Ohm's Law

Ohm's Law is one of the most fundamental laws of electrotechnics. It describes the relationship betweenelectric voltage, electric current, and electrical resistance in an electrical circuit. This law allows us to calculate one of these quantities if we know the other two.

Basic equation

Ohm's Law is expressed by the equation:

where:

• is electric current
• is electrical voltage
• is electrical resistance

This equation states that electric current increases with increasing voltage and decreases with increasing resistance.

Equations adjustments

Ohm's Law can be adjusted depending on which quantity we need to calculate.

Voltage:

Resistance:

These relationships are used in calculations in electrical circuits.

Electrical resistance of a conductor

The resistance of a conductor depends on its material and geometric dimensions. The equation holds:

where:

• is the resistivity of the material
• is the length of the conductor
• is the cross-sectional area of the conductor

It follows:

• a longer conductor has a higher resistance
• a larger cross-sectional area has a lower resistance

Validity conditions

Ohm's Law applies to so-called ohmic conductors, where the relationship between voltage and current is linear.

It does not hold exactly for some electronic components, such as diodes or transistors.

Summary

Ohm's Law describes the fundamental relationship between voltage, current, and resistance:

It is one of the most important laws of electrotechnics and is used in the analysis and design of electrical circuits.