A magnet is pointing towards geographic north at a place where horizontal component of earth's magnetic field is `40 mu T ` . Magnetic dipole moment of the bar magnet is `60 Am^(2)` and torque acting on the magnet is `1.2 xx 10^(-3) N` m . What is declination at this place ?

Explanation

`B _(H)= 40 xx 10 ^(-6) T`
` rau = 1.2 xx 10 ^(-3) Nm`
`M = 60 A m ^(2)`
` tau = M. B. sin theta`
`1.2 xx 10 ^(-3) = 60 xx 40 xx 10^(-6) xx sin theta`
` 1.2 xx 10 ^(-3) = 24 xx 10 ^(-4) xx sin theta`
`1.2 = 2.4 xx sin theta`
`sin theta = 1.2`
`1.2 = 2.4 xx sin theta `
`sin theta = 1.2`
` therta = 30^(@)`