CBSE
Multiple Choice QuestionsA step-down transformer reduces the voltage of a transmission line from 2200 V to 220 V. The power delivered by it is 880 W and its efficiency is 88%. The input current is
4.65 mA
0.045 A
0.45 A
4.65 A
An inductance of , a capacitance of and a resistance of 10Ω are connected in series with an AC source 220 V, 50 Hz. The phase angle of the circuit is
In a LCR series circuit, the potential difference between the terminals of the inductance is 60 V, between the terminals of the capacitor, is 30 V and that across the resistance is 40 V. Then, the supply voltage will be equal to
50 V
70 V
130 V
10 V
The inductance of a coil in which a current of 0.2 A is increasing at the rate of 0.5 A/s represents a power flow of 0.5 W, is
2 H
5 H
10 H
20 H
Assertion: The quantity L/R possesses dimension of time.
Reason: To reduce the rate of increase of current through a solenoid, we should increase the time constant ( L/R ).
If both the assertion and reason are true and reason is a correct explanation of assertion
If both assertion and reason are true but assertion is not correct explanation of the assertion
If the assertion is true but the reason is false.
If both assertion and reason are false.
A choke is preferred to resistance for limiting current in AC circuit because
choke is cheap
there is no wastage of power
choke is compact in size
choke is a good absorber of heat
A capacitor of capacitance 2μF is connected in the tank circuit of an oscillator oscillating with a frequency of 1 kHz. If the current flowing in the circuit is 2 mA, the voltage across the capacitor will be
0.16 V
0.32 V
79.5 V
159 V
If emf E = 4 cos 1000t volt is applied to an L-R circuit of inductance 3 mH and resistance 4 Ω, the amplitude of the current in the circuit is
1.0 A
0.8 A
If in a circuit current lags behind EMF by . Then it is a/an
resistor circuit
capacitor
inductor circuit
CR circuit
A DC circuit contains 10Ω of resistance in series with 10 H coil. The impedance of the circuit is
10 Ω
20 Ω
1 Ω
zero
