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Alternating Currents — Revision Notes

Telangana Open School (TOSS) · Class 12 · Physics

Alternating Currents revision notes for Telangana Open School (TOSS) Class 12 Physics: 4 topics in quick points.

51 questions30 flashcards17 formulas & key relations5 concepts

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Key Topics to Revise

1

Alternating Current and Voltage

  • AC voltage and current vary sinusoidally with time.
  • General equations: \( V = V_m \cos \omega t \) and \( I = I_m \cos \omega t \).
  • Peak values: \( V_m \) and \( I_m \) are maximum voltage and current.
2

AC in Resistive, Inductive, and Capacitive Circuits

  • In a pure resistor, voltage and current are in phase (phase difference = 0).
  • In a pure inductor, current lags voltage by \( 90^\circ \) or \( \pi/2 \) radians.
  • In a pure capacitor, current leads voltage by \( 90^\circ \) or \( \pi/2 \) radians.
3

Series LCR Circuit and Resonance

  • In a series LCR circuit, impedance \( Z = \sqrt{R^2 + (X_L - X_C)^2} \).
  • Current \( I_{\text{rms}} = \frac{V_{\text{rms}}}{Z} \).
  • Phase angle \( \phi \) is given by \( \tan\phi = \frac{X_L - X_C}{R} \).
4

Power in AC Circuits and Transformers

  • Average power \( P_{\text{av}} = V_{\text{rms}} I_{\text{rms}} \cos\phi \).
  • Power factor \( \cos\phi = \frac{R}{Z} \), ranges from 0 to 1.
  • In pure resistor, power factor = 1; in pure L or C, power factor = 0.

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Full Notes

Key Concepts

AC voltage and current vary sinusoidallyPhasors are rotating vectors usedCapacitive reactance $ X_C = 1/(\omegaAverage power in an AC circuitTransformers change AC voltage levels using

Frequently Asked Questions

What are the important topics in Alternating Currents for Telangana Open School (TOSS) Class 12 Physics?
Key topics in Alternating Currents include Alternating Current and Voltage, AC in Resistive, Inductive, and Capacitive Circuits, Series LCR Circuit and Resonance, Power in AC Circuits and Transformers. Study these first, then practise questions on each for the Telangana Open School (TOSS) Class 12 board exam.
How should I revise Alternating Currents for the Telangana Open School (TOSS) Class 12 board exam?
Learn the core ideas first, then work through the 51 practice questions on Alternating Currents. Revise definitions regularly and use flashcards for quick recall 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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All Telangana Open School (TOSS) Class 12 Physics Revision Notes

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