प्रत्यावर्ती धारा — बार-बार पूछे जाने वाले प्रश्न
Last updated: 5 July 2026
Every RBSE Class 12 Physics board paper from 2013 to 2026 for Alternating Current, sorted and tagged so you know exactly which AC-generator, LCR-impedance and resonance questions to revise first.
Real previous-year questions with the exact RBSE board years they appeared in. 5 more high-yield questions — including transformer and power-factor numericals — are in the free PDF.
Draw a diagram of an AC generator and describe it. Derive an expression for the instantaneous value of the induced emf.
प्रत्यावर्ती धारा जनित्र का चित्र बनाकर वर्णन कीजिए। प्रेरित विद्युत वाहक बल के तात्क्षणिक मान के व्यंजक की व्युत्पत्ति कीजिए।
⭐ Core derivationProve that the average power supplied to an inductor over one complete cycle is zero. Also, for an LCR circuit with R = 24Ω, XL = 110Ω and XC = 110Ω, find the impedance of the circuit.
(A) सिद्ध कीजिए कि एक पूरे चक्र में प्रेरक को आपूर्त औसत शक्ति शून्य होती है। (B) यदि किसी LCR प्रत्यावर्ती धारा परिपथ में R = 24Ω, XL = 110Ω तथा XC = 110Ω हो तो परिपथ की प्रतिबाधा ज्ञात कीजिए।
⚙️ Core derivation + numericalDerive an expression for the impedance of a series LCR circuit connected to an alternating voltage source.
प्रत्यावर्ती वोल्टता स्रोत के साथ श्रेणीबद्ध LCR परिपथ की प्रतिबाधा का व्यंजक व्युत्पन्न कीजिए।
📌 Frequently examinedWhat is resonance? Determine the resonant frequency of a series L-C-R circuit and draw a graph showing the variation of current with angular frequency ω.
अनुनाद किसे कहते हैं? अनुनाद की स्थिति में श्रेणी L-C-R परिपथ की अनुनादी आवृत्ति ज्ञात कीजिए। कोणीय आवृत्ति ω के साथ धारा के परिवर्तन का आलेख खींचकर समझाइये।
⭐ High-weightageDescribe any two energy losses occurring in a transformer. How can these be minimized? Explain why electric power is transmitted at high voltage over large distances.
ट्रांसफार्मर में होने वाली कोई दो मुख्य ऊर्जा हानियों का उल्लेख कीजिए। इन्हें कैसे कम किया जा सकता है? लम्बी दूरियों तक विद्युत शक्ति का संचरण उच्च वोल्टता पर क्यों किया जाता है?
⚙️ Practical applicationThe other 5 are in the free PDF — and all 32 previous-year questions for this chapter are in the full book.
Get 10 hand-picked previous-year questions from Chapter 7. Every question includes the exam year, marks, and repeat count. Instant download—no signup required.
A quick map of the chapter before you download — so you know what the questions are testing.
If you have gone through the last decade of RBSE Class 12 Physics papers, you will notice Chapter 7 (Alternating Current) is tested every year without fail. It belongs to Unit IV — Electromagnetic Induction and Alternating Currents and is drawn from a pool of 32 previous-year questions spanning 2013–2026, spread across MCQs, very short, short and long-answer sections. The topics rotate, but the question patterns stay remarkably steady.
Expect 0.5 to 1-mark openers on rms/peak value relations and phase-angle basics. The 2 to 3-mark questions lean on transformer turns-ratio problems and power-factor calculations. The heavy marks sit in the 4-mark long answers, which rotate between deriving the AC generator's instantaneous emf, the impedance of a series LCR circuit, and resonance in an LCR circuit — this chapter has 32 questions in the full pool, so no single question repeats often, but these three derivations recur in some form nearly every year.
So the smart way to revise this chapter is not to read it end to end, but to practise the questions RBSE actually repeats. The five questions above — and the ten in the free sample PDF — are taken straight from real board papers and tagged with the exact years they appeared, so you can see for yourself what the full RBSE Physics chapterwise PYQ book offers before you decide to buy it.
The RBSE syllabus sub-topics this chapter's PYQs are drawn from — useful for scoping your revision even if you're not buying the full book.
"AC generator wala derivation free sample mein tha — poora chapter samajhna easy ho gaya."
"LCR impedance aur resonance wale questions bahut clearly tagged the, revision fast ho gaya."
"Year-wise tags dekh kar revision plan banana easy ho gaya. Poora 14-chapter book bhi le liya sirf ₹59 mein, paisa vasool."
The ₹59 full book unlocks all 32 tagged previous-year questions for Alternating Current — plus all 13 other chapters.
Every MCQ, VSA, SA and long-answer question for this chapter from RBSE papers 2013–2026 — 32 in total.
Each question labelled with year, marks and question type.
Highest-repeated questions listed first so revision time is spent well.
Full bilingual coverage — study in whichever medium you write your exam.
Quick-reference sheet of every alternating current formula — AC generator emf, impedance, resonant frequency and transformer formulas.
Updated to the latest RBSE board pattern, with access valid for the current 2026–27 exam session.
One booklet, every chapter, tagged and sorted by repeat priority — in English and Hindi.
See full book — ₹59 →