COMEDK202510 May 2025Morning ShiftPhysicsAlternating CurrentActual
An LCR series ac circuit is at resonance with 10 V each across L , C and R. If the resistance is halved, the respective voltage across R , C and L are
Options
- A5 ~V , 5 ~V , 5 ~V
- B10 ~V , 5 ~V , 5 ~V
- C10 ~V , 20 ~V , 20 ~V
- D5 ~V , 10 ~V , 10 ~V
Correct answer
C. 10 ~V , 20 ~V , 20 ~V
Step-by-step solution
In an LCR series circuit at resonance, the inductive reactance X_L is equal to the capacitive reactance X_C , and the impedance Z is equal to the resistance R . Given that the voltage across each component is V_R = V_L = V_C = 10 V , the current in the circuit is I = V_R R = 10 R . Since V_L = I X_L = 10 V and V_C = I X_C = 10 V , we have X_L = X_C = R . When the resistance is halved, the new resistance becomes R' = R 2 . The reactances X_L and X_C remain unchanged because the frequency of the source is constant. T