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Question
When a bar magnet is pushed towards (or away) from the coil connected to a galvanometer, the pointer in the galvanometer deflects. Identify the phenomenon causing this deflection and write the factors on which the amount and direction of the deflection depends. State the laws describing this phenomenon.
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Solution
When a bar magnet is pushed towards (or away) from the coil connected to a galvanometer, the pointer in the galvanometer deflects because of the phenomenon of electromagnetic induction.
Factors on which the amount and direction of deflection depend are
(i) Speed of the magnet
(ii) Polarity of the magnet
Laws describing electromagnetic induction are
(1) Faraday’s law of electromagnetic induction: The magnitude of the induced emf in a circuit is equal to the time rate of change of magnetic flux through the circuit.
`epsilon=-(dphi)/dt`
(2) Lenz’s law: The polarity of induced emf is such that it tends to produce a current which opposes the change in magnetic flux that produced it.
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