CBSE
Multiple Choice QuestionsThe given circuit diagram shows a series L-C-R circuit connected to a variable frequency 230 V, source: L =5.0 H, C = 80 µF, R = 40 Ω
The frequency and impedance of the circuit at the resonating frequency are
50 rad/s and 5.75 A
1000 rad/s and 3 A
10 rad/s and 2 A
20 rad/s and 4 A
An AC source, of voltage V =Vm sin ωt, is applied across a series RC circuit in which the capacitive impedance is 'a' times the resistance in the circuit. The value of the power factor of the circuit is
O
None of these
In a series L-C-R circuit, the voltages across an inductor, a capacitor and a resistor are 30V, 30V and 60 V respectively. The phase difference between the applied voltage and the current in the circuit is
O°
90°
30°
60°
In the inductive circuit given in the figure, the current rises after the switch is closed. At instant when the current is 15 mA, then potential difference across the inductor will be
zero
240 V
180 V
60 V
The ratio of inductive reactance to capacitive reactance in an AC circuit will be
ω LC
ω2 L
zero
ω2 LC
A step down transformer operated on a 2.5 kV line. It supplies a load with 20 A. The ratio of the primary winding to the secondary is 10 : 1. If the transformer is 90% efficient, the voltage in the secondary is
225 V
550 V
250 V
200 V
The instantaneous current and voltage of an AC circuit are given by I= 10 sin 300t A and V = 200 sin 300t V. The power dissipation in the circuit is
500 W
2000 W
1000 W
100 W
A step down transformer operated on a 2.5 kV line. It supplies a load with 20 A. The ratio of the primary winding to the secondary is 10 : 1. If the transformer is 90% efficient, the power output is
4.5 X 104 W
4.5 × 102 W
6 x 104 W
6 X 104 w
In a step up transformer, the turns ratio of field is primary and secondary is 1 : 4. A leclanche cell of emf 1.5 V is connected across the primary. The voltage developed across the secondary will be
3 V
6 V
1 V
zero
When a given coil of ohmic resistance 100 Ω and inductive reactance 100 Ω is connected to a 200 V DC source, the current flows in the circuit is
1 A
1.5 A
2 A
Ω
