R, C & L in A.C. Circuits

Here are some general formulae for working out values in an A.C. circuit:

Resistors:

Resistors are exactly the same as in D.C. circuits

I = V / R           P = I²R

Capacitors:

I = V / X_C

X_C is the capacitive reactance = 1 / (2pfC)
f is the frequency, C is the capacitance
(Remember Voltage lags Current by 90^o)

Inductors:

I = V / X_L

X_L is the inductive reactance = 2pfL
f is the frequency, L is the inductance
(Remember Voltage leads Current by 90^o)