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Revision Notes

Alternating Current

Kerala Board · Class 12 · Physics

Quick revision notes for Alternating Current — Kerala Board Class 12 Physics. Key concepts, formulas, and definitions for last-minute revision.

45 questions22 flashcards5 concepts

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A graph showing the instantaneous voltage and current waveforms in a purely resistive AC circuit, demonstrating that they are in phase with each other.
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Key Topics to Revise

1

Introduction to AC and AC through Resistor

  • AC voltage varies sinusoidally: v = vm sin ωt, where vm is peak voltage and ω is angular frequency
  • In a purely resistive circuit, current and voltage are in phase (φ = 0°)
  • Current through resistor: i = im sin ωt, where im = vm/R (Ohm's law applies)
2

Phasor Representation

  • Phasors are rotating vectors representing AC quantities
  • Magnitude of phasor = amplitude of AC quantity
  • Vertical projection gives instantaneous value
3

AC through Inductor

  • In pure inductor, current lags voltage by π/2 (90°)
  • Inductive reactance XL = ωL opposes current flow
  • XL increases with frequency and inductance
4

AC through Capacitor

  • In pure capacitor, current leads voltage by π/2 (90°)
  • Capacitive reactance XC = 1/(ωC) opposes current flow
  • XC decreases with increase in frequency and capacitance

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Full Notes

Key Concepts

AC voltage varies sinusoidally as vWhen AC voltage is appliedIn a pure inductorIn a pure capacitorPhasors are rotating vectors that represent

Frequently Asked Questions

What are the important topics in Alternating Current for Kerala Board Class 12 Physics?
Alternating Current covers several key topics that are frequently asked in Kerala Board Class 12 board exams. Focus on the core concepts listed on this page and practise related questions to build confidence.
How to score full marks in Alternating Current — Kerala Board Class 12 Physics?
Start by understanding all key concepts. Practise previous year questions from this chapter. Revise formulas and definitions regularly. Use flashcards for quick revision before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

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