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Q. No.A piece of soft iron is placed within the coils of a solenoid, the current through the solenoid being sufficiently large so that the iron is completely magnetised. If the current is increased further the magnetic field within the iron will:
| 1. | remain constant |
| 2. | increase slightly |
| 3. | increase proportionately with the current |
| 4. | decrease |
Subtopic: Magnetization & Magnetic Intensity |
Level 4: Below 35%
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Two materials \(A-a\) paramagnetic substance, and \(B-a\) diamagnetic substance are mixed together in equal amounts (equimolar) and made into a solid. They do not react or interact otherwise with each other. The mixture is expected to be:
1. Paramagnetic
2. Diamagnetic
3. Ferromagnetic
4. Non-magnetic
1. Paramagnetic
2. Diamagnetic
3. Ferromagnetic
4. Non-magnetic
Subtopic: Magnetic Materials |
Level 3: 35%-60%
Hints
A sample of magnetic material is placed in a magnetic field. As the magnetic field is increased, its magnetisation increases and finally, it becomes constant — even if the field is increased further.
Now, the temperature of the sample is decreased. The magnetisation:
Now, the temperature of the sample is decreased. The magnetisation:
| 1. | increases |
| 2. | decreases |
| 3. | remains unchanged |
| 4. | decreases first and then increases |
Subtopic: Magnetic Materials |
Level 3: 35%-60%
Hints
A paramagnetic substance is placed within the field of a solenoid and the current passing through the coils is doubled. The magnetic field within the substance:
| 1. | will double |
| 2. | will remain constant |
| 3. | will increase but only slightly |
| 4. | will decrease slightly |
Subtopic: Magnetic Materials |
Level 3: 35%-60%
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A ferromagnetic material consists of domains in which the magnetic moments of the atoms are in the same direction within each domain. However, the domains are randomly oriented. A ferromagnetic material is placed in an external magnetic field. Then,
| 1. | all the domains grow in size. |
| 2. | all the domains shrink in size. |
| 3. | some domains grow in size, others shrink. |
| 4. | domains rotate in the magnetic field. |
Subtopic: Magnetic Materials |
Level 3: 35%-60%
Hints
Two identical magnets are placed along the \(x\text-\)axis, equidistant from the origin and opposing each other. If a third magnet be placed at the origin along the \(y\text-\)axis, with its north-pole towards the positive \(y\text-\)axis, it will experience:
| 1. | force along +ve \(y\text-\)axis |
| 2. | force along -ve \(y\text-\)axis |
| 3. | zero force but a clockwise torque |
| 4. | zero force but an anticlockwise torque |
Subtopic: Bar Magnet |
53%
Level 3: 35%-60%
Hints
Two permanent magnets oriented in the same direction, when brought together:
| 1. | will attract each other |
| 2. | will repel each other |
| 3. | will not exert any force on each other |
| 4. | may attract or repel each other depending on how they are brought together |
Subtopic: Bar Magnet |
Level 3: 35%-60%
Hints
Two small paramagnetic samples are placed in an (otherwise uniform) strong external magnetic field \(B.\) If the two samples are placed with a separation that is along the direction of the external field \(B,\) then, the force exerted by the two samples on each other is:
| 1. | attractive. |
| 2. | repulsive. |
| 3. | zero. |
| 4. | any of the above depending on the external field \(B\) and the sample separation. |
Subtopic: Magnetic Materials |
56%
Level 3: 35%-60%
Hints
When a soft-iron core is inserted into a solenoid, the magnetic field is observed to increase by \(1500\) times near its opening. The turns density is \(1000\) m-1 and the solenoid carries a current \(100~\text{mA}.\) The field at its centre is (nearly):
1. \(0.2~\text T\)
2. \(0.02~\text T\)
3. \(0.4~\text T\)
4. \(0.04~\text T\)
1. \(0.2~\text T\)
2. \(0.02~\text T\)
3. \(0.4~\text T\)
4. \(0.04~\text T\)
Subtopic: Magnetization & Magnetic Intensity |
60%
Level 2: 60%+
Hints
A short bar magnet (moment: \(m\)) is placed at the centre of a solenoid, with its axis along the axis of the solenoid. The magnetic field of the solenoid is \(B,\) at its centre. The torque on the magnet is:
| 1. | \(mB\) | 2. | \(2mB\) |
| 3. | \(\dfrac12mB\) | 4. | zero |
Subtopic: Analogy between Electrostatics & Magnetostatics |
76%
Level 2: 60%+
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