(1) P=I*E, where P=Power, in watts; I=Current in amps; and E=Voltage, in volts

(2) E=I*R, where R=Resistance, measured in ohms (omega)

(3) In a series circuit, total resistance RT = R1 + R2 + R3 + ...

(4) In a parallel circuit, 1/RT = 1/R1 + 1/R2 + 1/R3 + ...