Class 12 Physics — Chapter 7: Alternating Current
90 practice questions · 30 Easy · 30 Medium · 30 Hard
Practise Class 12 Physics Chapter 7, "Alternating Current", with 90 NCERT-aligned multiple-choice questions. The set is split into 30 Easy, 30 Medium and 30 Hard questions, so you can warm up on the fundamentals and then push into the exam-level problems that separate top scorers in CBSE Board exams, JEE Main, JEE Advanced and NEET UG.
"Alternating Current" is one of the chapters where numerical problem-solving, derivations and conceptual application really pays off. Each MCQ on this chapter is timed and uses exam-grade marking (+2 correct, −1 wrong, 0 skipped), training the same accuracy-under-pressure that real papers demand. Every question carries a short explanation, so a wrong answer becomes a quick lesson rather than a dead end — the fastest way to close gaps before a test.
Use this chapter as targeted revision: attempt the Easy set first to confirm your basics on Alternating Current, then move to Medium and Hard to test application and problem-solving. Your accuracy, streaks and XP save automatically, and the chapter feeds into your overall Class 12 Physics mastery score. A few sample questions are shown below; sign in free to practise all 90.
Key concepts: Alternating Current (Class 12 Physics)
This chapter covers alternating current, RMS values, reactance and impedance, series LCR circuits, resonance, power, and the transformer.
- AC and RMS values
- AC varies sinusoidally; the RMS value is the effective value, e.g. I_rms = I₀/√2.
- Reactance
- Inductive reactance X_L = ωL (rises with frequency); capacitive reactance X_C = 1/ωC (falls with frequency).
- Impedance in LCR
- Total opposition Z = √[R² + (X_L − X_C)²]; current lags or leads voltage depending on the net reactance.
- Resonance
- At resonance X_L = X_C, so Z is minimum (= R) and current is maximum; resonant frequency ω = 1/√(LC).
- Power & transformer
- Average power = V_rms I_rms cosφ (cosφ is the power factor); a transformer changes voltage via the turns ratio with V/N constant.
Key formulas — Alternating Current
💡 Exam tips for Alternating Current
- At resonance the circuit is purely resistive (X_L = X_C), giving maximum current.
- Power is consumed only in the resistor; pure L or C consumes zero average power (power factor 0).
Sample questions
Vrms = Vpeak ÷
Vrms = V₀/√2.
Impedance of pure inductor:
X_L = ωL.
Average power in AC: P =
cosφ = power factor.
Alternating Current — FAQs
What are the key concepts in Class 12 Physics Alternating Current?+
This chapter covers alternating current, RMS values, reactance and impedance, series LCR circuits, resonance, power, and the transformer. Key ideas include AC and RMS values, Reactance, Impedance in LCR, Resonance, Power & transformer.
What does Class 12 Physics Chapter 7 (Alternating Current) cover on XamBaaz?+
It covers 90 NCERT-aligned MCQs on "Alternating Current" — 30 Easy, 30 Medium and 30 Hard — each with a timed quiz and an instant explanation, suitable for CBSE Board exams, JEE Main, JEE Advanced and NEET UG.
Are these "Alternating Current" questions free to practise?+
Yes — sign in with Google to practise "Alternating Current" free. Full unlimited access is ₹999/year (limited-time launch price), with no per-chapter charges.
How should I revise "Alternating Current" for the exam?+
Start with the Easy quiz to confirm your fundamentals, then attempt Medium and Hard for application-level practice. Review each explanation, retry the questions you miss, and track your accuracy on this chapter until it is consistently high.
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