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A uniform but time-varying magnetic fiel...

A uniform but time-varying magnetic field B(t) exists in a circular region of radius a and is directed into the plane of the paper, as shown. The magnitude of the induced electric field at point P at a distance r from the centre of the circular region

A

Is zero

B

Decreases a `1/r`

C

Increases as r

D

Decreases as `1/r^2`

Text Solution

Verified by Experts

The correct Answer is:
B
`e=ointvecE.dvecl=|(dphi)/(dt)|=d/(dt)(BA cos 0^@)=A(dB)/(dt)`
`implies E xx2pir=pia^2(dB)/(dt)` for `r gt a`
`E = a^2/(2r) (dB)/(dt)implies E prop1/r`
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