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Question
The selectivity of a series LCR a.c. circuit is large, when ______.
Options
L is large and R is large.
L is small and R is small.
L is large and R is small.
L = R
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Solution
The selectivity of a series LCR a.c. circuit is large, when L is large and R is small.
Explanation:
Selectivity of a circuit depends on the quality of resonance. The quality factor is given by:
Q = `(w_0 L)/R`
A high value of the quality factor ensures that the resonance curve is sharp. The sharper the resonance curve, the more selective the LCR circuit is. Thus, the selectivity of the LCR circuit is large when L is large and R is small. Hence, the L is large, and R is small.
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