Question

From figure shown below a series L – C – R circuit connected to a variable frequency 200 V source. L = 5H, C = 80$\mu$ F and R = 40$\Omega$. Then the source frequency which drive the circuit at resonance is

• A. $25Hz$
• B. $\frac{25}{\pi }Hz$
• C. $50Hz$
• D. $\frac{50}{\pi }Hz$

Answer 1

The correct option is B $\frac{25}{\pi }Hz$

$f=\frac{1}{2\pi \sqrt{LC}}=\frac{1}{2\pi \sqrt{5\times 80\times {10}^{-5}}}$
$\Rightarrow f=\frac{25}{\pi }Hz$