## 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, <math>I = \frac{V}{R}</math>

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:

<math>I = \frac{V}{Z}</math>

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