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Alternating Current · Question 5

JEE Main 2026 (Online) 2nd April Evening ShiftMCQMedium📈 Topic in 13% papers+4−1
1

The figure given below shows an LCR series circuit with two switches S1 and S2. When switch S1 is closed keeping S2 open, the phase difference ( ) between the current and source voltage is 30° and phase difference is 60° when S2 is closed keeping S1 open. The value of (3L1-L2) is H. [figure]

  1. 92
  2. 29
  3. 13
  4. 3

Answer

(2) 29

Solution

From the figure, S1 is across L2 and S2 is across L1; a closed switch shorts that inductor.

= 300 rad/s, XC = 1 C = 1300 100 10-6 = 1003 Ω

S1 closed (only L1 in circuit): 30° = L1 - XCR … (i)

S2 closed (only L2 in circuit): 60° = L2 - XCR … (ii)

(ii) ÷ (i): L2 - XC L1 - XC = 31/ 3 = 3

⇒ L2 - XC = 3 L1 - 3XC

⇒ (3L1 - L2) = 2XC

⇒ 3L1 - L2 = 2XC = 2 100/3300 = 29 H

Answer: (2)

JEE Main 2026 (Online) 2nd April Evening Shift

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