Ohm’s Law

Ohm’s Law is a simple mathematical law that shows how voltage, current and resistance are related.
It was discovered by Georg Simon Ohm in 1827, the three main equations given by Ohm’s Law are:

V = IR
I = V / R
R = V / I

Using Ohm’s Law it is possible to find the voltage, current and resistance in any circuit.

For example, a simple circuit containing one 9V battery and a resistor of 1kΩ it is possible to find the current through the resistor by using Ohm’s Law.
V = 9V
R = 1000Ω
I = 9V / 1000Ω = 9mA

It can also be used to find the resistance of the resistor or any other component.
V = 9V
I = 9mA
R = 9V / 9mA = 1000Ω

And the voltage drop over the resistor.
I = 9mA
R = 1000Ω
V = 9mA * 1000Ω = 9V