Electro Magnetic Induction And Alternating Currents Question 417

Question: A horizontal ring of radius $ r=1/2m $ is kept in a vertical constant magnetic field 1 T. The ring is collapsed from maximum area to zero area in 1 s. Then the emf induced in the ring is

Options:

A) $ 1,V $

B) $ (\pi /4),V $

C) $ (\pi /2),V $

D) $ \pi ,V $

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Answer:

Correct Answer: B

Solution:

  • $ | \varepsilon |=B\frac{dA}{dt} $ $ | \varepsilon |=B\frac{(A_{2}-A_{1})}{(t_{2}-t_{1})} $ $ | \varepsilon |=\frac{1( \frac{\pi }{4}-0 )}{(1-0)} $ $ \varepsilon =\frac{\pi }{4}V $


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