Which of the following statements is incorrect?

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?

$1. 0.80 A m^2$
$2. 0.40 A m^2$
$3. 0.29 A m^2$
$4. 0.60 A m^2$

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 $0.40~\text{Am}^{2}$)
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. $20~\text{A/m}$