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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceDiagram basedMediumMulti-step

JEE Main 26 February 2021, Shift 2, Physics Q18

Question 18 of 90 in this shift, Physics question 18 of 30, Section A.

Find the peak current and resonant frequency of the following circuit (as shown in figure).

The figure, in words

Rectangular series circuit. Top side: an inductor labelled 100 mH followed by a capacitor labelled 100 µF. Left side: an AC source symbol labelled V = 30 sin 100t. Bottom side: a resistor labelled 120 Ω.
  1. (1)2 A and 50 Hz
  2. (2)0.2 A and 50 HzOfficial answer
  3. (3)2 A and 100 Hz
  4. (4)0.2 A and 100 Hz

Official answer

Option 2

NTA final key.

Chapter
Alternating Current
Topic
LCR Resonance
Idea tested
Resonant Frequency Calculation

Same idea in other shifts

Asked 9× in all
  1. 5 Apr 2026, Shift 2 · Q48A series LCR circuit with R=20 ΩR=20\ \Omega, L=1.6L=1.6 H and C=40 μFC=40\ \mu\mathrm{F} is connected to a variable frequency a.c. source. The…EasyNumerical value
  2. 6 Apr 2024, Shift 2 · Q59For a given series LCR circuit it is found that maximum current is drawn when value of variable capacitance is 2.5 nF. If resistance of…EasyNumerical value
  3. 1 Feb 2024, Shift 1 · Q43In series LCR circuit, the capacitance is changed from C to 4C. To keep the resonance frequency unchanged, the new inductance should be :EasySingle correct
  4. 25 Jul 2022, Shift 1 · Q42To increase the resonant frequency in series LCR circuit,EasySingle correct
  5. 28 Jun 2022, Shift 1 · Q60A telegraph line of length 100 km has a capacity of 0.01 μ\muF/km and it carries an alternating current at 0.5 kilo cycle per second. If…EasyNumerical value
  6. 29 Jun 2022, Shift 2 · Q60An inductor of 0.5 mH, a capacitor of 200 μF and a resistor of 2 Ω are connected in series with a 220 VV ac source. If the current is in…EasyNumerical value
  7. 25 Feb 2021, Shift 1 · Q27A transmitting station releases waves of wavelength 960 m. A capacitor of 2.56 μ2.56\ \muF is used in the resonant circuit. The self…EasyNumerical value
  8. 25 Jul 2021, Shift 2 · Q25Two circuits are shown in the figure (a) & (b). At a frequency of __________ rad/s the average power dissipated in one cycle will be same…MediumNumerical valueHas a figure

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.