Electromagnetic Induction and Alternating Current 7 Question 22

25. Two metallic rings A and B, identical in shape and size but having different resistivities ρA and ρB, are kept on top of two identical solenoids as shown in the figure. When current I is switched on in both the solenoids in identical manner, the rings A and B jump to heights hA and hB, respectively, with hA>hB. The possible relation(s) between their resistivities and their masses mA and mB is (are)

(2009)

(a) ρA>ρB and mA=mB

(b) ρA<ρB and mA=mB

(c) ρA>ρB and mA>mB

(d) ρA<ρB and mA<mB

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Answer:

Correct Answer: 25. (b, d)

Solution:

  1. Induced emf e=dφdt. For identical rings induced emf will be same. But currents will be different. Given hA>hB.

Hence, vA>vB as h=v22g.

If ρA>ρB, then, IA<IB. In this case given condition can be fulfilled if mA<mB.

If ρA<ρB, then IA>IB. In this case given condition can be fulfilled if mAmB.



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