When a bar magnet is placed at `90^(@)` to a uniform magnetic firld, it is acted upon by a couple which is maxium. For the couple to be half of the maximum. For the couple to be half of the maxiumum vlaue, at what angle should the magnet be inclined to the magnetic fiels `(B)`?

Explanation

We know that, `tau=MB sin theta`
If `theta=90^(@)` then `tau_(max)=MB`……`(1)`
`(tau_(max))/(2)=MB sin theta` ……`(2)`
From equations `(1)` and `(2)`
`2=(1)/(sin theta)` or `sin theta=(1)/(2)` or `theta=30^(@)`