Physics

Physics

Problem

A capacitor of 80 μF80\,\mu\text{F} is connected in series with an inductor across a 50 Hz50\,\text{Hz} a.c. mains supply. Calculate the inductance required so that the circuit is in resonance.
Intuitive explanation

At resonance in an LC circuit, the inductive and capacitive reactances cancel each other out perfectly, so the impedance is minimized and current is maximized. The key is setting XL=XCX_L = X_C—that is, ωL=1ωC\omega L = \frac{1}{\omega C}—then solving for the unknown inductance using the given frequency and capacitance. This resonance condition is independent of resistance and depends only on LL, CC, and ω\omega.

Intuitive explanation

At resonance in an LC circuit, the inductive and capacitive reactances cancel each other out perfectly, so the impedance is minimized and current is maximized. The key is setting XL=XCX_L = X_C—that is, ωL=1ωC\omega L = \frac{1}{\omega C}—then solving for the unknown inductance using the given frequency and capacitance. This resonance condition is independent of resistance and depends only on LL, CC, and ω\omega.

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