CBSE Class 12 · 2010 · Electromagnetic InductionShort Answer

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A coil Q is connected to a low-voltage bulb B and placed near another coil P (connected to an a.c. source) as shown in the figure. Give reasons to explain the following observations:
(a) the bulb B lights;
(b) the bulb gets dimmer if the coil Q is moved towards the left (away from P).

Solution

(a) The alternating current in coil P produces a continuously changing magnetic flux. Part of this flux links coil Q, and by mutual induction an alternating emf — and hence a current — is induced in Q, which lights the bulb B.
(b) As Q is moved away from P, a smaller fraction of P's flux links Q, so the mutual inductance and the rate of change of linked flux both decrease. The induced emf and current in Q fall, and the bulb glows more dimly.

CBSE Class 12 Board · 2010 · Subjective

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