Alternating Current

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Alternating current (AC) is current that changes direction periodically with time, varying like a sine function. Unlike DC which flows in one direction only, AC current reverses direction every half c

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RMS value is the effective value of AC current that produces the same heating effect as DC current. For current: I = im/√2 = 0.707 im, where im is peak current. Similarly, for voltage: V = vm/√2 = 0.7

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Current through resistor: i = im sin ωt, where im = vm/R. The current is IN PHASE with voltage (phase difference = 0°). Both voltage and current reach maximum, minimum, and zero values at the same tim

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Inductive reactance (XL) is the opposition offered by an inductor to AC current. Formula: XL = ωL = 2πfL, where ω is angular frequency, f is frequency, and L is inductance. Unit: Ohm (Ω). XL increases

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In a pure inductor, current LAGS voltage by π/2 (90°). Current expression: i = im sin(ωt - π/2), where im = vm/XL. The current reaches maximum value one-quarter cycle (T/4) after voltage reaches maxim

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Capacitive reactance (XC) is the opposition offered by a capacitor to AC current. Formula: XC = 1/(ωC) = 1/(2πfC), where C is capacitance. Unit: Ohm (Ω). XC is INVERSELY proportional to frequency and

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In a pure capacitor, current LEADS voltage by π/2 (90°). Current expression: i = im sin(ωt + π/2), where im = vm/XC. The current reaches maximum value one-quarter cycle (T/4) before voltage reaches ma

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A phasor is a rotating vector that represents AC quantities (voltage/current). It rotates with angular velocity ω. The magnitude represents amplitude, and the vertical projection gives instantaneous v