Physicists have specific definitions for “energy” and “power” even though these words are often used interchangeably in common speech. Energy is the ability to do work, while power is the rate at which work is done. In this exhibit, a hand generator is used to create a charge which is stored in large capacitors; the capacitors hold a given amount of energy. The capacitors can then be discharged through one of several different light bulbs that vary in resistance. The energy is consumed at different rates and hence the bulbs have different power ratings (wattage).