A short bar magnet placed with its axis at with an external field of experiences a torque of The bar magnet is replaced by a solenoid of cross-sectional are and turns, but of the same magnetic moment. Determine the current flows through the solenoid.
Two identical looking iron bars and are given, one of which is definitely known to be magnetised. We do not know which one. How would one ascertain whether or not both are magnetised? If only one is magnetised, how does one ascertain which one? Use nothing else but the bars and
Figure shows a small magnetised needle placed at a point . The arrow shows the direction of its magnetic moment. The other arrows show different positions and orientations of the magnetic moment of another identical magnetised needle . In which configuration the system is not in equilibrium? Which configuration corresponds to the lowest potential energy among all the configurations shown?