In 1919, the 18th Amendment to the U.S. Constitution, which prohibited the sale and manufacture of alcohol, was ratified. It went into effect on January 16, 1920âbeginning the era known as Prohibition.
Because time constant calculations are important, and often needed, it is better to make the definition of the time constant (T) in a CR circuit: THE TIME TAKEN FOR THE VOLTAGE ACROSS A CAPACITOR TO INCREASE BY 63.2% OF THE DIFFERENCE BETWEEN ITS PRESENT AND FINAL VALUES.
That is called Ohm's Law. Ohm's Law describes the behavior of a theoretical circuit element called a resistor which usually has a constant value of resistance. Actual resistors (and actual conductors) behave very much like the theoretical model. Changing the current through a resistor does not have any effect on the resistance. If the current goes up, then according to Ohm's law, the voltage must have gone up in the same proportion. There is a circuit element called a variable resistor (a.k.a., potentiometer, or rheostat).