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. |
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. |
A conducting rod of length \(2l\) is rotating with constant angular speed \(\omega\) about its perpendicular bisector. A uniform magnetic field \(\vec {B}\) exists parallel to the axis of rotation. The emf induced between the two ends of the rod is:
1. \(B\omega l^2\)
2. \(\frac{1}{2} B \omega l^{2}\)
3. \(\frac{1}{8} B \omega l^{2}\)
4. zero
A conductor ABOCD moves along its bisector with a velocity of \(1\) m/s through a perpendicular magnetic field of \(1~\text{wb/m}^2\), as shown in fig. If all the four sides are of \(1\) m length each, then the induced emf between points A and D is:
1. \(0\)
2. \(1.41\) volt
3. \(0.71\) volt
4. None of the above
A wire cd of length \(l\) and mass \(m\) is sliding without friction on conducting rails \(ax\) and \(by\) as shown. The vertical rails are connected to each other with a resistance \(R\) between \(a\) and \(b\). A uniform magnetic field \(B\) is applied perpendicular to the plane \(abcd\) such that \(cd\) moves with a constant velocity of:
1. | \({mgR \over Bl}\) | 2. | \({mgR \over B^2l^2}\) |
3. | \({mgR \over B^3l^3}\) | 4. | \({mgR \over B^2l}\) |