A charge q(gt0) moves towards the centre of a circular loop of radius R along its axis. The magnitude of B along the periphery of the loop is

Options

A. zero
B. `(mu_(0))/(4pi) (qvR)/(sqrt((R^(2)+x^(2))^(3)))`
C. `(qvR)/(sqrt(R^(2)+x^(2)))`
D. None of these

Answer

d

Explanation

`B=(mu_(0))/(4pi) q(vxxr)/(r^(3))`
`B=(mu_(0)qvr sin theta)/(4pi (R^(2)+x^(2))^(3/2))`
`B=(mu_(0)q)/(4pi) (vR)/((R^(2)+x^(2))^(3/2)) [ :. r sin theta=R]`