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.
2.
3.
4.
The radius of a loop as shown in the figure is \(10~\mathrm {cm}.\) If the magnetic field is uniform and has a value \(10^{-2}~ T,\) then the flux through the loop will be:
1. | \(2 \pi \times 10^{-2}Wb\) | 2. | \(3 \pi \times 10^{-4}Wb\) |
3. | \(5 \pi \times 10^{-5}Wb\) | 4. | \(5 \pi \times 10^{-4}Wb\) |
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: one is labelled as Assertion (A) and the other is labelled as Reason (R):
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. |
In the light of the above statements choose the correct answer from the options given below:
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 net magnetic flux through any closed surface, kept in uniform magnetic field is:
1. Zero
2.
3.
4.
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
The current through a choke coil increases from zero to 6 A in 0.3 seconds and an induced emf of 30 V is produced. The inductance of the coil is:
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 \(I_{0}=10~A\) and = 100 rad/s. The maximum value of e.m.f. induced in the second coil is:
1. 5 Volt
2. 2 Volt
3. 4 Volt
4. Volt