Question

When a current carrying coil is placed in a uniform magnetic field with its magnetic moment anti-parallel to the field

• A. Torque on it is maximum
• B. Torque on it is zero
• C. Potential energy is maximum
• D. Dipole is in unstable equilibrium

Answer 1

Answer: (B), (C), (D)

Dipole is in unstable equilibrium
Potential energy is maximum
Torque on it is zero

$\tau =\overline{M}\times \overline{B}$. Thus it is in equilibrium and zero torque. $\theta ={180}^{\circ }$

But any small disturbance will bring it out of equilibrium. Will never attain the same state even after long time. unstable equilibrium.

P.E = $-\overline{M}.\overline{B}$ hence max at the state.