A choke is used as a resistance in :
1.dc circuits
2.ac circuits
3.both ac and dc circuits
4.neither (a) nor (b)
Posted Date:-2021-12-16 07:37:14
A metal conductor of length 1 m rotates vertically about one of its ends at angular velocity 5 rad s-1 . If the horizontal component of earth’s magnetism is 2 × 10-5 T, then e.m.f. developed between the two ends of the conductor is:
1. 5 µV
2. 50 µV
3. 5 mV
4.50 mV
Posted Date:-2021-12-16 06:07:59
A transformer is used to light 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 A. Then the efficiency of the transformer is:
1.11%
2.50%
3.80%
4.90%
Posted Date:-2021-12-16 06:03:41
An e– and a p– are moving parallel to each other in a magnetic field. The magnetic force acting on the p+ is:
1.1840 times that on e–
2. less than that of e–
3.same as that of e–
4.slightly more than that of e–
Posted Date:-2021-12-16 06:02:51
coil of L = 8.4 mH and R = 6 Ω is connected to a 12 V battery. The current in the coil is 1.0 A at approx’time of:
1.500 s
2.20 s
3.35 ms
4.1 ms
Posted Date:-2021-12-16 06:09:00
For purely capacitive circuits, power factor is:
1.0
2.-1
3.1
4.infinity
Posted Date:-2021-12-16 07:38:45
If I current is flowing inductance L, then the dimension of 32 LI² is equivalent to:
1.charge
2.force
3.momentum
4.energy
Posted Date:-2021-12-16 06:09:52
If the magnetic flux linked with a coil through which a current off ampere is set up is ∅, then the coefficient of self-inductance of the coil is:
1.l/∅
2.∅/l
3.∅l
4.None of the above
Posted Date:-2021-12-16 06:06:32
The core of a transformer is laminated because:
1.rusting of core may be prevented
2.ratio of voltage in primary and secondary may be increased.
3.energy losses due to eddy current may be minimised
4.The weight of transformer may be reduced
Posted Date:-2021-12-16 07:43:51
The coupling co-efficient of the perfectly coupled coils is:
1.Zero
2.1
3. slightly more than 1
4.infinite
Posted Date:-2021-12-16 05:59:31
The energy stored in a 50 mH inductor carrying a current of 4 A is:
1.0.1 J
2.0.4 J
3.0.04 J
4.0.01 J
Posted Date:-2021-12-16 07:41:05
The flux linked with a coif at any instant t is given by ∅ = 10t² – 50t + 250. The induced emf at t = 35 is:
1.10 V
2.190 V
3.-190
4.-10 V
Posted Date:-2021-12-16 07:41:52
The magnetic field is parallel to a surface, then the magnetic flux through the surface is :
1. zero
2.small but not zero
3.infinite
4.large but not infinite
Posted Date:-2021-12-16 06:01:35
The magnetic flux (∅) lined with a coil is related to its area (s) as:
1.∅ ∝ s
2.∅ ∝ s²
3.∅ ∝ s1/2
4.∅ ∝ s-1/2
Posted Date:-2021-12-16 06:05:15
The magnetic flux (∅) linked with a coil is related to the number of turns (N) ofthe coil as:
1.f ∝ N
2.f ∝ N-1
3.f ∝ N2
4. f ∝ N-2
Posted Date:-2021-12-16 06:04:31
The magnetic flux linked with a coil is inversely proportional to the?
1. magnetic field
2.area of cross section
3.number of turns
4.None of the above
Posted Date:-2021-12-16 07:39:37
The phase difference between the flux linkage and the emf in a rotating coil in a uniform magnetic field is:
1.zero
2.π/2
3.π/4
4.π
Posted Date:-2021-12-16 07:36:07
The role of inductance is equivalent to:
1.inertia
2.force
3.energy
4.momentum
Posted Date:-2021-12-16 06:07:10
The SI unit of magnetic flux is:
1.T
2.Tn-2
3.Wb
4.Wb m-2
Posted Date:-2021-12-16 07:38:05
Two coils of self inductance 2 mil and 8 mil are placed so close together that the effective flux in one coil is completely linked with other. The mutual inductance between these coils is :
1.4 mH
2.16 mH
3.10 mH
4.6 mH
Posted Date:-2021-12-16 07:42:50
When the magnetic field is parallel to a surface, then the magnetic flux through the surface is:
1.infinite
2.zero
3. small but not zero
4.large but not infinite.
Posted Date:-2021-12-16 07:40:18