# Ohm's Law and resistor calculation

Despription of the Ohm's Law definition and resistor calculation

## Ohm's Law

The Ohm's Law defines one of the most important rules for calculating electrical circuits.

In its original form, it determines the resistance in ohms from a current and voltage
measurement when \(U\) in volts and \(I\) in amps are known

\(\displaystyle R=\frac{U}{I}\) \(\displaystyle 1Ω=\frac{1V}{1A}\)

Calculation of current \(I\), if \(U\) in volts and \(R\) in ohms are known

\(\displaystyle I=\frac{U}{R}\) \(\displaystyle 1A=\frac{1V}{1Ω}\)

Calculation of the voltage \(U\), if \(I\) in amperes and \(R\) n ohms are known

\(\displaystyle U=I· R\) \(\displaystyle 1V = 1A· 1Ω\)

Example

Calculation of the resistance of a load at \(230\) volts a current of \(4.5\) amperes

\(U=230V\)

\(I=4.5A\)

\(\displaystyle R=\frac{U}{I}=\frac{230}{4.5}=51.1Ω\)