A circular wire loop of mass M and radius R carries a current I . It hangs from a hinge that allows it to swing in the direction perpendicular to the plane of the loop. A uniform magnetic field B exists everywhere in space pointing upwards. What angle THETA does the plane of the loop make with the vertical when it is in static equilibrium?

Question

A circular wire loop of mass M and radius R carries a current I  . It hangs from a hinge that allows it to swing in the direction perpendicular to the plane of the loop. A uniform magnetic field B  exists everywhere in space pointing upwards. What angle  THETA  does the plane of the loop make with the vertical when it is in static equilibrium?

Elena · Answer

The current in the loop and magnetic field direction are connected according to the right hand rule: curl fingers to the direction of the current in the loop, the thumb points in the direction of magnetic moment of the loop that coincides with the direction of B. =>
The plane of the loop must be perpendicular to the direction of magnetic field.