#Applications__of__eddy__Current #Class__12 Unit: Electricity and magnetism Applications of eddy Current 1. Induction Furnace: It is based on the heating effect of eddy currents. The metallic block to be melts is placed in a high frequency changing magnetic field. Strong eddy current are induced in the block. Due to the high resistance of the metal, large amount of heat is produced in it. This heat ultimately melts the metallic block. So the induction furnace is used to separate metals from their ores and to make some alloys. 2. Diathermy: Eddy currents are used for the localized heating of tissues in human body. This type of treatment is called diathermy. 3. Speedometer: Speedometer is a device used to measure to measure the instantaneous speed of vehicle. In a speedometer, a small magnet is attached to the axle of the wheel. This magnet rotates according to the speed of a vehicle in an aluminium drum. Due to the rotation of the magnet ,magnetic flux linked with the aluminium drum changes and hence eddy currents are produced in it. A pointer attached to the drum is deflected in the direction of the rotation of the drum. This speed is measured which corresponds to the deflection of the pointer. 4. Eddy current damping or dead beat galvanometer: According to Lenz’s law, eddy currents always flow in such a direction so as to oppose the motion which has produced them. So they can reduce the oscillations of a vibrating system. A familiar example is that of moving coil galvanometer. The coil of the galvanometer is generally wound on a metal frame. As the coil swings in the magnetic field of the instrument, eddy currents are induced in the frame. These eddy currents oppose the motion of the coil and hence the pointer attached to it. Consequently the pointer quickly attains the final position without overshooting or oscillating violently. Thus eddy current damps (reduce) the oscillations of the pointer. This is known as electromagnetic damping or eddy current damping. Such a galvanometer is called dead beat galvanometer. 5. Electromagnetic brakes: Eddy current breaking can be used to control the speed of electric trains. In order to reduce the speed of train an electromagnet is turned on that applies its speed to the wheels. Large eddy currents are set up which produce the retarding effects. 6. Energy meters: Concept of eddy currents is used in energy meters to record the consumption of electricity.
Posted on: Fri, 24 Jan 2014 10:11:24 +0000