A bar magnet has coercivity \(4\times 10^{3}~\text{Am}^{-1}\). It is desired to demagnetize it by inserting it inside a solenoid \(12~\text{cm}\) long and having \(60\) turns. The current that should be sent through the solenoid is:
1. \(2\) A
2. \(4\) A
3. \(6\) A
4. \(8\) A
A uniform magnetic field, parallel to the plane of the paper existed in space initially directed from left to right. When a bar of soft iron is placed in the field parallel to it, the lines of force passing through it will be represented by:
1. | 2. | ||
3. | 4. |
A dip needle vibrates in the vertical plane perpendicular to the magnetic meridian. The time period of vibration is found to be 2 seconds. If the same needle is then allowed to vibrate in the horizontal plane and the time period is again found to be 2 seconds, then the angle of dip is:
1. 0o
2. 30o
3. 45o
4. 90o
A dip needle in a plane perpendicular to magnetic meridian will remain:
1. Vertical
2. Horizontal
3. In any direction
4. At an angle of dip to the horizontal
The earth's magnetic field at a certain place has a horizontal component 0.3 Gauss and the total strength 0.5 Gauss. The angle of dip is:
1.
2.
3.
4.
A superconductor exhibits perfect:
1. Ferrimagnetism
2. Ferromagnetism
3. Paramagnetism
4. Diamagnetism
Two short magnets of equal dipole moments \(M\) are fastened perpendicularly at their centres (figure). The magnitude of the magnetic field at a distance \(d\) from the centre on the bisector of the right angle is:
1. | \(\frac{\mu_{0}}{4 \pi}\frac{M}{d^{3}}\) | 2. | \(\frac{\mu_{0}}{4 \pi}\frac{M \sqrt{2}}{d^{3}}\) |
3. | \(\frac{\mu_{0}}{4 \pi}\frac{2 \sqrt{2} M}{d^{3}}\) | 4. | \(\frac{\mu_{0}}{4 \pi}\frac{2 M}{d^{3}}\) |
The variation of magnetic susceptibility with temperature for a diamagnetic substance is best represented by:
1. | 2. | ||
3. | 4. |
The variation of the intensity of magnetisation \((I)\) with respect to the magnetising field \((H)\) in a diamagnetic substance is described by the graph:
1. | \(OD\) | 2. | \(OC\) |
3. | \(OB\) | 4. | \(OA\) |
There are four light-weight-rod samples; A, B, C, D separately suspended by threads. A bar magnet is slowly brought near each sample and the following observations are noted:
i. | A is feebly repelled |
ii. | B is feebly attracted |
iii. | C is strongly attracted |
iv. | D remains unaffected |
Which one of the following is true?
1. | C is of a diamagnetic material |
2. | D is of a ferromagnetic material |
3. | A is of a non-magnetic material |
4. | B is of a paramagnetic material |