Q. No.
A small bar magnet is placed with its north pole facing the magnetic north pole. The neutral points are located at a distance r from its centre. If the magnet is rotated by 180o, the neutral point shall be obtained at a distance of:
1. \(2r\)
2. \(\sqrt{2}r\)
3. \(2^{\frac{1}{3}}r\)
4. \(\frac{r}{2\sqrt{2}}\)
If the angles of dip at two places are 30o and 45o respectively, then the ratio of horizontal components of earth's magnetic field at the two places will be:
(Assume net magnetic field to be equal at the two places)
1. √3 : √2
2. 1 : √2
3. 1 : √3
4. 1 : 2
A magnet is suspended in such a way that it oscillates in the horizontal plane. It makes 20 oscillations per minute at a place where dip angle is 30o and 15 oscillations per minute at a place where dip angle is 60o. The ratio of total earth's magnetic field at the two places is:
1.
2.
3. 4:9
4.
| Assertion (A): | If a compass needle is kept at the magnetic north pole of the earth, the compass needle may stay in any direction. |
| Reason (R): | The dip needle will stay vertical at the north pole of the earth. |
| 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. | Both (A) and (R) are false. |
Given below are two statements:
| Assertion (A): | The earth's magnetic field is due to iron present in its core. |
| Reason (R): | At a high-temperature magnet losses its magnetic property or magnetism. |
| 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. | Both (A) and (R) are false. |
Given below are two statements:
| Assertion (A): | At most of the points in northern hemisphere, the magnetic field is inclined to an angle below horizontal, whereas in the southern hemisphere, the magnetic field is inclined to an angle above horizontal. |
| Reason (R): | The magnetic south pole is near the geographic north pole and vice versa. |
| 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. | Both (A) and (R) are false. |
If \(\phi_1\) and \(\phi_2\) are the apparent angles of dip observed in two vertical planes at right angles to each other, then the true angle of dip \(\phi\) is given by:
1. \(cos^2{\phi}=cos^2{\phi_1}+cos^2{\phi_2}\)
2. \(sec^2{\phi}=sec^2{\phi_1}+sec^2{\phi_2}\)
3. \(tan^2{\phi}=tan^2{\phi_1}+tan^2{\phi_2}\)
4. \(cot^2{\phi}=cot^2{\phi_1}+cot^2{\phi_2}\)
A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole. It:
1. will become rigid showing no movement
2. will stay in any position
3. will stay in north-south direction only
4. will stay in east-west direction only
At point A on the earth's surface, the angle of dip is, . At a point B on the earth's surface, the angle of dip is, . We can interpret that:
| 1. | A and B are both located in the southern hemisphere. |
| 2. | A and B are both located in the northern hemisphere. |
| 3. | A is located in the southern hemisphere and B is located in the northern hemisphere. |
| 4. | A is located in the northern hemisphere and B is located in the southern hemisphere. |
The current of 30 A is flowing in a vertical straight wire. If the horizontal component of the earth's magnetic field is 2 x 10-5 Tesla, then the position of the null point will be:
1. 0.9 m
2. 0.3 mm
3. 0.3 cm
4. 0.3 m
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