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A conducting circular loop is placed in ...

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

A

`4.8 (pi)/(mu V)`

B

`0.8 (pi)/(mu V)`

C

`1.6 (pi)/(mu V)`

D

`3.2 (pi)/(mu V)`

Text Solution

Verified by Experts

The correct Answer is:
D
Magnetic flux `phi =B.A= Bpir^(2)`
emf induced,
`epsilon= (dphi)/(dt)= Bpi(d(r^(2))/(dt))= Bpi(2r(dr)/(dt))`
`r= 2cm= 2 xx 10^(-2)m`
`(dr)/(dt)= 2 xx 10^(-3)m//s`
`epsilon= 0.04 xx 2pi xx 2 xx 10^(-2) xx 2 xx 10^(-3)V`
`= 4 xx 10^(-2) xx 2pi xx 4 xx 10^(-5)V = (3.2pi)muV`
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Knowledge Check

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

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    B
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    C
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    D
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