In the figure, the magnetic needle has a magnetic moment of 6.7 × 10^–2 Am² and a moment of inertia I = 7.5 × 10^–6 kg m². It performs 10 complete oscillations in 6.70 s in a magnetic field. What is the magnitude of the magnetic field?

1. 0.02 T

2. 0.01 T

3. 003 T

4. 0.001 T

A short bar magnet placed with its axis at 30° with an external field of 800 G experiences a torque of 0.016 Nm. What is the magnetic moment of the magnet?

$1.<mspace\; width="1em"></mspace>0.80<mspace\; width="1em"></mspace>A<mspace\; width="1em"></mspace>m^2$
$2.<mspace\; width="1em"></mspace>0.40<mspace\; width="1em"></mspace>A<mspace\; width="1em"></mspace>m^2$
$3.<mspace\; width="1em"></mspace>0.29<mspace\; width="1em"></mspace>A<mspace\; width="1em"></mspace>m^2$
$4.<mspace\; width="1em"></mspace>0.60<mspace\; width="1em"></mspace>A<mspace\; width="1em"></mspace>m^2$

A short bar magnet placed with its axis at \(30^{\circ}\) with an external field of \(800~\text{G}\) experiences a torque of \(0.016~\text{N-m}\). What is the work done in moving it from its most stable to the most unstable position?
1. \(0.036~\text{J}\)
2. \(0.016~\text{J}\)
3. \(0.064~\text{J}\)
4. \(0\)

A solenoid of cross-sectional area \(2\times 10^{-4}~\text{m}^2\) and \(1000\) turns placed with its axis at \(30^\circ\) with an external field of \(800~\text{G}\) experiences a torque of \(0.016~\text{Nm}.\) The current flowing through the solenoid is:
1. \(2~\text{A}\)
2. \(4~\text{A}\)
3. \(1~\text{A}\)
4. \(5~\text{A}\)

The ratio of the magnitudes of the equatorial and axial fields due to a bar magnet of length \(5.0~\text{cm}\) at a distance of \(50~\text{cm}\) from its mid-point is:
(given, the magnetic moment of the bar magnet is \(0.40~\text{Am}^{2}\)${\mathrm{}}^{}$)
1. \(\dfrac{1}{2}\)

2. \(2\)

3. \(1\)

4. \(\dfrac{3}{2}\)

The figure shows a small magnetized needle \(P\) placed at a point \(O.\) The arrow shows the direction of its magnetic moment. The other arrows show different positions (and orientations of the magnetic moment) of another identical magnetized needle \(Q.\) Then:

Which of the following is the correct representation of magnetic field lines?

Which one of the following is correct?

A solenoid has a core of material with relative permeability \(400.\) The windings of the solenoid are insulated from the core and carry a current of \(2~\text A.\) If the number of turns is \(1000\) per metre, the magnetic field intensity \(H\) is:
1. \(2\times10^2~\text{A/m}\)
2. \(2\times10^3~\text{A/m}\)
3. \(2~\text{A/m}\) 
4. \(20~\text{A/m}\)

A solenoid has a core of material with relative permeability \(400.\) The windings of the solenoid are insulated from the core and carry a current of \(2~\text{A}\). If the number of turns is \(1000\) per metre, the magnetising field \(B\) is: