Alternating Current - Result Question 29
30. A capacitor has capacity $C$ and reactance $X$. If capacitance and frequency become double, then reactance will be
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Answer:
Correct Answer: 30. (c)
Solution:
(c) Capacitive reactance, $X=\frac{1}{\omega C}=\frac{1}{2 \pi f C}$
$\Rightarrow X \propto \frac{1}{f C}$
$\therefore \frac{X^{\prime}}{X}=\frac{f}{f^{\prime}} \times \frac{C}{C^{\prime}}=\frac{f}{2 f} \times \frac{C}{2 C}=\frac{1}{4}$
$\Rightarrow X^{\prime}=\frac{X}{4}$
(d) Quality factor
$=\underline{\text{ Potential drop across capacitor or inductor }}$
Potential drop across R
$=\frac{I \omega L}{I R}=\frac{\omega L}{R}$
