Electromagnetic Induction - Result Question 12

12. A conducting circular loop is placed in a uniform magnetic field of 0.04T with its plane perpendicular to the magnetic field. The radius of the loop starts shrinking at 2mm/s. The induced emf in the loop when the radius is 2cm is

(a) 4.8πμV

(b) 0.8πμV

(c) 1.6πμV

(d) 3.2πμV

[2009]

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Answer:

Correct Answer: 12. (d)

Solution:

  1. (d) Induced emf in the loop is given by e=BdAdt where A is the area of the loop.

e=Bddt(πr2)=Bπ2rdrdt

r=2cm=2×102m

dr=2mm=2×103m

dt=1s

e=0.04×3.14×2×2×102×2×1031V

=0.32π×105V

=3.2π×106V

=3.2πμV



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