Two current loops are shown to the right One loops is in a s

Two current loops are shown to the right. One loops is in a stable position, so it will return to this position if it is rotated slightly. The other loop is unstable, like an upside-down pendulum. Which loop is which? Give a careful explanation, including force diagrams and magnetic moments.

Solution

Here

for loop 1 ,

direction of magnetic moment is to the right

same as of magnetic field

for loop 2 ,

the direction of magnetic moment is to the left

oposite of magentic field

Now ,as the potential energy of a magnetic moment is given as

potential energy = - u . B

Now , for stable , u and B must be in the same direction

hence , loop 1 is in the stable equilibrium

and loop2 is in unstable equilibrium