Q. No.Which of the following statements is incorrect?
| 1. | If a bar magnet is cut into two pieces transverse to its length and along its length, in either case, one gets two magnets, each with a north and south pole. |
| 2. | A magnetized needle in a uniform magnetic field experiences a torque but no net force. An iron nail near a bar magnet, however, experiences a force of attraction in addition to torque. |
| 3. | Every magnetic configuration must have a north pole and a south pole. |
| 4. | In a bar magnet, the intensity of the magnetic field is the strongest at the two ends (poles) and weakest at the central region. |
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?
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:
| 1. | In \(P Q_1\) and \(P Q_2\) configuration, the system is not in equilibrium. |
| 2. | In \(P Q_3 \) and \(P Q_6\) configuration, the system is unstable. |
| 3. | In \(P Q_5\) and \(P Q_4\) configuration, the system is stable. |
| 4. | \(P Q_5\) configuration corresponds to the lowest potential energy among all the configurations shown. |
Which of the following is the correct representation of magnetic field lines?
| 1. | (g), (c) | 2. | (d), (f) |
| 3. | (a), (b) | 4. | (c), (e) |
Which one of the following is correct?
| 1. | The magnetic field lines also represent the lines of force on a moving charged particle at every point. |
| 2. | The magnetic field lines can be entirely confined within the core of a toroid, but not within a straight solenoid. |
| 3. | A bar magnet exerts a torque on itself due to its own field. |
| 4. | The magnetic field arises due to stationary charges. |
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. \(20~\text{A/m}\)
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