A compass needle whose magnetic moment is `60Am^2` pointing geographic north at a certain place where horizontal component of earth's magnetic field is `40muWb//m^2` experiences a torque of `1*2xx10^-3Nm`. What is the declination of the place?

Explanation

If `theta` is the declination of the place, then the torque acting on the needle is `tau=M B_(H) sin theta`
`rArr sin theta=(tau)/(M B_(H))=(1.2xx10^(-3))/(60xx40xx10^(-6))=(1)/(2) there theta=30^(@)`