Let r be the distance of a point on the axis of a bar magnet from its centre. The magnetic field at such a point is proportional to

1.   \(1 \over r\)

2.    \(1 \over r^2\)

3.     \(1 \over r^3\)

4.   none of these

Let r be the distance of a point on the axis of a magnetic dipole from its centre. The magnetic field at such a point is proportional to

1.   \(1 \over r\)

2.   \(1 \over r^2\)

3.   \(1 \over r^3\)

4.   none of these

1.  \(\frac{\mu_{\mathrm{0}}}{4 \pi} \frac{\mathrm{M}}{\mathrm{d}^{3}}\)

2.  \(\frac{\mu_{0}}{4 \pi} \frac{\sqrt{2} \mathrm{M}}{\mathrm{d}^{3}}\)

3.   \(\frac{\mu_{0}}{4 \pi} \frac{2\sqrt{2} \mathrm{M}}{\mathrm{d}^{3}}\)

4.   \(\frac{\mu_{\mathrm{0}}}{4 \pi} \frac{\mathrm{2M}}{\mathrm{d}^{3}}\)

Magnetic meridian is :

1.  a point

2.  a line along north-south

3.  a horizontal plane

4.  a vertical plane

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

1.  will stay in north-south direction only 

2.  will stay in east-west direction only 

3.  will become rigid showing no movement 

4.  will stay in any position

A dip circle is taken to geomagnetic equator. The needle is allowed to move in a vertical plane perpendicular to the magnetic meridian. The needle will stay 

1.  in horizontal direction only 

2.  in vertical direction only 

3.  in any direction except vertical and horizontal 

4.  in any direction it is released

Which of the following four graphs may best represent the current-deflection relation in a tangent galvanometer? 

  
1. a
2. b 
3. c
4. d

A tangent galvanometer is connected directly to an ideal battery. If the number of turns in the coil is doubled, the deflection will 

1.  increase

2.  decrease 

3.  remain unchanged

4.  either increase or decrease. 

Pick the correct options.

(a) Magnetic field is produced by electric charges only.

(b) Magnetic poles are only mathematical assumptions having no real existence.

(c) A north pole is equivalent to a clockwise current and a south pole is equivalent to an anticlockwise current.

(d) A bar magnet is equivalent to a long, straight current

Choose the correct option 

1.  (a) , (b) 

2. (b) , (c) 

3. (c) , (d) 

4. (a) , (d) 

A horizontal circular loop carries a current that looks clockwise when viewed from above. It is replaced by an equivalent magnetic dipole consisting of a south pole S and a north pole N.

(a) The line SN should be along a diameter of the loop.

(b) The line SN should be perpendicular to the plane of the loop.

(c) The south pole should be below the loop.

(d) The north pole should be below the loop

Choose the correct option 

1.  (a) , (b) 

2. (b) , (d) 

3. (c) , (d) 

4. (a) , (d)