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. |
A uniform but time-varying magnetic field B(t) exists in a circular region of radius a and is directed into the plane of the paper, as shown. The magnitude of the induced electric field at point P at a distance r from the centre of the circular region:
1. is zero
2. decreases as
3. increases as r
4. decreases as
Two circular coils can be arranged in any of the three situations shown in the figure. Their mutual inductance will be:
1. | maximum in the situation (A). |
2. | maximum in the situation (B). |
3. | maximum in the situation (C). |
4. | the same in all situations. |
A conducting rod of length 2l is rotating with constant angular speed about its perpendicular bisector. A uniform magnetic field exists parallel to the axis of rotation. The e.m.f. induced between the two ends of the rod is:
1. \(B\omega l^2\)
2.
3.
4. Zero