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 Multiple Choice QuestionsMultiple Choice Questions

1.

A resistance 'R' draws power 'P' when connected to an AC source. If an inductance is now placed in series with the resistance such that the impedance of the circuit becomes 'Z' the power drawn will be

  • straight P open parentheses straight R over straight Z close parentheses squared
  • straight P square root of straight R over straight Z end root
  • straight P open parentheses straight R over straight Z close parentheses
  • straight P open parentheses straight R over straight Z close parentheses
2497 Views

2.

A small signal voltage V(t) = Vo sin ωt is applied across an ideal capacitor C:

  • over a full cycle the capacitor C does not consume any energy from the voltage source

  • current I(t) is in phase with voltage V(t)

  • Current I(t) leads voltage V(t) by 180o

  • Current I(t) leads voltage V(t) by 180o

1685 Views

3.

An inductor of 20 mH, a capacitor of 50 μF and a resistor of 40 ohm are connected in series across a source of emf V = 10 sin 340 t. the power loss in the ac circuit is,

  • 0.67 W

  • 0.76 W

  • 0.89 W

  • 0.89 W

5031 Views

4.

The instantaneous values of alternating current and voltages in a circuit are given as

straight i space equals space fraction numerator 1 over denominator square root of 2 end fraction space sin space left parenthesis 100 πt right parenthesis space ampere
straight e space equals fraction numerator 1 over denominator square root of 2 space end fraction space sin space left parenthesis 100 πt space plus straight pi over 3 right parenthesis space volt
The average power in Watts consumed in the circuit is

  • 1/4

  • fraction numerator square root of 3 over denominator 4 end fraction
  • 1/2

  • 1/2

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5.

If voltage across a bulb rated 220 V -100W drops by 2.5% of its rated value, the percentage of the rated value by which the power would decrease is

  • 20%

  • 2.5%

  • 5%

  • 5%

552 Views

6.

A transformer having efficiency of 90% is working on 200 V and 3 kW power supply. If the current in the secondary coil is 6 A, the voltage across the secondary coil and the current in the primary coil respectively are: 

  • 300 V, 15 A

  • 450 V, 15 A

  • 450 V, 13.5 A

  • 450 V, 13.5 A

895 Views

7.

In an AC circuit, an alternating voltage straight e space equals space 200 square root of 2 100t volt is connected to a capacitor of capacity 1μF. The rms value of the current in the circuit is 

  • 100 mA

  • 200 mA

  • 20 mA

  • 20 mA

378 Views

8.

An AC voltage is applied to a resistance R and an inductor L in series. If R and the inductive reactance are both equal to 3Ω, the phase difference between the applied voltage and the current in the circuit is 

  • π/4

  • π/2

  • zero

  • zero

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9.

In the given figure, a diode D is connected to an external resistance R = 100 Ω and an e. m. f of 3.5 V. If the barrier potential developed across the diode is 0.5 V, the current in the circuit will be 


  • 30 mA

  • 40 mA

  • 20 mA

  • 20 mA


A.

30 mA

Given, external resistance R = 100 Ω and an emf is 3.5 V.

Potential barrier across the diode is 0.5 V




Potential difference on R = 3.5 V - 0.5 V  = 3.0 V

Current in circuit, I = V/R  = 3/100
 = 0.03 A  = 30 mA

947 Views

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10.

The rms value of potential difference V shown in the figure is 




  • Vo

  • fraction numerator straight V subscript straight o over denominator square root of 2 end fraction
  • Vo/2

  • Vo/2

880 Views

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