Name  Formula  Notes 

Ohm's Law  E = IR  E = voltage (in volts) I = current (in amps) R = resistance (in ohms) 
Watt's Law  P = IE  P = power (in watts) I = current (in amps) E = voltage (in volts) 
Joule's Law  P = I^{2}R  P = power (in watts) I = current (in amps) R = resistance (in ohms) 
Twelve formulas can be derived from the preceding laws, as shown here:
Name  Formula  Notes 

Resistance in a DC series circuit  R_{T} = R_{1} + R_{2} + R_{3} + ... + R_{n}  R = resistance 
Resistance in a DC parallel circuit  R = resistance  
Capacitance in a DC series circuit  C = capacitance  
Capacitance in a DC parallel circuit  C_{T} = C_{1} + C_{2} + C_{3} + ... + C_{n}  C = capacitance 
Inductance in a DC series circuit  L_{T} = L_{1} + L_{2} + L_{3} + ... + L_{n}  L = inductance 
Inductance in a DC parallel circuit  L = inductance  
Capacitive reactance  f = frequency (in hertz) C = capacitance (in farads) 

Inductive reactance  f = frequency (in hertz) L = inductance (in henries) 

Resonance (X_{C} = X_{L})  f_{R} = resonant frequency (in hertz) L = inductance (in henries) C = capacitance (in farads) 

Admittance (reciprocal of impedance)  Y = admittance (in mhos) R = resistance (in ohms) X = reactance (in ohms) 

Susceptance (reciprocal of reactance)  B = susceptance (in mhos) X = reactance (in ohms) R = resitance in ohms) 

Conductance (reciprocal of resistance)  G = conductance (in mhos) R = resistance (in ohms) 

Impedance (reciprocal of admittance)  parallel circuit 
or  Z = impedance (in ohms) G = conductance (in mhos) B = susceptance (in mhos) 
Impedance (reciprocal of admittance)  series circuit 
Z = impedance (in ohms) R = resistance (in ohms) X = reactance (in ohms) 

Frequency  f = frequency (in hertz) λ = wavelength (in meters) 

Wavelength  f = frequency (in hertz) λ = wavelength (in meters) 