Practice question · Multiple choice
A motor turns electrical energy into motion and a generator does the reverse, and the two are essentially the same device. Why does one mechanism run in both directions?
Hints
- State the two electromagnetic effects involved. Are they two facts or one relationship seen twice?
- Ask what happens if you spin a motor's shaft by hand with nothing connected.
Show the answer
C. Because the underlying relationship is symmetric in both directions.
Why
Two effects, two faces of one relationship: a current-carrying conductor in a field feels a force, and a conductor moved through a field has a voltage induced across it. Spin a small DC motor's shaft by hand with a voltmeter attached and it generates. Regenerative braking exploits the reversibility, which is why an electric car's range improves in hilly driving where a petrol car's does not.
Practise Magnetism and Electromagnetism
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