Alternating Current
Gujarat Board · Class 12 · Physics
Quick revision notes for Alternating Current — Gujarat Board Class 12 Physics. Key concepts, formulas, and definitions for last-minute revision.
Key Topics to Revise
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)
Phasor Representation
- Phasors are rotating vectors representing AC quantities
- Magnitude of phasor = amplitude of AC quantity
- Vertical projection gives instantaneous value
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
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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Sources & Official References
Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.
Previous Chapter
Semiconductor Electronics: Materials, Devices and Simple Circuits
Next Chapter
Electromagnetic Waves
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