Q. No.The net magnetic flux through any closed surface, kept in uniform magnetic field is:
1.
zero
2.
\(\dfrac{\mu_{0}}{4 \pi}\)
3.
\(4\pi μ_{0}\)
4.
\(\dfrac{4\mu_{0}}{\pi}\)
If a current is passed through a circular loop of radius \(R\) then magnetic flux through a coplanar square loop of side \(l\) as shown in the figure \((l<<R)\) is:
| 1. | \(\frac{\mu_{0} l}{2} \frac{R^{2}}{l}\) | 2. | \(\frac{\mu_{0} I l^{2}}{2 R}\) |
| 3. | \(\frac{\mu_{0} l \pi R^{2}}{2 l}\) | 4. | \(\frac{\mu_{0} \pi R^{2} I}{l}\) |
The radius of a loop as shown in the figure is \(10~\text{cm}.\) If the magnetic field is uniform and has a value \(10^{-2}~ \text{T},\) then the flux through the loop will be:
| 1. | \(2 \pi \times 10^{-2}~\text{Wb}\) | 2. | \(3 \pi \times 10^{-4}~\text{Wb}\) |
| 3. | \(5 \pi \times 10^{-5}~\text{Wb}\) | 4. | \(5 \pi \times 10^{-4}~\text{Wb}\) |
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R):
| Assertion (A): | Self-inductance is called the inertia of electricity. |
| Reason (R): | It is on account of self-inductance that the coil opposes any change in current passing through it. |
| 1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
| 3. | (A) is True but (R) is False. |
| 4. | Both (A) and (R) are False. |
Given below are two statements:
| Assertion (A): | When a piece of non-metal and a metal are dropped from the same height near the surface of the earth, the non-metallic piece will reach the ground first. |
| Reason (R): | Induced current in metal will decrease the acceleration. |
| 1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
| 3. | (A) is True but (R) is False. |
| 4. | Both (A) and (R) are False. |
The magnetic flux linked with a coil varies with time as \(\phi = 2t^2-6t+5,\) where \(\phi \) is in Weber and \(t\) is in seconds. The induced current is zero at:
| 1. | \(t=0\) | 2. | \(t= 1.5~\text{s}\) |
| 3. | \(t=3~\text{s}\) | 4. | \(t=5~\text{s}\) |
A short magnet is allowed to fall along the axis of a horizontal metallic ring. Starting from rest, the distance fallen by the magnet in one second may be:
| 1. | \(4\) m | 2. | \(5\) m |
| 3. | \(6\) m | 4. | \(7\) m |
| 1. | \(5\) H | 2. | \(2.5\) H |
| 3. | \(1.5\) H | 4. | \(2\) H |
Two coils have a mutual inductance of \(5\) mH. The current changes in the first coil according to the equation \(I=I_{0}\cos\omega t,\) where \(I_{0}=10~\text{A}\) and \(\omega = 100\pi ~\text{rad/s}\). The maximum value of emf induced in the second coil is:
1. \(5\pi~\text{V}\)
2. \(2\pi~\text{V}\)
3. \(4\pi~\text{V}\)
4. \(\pi~\text{V}\)
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