Electro Magnetic Induction And Alternating Currents Question 448

Question: A rod PQ of length L moves with a uniform velocity v parallel to a long straight wire carrying a current i, the end P remaining at a distance r from the wire. The emf induced across the rod is

Options:

A) μ0iv22πln(r+LR)

B) B

C) μ0iv2πln(r+LR)

D) μ0iv2πln(r2+L2L2)

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Answer:

Correct Answer: C

Solution:

  • Consider a small element of length dx of the rod at a distance x and (x+dx) from the wire. The emf induced across the element

de=Bvdx -.(i)

We know that magnetic field B at a distance x from a wire carrying a current; is given by

B=μ02π.ix .. (ii)

From eqs. (i) and (ii),

de=μ0i2πxvdx …(iii) The emf induced in the entire length of the rod PQ is given by

e=de=PQμ02πixvdx

=rr+Lμ02πixvdx=μ02πivrr+Ldxx

=μ0iv2πloge(r+Lr)



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