Q. No.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 |
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. |
A conducting wire is moving towards the right in a magnetic field B. The direction of the induced current in the wire is shown in the figure. The direction of the magnetic field will be:
| 1. | In the plane of paper pointing towards the right. |
| 2. | In the plane of paper pointing towards the left. |
| 3. | Perpendicular to the plane of the paper and downwards. |
| 4. | Perpendicular to the plane of the paper and upwards. |
The magnitude of the earth’s magnetic field at a place is B0 and the angle of dip is δ. A horizontal conductor of length l lying along the magnetic north-south moves eastwards with a velocity v. The emf induced across the conductor is:
1. Zero
2. B0lv sinδ
3. B0lv
4. B0lv cosδ
Two circuits have coefficient of mutual induction of 0.09 henry. Average e.m.f. induced in the secondary by a change of current from 0 to 20 ampere in 0.006 second in the primary will be:
1. 120 V
2. 80 V
3. 200 V
4. 300 V
In the figure magnetic energy stored in the coil is:
| 1. | Zero | 2. | Infinite |
| 3. | 25 joules | 4. | None of the above |
Consider the situation shown in the figure. The wire AB is sliding on the fixed rails with a constant velocity. If the wire AB is replaced by semicircular wire, the magnitude of the induced current will:
| 1. | increase. |
| 2. | remain the same. |
| 3. | decrease. |
| 4. | increase or decrease depending on whether the semicircle bulges towards the resistance or away from it. |
A circular loop of radius R carrying current i lies in the x-y plane. If the centre of the loop coincides with the origin, then the total magnetic flux passing through the x-y plane will be:
| 1. | directly proportional to I. |
| 2. | directly proportional to R. |
| 3. | directly proportional to R2. |
| 4. | Zero. |
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