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Fig.3 shows a cross section of the coil. Looking at the coil if the current appears to be flowing through it in a counterclockwise direction, then the side of the coil facing the observer is its north pole. If the current appears Clockwise then the side towards the observer is the south pole. This is made clear in fig. 3.
Consider moving a bar magnet with its north pole towards the coil. When the magnet is moved towards the coil, if the induced current is such that the side of the coil facing the magnet becomes a south pole, then there would be a force of attraction between the magnet and the coil, and due to this force magnet would be further drawn nearer. Thus, the induced current would be generated 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 I2Rz. 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."
getet azil 37001 - 577, 2004
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