Contour maps like the one above show equally spaced lines of constant elevation at the Earth's surface. Please explain in what sense they are "equally spaced." Also, please explain in what sense these lines could be called gravitaional equipotentials.

Estimate the total charge that passes through a lightbulb in one second.

Hint: Assume that the voltage across the bulb is 120 V.

The electrical potential energy stored in a capacitor is given by U = (1/2)CV². It is also given by U = (1/2C)Q². Is the energy really proportional to C or to 1/C, or, is neither really true?

You and a close friend stand facing each other. You are as close as you can get without actually touching. If wires are attached to each of you, you can act as the two conductors in a capacitor. Estimate the capacitance of this "human capacitor".