Induced Potential and the Generator Effect [H]

The generator effect is the reverse of the motor effect — instead of a current causing motion, motion causes a current. In this lesson you will learn about electromagnetic induction, Faraday's law, Lenz's law at GCSE level, and how generators and dynamos work. This is Higher tier content from AQA GCSE Physics specification 4.7.3.

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What Is the Generator Effect?

The generator effect (also called electromagnetic induction) occurs when an electrical conductor moves through a magnetic field, or when a magnetic field changes around a conductor. A potential difference (voltage) is induced across the ends of the conductor, and if the conductor is part of a complete circuit, a current is induced.

Key principle: A changing magnetic field induces a potential difference in a conductor.

Exam Tip: The key word is "changing." If the magnetic field is constant and nothing is moving, no potential difference is induced. There must be relative motion between the conductor and the magnetic field, or the field must be changing in strength.

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Ways to Induce a Potential Difference

There are several ways to induce a potential difference: