Which of the following statement 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 \(800\) G experiences a torque of \(0.016\) Nm. The current flowing through the solenoid is:
1. \(2~\text{A}\)
2. \(4~\text{A}\)
3. \(1~\text{A}\)
4. \(5~\text{A}\)