Q. No.1. \(0.064~\text{J}\)
2. \(-0.064~\text{J}\)
3. zero
4. \(-0.082~\text{J}\)
A bar magnet of magnetic moment \(1.5~\text{J/T}\) lies aligned with the direction of a uniform magnetic field of \(0.22~\text{T}\). What is the amount of work required by an external torque to turn the magnet so as to align its magnetic moment normal to the field direction?
1. \(0.66\) J
2. \(0.33\) J
3. \(0\)
4. \(0.44\) J
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A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in the equilibrium state. The energy required to rotate it by \(60^{\circ}\) is \(W\). Now the torque required to keep the magnet in this new position is:
| 1. | \(\dfrac{W}{\sqrt{3}}\) | 2. | \(\sqrt{3}W\) |
| 3. | \(\dfrac{\sqrt{3}W}{2}\) | 4. | \(\dfrac{2W}{\sqrt{3}}\) |
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| Assertion (A): | Magnetic dipoles, when placed near a long straight current-carrying wire, are deflected perpendicular to the wire. |
| Reason (R): | The magnetic field lines of a straight current-carrying wire are oriented in a direction which is perpendicular to the wire. |
| 1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
| 3. | (A) is True but (R) is False. |
| 4. | (A) is False but (R) is True. |
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The work done in rotating a magnet of the magnetic moment \(100\) A-m2 through \(90^\circ\) from a direction parallel to the uniform magnetic field of strength \(0.4 \times 10^{-4}\) Tesla is:
1. \(4\) mJ
2. zero
3. \(6\) mJ
4. \(8\) mJ
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The magnetic field at the centre of a circular loop of area \(A\) is \(B.\) The magnetic moment of the loop is:
| 1. | \(\dfrac{BA^2}{\mu_0\pi}\) | 2. | \(\dfrac{BA\sqrt A}{\mu_0}\) |
| 3. | \(\dfrac{BA\sqrt A}{\mu_0\pi}\) | 4. | \(\dfrac{2BA\sqrt A}{\mu_0\sqrt\pi}\) |
| 1. | \(mB\) | 2. | \(2mB\) |
| 3. | \(\dfrac12mB\) | 4. | zero |
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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. \(\dfrac{3}{2}\)
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A magnetic needle suspended parallel to a magnetic field requires \(\sqrt{3}~\text{J}\) of work to turn it through \(60^\circ\)
1. \(3\) N-m
2. \(\sqrt{3} \) N-m
3. \(\frac32\) N-m
4. \(2\sqrt{3}\) N-m
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1. \(16 \times 10^{-2}\) J
2. zero
3. \(8 \times 10^{-2}\) J
4. \(4 \times 10^{-2}\) J
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