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JEE Main Syllabus 2025 PDF - Subject Wise Topics

Eddy Currents - Practice Questions & MCQ

Edited By admin | Updated on Sep 18, 2023 18:34 AM | #JEE Main

Quick Facts

  • 8 Questions around this concept.

Solve by difficulty

A spherical insulating ball and a spherical metallic ball of the same size and mass are dropped from the same height. Choose the correct statement out of the following Assume negligible air friction}

Certain galvanometers have a fixed core made of non-magnetic metallic material. The function of this metallic material is

Given below are two statements: one is labeled as Assertion A and the other is labeled as Reason R
Assertion A: A bar magnet dropped through a metallic cylindrical pipe takes more time to come down compared to a non-magnetic bar with the same geometry and mass.
Reason R: For the magnetic bar, Eddy currents are produced in the metallic pipe which opposes the motion of the magnetic bar.
In light of the above statements, choose the correct answer from the options given below

Concepts Covered - 1

Eddy currents

 Eddy currents:

An eddy current is a current set up in a conductor in response to a changing magnetic field. They flow in closed loops in a plane perpendicular to the magnetic field. By Lenz law, the current swirls in such a way as to create a magnetic field opposing the change. They are known as eddy currents as they are in the pattern of eddies in the water. Because of the tendency of eddy currents to oppose, eddy currents cause a loss of energy. Eddy currents are undesirable since they heat up the core and dissipate electrical energy in the form of heat.

 

 Direction of eddy current:

For the above figure, the magnetic flux associated with the plate keeps on changing as the plate moves in and out of the region between magnetic poles. The flux change induces eddy currents in the plate. Directions of eddy currents are opposite when the plate swings into the region between the poles and when it swings out of the region as shown in the above figure.

Eddy currents are used to advantage in certain applications like-

  1. Magnetic braking in trains-Strong electromagnets is situated above the rails in some electrically powered trains. When the electromagnets are activated, the eddy currents induced in the rails oppose the motion of the train. As there are no mechanical linkages, the braking effect is smooth.
  2. Induction furnace-Induction furnace can be used to produce high temperatures and can be utilized to prepare alloys, by melting the constituent metals. A high-frequency alternating current is passed through a coil that surrounds the metals to be melted. The eddy currents generated in the metals produce high temperatures sufficient to melt it.
  3. Electromagnetic damping
  4. Electric power meters

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Eddy currents

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