Important Questions of Alternating Current Physics | Zigya

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211.

In the given circuit, the AC source has ω = 100 rad/s, considering the inductor and capacitor to be ideal,

    

  • the current through the circuit  is 0.4 A

  • the current through the circuit is 0.32 A

  • the voltage across 100 Ω  resistor is 102 V

  • the voltage across 50 Ω resistor is 10 V


212.

The impedence of a circuit, when a resistance R and an inductor of inductance L are connected in series in an AC circuit of frequency f, is

  • R + 2π2 f2 L2

  • R + 4π2 f2 L2

  • R2 + 4π2 f2 L2

  • R2 + 2π2 f2 L2


213.

In a series LCR circuit, resistance R = 10 Ω and the impedance Z = 10 Ω. The phase difference between the current and the voltage is

  • 30°

  • 45°

  • 60°


214.

A circuit consists of an inductance of 0.5 mH and a capacitor of 20 µF. The frequency of the LC oscillations is approximately

  • 400 Hz

  • 88 Hz

  • 1600 Hz

  • 2400 Hz


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215.

The maximum value of AC voltage in a circuit is 707 V. Its rms value is

  • 70.7 V

  • 100 V

  • 500 V

  • 707 V


216.

If an alternating voltage is represented as E = 141 sin (628 t), then the rms value of the voltage and the frequency are respectively

  • 141 V, 628 Hz

  • 100 V, 50 Hz

  • 100 V, 100 Hz

  • 141 V, 100 Hz


217.

A step-down transformer is used on a 1000 V line to deliver 20 A at 120 V at the secondary coil. If the efficiency of the transformer is 80%, the current drawn from the line is

  • 3 A

  • 30 A

  • 0.3 A

  • 2.4 A


218.

An alternating current of rms value 10 A is passed through a 12 Ω resistor. The maximum potential difference across the resistor is

  • 20 V

  • 90 V

  • 169.68 V

  • None of these


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219.

In the circuit shown below, the switch is kept in position a for a long time and is then thrown to position b. The amplitude of the resulting oscillating current is given by

        

  • EL/C

  • E / R

  • infinity

  • EC/L


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