A square current loop of mass 10 g can rotate about a vertical axis through its centre. In B=0.1 T it carries current 2 A. Find the period of small oscillations about stable equilibrium, in seconds.

Question

G1 Physics · Accepted Answer

For a small angular displacement, magnetic restoring torque is τ≈-μBθ=-I(current)ABθ. With the loop's rotational inertia about the stated axis, Ω=√[6 I(current) B/m]. Therefore T=2π√[m/(6 I(current) B)]≈0.57 s.