Electromagnetic Induction Class 12 Physics Chapter 6 - Eddy Current

Electromagnetic Induction Class 12 Physics Chapter 6 - Eddy Current
Topics explained in this video are:
1. Introduction - Eddy Currents
2. Eddy Currents Experiment

A case in which current get induced in the body however their flow pattern resembles swirling eddies. Just like eddies in water. This effect is discovered by Foucault and such current are called eddy currents. Even when stationary bulk pieces of conductors are subjected to time varying magnetic field, eddy currents are produced in them.
Suspend a metal plate in a pole pieces of an electromagnet. If the plate is allowed to oscillate when the magnetic field is off, it oscillates for longer time. However, when the magnetic field is on, the plate oscillates for short time as some form of damping can be seen. This phenomena can be explained with the help of eddy currents. During motion towards the extreme position, magnetic flux linked with the plate decreases. As there is change in flux, therefore, eddy currents get developed in the plate. According to Lenz law, this current oppose the decrease in flux and therefore oppose the motion of plate towards extreme position.
Similarly, during motion of the plate from extreme position to mean position, magnetic flux linked with plate increases. This time also eddy currents get developed in the metal plate. However, according to Lenz law, eddy current opposes the increase in flux. Therefore this time also, motion of plate towards mean position is opposed by eddy currents. So in both cases, eddy currents oppose motion of plate, which causes damped motion of the plate ultimately plate come to rest early.
In case of plate within the region of magnetic field and in case of plate out of the region, eddy currents are opposite.
Eddy currents are undesirable as it causes heating effect and therefore causes loss of electrical energy. Greater eddy currents cause greater heating effect. And hence we need to take the measures to lower down the eddy currents. This is necessary in case of devices such as transformers, electric motors where coil is wound over the core.
In order to reduce the eddy currents, core is made of several metal plates stacked one over another and separated from each other by insulating material such as lacquer. The plane of the laminations, must be kept parallel to the magnetic field so that they cut across the eddy current paths. With this arrangement, strength of eddy currents get reduced. According to Joule's law H ∝ I2 and therefore dissipation of electrical energy as heat also reduces.

CBSE Class 12 Physics syllabus -
Chapter 1 Electric Charges and Fields
Chapter 2 Electrostatic Potential and Capacitance
Chapter 3 Current Electricity
Chapter 4 Moving Charges and Magnetism
Chapter 5 Magnetism and Matter
Chapter 6 Electromagnetic Induction
Chapter 7 Alternating Current
Chapter 8 Electromagnetic Waves
Chapter 9 Ray Optics and Optical Instruments
Chapter 10 Wave Optics
Chapter 11 Dual Nature of Radiation and Matter
Chapter 12 Atoms
Chapter 13 Nuclei
Chapter 14 Semiconductor Electronics: Materials, Devices and Simple Circuits
Chapter 15 Communication Systems