b
Length of a side of the square coil, \(l=10 \,cm =0.1\, m\)

Current flowing in the coil, \(I=12\, A\)

Number of turns on the coil, \(n=20\)

Angle made by the plane of the coil with magnetic field, \(\theta=30^{\circ}\)

Strength of magnetic field, \(B=0.80\, T\)

Magnitude of the magnetic torque experienced by the coil in the magnetic field is given by the relation,

\(\tau=n B L A \sin \theta\)

\(\Rightarrow l \times l=0.1 \times 0.1=0.01\, m^{2}\)

\(\therefore \tau=20 \times 0.8 \times 12 \times 0.01 \times \sin 30^{\circ}\)

\(=0.96 \,Nm\)

Hence, the magnitude of the torque experienced by the coil is \(0.96 \,N m\)