CBSE
Multiple Choice QuestionsWhen a given coil is connected to a 200V, 50 Hz AC source, 1 A current flows in the circuit. The inductive reactance of the coil used is
A current I= 5.0 A flows along a thin wire shaped as shown in given figure. The radius of the curved part of the wire is equal to R = 120 mm and the angle 2 = 90°. Find the magnetic induction of the field at point O.
4.2 × 10-4 T
8.8 × 10-5 T
2.8 × 10-4 T
4.2 × 10-3 T
Current in a circuit falls steadily from 2.0 A to 0.0 A in 10 ms. If an average emf of 200 V is induced, then the self-inductance of the circuit is
1 H
2 H
1/2 H
2 H
The magnetic flux in a closed circuit of resistance 10 Ω varies with time t (in second) as = (4t2 − 5t + 1)Wb. The magnitude of induced current at t = 0.20 s is
0.12 A
0.38 A
0.34 A
0.12 A
A small piece of metal wire is dragged across the gap between the poles of a magnet in 0.4 s. If change in magnetic flux in the wire is 8 x 10-4 Wb, then emf induced in the wire is
8 × 10-3 V
6 × 10-3 V
4 × 10-3 V
2 × 10-3 V
The polarity of the capacitor in the situation described by Fig.
Plate A and plate B both positive
Plate A negative and plate B positive
Plate A positive and plate B negative
Plate A and plate B both negative
Three solenoid coils of same dimensions, same number of turns and same number of layers of windings are taken. Coil 1 with inductance L1 was wound using a wire of resistance 11 Ω /m, coil 2 with inductance L2 was wound using the similar wire but the direction of winding was reversed in each layer, coil 3 with inductance L3 was wound using a superconducting wire. The self inductance of the coils L1 , L2 and L3 are
L1 = L2 = L3
L1 = L2 , L3 = 0
L1 = L3 , L2 = 0
L1 > L2 > L3
The sun delivers 104 W/m2 of electromagnetic flux to the earth's surface. The total power that is incident on a roof of dimension (10 x 10) m2 will be
104 W
105 W
106 W
107 W
The self-inductance of the motor of an electric fan is 10H. In order to impart maximum power at 50 Hz, it should be
connected to a capacitance of
4µF
8µF
1µF
2µF
The magnetic flux through a circuit of resistance R changes by Δ in times Δt. Then, the-total amount of electric charge that passes in any point in the circuit during this time 'Δt' will be
