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 emf 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. |
1. | directly proportional to \(i\). |
2. | directly proportional to \(R\). |
3. | directly proportional to \(R^2\). |
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 \(\frac{1}{r}\)
3. increases as \(r\)
4. decreases as \(\frac{1}{r^2}\)
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. |