Question

In a series L-R circuit (L = 35 mH and R = 11 $\Omega$), a variable emf source ($V=V_{0}sin\omega t)$ of $V_{rms}$ = 220 V and frequency 50 Hz is applied. The current amplitude in the circuit is

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

Answer 1

The correct option is B 20 A

$X_L=\omega L=(2\pi \times 50)(35\times {10}^{-3})=11\Omega$

$\therefore ImpedanceZ=\sqrt{R^2+X_L^2};Z=\sqrt{(11{)}^2+(11{)}^2}=11\sqrt{2}\Omega$

$\therefore I_0=\frac{V_0}{Z}=\frac{V_{rms}\times \sqrt{2}}{11\sqrt{2}}=\frac{220}{11}=20A$