A short magnet porduces a deflection of `30^(@)` when placed at certain distance in tanA position of magnetometer. If another short magnet of double the length and thrice the pole strength is placed at the same distance in tan B position of the magnetometer, the deflection produced will be-

Options

A. `60^(@)`
B. `30^(@)`
C. `45^(@)`
D. None

Answer

A

Explanation

In tan position,
`(mu_(0))/(4pi)(2M)/(d^(3)) =B_(H) tan 30^(@) =(B_(H))/(sqrt(3))" " ....(1)`
Magnetic moment of second magent,
`M'=(3m)(2xx2l)=6M`
In tan B position,
`(mu_(0))/(4pi)(6M)/(d^(3))-B_(H)tan theta " " ....(2)`
dividing eq. (2) by (1) we get
`(6)/(2)=(tantheta)/(1//sqrt(3))`
or `tan theta=(sqrt(3))`
or `theta =60^(@)`