Question

A resistor $R$, an inductor $L$ and a capacitor $C$ are connected in series to an oscillator of frequency $n$. If the resonant frequency is $n_{r}$, then the current lags behind voltage when

• A. $n = 0$
• B. $n < n_{r}$
• C. $n = n_{r}$
• D. $n > n_{r}$

Answer 1

Answer: (D)

The current will lag behind the voltage when reactance of inductance is more than the reactance of condenser.
Thus, $\omega L > \frac{1}{\omega C}$ or $\omega > \frac{1}{\sqrt{L C}}$
or $n > \frac{1}{2 \pi \sqrt{L C}}$ or $n > n_{r}$, where $n_{r}=$ resonant frequency