A closely wouhnd flat circular coil of 25 turns of wire has diameter of 10 cm which carries current fo `4 A` , the flux density at the centre of a coil will be

Options

A. `1.679 xx 10^(-5)` tesla
B. `2.028 xx 10^(-4)` tesla
C. `1.257 xx 10^(-3)` tesla
D. `1.512 xx 10^(-6)` tesla

Answer

C

Explanation

`B = (mu_(0) nI)/(2 r) = (4pi xx 10^(-7) xx 25 xx 4)/(2 xx (0.1)/(2)) = 1.256 xx 10^(-3) T`