Q. No.If all linear dimensions of an inductor are tripled, then self-inductance will become (keeping the total number of turns per unit length constant)
1. 3 times
2. 9 times
3. 27 times
4. 1/3 times
| 1. | \(250\) J | 2. | \(125\) J |
| 3. | \(500\) J | 4. | \(100\) J |
Two coils have a mutual inductance of 5 mH. Current changes in the first coil according to the equation I = cos wt, where = 10 A and rad/s. Maximum value of e.m.f. induced in the second coil is
1. 5 volt
2. 2 volt
3. 4 volt
4. volt
Lenz's law is a consequence of the law of conservation of
(1) Charge
(2) Momentum
(3) Mass
(4) Energy
A copper ring is held horizontally and a bar magnet is dropped through the ring with its length along the axis of the ring. The acceleration of the falling magnet while it is passing through the ring is
(1) Equal to that due to gravity
(2) Less than that due to gravity
(3) More than that due to gravity
(4) Depends on the diameter of the ring and the length of the magnet
A magnet is brought towards a coil first (i) speedily (ii) slowly. It can be concluded that the induced e.m.f. and the induced charge in the two cases, will be respectively:
| 1. | More in the first case, more in the first case. |
| 2. | More in the first case, equal in both cases. |
| 3. | Less in the first case, more in the second case. |
| 4. | Less in the first case, equal in both cases. |
As shown in the figure, a magnet is moved at a fast speed towards a coil at rest. Due to this induced electromotive force, induced current and induced charge in the coil is \(E\), \(I\), and \(Q\) respectively. If the speed of the magnet is doubled, the incorrect statement is:
| 1. | \(E\) increases |
| 2. | \(I\) increases |
| 3. | \(Q\) remains the same |
| 4. | \(Q\) increases |
The magnetic field in a coil of 100 turns and 40 square cm area is increased from 1 Tesla to 6 Tesla in 2 second. The magnetic field is perpendicular to the coil. The e.m.f. generated in it is
(1) 104 V
(2) 1.2 V
(3) 1.0 V
(4) 10–2 V
A metallic ring connected to a rod oscillates freely like a pendulum. If now a magnetic field is applied in the horizontal direction so that the pendulum now swings through the field, the pendulum will:
| 1. | Keep oscillating with the old-time period. |
| 2. | Keep oscillating with a smaller time period. |
| 3. | Keep oscillating with a larger time period. |
| 4. | Come to rest very soon. |
An aluminium ring \(B\) faces an electromagnet \(A\). If the current \(I\) through \(A\) can be altered, then:
| 1. | whether \(I\) increases or decreases, \(B\) will not experience any force. |
| 2. | if \(I\) decreases, \(A\) will repel \(B\). |
| 3. | if \(I\) increases, \(A\) will attract \(B\). |
| 4. | if \(I\) increases, \(A\) will repel \(B\). |
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