Domain formation is the necessary feature of: 
1. ferromagnetism
2. diamagnetism
3. paramagnetism
4.  all of these

The work done in rotating a magnet of the magnetic moment \(100\) A-m² through \(90^\circ\) $$from a direction parallel to the uniform magnetic field of strength \(0.4 \times 10^{-4}\) Tesla is:
1. \(4\) mJ

2. zero

3. \(6\) mJ

4. \(8\) mJ

A long magnetic needle of length 2L, magnetic moment M and pole strength m units is broken into two pieces at the middle. The magnetic moment and pole strength of each piece will be

1. $\frac{M}{2},\frac{m}{2}$

2. $M,\frac{m}{2}$

3. $\frac{M}{2},m$

4. M, m

The magnetic field lines due to a bar magnet are correctly shown in:

1.		2.
3.		4.

Four small identical bar magnets, each of magnetic dipole moment \(M\), are placed on the vertices of a square of side \(a\) such that the diagonals of the square coincide with the perpendicular bisectors of the respective magnets. The net magnetic field at the centre of the square is:

           
1. zero

2. \(\dfrac{\mu_{0}}{\sqrt{2 \pi}} \dfrac{M}{a^{3}}\)

3. \(\dfrac{2 \sqrt{2} \mu_{0}}{\pi} \cdot \dfrac{M}{a^{3}}\)

4. \(\dfrac{\mu_{0}}{\pi} \cdot \dfrac{M}{a^{3}}\)

The coercivity of a bar magnet is 100A/m. It is to be demagnetised by placing it inside a solenoid of length 100 cm and number of turns 50. The current flowing the solenoid will be :-

1. 4A

2. 2A

3. 1A

4. zero

Magnetic lines of force due to a bar magnet do not intersect because

Of the following Fig., the lines of magnetic induction due to a magnet SN, are given by

1.		2.
3.		4.