Compare an electric motor and an electric generator…

Contributed by StemPy Lab

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

Compare an electric motor and an electric generator. For each, say what goes in and what comes out, which of Fleming's rules is used, and which effect makes it work.

Need a reminder? The key ideaShow

A generator turns a coil in a magnetic field. With slip rings it gives alternating current (AC), which changes direction twice in every turn; with a split ring it gives a pulsing direct current (DC). Frequency $f$ = turns each second, in hertz; one cycle takes $T = \dfrac{1}{f}$ .

The worked solution

Have you tried it?

Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

Step 1. The table.

	Electric motor	Electric generator
In	Electrical energy	Mechanical energy (the coil is turned)
Out	Mechanical energy (the coil turns)	Electrical energy
Rule	Fleming's left-hand rule	Fleming's right-hand rule
Effect	The force on a current in a field	Electromagnetic induction

Answer: a motor turns electrical energy into mechanical energy by the force on a current; a generator turns mechanical energy into electrical energy by induction.

Check. Both have a coil and a magnet. In the motor the current is given and the motion follows; in the generator the motion is given and the current follows.

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