Q126 / 180 · AIIMS 2007 · Physics

Assertion : No power loss associated with pure capacitor in ac circuit. Reason : No current is flowing in this circuit.

  • A
    If both assertion and reason are true and reason is the correct explanation of assertion
  • B
    If both assertion and reason are true but reason is not the correct explanation of assertion
  • Correct answer
    C
    If assertion is true but reason is false
  • D
    If both assertion and reason are false.

Solution

Assertion is true. When a capacitor is connected to an a.c. circuit, \(\varepsilon_{r m s}=i_{r m s}\left(\frac{1}{C \omega}\right)\) where \(\frac{1}{C \omega}\) is the impedance due to capacitative resistance. The power consumed in this circuit is zero because the phase difference \(\phi\) between \(\mathrm{emf}\) and current in a pure capacitance a.c. circuit is \(\frac{\pi}{2}\). Power factor \(\cos \phi=0\). It is only for d.c. that a current does not flow. Reason is false.

Hence, the correct answer is option: 'C'.

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