Question

What is the initial angle in degrees between the dipole moment and the magnetic field?

Answer 1

Potential energy due to magnetic dipole is $U=-MB\cos \theta$ where

$M=$ dipole moment.

By conservation of energy, $U_i+K{E}_i=U_f+K{E}_f$

or $-MB\cos \theta +0=-MB\cos 0+0.80\times {10}^{-3}$

or $(1-\cos \theta )MB=0.80\times {10}^{-3}$

or $\cos \theta =1-\frac{0.80\times {10}^{-3}}{0.020\times 50\times {10}^{-3}}=1-0.8=0.2$

or $\theta \sim {77}^0$