An electruc field of `300V//m` is confined to a circular area `10 cm` in diameter. If the field is increasing at the rate of `20V//m-s`, the magnitude of magnetic field at a point `15cm` from the centre of the circle will be-

Options

A. `1.85 xx 10^(-15)` T
B. `1.85 xx 10^(-16)` T
C. `1.85 xx 10^(-17)` T
D. `1.85 xx 10^(-18)` T

Answer

A

Explanation

`B = (mu_(0) epsilon_(0))/(2 pi R ) ( (pi d^(2))/(4 ) ) (dE)/(dt)`
= `(2 xx 10^(-7) xx 8.85 xx 10^(-12) xx 3.14 xx 0.01 xx 20 )/(4 xx 0.15)`
` = 1.85 xx 10^(-18) `T