A magnetised needle of magnetic moment `4*8xx10^-2JT^-1` is placed at `30^@` with the direction of uniform magnetic field of magnitude `3xx10^-2T`. What is the torque acting on the needle?

Answer

`7*2xx10^-4N-m`

Explanation

Here, `M=4*8xx10^-2JT^-1`, `theta=30^@`,
`B=3xx10^-2T`, `tau=?`
`tau=MBsin theta=4*8xx10^-2xx3xx10^-2xxsin30^@`
`=7*2xx10^-4N-m`