Ohm's Law

relationship between current and electrical resistance

ohm resistenza simbolo omega

Among the strength ( R ) of the current ( I ) and the tension ( V ) there is a simple relationship:


Resistance (R) x Current (I) = Volatage (V)


Since knowing two of these magnitudes we can simply get the third one.

I = V / R or inversely R = V / I

Also electric power ( P ) can be calculated as:

P = V x I or P = R x I x I

or by concluding the expression:

P = R x I ²

That is, the resistance is directly proportional to the power and square of the current.

joule electric resistance effect

Joule Effect

When an electric current circuit creates a resistance to current passage, it results in an increase in its temperature.

This property is exploited to create resistors used in various electrical equipment to heat up.

An example of these applications are ironing irons, ovens, heat fans, phoners, etc ..


Single-phase and three-phase electrical system


Neutral cable and phase cable


Alternating current and appliances




A voltage generator


Electrical circuit

Portaombrelli design Luca Perlini

Share your experence