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Q. No.A circular current loop of magnetic moment \(M\) is in an arbitrary orientation in an external magnetic field \(B\). The work done to rotate the loop by \(30^{\circ}\) about an axis perpendicular to its plane is:
| 1. | \(MB\) | 2. | \(\dfrac{\sqrt{3}~MB}{2}\) |
| 3. | \(\dfrac{MB}{2}\) | 4. | zero |
Subtopic: Â Magnetic Field & Field Lines |
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The magnetic field of Earth can be modelled by that of a point dipole placed at the centre of the Earth. The dipole axis makes an angle of \(11.3^{\circ}\) with the axis of Earth. At Mumbai, declination is nearly zero. Then,
1. the declination varies between \(11.3^{\circ} \mathrm{W}\) to \(11.3^{\circ} \mathrm{E}\).
2. the least declination is \(0^{\circ}\).
3. the plane defined by dipole axis and Earth axis passes through Greenwich.
4. declination averaged over Earth must be always negative.
1. the declination varies between \(11.3^{\circ} \mathrm{W}\) to \(11.3^{\circ} \mathrm{E}\).
2. the least declination is \(0^{\circ}\).
3. the plane defined by dipole axis and Earth axis passes through Greenwich.
4. declination averaged over Earth must be always negative.
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In a permanent magnet at room temperature
1. magnetic moment of each molecule is zero.
2. the individual molecules have non-zero magnetic moment which are all perfectly aligned.
3. domains are partially aligned.
4. domains are all perfectly aligned.
1. magnetic moment of each molecule is zero.
2. the individual molecules have non-zero magnetic moment which are all perfectly aligned.
3. domains are partially aligned.
4. domains are all perfectly aligned.
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A paramagnetic sample shows a net magnetisation of \(8 \mathrm{Am}^{-1}\) when placed in an external magnetic field of \(0.6 \mathrm{~T}\) at a temperature of \(4 \mathrm{~K}\). When the same sample is placed in an external magnetic field of \(0.2 \mathrm{~T}\) at a temperature of \(16 \mathrm{~K}\), the magnetisation will be
1. \(\frac{32}{3} \mathrm{Am}^{-1}\)
2. \(\frac{2}{3} \mathrm{Am}^{-1}\)
3. \(6 \mathrm{Am}^{-1}\)
4. \(2.4 \mathrm{Am}^{-1}.\)
1. \(\frac{32}{3} \mathrm{Am}^{-1}\)
2. \(\frac{2}{3} \mathrm{Am}^{-1}\)
3. \(6 \mathrm{Am}^{-1}\)
4. \(2.4 \mathrm{Am}^{-1}.\)
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\(S\) is the surface of a lump of magnetic material.
Choose the correct option:
| (a) | Lines of \(B\) are necessarily continuous across \(S\). |
| (b) | Some lines of \(B\) must be discontinuous across \(S\). |
| (c) | Lines of \(H\) are necessarily continuous across \(S\). |
| (d) | Lines of \(H\) cannot all be continuous across \(S\). |
| 1. | (a), (d) | 2. | (a), (b), (c) |
| 3. | (b), (d) | 4. | (c), (d) |
Subtopic: Â Magnetic Field & Field Lines |
From NCERT
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The primary origin(s) of magnetism lies in
Choose the correct options:
1. (a), (d)
2. (a), (b), (c)
3. (b), (d)
4. (c), (d)
| (a) | atomic currents. |
| (b) | Pauli exclusion principle. |
| (c) | polar nature of molecules. |
| (d) | intrinsic spin of electron. |
Choose the correct options:
1. (a), (d)
2. (a), (b), (c)
3. (b), (d)
4. (c), (d)
Subtopic: Â Magnetic Materials |
From NCERT
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A long solenoid has 1000 turns per metre and carries a current of \(1 \mathrm{~A}\). It has a soft iron core of \(\mu_r=1000\). The core is heated beyond the Curie temperature, \(T_c\).
1. The \({H}\) field in the solenoid is (nearly) unchanged but the \({B}\) field decreases drastically.
2. The \({H}\) and \({B}\) fields in the solenoid are nearly unchanged.
3. The magnetisation in the core reverses direction.
4. The magnetisation in the core diminishes by a factor of about \(10^8\).
Choose the correct option:
1. (a), (d)
2. (a), (b), (c)
3. (b), (d)
4. (c), (d)
1. The \({H}\) field in the solenoid is (nearly) unchanged but the \({B}\) field decreases drastically.
2. The \({H}\) and \({B}\) fields in the solenoid are nearly unchanged.
3. The magnetisation in the core reverses direction.
4. The magnetisation in the core diminishes by a factor of about \(10^8\).
Choose the correct option:
1. (a), (d)
2. (a), (b), (c)
3. (b), (d)
4. (c), (d)
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Essential difference between electrostatic shielding by a conducting shell and magnetostatic shielding is due to
Choose the correct option:
1. (a), (c)
2. (a), (c), (d)
3. (b), (d)
4. (c), (d)
| (a) | electrostatic field lines can end on charges and conductors have free charges. |
| (b) | lines of \(B\) can also end but conductors cannot end them. |
| (c) | lines of \(B\) cannot end on any material and perfect shielding is not possible. |
| (d) | shells of high permeability materials can be used to divert lines of \(B\) from the interior region. |
Choose the correct option:
1. (a), (c)
2. (a), (c), (d)
3. (b), (d)
4. (c), (d)
Subtopic: Â Analogy between Electrostatics & Magnetostatics |
From NCERT
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Let the magnetic field on earth be modelled by that of a point magnetic dipole at the centre of earth. The angle of dip at a point on the geographical equator
a. is always zero.
b. can be zero at specific points.
c. can be positive or negative.
d. is bounded.
Choose the correct option:
1. (a), (c)
2. (a), (b)
3. (b), (c), (d)
4. (c), (d)
a. is always zero.
b. can be zero at specific points.
c. can be positive or negative.
d. is bounded.
Choose the correct option:
1. (a), (c)
2. (a), (b)
3. (b), (c), (d)
4. (c), (d)
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Q. No.
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