Generators work by rotating a coil of wire in a magnetic field, causing a current to flow in the wire. A generator may be a huge spinning turbine powered by water, wind, steam, gas, or nuclear reactions, which sends electricity out through power lines to thousands of customers. But normally when we use the word, we're thinking of a small machine powered by gasoline or diesel, such as you might keep in your basement for those times when a storm knocks out your power, to create electricity right in front of your eyes. A special kind of generator called an alternator powers a car's electrical system (including its lights, power steering, etc.) while the car is running.