Question

Which of the following is the best method to reduce eddy currents?
A. Laminating core.
B. Using thick wires.
C. Reducing hysteresis loss.
D. None of these

Answer 1

Hint: Whenever magnetic flux linked with a circuit changes an emf is developed in the coil and is called induced emf. Due to this induced emf an induced current flows through the circuit. So these induced currents can be produced in conducting plates or blocks. Whenever the magnetic flux linked with a metal plate sheet or block changes an emf is induced in it. The induced currents flow in closed paths in planes perpendicular to the lines of force throughout the body of the metal. These currents look like eddy or whirl-pool in water so they are known as eddy currents. These eddy currents produce unnecessary heating of the plate so this current should be reduced.

Complete step by step answer:
When Eddy currents developed inside the iron cores of the rotating armatures of electric motors and dynamos, and also in the cores of the transformers, which experience flux changes, when they are used. Eddy currents cause unnecessary heating and wastage of power. The heat produced due to Eddy currents may even damage the insulation of the coils.
So due to these heating effects Eddy currents should be minimised. The Eddy currents can be minimised by using laminated core, which consists of thin sheets of metals insulated from each other by a thin layer of varnish instead of single solid mass.
The planes of the sheet are placed perpendicular to the direction of the currents that would be setup by the emf induced in the material. The insulation between the sheets then offers high resistance to the induced emf and the eddy currents are substantially reduced.

So, the correct answer is “Option A”.

Note: Eddy currents are basically the induced currents setup inside the body of a conductor whenever the magnetic flux linked with it changes. Eddy currents tend to follow the path of least resistance inside a conductor so they form irregularly shaped loops. However their directions were not random but gained by Lenz’s law. Eddy currents have both undesirable effects and useful applications. The useful applications are (i)Induction furnace ,(ii) Electromagnetic damping, (iii)Electric brakes, (iv)Speedometers, (v) Induction motors, (vi)Electromagnetic shielding, (vii)Energy meters, etc.