Problem: I read this background article the other day: Charging an object by touching it with another charged object is called charging by conduction. By bringing a charged object into contact with an uncharged object, some electrons will migrate to even out the charge on both objects. Charging by conduction gives the previously uncharged object a permanent charge. An uncharged object can also be charged using a method called charging by induction . This process allows a change in charge without actually touching the charged and uncharged objects to each other. Imagine a negatively charged rod held near the knob, but not touching. If we place a finger on the knob, some of the electrons will escape into our body, instead of down the stem and into the leaves. When both our finger and the negatively charged rod are removed, the previously uncharged electroscope now has a slight positive charge. It was charged by induction. Notice that charging by induction causes the newly charged object to have the opposite charge as the originally charged object, while charging by conduction gives them both the same charge.  I am facing a new situation today: John wanted to charge his electronic gadgets remotely. To that end, he first conducted two experiments, case A and case B. In case A he used conduction, and in case B he used induction. In both cases he used same two objects. Finally, John tried to  charge his phone remotely. He called this test as case C.  Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: In which case the objects would be closer to each other, case A or case B?

A: case A


Problem: I read this background article the other day: A dilution effect is seen when animals living in a group "dilute" their risk of attack, each individual being just one of many in the group. George C. Williams and W.D. Hamilton proposed that group living evolved because it provides benefits to the individual rather than to the group as a whole, which becomes more conspicuous as it becomes larger. One common example is the shoaling of fish. Experiments provide direct evidence for the decrease in individual attack rate seen with group living, for example in Camargue horses in Southern France. The horse-fly often attacks these horses, sucking blood and carrying diseases. When the flies are most numerous, the horses gather in large groups, and individuals are indeed attacked less frequently. Water striders are insects that live on the surface of fresh water, and are attacked from beneath by predatory fish. Experiments varying the group size of the water striders showed that the attack rate per individual water strider decreases as group size increases.  I am facing a new situation today: Mike was visiting the African Savannah. One animal that interested him most was the African Buffalo. He noticed that the buffaloes would usually live in a large herd, often exceeding few hundreds. He noted that as case A. But sometimes the buffaloes would live in a small herd. He noted that as case B. Interestingly, there are incidents when an aggressive male buffalo would live by itself. He noted that as case C.  Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: In which case the group would get less benefit as a whole, case A or case B?

A: case A


Problem: I read this background article the other day: Excess intake of calcium may cause hypercalcaemia. However, because calcium is absorbed rather inefficiently by the intestines, high serum calcium is more likely caused by excessive secretion of parathyroid hormone (PTH) or possibly by excessive intake of vitamin D, both which facilitate calcium absorption. It may also be due to bone destruction that occurs when tumours metastasize within bone. All these conditions result in excess calcium salts being deposited in the heart, blood vessels, or kidneys. Symptoms include anorexia, nausea, vomiting, memory loss, confusion, muscle weakness, increased urination, dehydration, and metabolic bone disease. Chronic hypercalcaemia typically leads to calcification of soft tissue and its serious consequences: for example, calcification can cause loss of elasticity of vascular walls and disruption of laminar blood flow—and thence to plaque rupture and thrombosis. Conversely, inadequate calcium or vitamin D intakes may result in hypocalcaemia, often caused also by inadequate secretion of parathyroid hormone or defective PTH receptors in cells. Symptoms include neuromuscular excitability, which potentially causes tetany and disruption of conductivity in cardiac tissue.  I am facing a new situation today: Two friends went to the doctor because they weren't feeling well. As it turns out Danny had a condition called hypercalcaemia, while Greg had hypocalcaemia.  Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Which friend had an excessive secretion of parathyroid hormone (PTH)?

A: Danny


Problem: I read this background article the other day: Machines make work easier by increasing the amount of force that is applied, increasing the distance over which the force is applied, or changing the direction in which the force is applied. Contrary to popular belief, machines do not increase the amount of work that is done. They just change how the work is done. So if a machine increases the force applied, it must apply the force over a shorter distance. Similarly, if a machine increases the distance over which the force is applied, it must apply less force.  I am facing a new situation today: Archimedes was a great scientist. He was also a great inventor of machines. He once said that if he could stand somewhere, he could move the earth with his machine. Hearing that, king of Sicily called Archimedes and his fellow scientist Ptolemy to come up with great inventions. Archimedes, as everyone expected, came up with a great machine. But Ptolemy couldn't do much in such a limited time. So, his device was not a machine.  Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Would Archimedes' device more likely or less likely make work easier than Ptolemy's one?

A:
more likely