| 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 = I2R | 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 | RT = R1 + R2 + R3 + ... + Rn | R = resistance |
| Resistance in a DC parallel circuit |  |
R = resistance |
| Capacitance in a DC series circuit |  |
C = capacitance |
| Capacitance in a DC parallel circuit | CT = C1 + C2 + C3 + ... + Cn | C = capacitance |
| Inductance in a DC series circuit | LT = L1 + L2 + L3 + ... + Ln | 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 (XC = XL) |  |
fR = 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) |