Energy Transferred by Working
Electricity and Magnetism

Electrical generators - how do they work?

Teaching Guidance for 14-16 Supporting Physics Teaching

Generators do not make charge!

Wrong Track: Electric generators are the opposite of electric motors. Instead of changing electricity into movement, they change movement into electricity.

Right Lines: A common form of generator switches power from a mechanical to an electrical pathway.

Getting charge moving by working

Thinking about the learning

The wrong track thinking set out here takes us back to the world of forms of energy, where the working of a generator is described in terms of movement (or kinetic) energy being changed into electrical energy. Let's think about a simple hand-turned generator, running at a steady rate and connected to an electric bulb, in terms of energy being shifted along pathways.

The physical description is simple:

Teacher: I turn the handle and the bulb lights.

The energy description:

Teacher: Energy is shifted from the chemical store associated with my body to the thermal stores of the surroundings.

The power description:

Teacher: Power is switched from the mechanical working pathway to the electrical working pathway.

Seen in these terms it's clear that the generator is a very useful device because of the way in which it switches the power from one pathway to another (from mechanical working to electrical working).

Energy Transferred by Working
appears in the relation dU=dQ+dW
is used in analyses relating to Working Engines Thermionic Emission
is a special case of Work
has the special case Potential Energy Kinetic Energy
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