The relative permeability $\left({\mu }_r\right)$ of a ferromagnetic substance varies with temperature (T) according to the curve

(1) A                              

(2) B

(3) C                              

(4) D

The variation of the intensity of magnetisation \((I)\) with respect to the magnetising field \((H)\) in a diamagnetic substance is described by the graph:

If ${\theta }_1 and {\theta }_2$ be the apparent angles of dip observed in two vertical planes at right angles to each other, then the true angle of dip $\theta$ is given by 

(a) $co{t}^2\theta =co{t}^2{\theta }_1+co{t}^2{\theta }_2$

(b) ${\tan }^2\theta ={\tan }^2{\theta }_1-{\tan }^2{\theta }_2$

(c) $co{t}^2\theta =co{t}^2{\theta }_1-{\tan }^2{\theta }_2$

(d) ${\tan }^2\theta ={\tan }^2{\theta }_1-{\tan }^2{\theta }_2$

The magnetic susceptibility is negative for

1. paramagnetic material only

2. ferromagnetic material only

3. paramagnetic and ferromagnetic materials

4. diamagnetic material only

The following figures show the arrangement of bar magnet in different configurations. Each magnet has magnetic dipole moment m. Which configuration has the highest net magnetic dipole moment?
(i) (ii) (iii) (iv)

1. (i)

2. (ii)

3. (iii)

4. (iv)

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:

Which one of the following is true?

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 

1. zero

2. directed along OP

3. directed along PO

4. directed perpendicular to the plane of the paper

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

A bar magnet having a magnetic moment of $2\times {10}^4 J{T}^{-1}$ is free to rotate in a horizontal plane. A horizontal magnetic field $B=6\times {10}^{-4}T$ exists in the space. The work done in taking the magnet slowly from a direction parallel to the field to a direction $60°$ from the field is 

(a) 0.6 J                            (b) 12 J

(c) 6 J                               (d) 2 J