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


(1)M

(2)3M/π

(3)2/πM

(4)M/2

A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole.It

(1) will become rigid showing no movement

(2) will stay in any position

(3) will stay in north-south direction only

(4) will stay in east-west direction only

A magnetic needle suspended parallel to a magnetic field requires $\sqrt{3}$ J of work to turn it through $60°$. The torque needed to maintain the needle in this position will be

1. $2\sqrt{3}$J                     

2. 3 J

3. $\sqrt{3}$ J                       

4. $\frac{3}{2}$ J

There are four light-weight-rod samples; A, B, C, D separately suspended by threads. A bar magnet is slowly brought near each sample and the following observations are noted:

(i) A is feebly repelled 

(ii) B is feebly attracted

(iii) C is strongly attracted

(iv) D remains unaffected

Which one of the following is true?

1. C is of a diamagnetic material

2. D is of a ferromagnetic material

3. A is of a non-magnetic material

4. B is of a paramagnetic material

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

A vibration magnetometer placed in a magnetic meridian has a small bar magnet. The magnet executes oscillations with a time period of 2s in earth's horizontal magnetic field of 24 $\mu$T. When a horizontal field is 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

(a) 1s          (b) 2s

(c) 3s          (d) 4s

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.

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

1. repelled by both the poles

2. repelled by the north pole and attracted by the south pole

3. attracted by the north pole and repelled by the south pole

4. attracted by both the poles

Curie temperature is the temperature above which -

1. ferromagnetic material becomes paramagnetic material 

2. paramagnetic material becomes diamagnetic material 

3. paramagnetic material becomes ferromagnetic material 

4. ferromagnetic material becomes diamagnetic material  

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

1.		2.
3.		4.