Two identical bar magnets are fixed with their centres at a distance \(d\) apart. A stationary charge \(Q\) is placed at \(P\) in between the gap of the two magnets at a distance \(D\) from the centre \(O\) as shown in the figure:

       

The force on the charge \(Q\) is in:

1.	direction along \(OP\)
2.	direction along \(PQ\)
3.	direction perpendicular to the plane of the paper
4.	zero

The magnetic moment of a diamagnetic atom is:

1. 1

2. between zero and one

3. equal to zero

4. much greater than one

A short bar magnet of magnet moment \(0.4\) ${\mathrm{JT}}^{-1}$ is placed in a uniform magnetic field of \(0.16\) $\mathrm{T}$. The magnet is in stable equilibrium when the potential energy is:
1. \(0.064\) J
2. \(-0.064\) J
3. zero
4.\(-0.082\) J

A magnetic needle suspended parallel to a magnetic field requires \(\sqrt{3}~\text{J}\) of work to turn it through $\mathrm{}$\(60^\circ\). The torque needed to maintain the needle in this position will be:
1. \(3\) N-m
2. \(\sqrt{3} \) N-m
3. \(\frac32\) N-m
4. \(2\sqrt{3}\) N-m

Nickel shows the ferromagnetic property at room temperature. If the temperature is increased beyond Curie's temperature, then it will show:
1. paramagnetism
2. anti-ferromagnetism
3. no magnetic property
4. diamagnetism

If a diamagnetic substance is brought near the north or the south pole of a bar magnet, it is:

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 $\mu$T. When a horizontal field of 18 $\mu$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