Question

If a capacitor of 8 $\mu$F is connected to a 220 V. 100 Hz ac source and the current passing through it is 65 mA, then the rms voltage across it is

• A. 129.4 V
• B. 12.94 V
• C. 1.294V
• D. 15V

Answer 1

The correct option is B 12.94 V

$I_{rms}=65mA=0.065A$
$C=8\mu F=8\times {10}^{-6}F,\nu =100Hz$

Capacitive reactance,
$X_C=\frac{1}{2\pi \nu C}$

$=\frac{1}{2\times 3.14\times 100\times 8\times {10}^{-6}}=199\Omega$

Then RMS voltage across the capacitor is:

$V_{rms}=I_{rms}{X}_C$

$=0.065\times 199$

$\Rightarrow 12.94V$