|We supply electrical energy to an electric motor. An efficient motor transfers most of this energy as kinetic energy (useful work). Only a small fraction is wasted as it heats up the surroundings. We can show this in a Sankey diagram (picture 6). The size of the arrows represents the amount of each type of energy. |
Energy is lost as the electric current flows through the motors coils. The wire coils have electrical resistance; the greater the resistance, the harder it is for the current to flow and the more energy is wasted.
Copper is a good metal to use for a motors coils because:
- it has less resistance than almost any other metal (see conducting properties)
- it is easily made into wires
- it is not too expensive
- it can survive to a high temperature
- it can be easily recycled when the motor is replaced.