Question

An ac source of $50V$ (r.m.s value) is connected across a series $R-C$ circuit. If the r.m.s voltage across the resistor is $40V$ , then the r.m.s voltage across the capacitor is

• A. $10V$
• B. $20V$
• C. $30V$
• D. $40V$

Answer 1

Answer: (C)

For an R - C circuit
Applied voltage, $V=\sqrt{V_{R}^{2} + V_{C}^{2}}$ , where $V_{R}\&V_{C}$ represents voltage across resistance and voltage across capacitor.
$\therefore \, \, 50=\sqrt{\left(40\right)^{2} + V_{C}^{2}}$
$\Rightarrow \, \, V_{C}=30 \, V$