In order to keep one magnetic needle, perpendicular to two magnetic fields `B_1 and B_2`, if the torques required are respectively `tau_(1) and tau_(2)` then `(B_1)/( B_2) = ….....`

Options

A. `tau_2/tau_1`
B. `tau_1/tau_2`
C. `(tau_1 + tau_2)/( tau_1- tau_2)`
D. `(tau_1 - tau_2)/(tau_1 + tau_2)`

Answer

B

Explanation

`tau= mB sin theta = m B`
`therefore B= (tau)/(m)`
`therefore B prop tau" "(because m= " constant for a given magnetic needle" )`
`therefore (B_1)/(B_2) = (tau_1)/( tau_2)`