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. | \(\dfrac{2 \mu_{0} M}{4 \pi d^{3}}\) | 2. | \(\dfrac{\mu_{0} M}{4 \pi d^{3}}\) |
| 3. | zero | 4. | \(\dfrac{\sqrt{5}\mu_{0} M}{4\pi d^{3}}\) |
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. |
Choose the correct statement regarding magnetism.
| 1. | Paramagnetic sample displays greater magnetization when cooled. |
| 2. | Diamagnetism is almost independent of temperature. |
| 3. | Ferromagnetic substances show hysteresis. |
| 4. | All of these. |
A Gaussian surface is drawn enclosing the N-pole of a bar magnet. The net magnetic flux through the Gaussian surface will be:
(pole strength of N-pole is treated as positive and S-pole as negative)
| 1. | positive. |
| 2. | negative. |
| 3. | positive or negative. |
| 4. | zero. |
The magnetization of a piece of iron or steel:
| 1. | depends on the strength of the magnetizing field. |
| 2. | depends on external conditions such as temperature. |
| 3. | cannot be done beyond the saturation point. |
| 4. | all of these. |
When a magnetic material is subjected to a very small magnetising force \(H,\) the intensity of magnetisation is proportional to:
| 1. | \(\frac{1}{\sqrt{H}} \) | 2. | \(\sqrt{H} \) |
| 3. | \(H \) | 4. | \(H^2\) |
The bar magnet \(A\) of magnetic moment \(M_A\) is found to oscillate at a frequency twice that of magnet \(B\) of magnetic moment \(M_B\) and the same moment of inertia when placed in a vibration magnetometer. We may say that:
| 1. | \(M_B=8M_A\) | 2. | \(M_A= 4M_B\) |
| 3. | \(M_A=8M_B\) | 4. | \(M_A=2M_B\) |
The possible value of magnetic susceptibility of a diamagnetic material can be:
1. \(-2.45\)
2. \(0.75\)
3. \(-0.5\)
4. \(1.67\)
| 1. | \(9~\text{gauss}\) | 2. | \(4~\text{gauss}\) |
| 3. | \(36~\text{gauss}\) | 4. | \(4.5~\text{gauss}\) |
A ferromagnetic material is placed in an external magnetic field. The magnetic domains:
| 1. | must increase in size. |
| 2. | must decrease in size. |
| 3. | may increase or decrease in size. |
| 4. | disappear. |
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