Bar Magnet

A bar magnet having a magnetic moment of JT^-1 is free to rotate in a horizontal plane. A horizontal magnetic field T exists in the space. The work done in taking the magnet slowly from a direction parallel to the field to a direction from the field is:
1. J
2. J
3. J
4. J

A vibration magnetometer placed in a magnetic meridian has a small bar magnet. The magnet executes oscillations with a time period of 2 s in the earth's horizontal magnetic field of 24 $\mathrm{\backslash mu}$T. When a horizontal field of 18 $\mathrm{\backslash mu}$T is produced opposite to the earth's field by placing a current-carrying wire, the new time period of the magnet will be:

1. 1 s

2. 2 s

3. 3 s

4. 4 s

A bar magnet of length and magnetic dipole moment is bent in the form of an arc as shown in the figure. The new magnetic dipole moment will be:

1.		2.
3.		4.

In a uniform magnetic field of , a magnetic needle performs complete oscillations in seconds as shown. The moment of inertia of the needle is . If the magnitude of magnetic moment of the needle is then the value of ' ' is:

1.		2.
3.		4.

An iron bar of length has a magnetic moment It is bent at the middle of its length such that the two arms make an angle with each other. The magnetic moment of this new magnet is:

1.		2.
3.		4.