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Question: Answered & Verified by Expert
Which graph shows the correct variation of r.m.s. current ' $\mathrm{I}$ ' with frequency ' $\mathrm{f}$ ' of a.c. in case of (LCR) series resonance circuit?

PhysicsAlternating CurrentMHT CETMHT CET 2021 (23 Sep Shift 1)
Options:
  • A Q
  • B P
  • C R
  • D S
Solution:
1117 Upvotes Verified Answer
The correct answer is: S
In series, $\mathrm{Z}=\sqrt{\left(2 \pi \mathrm{fL}-\frac{1}{2 \pi \mathrm{fC}}\right)^2+\mathrm{R}^2}$
Current, $I=\frac{\mathrm{V}}{\sqrt{\left(2 \pi \mathrm{fL}-\frac{1}{2 \pi \mathrm{fC}}\right)^2+\mathrm{R}^2}}$
As frequency increases, current first increases and then decreases. Current is maximum at resonance when $\mathrm{X}_{\mathrm{L}}=\mathrm{X}_{\mathrm{C}}$

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