# Ohm’s Law: Everything You Need to Know

## What is it?

Ohm’s Law is named after Georg Ohm, a German physicist who postulated it in 1827. His treatise described measurements of voltage and current in simple circuits, using various lengths of wire as resistors. The following diagram shows a voltage source V passing through a resistor R creating a current I

The following diagram shows a current source I through a resistor R, causing a potential drip (voltage V)

Ohm’s Law states that the current that passes between two points on a conductor is directly proportional to the potential difference (voltage) between the points and inversely proportional to the resistance of the conductor between the points.

so, $I = \frac{V}{R}$

where

“I” is the current in amperes,
” V” is the potential difference between the ends of the resistor in volts, and
“R” is the resistance of the resistor, measured in ohms

Ohms Law can also be used in impedance (resistance to AC) calculations thus:

$I = \frac{V}{Z}$

where

“I” is the current in amperes,
” V” is the potential difference between the ends of the resistor in volts, and
“Z” is the Impedance (AC resistance) of the resistor, measured in ohms