# Ohm's law

Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. The constant of proportionality is known as the resistance and the relationship can be expressed as:

$I = {U \over R}$,

where I is the current, U is the voltage an R the resistance.

Multiplying R on each side of the equation means this equation can also be written as:

$U = R \cdot I$,

which is probably how much people remember it.

## Example

Consider the following circuit:

consisting of a voltage source G1 (a battery or a power supply) of 1 V and a resistor R1 of 1 kΩ, the current I flowing through the circuit can be calculated as:

$I = {1.5 V \over 1 k\Omega} = {1.5 V \over 1 \cdot 10^3 \Omega} = 1.5 \cdot 10^{-3} A = 1.5 mA$