A uniform but time-varying magnetic field B(t) exists in a cylindrical 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

Options

A. is zero
B. decreases as` 1/r`
C. increases as r
D. decreases as `1/r^(2)`

Answer

2

Explanation

Magnitude of induced electric field (r>a)
`E=(a^(2) dB)/(2pidt)`Thus, the magnitude of the electric field increases linearly from zero at the center of electric field to` (a/2) (dB/dt)` at the edge of circular region of radius a, and then decreases inversely with distance.