Q. No.According to Curie's law, the magnetic susceptibility of a substance at an absolute temperature T is proportional to:
1. 1/T
2. T
3. 1/T2
4. T2
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1. Ferromagnetic material becomes paramagnetic material.
2. Paramagnetic material becomes diamagnetic material.
3. Paramagnetic material becomes ferromagnetic material.
4. Ferromagnetic material becomes diamagnetic material.
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The figure illustrates how B, the flux density, inside a sample of unmagnetized ferromagnetic material varies with B0, the magnetic flux density, in which the sample is kept. For the sample to be suitable for making a permanent magnet:
1. OQ should be large and OR should be small
2. OQ and OR should both be large
3. OQ should be small and OR should be large
4. OQ and OR should both be small
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A ferromagnetic substance is placed in the varying magnetising field H. The magnetic induction B is a measure for various values of the direct and reverse magnetising field. The following graph has been plotted for B versus H. Choose the wrong statement:
| 1. | There is a limit of direct and reverse external magnetising field at which the magnetisation and hence the magnetic induction saturates. |
| 2. | Even after removing the external magnetising field, some residual magnetisation called 'retentivity' is left over the substance. |
| 3. | On increasing the reverse magnetising field, the magnetic induction decreases to zero for a value of the magnetising field which is known as 'susceptibility'. |
| 4. | On increasing the reverse magnetising field, the magnetic induction decreases to zero for a value of magnetising field known as 'coercivity'. |
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A material when heated suddenly changes its magnetic property at a particular temperature and above this temperature, its susceptibility is found to be inversely proportional to the absolute temperature. The material may be:
1. Ferromagnetic
2. Diamagnetic
3. Paramagnetic
4. Ferromagnetic or Paramagnetic
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For substances hysteresis (B - H) curves are given as shown in figure. For making temporary magnet which of the following is best?
| 1. |  |
2. |  |
| 3. |  |
4. |  |
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The magnetic susceptibility χ of a ferromagnetic material varies with temperature, as:
| 1. |  |
2. |  |
| 3. |  |
4. |  |
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The material suitable for making electromagnets should have:
1. High retentivity and high coercivity
2. High retentivity and low coercivity
3. Low retentivity and high coercivity
4. Low retentivity and low coercivity
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A long solenoid has 1500 turns per metre and an iron core of = 1100 is kept inside it. 2A current flows in the coil of the solenoid. If the core is heated beyond curie temperature, then:
| 1. | The H and B fields in the solenoid reduce to zero. |
| 2. | The H and B fields in the solenoid remain unchanged. |
| 3. | The H field in the solenoid is nearly unchanged but B field decreases significantly. |
| 4. | The B field in the solenoid is nearly unchanged but the H field decreases significantly. |
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The relative permeability of a ferromagnetic substance varies with temperature (T) according to the curve:
1. A
2. B
3. C
4. D
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