Question

Question.What are eddy currents, give an experiment to explain their origin?

Answer 1

$\underline{\mathfrak{Answer}}$

When a metal piece is rotated in a magnetic field, the magnetic flux linked with the piece changed, induced currents are set up in it. These currents circulating on the surface of piece are called $\bold{eddy\:currents}$.

$\bold{Experiment}$: If a light metallic disc D is placed at the top of electromagnet as shown in figure and when a.c. is passed through the coil, the disc is thrown up due to eddy currents.

$\bold{Explaination}$ : When the current is passed through the coil, the magnetic flux linked with the coil and hence with the disc also increases, as a result induced current is produced in the disc which converts it into a small magnet. The upper end of the iron core and lower face of the disc acquire same polarity in accordance with the Lenz's law. Due to repulsion between the upper end of soft iron and lower face of disc D the disc is thrown up.

$\underline{\mathfrak{thanks}}$.

$\bold{Hope\: it\: helps}$

Answer 2

This is the principle of electromagnetic induction, and it is responsible for making electric generators and motors work. When a solid metal object is placed in a changing magnetic field, loops of current called eddy currents can be induced within the metal, causing it to get hot.

Eddy currents (also called Foucault currents) are loops of electrical current induced within conductors by a changing magnetic field in the conductor according to Faraday's law of induction.

Use an Ac current in a solenoid with an ammeter in the circuit.

Bring a flat plate up towards the coil.

The current should increase.

Try a non conductive surface, a steel magnetic surface, an aluminium surface.

Try a surface made of several smaller pieces separated by thin insulating strips.

In each case observe the effects upon the electric current in the primary.

The higher the current the greater the loss in eddy currents.

and vice versa.

Try rotating the plates to various angles to find the worst angle and the best angle.

If you do all of this then you may start to understand electrical eddy currents and why manufacturers do various things to reduce them.

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