ethics," or the moral principles of the writer: ethos is the author's way of establishing trust with his or her reader. |
|
|
|
Appeal to emotion You may want to think of pathos as "empathy," which pertains to the experience of or sensitivity toward emotion. |
|
|
|
Appeal to logic
You may want to think of logos as "logic," because
|
|
|
|
Appeal to timeliness You may want to think of kairos as the type of persuasion that pertains to "the right place and the right time." |
|
How the Appeals Work Together to Persuade
Understanding how logos, pathos, and ethos should work together is very important for writers who use research. Often, research writing assignments are written in a way that seems to emphasize logical proofs over emotional or ethical ones. Such logical proofs in research papers typically consist of factual information, statistics, examples, and other similar evidence. According to this view, writers of academic papers need to be unbiased and objective, and using logical proofs will help them to be that way.
Because of this emphasis on logical proofs, you may be less familiar with the kinds of pathetic and ethical proofs available to you. Pathetic appeals, or appeals to emotions of the audience were considered by ancient rhetoricians as important as logical proofs. Yet, writers are sometimes not easily convinced to use pathetic appeals in their writing. As modern rhetoricians and authors of the influential book Classical Rhetoric for the Modern Student (1998), Edward P.J. Corbett and Robert Connors said, “People are rather sheepish about acknowledging that their opinions can be affected by their emotions” (86). According to Corbett, many of us think that there may be something wrong about using emotions in argument. But, I agree with Connors, pathetic proofs are not only admissible in argument, but necessary (86-89). The most basic way of evoking appropriate emotional responses in your audience, according to Corbett, is the use of vivid descriptions (94). This is demonstrated at the beginning of many newspaper and magazine feature articles.
Using ethical appeals, or appeals based on the character of the writer, involves establishing and maintaining your credibility in the eyes of your readers. In other words, when writing, think about how you are presenting yourself to your audience.  Consider all the times when your decision about the merits of a given argument was affected by the person or people making the argument. For example, when watching television news, are you predisposed against certain cable networks and more inclined toward others because you trust them more?
So, how can writers establish credible personas for their audiences? One way to do that is through external research. Conducting research and using it well in your writing help you with the factual proofs (logos), but it also shows your readers that you, as the author, have done your homework and know what you are talking about. This knowledge, the sense of your authority that using logos creates among your readers, will help you be a more effective writer.
The logical, pathetic, and ethical appeals work in a dynamic combination with one another. It is sometimes hard to separate one kind of proof from another and the methods by which the writer achieves the desired rhetorical effect.  The key to using the three appeals is to use them in combination with each other and in moderation. It is impossible to construct a successful argument by relying too much on one or two appeals while neglecting the others.
Using Rhetorical Appeals in Your Own Writing
Identifying these appeals in persuasive writing is a valuable skill to learn; understanding how to use these appeals in your persuasive writing can prove to be an even more powerful ability to develop. To begin, several ways to appeal to logic exist. Consider the structure and quality of your argument. Digital strategist and rhetorician, Daniel T. Richards, asks writers to consider these questions : “Does your conclusion follow from your premises? Will your audience be able to follow the progression? Does your argument provide sufficient evidence for your audience to be convinced?” To improve the quality of your argument, consider:
- Referring to facts and figures.
- Citing relevant, current statistics.
- Providing examples.
- Including and addressing an opposing view.
- Using visual representations.
In addition, as Lane, McKee, and McIntyre recommend in their article regarding logos: maintain consistency in your argument, and avoid fallacious, or faulty, appeals to logic. For example, in “ Fallacious Logos ,” they provide an overview of several false appeals to logic , including the false dilemma, which assumes that there are only two options when there are more.
Writers may employ several methods to appeal to pathos. Read “ Pathos ” to explore several suggestions which include:
- Referring to other emotionally compelling stories.
- Citing stark, startling statistics that will invoke a specific emotion in audience members.
- Showing empathy and/or understanding for an opposing view.
- Using humor, if appropriate.
However, in your efforts to appeal to the audience’s emotions, avoid relying on faulty appeals. For example, “ Fallacious Pathos ” points out that using emotional words that evidence does not support leads to the argument by emotive language fallacy.
In pondering how to effectively employ rhetorical devices and aptly avoid fallacies, writers tend to miss the relationship among the rhetorical appeals. Consequently, there is something very right about such arguments as the one advanced by Richards, who argues that “your argument could be sound. It could even be emotionally compelling. But if your audience doesn’t trust you, if they don’t think you have their interest at heart, it won’t matter” (“The 3 Rhetorical Appeals”). Enhance the effectiveness of appeals to pathos and logos with appeals to ethos.
To demonstrate your credibility, try:
- Referring to relevant work and/or life experience.
- Citing your relevant awards, certificates, and/or degrees.
- Providing evidence from relevant, current, and credible sources.
- Carefully proofreading your work, and asking a few other people to so as well.
Additionally, follow McKee and McIntyre’s advice in “ Fallacious Ethos .” McKee and McIntyre provide specific examples of fallacious ethos.
Conversely, appeals to kairos can help you make use of the particular moment (Pantelides, McIntyre, and McKee). Ask yourself if you can capitalize on any of the audience’s fast-approaching moments to create a sense of urgency. However, avoid false appeals to kairos. Read “ Fallacious Appeals to Kairos ” to learn more about this topic.
Good writers write to win. As such, rhetorical appeals underlie much of the successful persuasive writing in society, whether in the form of written arguments, television commercials, or educational campaigns. As previously discussed, some thoughtful, strategic anti-smoking campaigns have reduced smoking-related diseases and death. Additionally, Ariel Chernin, advertising researcher, observes that a large body of literature proves that food marketing affects children’s food preferences. Similarly, appealing to logos, pathos, ethos, and kairos in your persuasive writing can help you achieve your goals. Approaching rhetorical appeals from the inside out—from the perspective of the writer—one can note their effectiveness in persuasive writing, and one can write to win.
Contributors
- Adapted from What is Rhetoric by WikiBooks, CC-BY-SA
- Adapted from Methods of Discovery by Pavel Zemliansky, provided by Three Rivers Digication, CC-NC-SA 3.0.
- Adapted from The Writing Commons . byThe Writing Commons, CC-NC-ND
- Adapted from RhetPrimer by Alissa Messer, CC-BY-SA
This page most recently updated on June 5, 2020.


19.5: Capacitors and Dielectrics
Learning Objectives
By the end of this section, you will be able to:
- Describe the action of a capacitor and define capacitance.
- Explain parallel plate capacitors and their capacitances.
- Discuss the process of increasing the capacitance of a dielectric.
- Determine capacitance given charge and voltage.
A capacitor is a device used to store electric charge. Capacitors have applications ranging from filtering static out of radio reception to energy storage in heart defibrillators. Typically, commercial capacitors have two conducting parts close to one another, but not touching, such as those in Figure \(\PageIndex{1}\). (Most of the time an insulator is used between the two plates to provide separation—see the discussion on dielectrics below.)
Definition: CAPACITOR
A capacitor is a device used to store electric charge.
When battery terminals are connected to an initially uncharged capacitor, equal amounts of positive and negative charge, \(+Q\) and \(-Q\), are separated into its two plates. The capacitor remains neutral overall, but we refer to it as storing a charge \(Q\) in this circumstance. The amount of charge \(Q\) a capacitor can store depends on two major factors—the voltage applied and the capacitor’s physical characteristics, such as its size.
A system composed of two identical, parallel conducting plates separated by a distance, as in Figure \(\PageIndex{2}\), is called a parallel plate capacitor . It is easy to see the relationship between the voltage and the stored charge for a parallel plate capacitor, as shown in Figure \(\PageIndex{2}\). Each electric field line starts on an individual positive charge and ends on a negative one, so that there will be more field lines if there is more charge. (Drawing a single field line per charge is a convenience, only. We can draw many field lines for each charge, but the total number is proportional to the number of charges.) The electric field strength is, thus, directly proportional to \(Q\).
The field is proportional to the charge:
\[E\propto Q,\]
where the symbol \(\propto\) means “proportional to.” From the discussion in Electric Potential in a Uniform Electric Field , we know that the voltage across parallel plates is \(V=Ed\). Thus,
\[V\propto E.\]
It follows, then, that \(V \propto Q\), and conversely,
\[Q\propto V.\]
This is true in general: The greater the voltage applied to any capacitor, the greater the charge stored in it.
Different capacitors will store different amounts of charge for the same applied voltage, depending on their physical characteristics. We define their capacitance \(C\) to be such that the charge \(Q\) stored in a capacitor is proportional to \(C\). The charge stored in a capacitor is given by
\[Q=CV.\]
This equation expresses the two major factors affecting the amount of charge stored. Those factors are the physical characteristics of the capacitor, \(C\), and the voltage, \(V\). Rearranging the equation, we define the c apacitance \(C\) of a capacitor.
Definition: CAPACITANCE
Capacitance \(C\) is the amount of charge stored per volt, or
\[C=\dfrac{Q}{V}.\]
The unit of capacitance is the farad (F), named for Michael Faraday (1791–1867), an English scientist who contributed to the fields of electromagnetism and electrochemistry. Since capacitance is charge per unit voltage, we see that a farad is a coulomb per volt, or
\[1\: \mathrm{F}=\dfrac{1\: \mathrm{C}}{1\: \mathrm{V}}.\]
A 1-farad capacitor would be able to store 1 coulomb (a very large amount of charge) with the application of only 1 volt. One farad is, thus, a very large capacitance. Typical capacitors range from fractions of a picofarad \((1\: \mathrm{pF}=10^{-12}\mathrm{F})\) to millifarads \((1\: \mathrm{mF}=10^{-3}\mathrm{F})\).
Figure \(\PageIndex{3}\) shows some common capacitors. Capacitors are primarily made of ceramic, glass, or plastic, depending upon purpose and size. Insulating materials, called dielectrics, are commonly used in their construction, as discussed below.
Parallel Plate Capacitor
The parallel plate capacitor shown in Figure \(\PageIndex{4}\) has two identical conducting plates, each having a surface area \(A\), separated by a distance \(d\) (with no material between the plates). When a voltage \(V\) is applied to the capacitor, it stores a charge \(Q\), as shown. We can see how its capacitance depends on \(A\) and \(d\) by considering the characteristics of the Coulomb force. We know that like charges repel, unlike charges attract, and the force between charges decreases with distance. So it seems quite reasonable that the bigger the plates are, the more charge they can store—because the charges can spread out more. Thus \(C\) should be greater for larger \(A\). Similarly, the closer the plates are together, the greater the attraction of the opposite charges on them. So \(C\) should be greater for smaller \(d\).
It can be shown that for a parallel plate capacitor there are only two factors (\(A\) and \(d\)) that affect its capacitance \(C\). The capacitance of a parallel plate capacitor in equation form can be defined:
Definition: CAPACITANCE OF A PARALLEL PLATE CAPACITOR
The capacitance of a parallel plate capacitor in equation form is given by
\[C=\varepsilon _{0} \dfrac{A}{d}.\]
\(A\) is the area of one plate in square meters, and \(d\) is the distance between the plates in meters. The constant \(\varepsilon _{0}\) is the permittivity of free space; its numerical value in SI units is \(\varepsilon _{0}=8.85\times 10^{-12} \mathrm{F/m}\). The units of F/m are equivalent to \(\mathrm{C^{2}/N\cdot m^{2}}\). The small numerical value of \(\varepsilon _{0}\) is related to the large size of the farad. A parallel plate capacitor must have a large area to have a capacitance approaching a farad. (Note that the above equation is valid when the parallel plates are separated by air or free space. When another material is placed between the plates, the equation is modified, as discussed below.)
Example \(\PageIndex{1}\): Capacitance and Charge Stored in a Parallel Plate Capacitor
- What is the capacitance of a parallel plate capacitor with metal plates, each of area \(1.00 \mathrm{m^{2}}\), separated by 1.00 mm?
- What charge is stored in this capacitor if a voltage of \(3.00\times 10^{3} \mathrm{V}\) is applied to it?
Strategy
Finding the capacitance \(C\) is a straightforward application of the equation \(C=\varepsilon _{0} A/d\). Once \(C\) is found, the charge stored can be found using the equation \(Q=CV\).
Solution for (a)
Entering the given values into the equation for the capacitance of a parallel plate capacitor yields
\[\begin{align*} C&=\varepsilon \dfrac{A}{d} \\[4pt] &=(8.85\times 10^{-12} \mathrm{\dfrac{F}{m}}) \dfrac{1.00 \mathrm{m^{2}}}{1.00\times 10^{-3} \mathrm{m}} \\[4pt] &=8.85\times 10^{-9} \mathrm{F} =8.85 \mathrm{nF}. \end{align*}\]
Discussion for (a)
This small value for the capacitance indicates how difficult it is to make a device with a large capacitance. Special techniques help, such as using very large area thin foils placed close together.
Solution for (b)
The charge stored in any capacitor is given by the equation \(Q=CV\). Entering the known values into this equation gives
\[ \begin{align*} Q &=CV\\[5pt] &=(8.85 \times 10^{-9}\mathrm{F})(3.00\times 10^{3}\mathrm{V}) \\[5pt] &=26.6 \mathrm{ \mu C}. \end{align*}\]
Discussion for (b)
This charge is only slightly greater than those found in typical static electricity. Since air breaks down at about \(3.00\times 10^{6} \mathrm{V/m}\), more charge cannot be stored on this capacitor by increasing the voltage.
Membrane Potential
Another interesting biological example dealing with electric potential is found in the cell’s plasma membrane. The membrane sets a cell off from its surroundings and also allows ions to selectively pass in and out of the cell. There is a potential difference across the membrane of about \(-70 \mathrm{mV}\). This is due to the mainly negatively charged ions in the cell and the predominance of positively charged sodium (\(\mathrm{Na}^{+}\)) ions outside. Things change when a nerve cell is stimulated. \(\mathrm{Na}^{+}\) ions are allowed to pass through the membrane into the cell, producing a positive membrane potential— the nerve signal . The cell membrane is about 7 to 10 nm thick. An approximate value of the electric field across it is given by
\[ \begin{align*} E&=\dfrac{V}{d} \\[5pt] &=\dfrac{-70\times 10^{-3}\mathrm{V}}{8\times 10^{-9} \mathrm{m}} \\[5pt] &= -9\times 10^{6} \mathrm{V/m}. \end{align*}\]
This electric field is enough to cause a breakdown in air.
Dielectric
The previous example highlights the difficulty of storing a large amount of charge in capacitors. If \(d\) is made smaller to produce a larger capacitance, then the maximum voltage must be reduced proportionally to avoid breakdown (since \(E=V/d\)). An important solution to this difficulty is to put an insulating material, called a dielectric , between the plates of a capacitor and allow \(d\) to be as small as possible. Not only does the smaller \(d\) make the capacitance greater, but many insulators can withstand greater electric fields than air before breaking down.
There is another benefit to using a dielectric in a capacitor. Depending on the material used, the capacitance is greater than that given by the equation \(C=\varepsilon \dfrac{A}{d}\) by a factor \(\kappa\), called the dielectric constant . A parallel plate capacitor with a dielectric between its plates has a capacitance given by
\[C=\kappa \varepsilon _{0} \dfrac{A}{d} (\mathrm{parallel\: plate\: capacitor\: with\: dielectric}).\]
Values of the dielectric constant \(\kappa\) for various materials are given in Table \(\PageIndex{1}\). Note that \(\kappa\) for vacuum is exactly 1, and so the above equation is valid in that case, too. If a dielectric is used, perhaps by placing Teflon between the plates of the capacitor in Example \(\PageIndex{1}\), then the capacitance is greater by the factor \(\kappa\), which for Teflon is 2.1.
TAKE-HOME EXPERIMENT: BUILDING A CAPACITOR
How large a capacitor can you make using a chewing gum wrapper? The plates will be the aluminum foil, and the separation (dielectric) in between will be the paper.
| Material | Dielectric constant ( \(\mathbf{\kappa}\)) | Dielectric Strength ( \(\mathbf{\mathrm{V/m}}\)) |
|---|---|---|
| Vacuum | \(1.00000\) | \(-\) |
| Air | \(1.00059\) | \(3\times 10^{6}\) |
| Bakelite | \(4.9\) | \(24\times 10^{6}\) |
| Fused quartz | \(3.78\) | \(8\times 10^{6}\) |
| Neoprene rubber | \(6.7\) | \(12\times 10^{6}\) |
| Nylon | \(3.4\) | \(14\times 10^{6}\) |
| Paper | \(3.7\) | \(16\times 10^{6}\) |
| Polystyrene | \(2.56\) | \(24\times 10^{6}\) |
| Pyrex glass | \(5.6\) | \(14\times 10^{6}\) |
| Silicon oil | \(2.5\) | \(15\times 10^{6}\) |
| Strontium titanate | \(233\) | \(8\times 10^{6}\) |
| Teflon | \(2.1\) | \(60\times 10^{6}\) |
| Water | \(80\) | \(-\) |
Note also that the dielectric constant for air is very close to 1, so that air-filled capacitors act much like those with vacuum between their plates except that the air can become conductive if the electric field strength becomes too great. (Recall that \(E=V/d\) for a parallel plate capacitor.) Also shown in Table \(\PageIndex{1}\) are maximum electric field strengths in V/m, called dielectric strengths , for several materials. These are the fields above which the material begins to break down and conduct. The dielectric strength imposes a limit on the voltage that can be applied for a given plate separation. For instance, in Example , the separation is 1.00 mm, and so the voltage limit for air is
\[\begin{align*} V&=E\cdot V \\[4pt] &=(3\times 10^{6} \mathrm{V/m})(1.00\times 10^{-3}\mathrm{m}) \\[4pt] &=3000\mathrm{V}. \end{align*}\]
However, the limit for a 1.00 mm separation filled with Teflon is 60,000 V, since the dielectric strength of Teflon is \(60\times 10^{6} \mathrm{V/m}\) V/m. So the same capacitor filled with Teflon has a greater capacitance and can be subjected to a much greater voltage. Using the capacitance we calculated in the above example for the air-filled parallel plate capacitor, we find that the Teflon-filled capacitor can store a maximum charge of
\[\begin{align*} Q&=CV \\[4pt] &=\kappa C_{air}V \\[4pt] &=(2.1)(8.85\mathrm{nF})(6.0\times 10^{4} \mathrm{V}) \\[4pt] &=1.1 \mathrm{mC}. \end{align*}\]
This is 42 times the charge of the same air-filled capacitor.
DIELECTRIC STRENGTH
The maximum electric field strength above which an insulating material begins to break down and conduct is called its dielectric strength.
Microscopically, how does a dielectric increase capacitance? Polarization of the insulator is responsible. The more easily it is polarized, the greater its dielectric constant \(\kappa\). Water, for example, is a polar molecule because one end of the molecule has a slight positive charge and the other end has a slight negative charge. The polarity of water causes it to have a relatively large dielectric constant of 80. The effect of polarization can be best explained in terms of the characteristics of the Coulomb force. Figure \(\PageIndex{5}\) shows the separation of charge schematically in the molecules of a dielectric material placed between the charged plates of a capacitor. The Coulomb force between the closest ends of the molecules and the charge on the plates is attractive and very strong, since they are very close together. This attracts more charge onto the plates than if the space were empty and the opposite charges were a distance \(d\) away.
Another way to understand how a dielectric increases capacitance is to consider its effect on the electric field inside the capacitor. Figure \(\PageIndex{5}\)(b) shows the electric field lines with a dielectric in place. Since the field lines end on charges in the dielectric, there are fewer of them going from one side of the capacitor to the other. So the electric field strength is less than if there were a vacuum between the plates, even though the same charge is on the plates. The voltage between the plates is \(V=Ed\), so it too is reduced by the dielectric. Thus there is a smaller voltage \(V\) for the same charge \(Q\); since \(C=Q/V\), the capacitance \(C\) is greater.
The dielectric constant is generally defined to be \(\kappa =E_{0}/E\), or the ratio of the electric field in a vacuum to that in the dielectric material, and is intimately related to the polarizability of the material.
THINGS GREAT AND SMALL: The Submicroscopic Origin of Polarization
Polarization is a separation of charge within an atom or molecule. As has been noted, the planetary model of the atom pictures it as having a positive nucleus orbited by negative electrons, analogous to the planets orbiting the Sun. Although this model is not completely accurate, it is very helpful in explaining a vast range of phenomena and will be refined elsewhere, such as in the Chapter on Atomic Physics . The submicroscopic origin of polarization can be modeled as shown in Figure \(\PageIndex{6}\).
We will find in Atomic Physics that the orbits of electrons are more properly viewed as electron clouds with the density of the cloud related to the probability of finding an electron in that location (as opposed to the definite locations and paths of planets in their orbits around the Sun). This cloud is shifted by the Coulomb force so that the atom on average has a separation of charge. Although the atom remains neutral, it can now be the source of a Coulomb force, since a charge brought near the atom will be closer to one type of charge than the other.
Some molecules, such as those of water, have an inherent separation of charge and are thus called polar molecules.Figure \(\PageIndex{7}\) illustrates the separation of charge in a water molecule, which has two hydrogen atoms and one oxygen atom (\(\mathrm{H_{2}O}\)). The water molecule is not symmetric—the hydrogen atoms are repelled to one side, giving the molecule a boomerang shape. The electrons in a water molecule are more concentrated around the more highly charged oxygen nucleus than around the hydrogen nuclei. This makes the oxygen end of the molecule slightly negative and leaves the hydrogen ends slightly positive. The inherent separation of charge in polar molecules makes it easier to align them with external fields and charges. Polar molecules therefore exhibit greater polarization effects and have greater dielectric constants. Those who study chemistry will find that the polar nature of water has many effects. For example, water molecules gather ions much more effectively because they have an electric field and a separation of charge to attract charges of both signs. Also, as brought out in the previous chapter, polar water provides a shield or screening of the electric fields in the highly charged molecules of interest in biological systems.
PHET EXPLORATIONS: CAPACITOR LAB
Explore how a capacitor works! Change the size of the plates and add a dielectric to see the effect on capacitance. Change the voltage and see charges built up on the plates. Observe the electric field in the capacitor. Measure the voltage and the electric field.
Summary
- A capacitor is a device used to store charge.
- The amount of charge \(Q\) a capacitor can store depends on two major factors—the voltage applied and the capacitor’s physical characteristics, such as its size.
- The capacitance \(C\) is the amount of charge stored per volt , or \(C=\dfrac{Q}{V}.\)
- The capacitance of a parallel plate capacitor is \(C=\varepsilon _{0} \dfrac{A}{d}\), when the plates are separated by air or free space. \(\varepsilon _{0}\) is called the permittivity of free space.
- A parallel plate capacitor with a dielectric between its plates has a capacitance given by \(C=\kappa \varepsilon _{0} \dfrac{A}{d},\) where \(\kappa\) is the dielectric constant of the material.
- The maximum electric field strength above which an insulating material begins to break down and conduct is called dielectric strength.
Glossary
- capacitor
- a device that stores electric charge
- capacitance
- amount of charge stored per unit volt
- dielectric
- an insulating material
- dielectric strength
- the maximum electric field above which an insulating material begins to break down and conduct
- parallel plate capacitor
- two identical conducting plates separated by a distance
- polar molecule
- a molecule with inherent separation of charge


4.5.2: Notes on the State of Virginia (Excerpt) (3500 words)
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- Robin DeRosa, Abby Goode et al.
- Plymouth State University/
from QUERY VI
…The Indian of North America being more within our reach, I can speak of him somewhat from my own knowledge, but more from the information of others better acquainted with him, and on whose truth and judgment I can rely. From these sources I am able to say, in contradiction to this representation, that he is neither more defective in ardor, nor more impotent with his female, than the white reduced to the same diet and exercise: that he is brave, when an enterprize depends on bravery; education with him making the point of honor consist in the destruction of an enemy by stratagem, and in the preservation of his own person free from injury; or perhaps this is nature; while it is education which teaches us to (* 8) honor force more than finesse: that he will defend himself against an host of enemies, always chusing to be killed, rather than to (* 9) surrender, though it be to the whites, who he knows will treat him well: that in other situations also he meets death with more deliberation, and endures tortures with a firmness unknown almost to religious enthusiasm with us: that he is affectionate to his children, careful of them, and indulgent in the extreme: that his affections comprehend his other connections, weakening, as with us, from circle to circle, as they recede from the center: that his friendships are strong and faithful to the uttermost (* 10) extremity: that his sensibility is keen, even the warriors weeping most bitterly on the loss of their children, though in general they endeavour to appear superior to human events: that his vivacity and activity of mind is equal to ours in the same situation; hence his eagerness for hunting, and for games of chance. The women are submitted to unjust drudgery. This I believe is the case with every barbarous people. With such, force is law. The stronger sex therefore imposes on the weaker. It is civilization alone which replaces women in the enjoyment of their natural equality. That first teaches us to subdue the selfish passions, and to respect those rights in others which we value in ourselves. Were we in equal barbarism, our females would be equal drudges. The man with them is less strong than with us, but their woman stronger than ours; and both for the same obvious reason; because our man and their woman is habituated to labour, and formed by it…
… Instances are known, under these circumstances, of their rearing a dozen children. An inhuman practice once prevailed in this country of making slaves of the Indians…
from QUERY XI
Great question has arisen from whence came those aboriginal inhabitants of America? Discoveries, long ago made, were sufficient to shew that a passage from Europe to America was always practicable, even to the imperfect navigation of ancient times. In going from Norway to Iceland, from Iceland to Groenland, from Groenland to Labrador, the first traject is the widest: and this having been practised from the earliest times of which we have any account of that part of the earth, it is not difficult to suppose that the subsequent trajects may have been sometimes passed. Again, the late discoveries of Captain Cook, coasting from Kamschatka to California, have proved that, if the two continents of Asia and America be separated at all, it is only by a narrow streight. So that from this side also, inhabitants may have passed into America: and the resemblance between the Indians of America and the Eastern inhabitants of Asia, would induce us to conjecture, that the former are the descendants of the latter, or the latter of the former: excepting indeed the Eskimaux, who, from the same circumstance of resemblance, and from identity of language, must be derived from the Groenlanders, and these probably from some of the northern parts of the old continent. A knowledge of their several languages would be the most certain evidence of their derivation which could be produced. In fact, it is the best proof of the affinity of nations which ever can be referred to. How many ages have elapsed since the English, the Dutch, the Germans, the Swiss, the Norwegians, Danes and Swedes have separated from their common stock? Yet how many more must elapse before the proofs of their common origin, which exist in their several languages, will disappear? It is to be lamented then, very much to be lamented, that we have suffered so many of the Indian tribes already to extinguish, without our having previously collected and deposited in the records of literature, the general rudiments at least of the languages they spoke. Were vocabularies formed of all the languages spoken in North and South America, preserving their appellations of the most common objects in nature, of those which must be present to every nation barbarous or civilised, with the inflections of their nouns and verbs, their principles of regimen and concord, and these deposited in all the public libraries, it would furnish opportunities to those skilled in the languages of the old world to compare them with these, now, or at any future time, and hence to construct the best evidence of the derivation of this part of the human race.
from QUERY XIV
To emancipate all slaves born after passing the act. The bill reported by the revisors does not itself contain this proposition; but an amendment containing it was prepared, to be offered to the legislature whenever the bill should be taken up, and further directing, that they should continue with their parents to a certain age, then be brought up, at the public expence, to tillage, arts or sciences, according to their geniusses, till the females should be eighteen, and the males twenty-one years of age, when they should be colonized to such place as the circumstances of the time should render most proper, sending them out with arms, implements of houshold and of the handicraft arts, feeds, pairs of the useful domestic animals, &c. to declare them a free and independant people, and extend to them our alliance and protection, till they shall have acquired strength; and to send vessels at the same time to other parts of the world for an equal number of white inhabitants; to induce whom to migrate hither, proper encouragements were to be proposed. It will probably be asked, Why not retain and incorporate the blacks into the state, and thus save the expence of supplying, by importation of white settlers, the vacancies they will leave? Deep rooted prejudices entertained by the whites; ten thousand recollections, by the blacks, of the injuries they have sustained; new provocations; the real distinctions which nature has made; and many other circumstances, will divide us into parties, and produce convulsions which will probably never end but in the extermination of the one or the other race. — To these objections, which are political, may be added others, which are physical and moral. The first difference which strikes us is that of colour. Whether the black of the negro resides in the reticular membrane between the skin and scarf-skin, or in the scarf-skin itself; whether it proceeds from the colour of the blood, the colour of the bile, or from that of some other secretion, the difference is fixed in nature, and is as real as if its seat and cause were better known to us. And is this difference of no importance? Is it not the foundation of a greater or less share of beauty in the two races? Are not the fine mixtures of red and white, the expressions of every passion by greater or less suffusions of colour in the one, preferable to that eternal monotony, which reigns in the countenances, that immoveable veil of black which covers all the emotions of the other race? Add to these, flowing hair, a more elegant symmetry of form, their own judgment in favour of the whites, declared by their preference of them, as uniformly as is the preference of the Oranootan for the black women over those of his own species. The circumstance of superior beauty, is thought worthy attention in the propagation of our horses, dogs, and other domestic animals; why not in that of man? Besides those of colour, figure, and hair, there are other physical distinctions proving a difference of race. They have less hair on the face and body. They secrete less by the kidnies, and more by the glands of the skin, which gives them a very strong and disagreeable odour. This greater degree of transpiration renders them more tolerant of heat, and less so of cold, than the whites. Perhaps too a difference of structure in the pulmonary apparatus, which a late ingenious (* 1) experimentalist has discovered to be the principal regulator of animal heat, may have disabled them from extricating, in the act of inspiration, so much of that fluid from the outer air, or obliged them in expiration, to part with more of it. They seem to require less sleep. A black, after hard labour through the day, will be induced by the slightest amusements to sit up till midnight, or later, though knowing he must be out with the first dawn of the morning. They are at least as brave, and more adventuresome. But this may perhaps proceed from a want of forethought, which prevents their seeing a danger till it be present. When present, they do not go through it with more coolness or steadiness than the whites. They are more ardent after their female: but love seems with them to be more an eager desire, than a tender delicate mixture of sentiment and sensation. Their griefs are transient. Those numberless afflictions, which render it doubtful whether heaven has given life to us in mercy or in wrath, are less felt, and sooner forgotten with them. In general, their existence appears to participate more of sensation than reflection. To this must be ascribed their disposition to sleep when abstracted from their diversions, and unemployed in labour. An animal whose body is at rest, and who does not reflect, must be disposed to sleep of course. Comparing them by their faculties of memory, reason, and imagination, it appears to me, that in memory they are equal to the whites; in reason much inferior, as I think one could scarcely be found capable of tracing and comprehending the investigations of Euclid; and that in imagination they are dull, tasteless, and anomalous. It would be unfair to follow them to Africa for this investigation. We will consider them here, on the same stage with the whites, and where the facts are not apocryphal on which a judgment is to be formed. It will be right to make great allowances for the difference of condition, of education, of conversation, of the sphere in which they move. Many millions of them have been brought to, and born in America. Most of them indeed have been confined to tillage, to their own homes, and their own society: yet many have been so situated, that they might have availed themselves of the conversation of their masters; many have been brought up to the handicraft arts, and from that circumstance have always been associated with the whites. Some have been liberally educated, and all have lived in countries where the arts and sciences are cultivated to a considerable degree, and have had before their eyes samples of the best works from abroad. The Indians, with no advantages of this kind, will often carve figures on their pipes not destitute of design and merit. They will crayon out an animal, a plant, or a country, so as to prove the existence of a germ in their minds which only wants cultivation. They astonish you with strokes of the most sublime oratory; such as prove their reason and sentiment strong, their imagination glowing and elevated. But never yet could I find that a black had uttered a thought above the level of plain narration; never see even an elementary trait of painting or sculpture. In music they are more generally gifted than the whites with accurate ears for tune and time, and they have been found capable of imagining a small catch (* 2). Whether they will be equal to the composition of a more extensive run of melody, or of complicated harmony, is yet to be proved. Misery is often the parent of the most affecting touches in poetry. — Among the blacks is misery enough, God knows, but no poetry. Love is the peculiar ;oestrum of the poet. Their love is ardent, but it kindles the senses only, not the imagination. Religion indeed has produced a Phyllis Whately; but it could not produce a poet. The compositions published under her name are below the dignity of criticism. The heroes of the Dunciad are to her, as Hercules to the author of that poem. Ignatius Sancho has approached nearer to merit in composition; yet his letters do more honour to the heart than the head. They breathe the purest effusions of friendship and general philanthropy, and shew how great a degree of the latter may be compounded with strong religious zeal. He is often happy in the turn of his compliments, and his stile is easy and familiar, except when he affects a Shandean fabrication of words. But his imagination is wild and extravagant, escapes incessantly from every restraint of reason and taste, and, in the course of its vagaries, leaves a tract of thought as incoherent and eccentric, as is the course of a meteor through the sky. His subjects should often have led him to a process of sober reasoning: yet we find him always substituting sentiment for demonstration. Upon the whole, though we admit him to the first place among those of his own colour who have presented themselves to the public judgment, yet when we compare him with the writers of the race among whom he lived, and particularly with the epistolary class, in which he has taken his own stand, we are compelled to enroll him at the bottom of the column. This criticism supposes the letters published under his name to be genuine, and to have received amendment from no other hand; points which would not be of easy investigation. The improvement of the blacks in body and mind, in the first instance of their mixture with the whites, has been observed by every one, and proves that their inferiority is not the effect merely of their condition of life. We know that among the Romans, about the Augustan age especially, the condition of their slaves was much more deplorable than that of the blacks on the continent of America. The two sexes were confined in separate apartments, because to raise a child cost the master more than to buy one. Cato, for a very restricted indulgence to his slaves in this particular, (* 3) took from them a certain price. But in this country the slaves multiply as fast as the free inhabitants. Their situation and manners place the commerce between the two sexes almost without restraint. — The same Cato, on a principle of ;oeconomy, always sold his sick and superannuated slaves. He gives it as a standing precept to a master visiting his farm, to sell his old oxen, old waggons, old tools, old and diseased servants, and every thing else become useless. `Vendat boves vetulos, plaustrum vetus, ferramenta vetera, servum senem, servum morbosum, & si quid aliud supersit vendat.’ Cato de re rustica. c. 2. The American slaves cannot enumerate this among the injuries and insults they receive. It was the common practice to expose in the island of Aesculapius, in the Tyber, diseased slaves, whose cure was like to become tedious. The Emperor Claudius, by an edict, gave freedom to such of them as should recover, and first declared, that if any person chose to kill rather than to expose them, it should be deemed homicide. The exposing them is a crime of which no instance has existed with us; and were it to be followed by death, it would be punished capitally. We are told of a certain Vedius Pollio, who, in the presence of Augustus, would have given a slave as food to his fish, for having broken a glass. With the Romans, the regular method of taking the evidence of their slaves was under torture. Here it has been thought better never to resort to their evidence. When a master was murdered, all his slaves, in the same house, or within hearing, were condemned to death. Here punishment falls on the guilty only, and as precise proof is required against him as against a freeman. Yet notwithstanding these and other discouraging circumstances among the Romans, their slaves were often their rarest artists. They excelled too in science, insomuch as to be usually employed as tutors to their master’s children. Epictetus, Terence, and Phaedrus, were slaves. But they were of the race of whites. It is not their condition then, but nature, which has produced the distinction. — Whether further observation will or will not verify the conjecture, that nature has been less bountiful to them in the endowments of the head, I believe that in those of the heart she will be found to have done them justice. That disposition to theft with which they have been branded, must be ascribed to their situation, and not to any depravity of the moral sense. The man, in whose favour no laws of property exist, probably feels himself less bound to respect those made in favour of others. When arguing for ourselves, we lay it down as a fundamental, that laws, to be just, must give a reciprocation of right: that, without this, they are mere arbitrary rules of conduct, founded in force, and not in conscience: and it is a problem which I give to the master to solve, whether the religious precepts against the violation of property were not framed for him as well as his slave? And whether the slave may not as justifiably take a little from one, who has taken all from him, as he may slay one who would slay him? That a change in the relations in which a man is placed should change his ideas of moral right and wrong, is neither new, nor peculiar to the colour of the blacks. Homer tells us it was so 2600 years ago.
from QUERY XVII
Millions of innocent men, women, and children, since the introduction of Christianity, have been burnt, tortured, fined, imprisoned; yet we have not advanced one inch towards uniformity. What has been the effect of coercion? To make one half the world fools, and the other half hypocrites. To support roguery and error all over the earth. Let us reflect that it is inhabited by a thousand millions of people. That these profess probably a thousand different systems of religion. That ours is but one of that thousand. That if there be but one right, and ours that one, we should wish to see the 999 wandering sects gathered into the fold of truth. But against such a majority we cannot effect this by force. Reason and persuasion are the only practicable instruments. To make way for these, free enquiry must be indulged; and how can we wish others to indulge it while we refuse it ourselves…


9.1: Introduction to Differential Analysis
Managerial decision making often involves choosing among alternative courses of action. From a financial perspective, the better of two options is either the one that yields the highest amount of income or, if neither produces income, the one that results in the least amount of loss.
Differential analysis is a decision-making technique that examines the benefits and costs associated with each of two options and compares the net results of the two. The alternative selected is the one with the most favorable (or least unfavorable) financial impact. The evaluation includes only those costs that will change if one alternative is selected over another. Fixed costs or other costs that are constant for the two options are excluded from the analysis since they will not differentiate one choice from the other. Sunk costs, which are past expenditures that have already been incurred and cannot be recovered, are also ignored since the amount will be the same regardless of the alternative selected.
A bed & breakfast inn owner uses differential analysis to decide whether to renovate a first-floor guest bedroom or to convert that space to a gift shop. A summary of the year’s revenues and costs for the two alternatives follows.
|
Guest Room |
Gift Shop |
Difference |
|
|
Revenues |
$36,000 |
$42,000 |
|
|
Costs |
(11,000) |
(15,000) |
|
|
Income |
$47,000 |
$57,000 |
$10,000 |
Since the gift shop will yield $2,000 more in operating income than the guest room, the gift shop alternative should be selected.
Seven additional examples will be used to illustrate how differential analysis can be applied to specific business decisions.
- Make or buy a component part
- Continue with or discontinue a business segment
- Lease or sell equipment
- Sell a product or process further
- Keep or replace a fixed asset
- Accept business at reduced price
- Capital investment analysis


6.1: Making Healthy Choices- Eating, Exercise, and Drug Use
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Introduction
Before we explore ways to keep your body healthy, let’s do a little bit of investigation. Ask yourself the following questions, answering as honestly as you can:
- Do you sometimes find yourself feeling sluggish during the day, unable to finish writing that essay or start studying?
- Do you wish you had more energy to keep up with school, work, and family commitments?
- Does drug or alcohol use interfere with your ability to balance daily responsibilities?
Just like proper maintenance and quality fuel keeps your car running smoothly along the highway, our bodies also require care and effort to support all of the demands of today’s fast-paced lifestyle. Scientific data tell us that good nutrition and hydration improve cognitive health, including memory. Fueling our bodies is more than simply eating when hungry; proper nutrients—or lack thereof—affect how our brains function.
Whether you dream of running a marathon or would rather watch a movie marathon on the couch, you should know that exercise is a vital part of keeping both your body and mind vibrant. Regular physical activity boasts a variety of benefits, from disease prevention to improved mental focus.
Drug and alcohol consumption also affects both our physical and mental state of wellness. While occasional imbibing may reduce stress, prolonged overindulgence in any substance creates negative patterns and often leads to unhealthy consequences.
How do we find the balance between recreation and getting wrecked? What tools can we use to create positive physical behaviors for a healthy body? In this module, we explore ways to make good decisions about health choices that can positively affect your academic journey.
What is Good Health?
Some people see health as just a matter of common sense. These people might see little value in reading a health chapter. After all, they already know how to take care of themselves. Yet knowing and doing are two different things. Health information does not always translate into healthy habits.
We expect to experience health challenges as we age, although even youth is no guarantee of good health. Over the past three decades, obesity among young adults has tripled. Twenty-nine percent of young men smoke, and 70 percent of deaths among adults aged 18 to 29 years result from unintentional injuries, accidents, homicide, and suicide (Centers for Disease Control and Prevention 2009).
As a student, your success in school is directly tied to your health. Lack of sleep and exercise have been associated with lower GPAs among undergraduate students. So have alcohol use, tobacco use, gambling, and chronic health conditions (University of Minnesota 2007).
Any health habit that undermines your success in school can also undermine your success in later life. On the other hand, you can adopt habits that sustain your well-being. One study found that people lengthened their lives an average of 14 years by adopting just four habits (Khaw and colleagues 2008):
- staying tobacco-free;
- eating more fruits and vegetables;
- exercising regularly; and
- drinking alcohol in moderation, if at all.
Health also hinges on a habit of exercising some tissue that lies between your ears—the organ called your brain. One path to greater health starts not with new food or a new form of exercise but with new ideas.
Consider the power of beliefs, some of which create barriers to higher levels of health: “Your health is programmed by your heredity,” “Some people are just low on energy,” “Healthy food doesn’t taste very good,” and “Over the long run, people just don’t change their habits.” Be willing to test these ideas and change them when it serves you.
People often misunderstand what the word health means. Remember that this word is similar in origin to whole, hale, hardy , and even holy . Implied in these words are qualities that most of us associate with healthy people: alertness, vitality, and vigor. Healthy people meet the demands of daily life with energy to spare. Illness or stress might slow them down for a while, but they bounce back. They know how to relax, create loving relationships, and find satisfaction in their work.
References
Centers for Disease Control and Prevention. “Health habits of adults aged 18–29 highlighted in report on nation’s health.” CDC.gov. www.cdc.gov/media/pressrel/2009/r090218.htm (published February 18, 2009; accessed March 15, 2011).
Khaw, Kay-Tee, Nicholas Wareham, Sheila Bingham, Ailsa Welch, Robert Luben, and Nicholas Day. “Combined impact of health behaviours and mortality in men and women: The EPIC-Norfolk prospective population study.” PLoS Medicine 5 (2008): e70.www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.0050012 (accessed November 8, 2012).
University of Minnesota. “Health and academic performance: Minnesota undergraduate students.” University of Minnesota, Boynton Health Service.
boynton.umn.edu/sites/boynto...du/files/2017- 09/HealthAcademicPerformanceReport_2007.pdf (accessed April 10, 2009).
Opening Your Mind to Good Health
When you think about health, what ideas come to mind? Perhaps you think about a loved one who has faced an illness, or a friend who is into fitness. Health involves many different things and can be looked at in a variety of ways. To open up your inquiry into health—and to open up new possibilities for your life—consider these three ideas:
- Health is a continuum. On one end of that continuum is a death that comes too early. On the other end is a long life filled with satisfying work and fulfilling relationships. Many of us exist between those extremes at a point we might call average. Most of the time we’re not sick. And most of the time we’re not truly thriving, either.
- Health changes. Health is not a fixed state. In fact, health fluctuates from year to year, day to day, and moment to moment. Those changes can occur largely by chance. Or they can occur more often by choice, as we take conscious control of our thinking and behavior.
- Even when faced with health challenges, we have choices. We can choose attitudes and habits that promote a higher quality of life. For example, people with diabetes can often manage the disease by exercising more and changing their diet.
Health is one of those rich, multilayered concepts that we can never define completely. In the end, your definition of health comes from your own experience. The proof lies not on these pages but in your life—in the level of health that you create, starting now.
You have choices. You can remain unaware of habits that have major consequences for your health. Or you can become aware of current habits (discovery), choose new habits (intention), and take appropriate action.
Health is a choice you make every moment, with each thought and behavior. Wake up to this possibility by experimenting with the suggestions in this lesson.
Eating Disorders
Eating disorders affect many students. These disorders involve serious disturbances in eating behavior. Examples are overeating or extreme reduction of food intake as well as irrational concern about body shape or weight. Women are much more likely to develop these disorders than are men, although cases are on the rise among men.
Bulimia involves cycles of excessive eating and forced purges. A person with this disorder might gorge on a pizza, doughnuts, and ice cream and then force herself to vomit. Or she might compensate for overeating with excessive use of laxatives, enemas, or diuretics.
Anorexia nervosa is a potentially fatal illness marked by self-starvation. People with anorexia may practice extended fasting or eat only one kind of food for weeks at a time.
These disorders are not due to a failure of willpower. They are real illnesses in which harmful patterns of eating take on a life of their own.
Eating disorders can lead to many complications, including life-threatening heart conditions and kidney failure. Many people with eating disorders also struggle with depression, substance abuse, and anxiety. They need immediate treatment to stabilize their health. This is usually followed by continuing medical care, counseling, and medication to promote a full recovery.
If you’re worried you might have an eating disorder, visit a doctor, campus health service, or local public health clinic. For more information, contact the National Eating Disorders Association at 1-<PHONE_NUMBER> or online at www.nationaleatingdisorders.org.
Choose to Exercise
Our bodies need to be exercised. The world ran on muscle power back in the era when we had to hunt down a woolly mammoth every few weeks and drag it back to the cave. Today, we can grab a burger at a drive-up window, so we need to make a special effort to exercise.
Exercise promotes weight control and reduces the symptoms of depression. It also helps to prevent heart attack, diabetes, and several forms of cancer (Harvard Medical School 2008).
Exercise also refreshes your body and your mind. If you’re stuck on a math problem or blocked on writing a paper, take an exercise break. Chances are that you’ll come back with a fresh perspective and some new ideas.
If you get moving, you’ll create lean muscles, a strong heart, and an alert brain. If the word exercise turns you off, think physical activity instead. Here are some things you can do:
- Stay active throughout the day. Park a little farther from work or school. Do your heart a favor by walking some extra blocks. Take the stairs instead of riding elevators. For an extra workout, climb two stairs at a time. An hour of daily activity is ideal, but do whatever you can. Some activity is better than none.
- No matter what you do, ease into it. For example, start by walking briskly for at least 15 minutes every day. Increase that time gradually, and add a little jogging.
- Adapt to your campus environment. Look for exercise facilities on campus. Search for classes in aerobics, swimming, volleyball, basketball, golf, tennis, and other sports. Intramural sports are another option. School can be a great place to get in shape.
- Do what you enjoy. Stay active with aerobic activities that you enjoy. You might like martial arts, kickboxing, yoga, ballroom dancing, stage combat classes, or mountain climbing. Check your school catalog for such courses.
- Vary your routine. Find several activities that you like to do, and rotate them throughout the year. Your main form of activity during winter might be ballroom dancing, riding an exercise bike, or skiing. In summer, you could switch to outdoor sports. Whenever possible, choose weight-bearing activities such as walking, running, or stair climbing.
- Get active early. Work out first thing in the morning. Then it’s done for the day. Make it part of your daily routine, just like brushing your teeth.
- Exercise with other people. Making exercise a social affair can add a fun factor and raise your level of commitment.
- Join a gym without fear . Many health clubs welcome people who are just starting to get in shape.
Look for gradual results. If your goal is to lose weight, be patient. Because 1 pound equals 3,500 calories, you might feel tempted to reduce weight loss to a simple formula: Let’s see ... if I burn away just 100 calories each day through exercise, I should lose 1 pound every 35 days.
Actually, the relationship between exercise and weight loss is complex. Many factors—including individual differences in metabolism and the type of exercise you do—affect the amount of weight you actually lose (Brody 2006). When you step on the bathroom scale, look for small changes over time rather than sudden, dramatic losses. Gradual weight loss is more healthy anyway—and easier to sustain over the long term.
Weight loss is just one potential benefit of exercise. Choosing to exercise can lift your mood, increase your stamina, strengthen your bones, stabilize your joints, and help prevent heart disease. It can also reduce your risk of high blood pressure, diabetes, and several forms of cancer. If you do resistance training—such as weight machines or elastic-band workouts—you’ll strengthen your muscles as well. For a complete fitness program, add stretching exercises to enjoy increased flexibility (Harvard Medical School 2009).
Before beginning any vigorous exercise program, consult a healthcare professional. This is critical if you are overweight, older than 60 years, in poor condition, or a heavy smoker, or if you have a history of health problems.
References
Brody, Jane. “Exercise = weight loss, except when it doesn’t.” New York Times, September 12, 2006. http://www.nytimes.com/2006/09/12/he...n/12brody.html (accessed November 8, 2012).
Harvard Medical School.  Boston: Harvard Health Publications, 2008.
Harvard Medical School. HEALTHbeat Extra: The Secret to Better Health—Exercise. Boston: Harvard Health Publications, 2009.
Alcohol, Tobacco, and Drugs: The Truth
The truth is that getting high can be fun. In our culture, and especially in our media, getting high has become synonymous with having a good time.
For centuries, human beings have devised ways to change their feelings and thoughts by altering their body chemistry. The Chinese were using marijuana 5,000 years ago. Herodotus, the ancient Greek historian, wrote about a group of people in Eastern Europe who threw marijuana on hot stones and inhaled the vapors. More recently, during the American Civil War, customers could buy opium and morphine at neighborhood stores (Weil and Rosen 1993, 45).
Today, we are still a drug-using society. Of course, some of those uses are therapeutic and lawful, including taking drugs as prescribed by a doctor or psychiatrist. The problem comes when we turn to drugs as the solution to any problem. Often, the first response to the question, “Are you uncomfortable?” is, “Take something.”
We live in times when reaching for instant comfort via chemicals is not only condoned but encouraged. If you’re bored, tense, or anxious, you can drink a can of beer, down a glass of wine, or light up a cigarette. If you want to enhance your memory, take a smart drug , which includes prescription stimulants and caffeine. And these are only the legal options. If you’re willing to take risks, you can pick from a large selection of illegal drugs on the street. And if that seems too risky, you can abuse prescription drugs.
There is a big payoff in using alcohol, tobacco, caffeine, cocaine, heroin, or other drugs—or people wouldn’t do it. The payoff can be direct, such as relaxation, self-confidence, comfort, excitement, or the ability to pull an all-nighter. At times, the payoff is avoiding rejection or defying authority.
In addition to the payoffs, there are costs. For some people, the cost is much greater than the payoff. Even if drug use doesn’t make you broke, it can make you crazy. This is not necessarily the kind of crazy where you dress up like Napoleon. Rather, it is the kind where you care about little else except finding more drugs—friends, school, work, and family be damned.
Substance abuse is only part of the picture. People can also relate to food, gambling, money, sex, and even work in compulsive ways.
Some people will stop abusing a substance or activity when the consequences get serious enough. Other people don’t stop. They continue their self-defeating behaviors, no matter the consequences for themselves, their friends, or their families. At that point, the problem goes beyond abuse. It’s addiction.
With addiction, the costs can include overdose, infection, and lowered immunity to disease. These can be fatal. Long-term heavy drinking, for example, damages every organ system in the human body. And about 440,000 Americans die annually from the effects of cigarette smoking, including secondhand smoke (Centers for Disease Control and Prevention 2011).
Lectures about the reasons for avoiding alcohol as well as drug abuse and addiction can be pointless. We don’t take care of our bodies because someone says we should. We might take care of ourselves when we see that the costs of using a substance outweigh the benefits.
Acknowledging that alcohol, tobacco, and other drugs can be fun infuriates a lot of people. Remember that this acknowledgment is not the same as condoning drug use. The point is this: People are more likely to abstain when they’re convinced that using these substances leads to more pain than pleasure over the long run. You choose. It’s your body.
References
Centers for Disease Control and Prevention. “Tobacco-related mortality.” CDC.gov.
http://www.cdc.gov/tobacco/data_stat...ted_mortality/
(published March 21, 2011; accessed November 8, 2012).
Weil, Andrew, and Winifred Rosen.
From Chocolate to Morphine: Everything You Need to Know
About Mind-Altering Drugs. Boston: Houghton Mifflin, 1993.


2.7: The Health of the Economy
What you’ll learn to do: describe how economists evaluate the health of an economy
This section will help you understand why economists use terms like GDP, CPI, and unemployment rates to assess how an economy is doing.
Learning Objectives
- Explain the use of GDP as an economic indicator
Health of the Economy
Economic Indicators
When you go to the doctor with the flu, one of the first things they do is they take your temperature. If your temperature is much above 98.6 degrees, they declare you to have a fever. Depending on your other symptoms, they may prescribe you medication to bring down your fever and fight the infection. How might you (or an economist) take the temperature of an economy, so to speak, to check for health or sickness? No single measurement like body temperature will give a complete picture, so instead economists rely on what are called economic indicators. An economic indicator is a statistic that provides valuable information about the economy. There is no shortage of economic indicators, and trying to follow them all would be an overwhelming task. Many different economic indicators are tracked in order to evaluate the economy in different ways or from different perspectives.
Statistics that report the status of the economy a few months in the past are called lagging economic indicators . One such lagging indicator is the average length of unemployment. If unemployed workers have remained out of work for a long time, we may infer that the economy has been slow. Indicators that predict the status of the economy three to twelve months into the future are called leading economic indicators . For example, the number of building permits issued is often a good way to assess the strength of the housing market. An increase in this statistic—which tells us how many new housing units are being built—indicates that the economy is improving because increased building brings money into the economy not only through new home sales but also through sales of furniture and appliances to furnish these homes. If such a leading indicator rises, the economy is likely to expand in the coming year. If it falls, the economy is likely to slow down.
Governments, businesses, and investors use economic indicators as a measure of how well an economy is meeting its goals.
Economic Goals
The world’s market-based economies all share the following three main goals:
- Growth
- High employment
- Price stability
Economic indicators reveal information about how the economy is doing relative to these goals. Let’s look more closely at growth, employment, and price stability and the means used to measure them.
Growth
GDP
The size of a nation’s overall economy is typically measured by its gross domestic product (GDP), which is the value of all officially recognized final goods and services produced within a country in a given period of time (usually a year). Intermediate goods (goods such as steel or plywood that are used as inputs in the production of other goods) are not included because they would cause double-counting to occur. GDP only refers to goods produced within a particular country. For instance, if a firm is located in one country but manufactures goods in another, those goods are counted as part of the manufacturing country’s GDP, not the firm’s home country. BMW is a German company, but cars manufactured in the U.S. are counted as part of the U.S. GDP.
The measurement of GDP involves counting up the production of millions of different goods and services—smart phones, cars, music downloads, computers, steel, bananas, college educations, and all other new goods and services produced in the current year—and summing them into a total dollar value. This task is straightforward: Take the quantity of everything produced, multiply it by the price at which each product sold, and add up the total. In 2014, the U.S. GDP totaled $17.4 trillion, the largest GDP in the world.
When a country’s GDP grows, its economy is likewise considered to be expanding and growing. Increases in GDP are expressed as a percentage rate of increase, and they are often expressed as GDP per capita (per person). In order to calculate GDP per capita, the GDP is divided by the total population of a country. Also, when measuring economic growth, agencies use “real GDP,” which is adjusted for inflation. If the GDP figures were not adjusted for inflation, then steep rises in prices (inflation) could be mistaken for growth. Likewise, if GDP is not expressed per capita, then a country like India with a massive population would always be regarded as having one of the largest, fastest growing economies. The map, below, shows the world’s GDP per capita by country.
High Employment
A country’s employment level—as defined by cyclical, structural, and frictional unemployment—is one of the most important economic indicators. Unemployment has an enormous impact on business operations, from the largest multinational corporation to the smallest mom-and-pop gift shop. When people are unemployed, even temporarily, they stop spending money on nonessential goods and services, which slows down the economy. Such a slowdown leads to a decrease in revenue for businesses, which causes companies to lay off more workers, which means more unemployed people who can’t purchase their goods and services. Because of this spiraling effect, unemployment is a closely watched economic indicator.
The Unemployment Rate
There are three important categories of unemployment levels that need to be understood in order to evaluate the effect of employment levels on overall economic performance: cyclical unemployment, structural unemployment, and frictional unemployment.
- Cyclical Unemployment
Cyclical unemployment occurs when there is not enough total demand in the economy to provide jobs for everyone who wants to work. When demand for most goods and services falls, less production is needed, and, as a result, fewer workers are needed; wages generally stay put and do not fall to meet the equilibrium level, and mass unemployment results. With cyclical unemployment, the number of unemployed workers exceeds the number of job vacancies, so that even if full employment were attained and all open jobs were filled, some workers would still be without jobs. In economics, full employment is the level of employment rate where there is no cyclical unemployment.
- Structural Unemployment
Structural unemployment occurs when a labor market is unable to provide jobs for everyone who wants to work because there is a mismatch between the skills of the unemployed workers and the skills needed for the available jobs. Structural unemployment may develop or increase as a result of persistent cyclical unemployment: If an economy suffers from long-lasting low aggregate demand, many of the unemployed may become disheartened, and their skills (including job-searching skills) become rusty and obsolete. The implication is that sustained high demand may lower structural unemployment. Seasonal unemployment can be seen as a kind of structural unemployment, since it’s a type of unemployment that is linked to certain kinds of jobs (construction work or migratory farm work, for instance).
- Frictional Unemployment
Frictional unemployment is the time period between jobs when a worker is searching for or transitioning from one job to another. It’s sometimes called “search unemployment” and can be voluntary depending on the circumstances of the unemployed individual. Frictional unemployment is always present in an economy, so the level of involuntary unemployment is really the unemployment rate minus the rate of frictional unemployment. Frictional unemployment exists because both jobs and workers are heterogeneous, and a mismatch can result between the characteristics of supply and demand. Such a mismatch can be related to any of the following reasons:
- Skills
- Payment
- Worktime
- Location
- Seasonal industries
- Attitude
- Taste
There can be a range of other factors, too. New entrants (such as graduating students) and reentrants (such as former homemakers) can also suffer a spell of frictional unemployment. Workers as well as employers accept a certain level of imperfection, risk, or compromise, but usually not right away; they will invest some time and effort to find a better match. This is in fact beneficial to the economy, since it results in a better allocation of resources.
practice Question \(\PageIndex{1}\)
Jane is an unemployed construction worker desperate to find employment so she can cover her mortgage and basic living expenses. She is willing to work for any wage, yet is unable to find any paid work given the poor state of the economy. She continues her search despite the lack of opportunities. Which of the following economic terms best describes Jane’s current predicament?
- Cyclical Unemployment
- Voluntary Unemployment
- Shortage of Labor
- Answer
-
A . Cyclical Unemployment
practice question \(\PageIndex{2}\)
Which of the following is an example of frictional unemployment as defined in the text?
- An auto worker has received a job offer two states away, and must take off one month between jobs in order to relocate.
- A nurse quits his job at a local hospital which is a poor fit personally. After a six month job search he becomes discouraged and exits the labor force.
- During a severe economic downturn a large steel plant hands out redundancy notices to 1,000 employees.
- Answer
-
a . Relocating to a new job offer is an example of frictional unemployment
Price Stability
The third major goal of all economies is maintaining price stability. Price stability occurs when prices remain largely unchanged and there isn’t rapid inflation or deflation. Inflation is a rise in the general price level of goods and services during a period of time; deflation is a decrease in the general price level of goods and services. Price stability means that the average price for goods and services either doesn’t change or changes very little. Most economists believe that steady levels of low-to-moderate inflation are ideal.
As inflation pushes prices higher (slowly), businesses increase their revenues, people put more money into the system, and assets increase in value, which are all positive economic indicators. This is why economists are careful to say that a steady level of low inflation is a positive sign in the economy. As inflation rises, prices rise and values rise, which both contribute to an increase in GDP—another measure of the health of an economy. During the past three decades, inflation has been relatively low (well below 10 percent) in the U.S. economy, and this has contributed to the general stability of the economy. Inflation doesn’t always increase slowly. A sudden, rapid rise in inflation is called hyperinflation . Argentina has recently (and repeatedly) experienced runaway inflation, with consumer prices increasing in some cases by 50 percent in a matter of days.
Figure \(\PageINdex{1}\), below, shows the U.S. inflation rate from 1989 to 2009. As you can see,. Looking back at the twentieth century, there have been several periods when inflation caused the price level to rise at double-digit rates, but nothing has come close to hyperinflation.
Consumer Price Index (CPI)
The most commonly cited measure of inflation in the United States is the consumer price index (CPI). The CPI measures changes in the price level of consumer goods and services purchased by households. The CPI in the United States is defined by the Bureau of Labor Statistics as “a measure of the average change over time in the prices paid by urban consumers for a market basket of consumer goods and services.”
The CPI market basket represents all the consumer goods and services purchased by urban households. Price data are collected for over 180 categories, which BLS has grouped into 8 major groups. These major groups, with examples of categories in each, are as follows:
- Food and beverages (ham, eggs, carbonated drinks, coffee, meals and snacks);
- Housing (rent of primary residence, fuel oil, bedroom furniture);
- Apparel (men’s shirts and sweaters, women’s dresses, jewelry);
- Transportation (new vehicles, gasoline, tires, airline fares);
- Medical care (prescription drugs and medical supplies, physicians’ services, eyeglasses and eye care, hospital services);
- Recreation (television sets, cable TV, pets and pet products, sports equipment, admissions);
- Education and communication (college tuition, postage, telephone services, computer software and accessories);
- Other goods and services (tobacco and smoking products, haircuts and other personal care services, funeral expenses)
The CPI simplifies the measurement of changes in prices over time. By selecting an appropriate reference base and setting the average index level for that time period equal to 100, it is possible to compare this month’s (or last year’s) price index level with the reference base period or to any other time period. The current standard reference base period is 1982–1984=100. That is, all price changes are measured from a base (100) that represents the average index level of the 36-month period encompassing 1982, 1983, and 1984. [1]
Consumer Price Index 2006 to Present (Source: US BLS)
Consumer Confidence Index
Another important economic indicator is the consumer confidence index . This indicator measures the degree of optimism that consumers feel about the overall state of the economy and their personal financial situation. How confident people feel about the stability of their incomes determines their spending activity and therefore serves as one of the key indicators for the overall shape of the economy. In essence, if the economy expands, causing consumer confidence to be higher, consumers will be making more purchases. On the other hand, if the economy contracts or is in bad shape, confidence is lower, and consumers tend to save more and spend less. A month-to-month diminishing trend in consumer confidence suggests that in the current state of the economy most consumers have a negative outlook on their ability to find and retain good jobs.
The ability to predict major changes in consumer confidence allows businesses to gauge the willingness of consumers to make new purchases. As a result, businesses can adjust their operations and the government can prepare for changing tax revenue. If confidence is dropping and consumers are expected to reduce their spending, most producers will tend to reduce their production volumes accordingly. For example, if manufacturers anticipate that consumers will reduce retail purchases, especially for expensive and durable goods, they will cut down their inventories in advance and may delay investing in new projects and facilities. The government will get ready for the reduction in future tax revenues. On the other hand, if consumer confidence is improving, people are expected to increase their purchases of goods and services. In anticipation of that change, manufacturers can boost production and inventories. Large employers can increase hiring rates. Government can expect improved tax revenues based on the increase in consumer spending.
Consumer confidence is formally measured by the Consumer Confidence Index (CCI), a monthly release designed to assess the overall confidence, relative financial health, and spending power of the average U.S. consumer. The CCI is an important measure used by businesses, economic analysts, and the government in order to determine the overall health of the economy.
practice Question \(\PageIndex{3}\)
The main economic indicators include
- the misery index and consumer confidence index
- gross domestic product, employment, and trade balance.
- gross domestic product, inflation, and unemployment
- Answer
-
c
the misery index which combines inflation and unemployment is one of the main economic indicators along with GDP but the consumer confidence index is not and neither is trade balance.
- Source: US Bureau of Labor Statistics http://www.bls.gov/cpi/ ↵