Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

Alternating Current question

2024 · 4 Apr · Shift 1 · Q67
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /JEE Main
  3. /Physics
  4. /Alternating Current
  5. /2024 · 4 Apr · Shift 1 · Q67

Alternating Current question

2024 · 4 Apr · Shift 1 · Q67

JEE MainPhysicsAlternating CurrentMCQ+4 / −1
In an ac circuit, the instantaneous current is zero, when the instantaneous voltage is maximum. In this case, the source may be connected to : A. pure inductor. B. pure capacitor. C. pure resistor. D. combination of an inductor and capacitor. Choose the correct answer from the options given below :
  1. A
    A, B and C only
  2. B
    A and B only
  3. C
    A, B and D only
  4. D
    B, C and D only
View written solutionFree

Correct answer: C

  1. Given condition

    The circuit is such that instantaneous current is zero when instantaneous voltage is maximum.

    Let v=V0sin⁡ωt.v = V_0 \sin \omega t.v=V0​sinωt. Then voltage is maximum when sin⁡ωt=1⇒ωt=π2.\sin \omega t = 1 \quad \Rightarrow \quad \omega t = \frac{\pi}{2}.sinωt=1⇒ωt=2π​.

    At this instant, we need i=0.i=0.i=0.

  2. Check each circuit element


    (A) Pure inductor

    For a pure inductor, current lags voltage by 90∘90^\circ90∘: i=I0sin⁡(ωt−π2)=−I0cos⁡ωt.i = I_0 \sin\left(\omega t - \frac{\pi}{2}\right)= -I_0\cos\omega t.i=I0​sin(ωt−2π​)=−I0​cosωt. At ωt=π2\omega t=\frac{\pi}{2}ωt=2π​, i=−I0cos⁡π2=0.i = -I_0 \cos \frac{\pi}{2} = 0.i=−I0​cos2π​=0. So, pure inductor satisfies the condition.


    (B) Pure capacitor

    For a pure capacitor, current leads voltage by 90∘90^\circ90∘: i=I0sin⁡(ωt+π2)=I0cos⁡ωt.i = I_0 \sin\left(\omega t + \frac{\pi}{2}\right)= I_0\cos\omega t.i=I0​sin(ωt+2π​)=I0​cosωt. At ωt=π2\omega t=\frac{\pi}{2}ωt=2π​, i=I0cos⁡π2=0.i = I_0 \cos \frac{\pi}{2} = 0.i=I0​cos2π​=0. So, pure capacitor also satisfies the condition.


    (C) Pure resistor

    For a pure resistor, current and voltage are in phase: i=I0sin⁡ωt.i = I_0 \sin \omega t.i=I0​sinωt. At ωt=π2\omega t=\frac{\pi}{2}ωt=2π​, i=I0sin⁡π2=I0≠0.i = I_0 \sin \frac{\pi}{2} = I_0 \neq 0.i=I0​sin2π​=I0​=0. So, pure resistor does not satisfy the condition.


    (D) Combination of inductor and capacitor

    For a circuit containing only LLL and CCC, the phase difference can be ±90∘\pm 90^\circ±90∘ depending on whether it behaves net inductive or net capacitive.

    In such a case, current can be zero when voltage is maximum, just like in purely reactive circuits.

    Hence, a combination of inductor and capacitor can satisfy the condition.

  3. Conclusion

    Correct statements are: A, B, DA,\ B,\ DA, B, D but not CCC.

  4. Match with given options

    Option listing A,BA, BA,B and DDD only is: C\boxed{\text{C}}C​

  5. Comparison with stored answer

    Stored correct answer = C.

    My derived answer also = C.

PreviousNext

More from Alternating Current

  • A alternating current at any instant is given by i=[6+56​sin(100πt+π/3)] A. The rms value of the current is ​ A.2024 · Numerical
  • Match List I with List II Choose the correct answer from the options given below: Includes table Includes diagram2024 · MCQ
  • An alternating voltage of amplitude 40 V and frequency 4 kHz is applied directly across the capacitor of 12μF. The maximum displacement current between the plates of the capacitor is nearly :2024 · MCQ
  • An ac source is connected in given series LCR circuit. The rms potential difference across the capacitor of 20μF is ​ V. Includes diagram2024 · Numerical
  • A series LCR circuit is subjected to an ac signal of 200 V,50 Hz. If the voltage across the inductor (L=10 mH) is 31.4 V, then the current in this circuit is…2024 · MCQ
  • Given below are two statements : Statement I : In an LCR series circuit, current is maximum at resonance. Statement II : Current in a purely resistive circuit can never be less than that in a series LCR circuit when connected to same…2024 · MCQ
  • When a dc voltage of 100 V is applied to an inductor, a dc current of 5 A flows through it. When an ac voltage of 200 V peak value is connected to inductor, its inductive reactance is found to be 203​Ω…2024 · Numerical
  • For 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 200Ω and 100 mH inductor is being used in the given circuit. The…2024 · Numerical