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erated without doing work. Heat? energy can now be obtained by connecting a resistance to its circuit, without spending any mechanical energy. One can see that this violates the conservation of energy. So, when a north pole of the magnet is brought near the coil, the side of the coil towards the magnet must become the north pole, so that the induced current resists the motion of the magnet. It is the work done is moving the magnet against this force, that gets converted to the electrical energy and can be used, for example to generate the heat energy as I?Rz. Thus, we see that the direction of the induced current and the corresponding direction of the resulting magnetic field is a consequence of the conservation of energy. This leads us to Lenz's law which states : “If an agency generates an induced emf through its action (such as motion of the magnet as illustrated) the induced emf would be such that the current produced by this emf would generate a magnetic field such as to oppose the action of the agency.” 3. Faraday's Law Faraday gave the law relating the induced emf in a circuit with the rate of change of the flux as "the negative time rate of change of magnetic flux linked with a circuit is equal to the induced emf in the circuit.” 4. Self Induction
We have learnt that when a current passes through a coil, some magnetic field is created so that the coil itself behaves like a magnet. The magnetic flux prroduced by the current in the coil is linked with the coil itself (fig. 8), and when the current in the coil changes, this flux linked with the coil also changes.Under such circumstances also, there would be an emf induced in the coil which is called the "self induction". If the number of turns in a coil is N and the flux linked with each turn is f, then the total flux linked with the coil is No.
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