Q.
Two identical incandescent light bulbs are connected as shown in the figure. When the circuit is an AC voltage source of frequency $f,$ which of the following observations will be correct?
A) Both bulbs will glow alternatively
B) Both bulbs will glow with same brightness provided frequency $f = \frac{1}{2\pi}\sqrt{(1/LC)}$
C) Bulb $b_{1}$ will light up initially and goes off, bulb $b_{2}$ will be ON constantly
D) Bulb $b_{1}$ will blink and bulb $b_{2}$ will be ON constantly
Explanation
(b) At resonance both bulbs will glow with same brightness. At resonance,
$X_{L} = X_{C}$
Or $2\pi fL = \frac{1}{2\pi fC}\ $
Or $f = \frac{1}{2\pi\sqrt{LC}}\ $
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.