Electromagnetic Induction

Electromagnetic InductionElectromagnetic Induction Motional Electromagnetic Induction

Use a magnetic field to create a current• emf (electromotive force) ~ potential

difference• Where does the energy come from? → work !

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Electromagnetic InductionElectromagnetic Induction Induction: a coil and a magnet

The amount of induced emf depends on• 1. Strength of the magnetic field• 2. Relative speed of the coil and magnet• 3. Area of the loops• 4. Number of loops

More work is required to move the magnet through a coil with many loops.

• Why?

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Electromagnetic InductionElectromagnetic Induction Electric guitars

The string oscillates above a permanent magnet and coil

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Electromagnetic InductionElectromagnetic Induction Magnetic flux

The amount of a magnetic field that passes through a surface: ΦB = BA cosθ

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Electromagnetic InductionElectromagnetic Induction Faraday’s Law

The emf is proportional to the number of loops times the rate of change of the magnetic field in the loops

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Electromagnetic InductionElectromagnetic Induction Generators

Mechanical energy input with electrical energy output

• Opposite of electric motors

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Electromagnetic InductionElectromagnetic Induction Transformers

Used to increase or decrease an alternating voltage Primary and secondary windings

• Step-up or step-down• The iron core transfers the magnetic field

from one coil to the other

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Electromagnetic InductionElectromagnetic Induction Transformers

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Electromagnetic InductionElectromagnetic Induction Transformers

Power pole

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