Everything Science Grade 12

CHAPTER 13. ELECTRODYNAMICS 13.2

generators of not usinga commutator, which makes them simpler, lighter, less costly,
and more rugged than aDC generator.

Activity: Alternators

Try to find out the different ampere values produced by alternators for dif-

ferent types of machines. Compare these to understand what numbersmake

sense in the real world.You will find different numbers for cars, trucks,buses,

boats etc. Try to find out what other machines might have alternators.

A car also contains a DCelectric motor, the starter motor, to turn over theengine to start
it. A starter motor consists of the very powerfulDC electric motor and starter solenoid
that is attached to the motor. A starter motor requires a very high current to crank the
engine, that’s why it’s connected to the battery with large cables.

Electricity Generation

AC generators are mainly used in the real-worldto generate electricity.

Step-up

Step-down

Power Plant

low voltage

high voltage

low voltage

... to other customers

Home or

Business

Figure 13.8: AC generators are used at the power plant to generate electricity.

Exercise 13 - 1

1. State the difference between a generator anda motor.


2. Use Faraday’s Law toexplain why a current isinduced in a coil that isrotated in
   a magnetic field.


3. Explain the basic principle of an AC generator in which a coil is mechanically
   rotated in a magnetic field. Draw a diagram to support your answer.