A `2 muC` charge moving around a circle with a frequency of `6.25xx10^(12)` Hz produces a magnetic field 6.28 tesla at the centre of the circle. The radius of the circle is

Options

A. 2.25 m
B. 0.25 m
C. 13.0 m
D. 1.25 m

Answer

D

Explanation

`q= 2mu C , f = 6.25 xx 10^(12)` Hz
`I = qf = 2 xx 10^(-6) xx 6.25 xx 10^(12) = 12.5 xx 10^(6) A`
`B = (mu_(0) I)/(12 R) implies 6.28 = (4pi xx 10^(-7) xx 12.5 xx 10^(6))/(2 xx R)`
`implies R = (4pi xx 10^(-7) xx 12.5 xx 10^(6))/(2 xx 6.28) = 1.25` m