Formula & Equations for Ohm’s, Kirchhoff’s & Coulomb’s Laws

Electrical Technology

Ohm’s Law, Kirchhoff’s Laws (KVL & KCL ) & Coulombs Laws Formulas & Equations

Table of Contents

Ohm’s Law Formulas

Ohm’s law shows the relationship between current “I” & the voltage “V” where the resistance “R” is a constant in an electrical circuit.

Ohm’s Law in DC Circuits

I = V/R For current calculation
V = IR For voltage calculation
R = V/I For resistance calculation

Ohm’s Law in AC Circuits

I = V/Z For current calculation
V = IZ For voltage calculation
Z = V/I For impedance calculation

Where

I = Current in Amperes (A)
V = Voltage in Volts (V)
R = Resistance in Ohms (Ω)
Z = Impedance in Ohms (Ω)

Kirchhoff’s Current Law – KCL

Summation of all currents entering a node or junction is 0. Or the sum of entering and leaving currents at a point is zero. In other words, the current entering at a point is equal to the current leaving that point.

∑I_Entering = ∑I_Leaving

∑I = 0

Current entering the node is denoted with positive sign (+).
Current leaving the node is written with a negative sign (-).

Kirchhoff’s Voltage Law – KVL

Summation of all potential differences in a circuit loop is 0. The product of I “Current” and R “Resistance” in a closed path (also known as mesh) located in a network is equal to the applied EMF.