An iron rod of susceptibility \(599\) is subjected to a magnetising field of \(1200~\text{A m}^{-1}\).  The permeability of the material of the rod is:\(\left(\mu_0 = 4 \pi\times 10^{-7}~\text{T m A}^{-1}\right)\)
1. \(8.0\times 10^{-5}~\text{T m A}^{-1}\)
2. \(2.4\pi\times 10^{-5}~\text{T m A}^{-1}\)
3. \(2.4\pi\times 10^{-7}~\text{T m A}^{-1}\)
4. \(2.4\pi\times 10^{-4}~\text{T m A}^{-1}\)

A thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnet is switched on, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence the rod gains gravitational potential energy. The work required to do this comes from:

A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in the equilibrium state. The energy required to rotate it by 60^o is W. Now the torque required to keep the magnet in this new position is:

1.  $\frac{W}{\sqrt{3}}$

2.  $\sqrt{3}W$

3.  $\frac{\sqrt{3}W}{2}$

4.  $\frac{2W}{\sqrt{3}}$

The following figures show the arrangement of bar magnets in different configurations. Each magnet has a magnetic dipole. Which configuration has the highest net magnetic dipole moment? 

1.		2.
3.		4.

A bar magnet of length \(‘l’\) and magnetic dipole moment \(‘M’\) is bent in the form of an arc as shown in the figure. The new magnetic dipole moment will be: