Alternating Currents

AC voltage and current vary sinusoidally

AC voltage and current vary sinusoidally with time and are expressed as $ V = V_m \cos \omega t $ and $ I = I_m \cos \omega t $. The peak values are $

Phasors are rotating vectors used

Phasors are rotating vectors used to represent AC quantities. The vertical component of a phasor gives the instantaneous value of voltage or current.

Capacitive reactance $ X_C = 1/(\omega

Capacitive reactance $ X_C = 1/(\omega C) $ and inductive reactance $ X_L = \omega L $ oppose AC flow like resistance but depend on frequency. In a se

Average power in an AC circuit

Average power in an AC circuit is $ P_{\text{av}} = V_{\text{rms}} I_{\text{rms}} \cos \phi $, where $ \cos \phi $ is the power factor. In pure induct

Transformers change AC voltage levels using

Transformers change AC voltage levels using electromagnetic induction. A step-up transformer increases voltage (decreases current), while a step-down