Working Knowledge; March 2000; Scientific American Magazine; by Rosenau; 1 Page(s)

The glass-enclosed meter that hangs on a wall of your home, in your basement or outside on a nearby pole, works by recording the energy flow into your residence from the power company. It measures both the current-that is, the flow of electrons, which is expressed in amperes-and the voltage, or pressure, that pushes electricity through the wire. To determine the wattage used, the meter automatically multiplies amperes by volts.