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Question #43320
The Question
An AC voltage source (where is in volts and is in seconds) is connected in series with a resistor and a parallel LC tank circuit. The LC tank consists of an ideal inductor and an ideal capacitor connected in parallel. In steady state, the total electromagnetic energy stored in the LC tank fluctuates. Calculate the maximum net work done on the LC tank by the rest of the circuit during any time interval of length (which corresponds to one quarter cycle of the driven AC voltage).
Options
- A.
- B.
- C.
- D.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Intuition_Breaker
Train your brain to resist "obvious" answers that are designed to deceive your intuition.
Concepts Behind This Question
LC Circuit Oscillations|Phasor Rotation Convention|Frequency Sensitivity of Z
Why This Question Is Tricky
Common Mistakes
The question tests the student's ability to analyze forced oscillations in an AC circuit, specifically distinguishing between the natural frequency of an LC tank () and the driven frequency ().
A common trap is assuming the LC circuit resonates at its natural frequency regardless of the source, leading to the incorrect conclusion that the energy is constant ( work done).
Another trap is calculating the maximum energy of the capacitor () but forgetting that the inductor holds a minimum non-zero energy () at the exact moment the capacitor is empty, because the driven frequency forces an unequal reactance balance.
This requires applying phasor rotation to find the true steady-state voltage and using the work-energy theorem to equate the work done against conservative forces to the net change in the tank's electromagnetic energy.
Quick Facts About This Question
Question Information
| Subject | Physics |
| Chapter | Electromagnetic Induction - Class 12 |
| Concept | LC Circuit Oscillations |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |