Question
The torque on a current loop is zero if the angle between the positive normal and the magnetic field is either $\theta=0^\circ$ or $\theta=180^\circ$ In which of the two orientations, the equilibrium is stable?
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Answer
As we know the potential energy.$\text{U}=-\vec{\text{m}}.\vec{\text{B}}$
In the case of stable equilibrium potential energy is minimum. So, far $\theta=0^\circ$ Potential Energy is -ve and minimum.
In the case of stable equilibrium potential energy is minimum. So, far $\theta=0^\circ$ Potential Energy is -ve and minimum.
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