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The above results can be understood as follows. When the bar magnet is near the coil some of the magnetic lines of force are passing through the coil; that is “some magnetic flux is linked with the coil”. Now when there is relative motion between the coil and the magnet, the amount of flux linked with the coil is changing. When the relative motion stops, there is no further change is the amount of the flux linked. So we conclude that, “when there is a change in the flux linked with the coil, there is an emf generated in the coil”. The observation that a faster motion of the magnet gives rise to a larger defection, shows that the emf generated depends upon the rate of change of the flux linking the coil. The current resulting from this “induced emf” is called the "induced current". To cause the change in the flux linked with the coil, it is not necessary to have a bar magnet. If two coils S and P are placed near each other as shown in fig. 2; and a key connected in the circuit of the coil P is switched on and off so that current alternately flows and stops flowing through the coil P, the galvenometer connected in the circuit with the coil S alternately shows a deflection on one and the other side. Further, if a steady current is maintained in the coil P and the two coils are moved relative to each other, then also a current is induced in the coil S. Here, it is the flux generated by the current in the coil P that links with the coil S and a change in that flux causes an induced emf in the coil S.
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2. Lenz's Law We have yet not said anything regarding the magnitude and the direction of the inducted emf. This direction of emf and the resulting direction of the induced current can be inferred from the considerations based on the principle of conservation of energy and this leads us to Lenz's law. When a current flows in a coil magnetic flux is produced due to this current and the coil now acts as a magnet. Which face of the coil acts like a north pole and which face becomes a south pole depends upon
the direction of the current in the coil. 62
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Tot yall 317 124
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