Electricity and Magnetism

Eddy Currents

Any conductor which is moving so as to "cut through" a magnetic field or is surrounded by a changing magnetic field has an emf induced in it.

The induced emf can cause a current to flow.

The name "eddy current" is used to refer to currents induced to flow in:

Eddy currents produce heat. The heat is wasted energy and so it reduces the efficiency of the machine.

To reduce the loss of energy due to eddy currents the core are "laminated" (made of thin sheets of iron separated by a layer of insulator).

The current induced in the former opposes the motion of the coil. This has the effect of damping the motion of the coil.

A meter in which the coil is wound on a plastic (insulating) former oscillates for a long time before finally giving reading.

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