Alternating Current
ICSE · Class 12 · Physics
All formulas from Alternating Current in ICSE Class 12 Physics. Key equations, constants, and identities for board exam preparation.
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1) Core Ideas and Waveforms
I = I0 sin ωt
V = V0 sin ωt
V0 = NBAω
T = 2π/ω
f = ω/(2π) = 1/T
2) Mean Value and RMS Value
Im = (2/π)I0 = 0.637 I0
Irms = I0/√2 = 0.707 I0
Vrms = V0/√2 = 0.707 V0
Im = 0
Irms for i = a + b sin ωt = √(a^2 + b^2/2)
3) Phasors and Phase Relations
tan φ = (XL − XC)/R = (ωL − 1/ωC)/R
In pure resistor, current is in phase with voltage
In pure inductor, current lags voltage by 90°
In pure capacitor, current leads voltage by 90°
4) Reactance, Impedance and Resonance
XL = ωL = 2πfL
XC = 1/ωC = 1/(2πfC)
Z = √(R^2 + (XL − XC)^2)
f0 = (1/2π)√(1/LC)
Q = (1/R)√(L/C)
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