Question:

The working of magnetic braking of trains is based on

Updated On: May 30, 2022

Alternating current
Eddy current
Steady current
Pulsating current

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The Correct Option is B

Solution and Explanation

Eddy current

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Concepts Used:

Eddy Currents - Induction Furnace

Eddy currents are loops of electrical current induced within conductors by a changing magnetic field in the conductor according to Faraday’s law of induction. Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field.

Some of the uses of the eddy current are as follows:

Automobile speedometers: Eddy currents are used to know the speed of a vehicle. A speedometer consists of a rotating magnet, which rotates based on the speed of the vehicle, producing Eddy Current in the drum. When the drum turns in the direction of the rotating magnet, the pointer attached to the drum indicates the speed of the vehicle.
Magnetic brakes: When you press the brakes, the metal wheels get exposed to a magnetic field which generates eddy currents in the wheels. The interaction between the eddy currents and the applied magnetic field slows the wheels down.
Energy meters: A metal disc in the electric power meter rotates due to eddy currents. The magnetic field induces the electric currents in the disc by alternating varying currents in a coil.
In induction furnaces: Eddy current is used for a uniform increase of temperatures in induction furnaces. Large eddy currents start flowing in rapidly changing magnetic fields, due to a large emf being produced. This produces high temperatures. A coil is wound over a constituent metal, placed in a highly oscillating magnetic field, produced by high frequency.
Free-fall devices (detecting coins in vending machines): Eddy current helps detect counterfeit coins and notes in vending machines. Eddy currents slow down the speed of the coins as they move past a stationary magnet.
Galvanometers (a device that measures small electrical currents): Eddy current is set up in the galvanometer by an oscillating coil, and its resistive forces oppose further oscillations of the coil. This enables the coil to quickly attain its equilibrium position.
Proximity/displacement sensors
Induction alternating current (AC) motors