Electromagnetic Induction, Alternating Current, the Generator and the Transformer
How a moving magnet makes electricity - and how that electricity reaches your home
Big Idea: In Topic 17 you saw that an electric current makes a magnetic field. Now we turn the idea around: a changing magnetic field makes an electric current. This one discovery - electromagnetic induction - is behind almost all the electricity produced on Earth, from the Toktogul hydroelectric station to the charger on your desk.
By the end of this topic you will be able to:
- describe Faraday's experiments and say what causes an induced current;
- explain that a changing magnetic flux through a coil produces an induced EMF;
- explain how a rotating coil produces alternating current (AC);
- describe how a generator turns motion into electricity;
- explain why electricity is sent over long distances at very high voltage;
- use a transformer and its turns-ratio rule U1/U2 = N1/N2.