When the battery is then connected to an electrical circuit, it converts its chemical energy into electrical energy as electrons flow between the negative and positive poles of the battery. Imagine a horse with a rope in its teeth. The rope is attached to a 55 pound block of cement. In one second, the horse pulls that block a distance of ten feet. That amount of work, or energy expended, is equal to 1 horsepower.
Electrical power is measured in units called kilowatts.
One kilowatt equals about 1.3 horse power. The electrical energy is then sent out to our homes, offices and factories through wires. This is a very clean way to transport energy, but there are drawbacks. To begin with, the copper wires that carry energy are expensive and tend to lose some of the energy that passes through them. One way to cut down on the cost of the wire is to make it thinner.