Q. No.Figure shows two small identical magnetic dipoles a and b of magnetic moments M each, placed at a separation 2d, with their axes perpendicular to each other. The magnetic field at the point P midway between the dipoles is:
1.
2.
3. Zero
4.
At a certain location in Africa, a compass points 12° west of the geographic north. The north tip of the magnetic needle of a dip circle placed in the plane of magnetic meridian points 60° above the horizontal. The horizontal component of the earth’s field is measured to be 0.16 G. The magnitude of the earth’s field at the location is:
1. 0.16 G
2. 0.48 G
3. 0.32 G
4. 0.30 G
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The vertical component of Earth’s magnetic field at a place is equal to the horizontal component. What is the value of the angle of dip at this place?
1.
2.
3.
4.
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A magnetic needle suspended by a silk thread is vibrating in the earth's magnetic field. If the temperature of the needle is increased, then:
| 1. | the time period decreases. |
| 2. | the time period remains unchanged. |
| 3. | the time period increases. |
| 4. | the time period first decreases then increases. |
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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For protecting a magnetic needle, it should be placed:
| 1. | In an iron box. |
| 2. | In a wooden box. |
| 3. | In a metallic box. |
| 4. | None of these. |
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If the magnetic dipole moment of an atom of diamagnetic material, paramagnetic material and ferromagnetic material are denoted by µd, µp, and µf respectively, then:
1. µp = 0 and µf ≠ 0
2. µd ≠ 0 and µp = 0
3. µd ≠ 0 and µf ≠ 0
4. µd = 0 and µp ≠ 0
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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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Diamagnetic material in a magnetic field moves:
| 1. | from stronger to the weaker parts of the field |
| 2. | from weaker to the stronger parts of the field |
| 3. | perpendicular to the field |
| 4. | in none of the above directions |
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Which of the following is the correct representation of magnetic field lines?
1. (g), (c)
2. (d), (f)
3. (a), (b)
4. (c), (e)
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