Q.
The work done in moving a dipole from its most stable to most unstable position in a 0.09T uniform magnetic field is
(dipole moment of this dipole =0.5Am2)
Since the most stable position is at θ=0 and the most unstable position is at θ=180∘, then the work done is given by W=θ=0∘∫θ=180∘τ(θ)dθ=0∘∫180∘mBsinθdθ= −mB[cosθ]0180∘ =−mB[cos180∘−cos0∘]=−mB[−1−1] =−mB[−2]=2mB
Here, m=0.5Am2 and B=0.09T ∴W=2×0.50×0.09=0.09J