Resistor and Conductance

Understand resistance and conductance, their formulas, and units

Overview

An electrical load provides resistance to the current in a circuit. The current is dependent on the applied voltage and the total resistance.

Core idea:

Higher resistance means less current for the same voltage.

Definition of Resistance

The resistance of a load is greater when the current is lower at a given voltage. The symbol for resistance is \(R\).

Definition:

Resistance is voltage divided by current.

\(\displaystyle R = \frac{U}{I}\)
Symbols and units
  • \(R\) = resistance
  • \(U\) = voltage
  • \(I\) = current
  • Unit: \(\Omega\) (ohm)

By definition, \(R = 1\,\Omega\) when \(U = 1\,\text{V}\) and \(I = 1\,\text{A}\).

\(\displaystyle 1\,\Omega = \frac{1\,\text{V}}{1\,\text{A}}\)

Definition of Conductance

The greater the resistance of a load, the lower its ability to conduct electricity. This ability is called conductance with symbol \(G\), measured in Siemens (\(S\)).

Key relationship:

Conductance is the reciprocal of resistance.

\(\displaystyle G = \frac{1}{R}\)     and     \(\displaystyle R = \frac{1}{G}\)

Starting from \(R = \frac{U}{I}\), we can derive the conductance definition:

\(\displaystyle G = \frac{I}{U}\)

Practice

Use the calculator below to quickly compute resistance, voltage, or current (Ohm’s law).

Ohm's law online calculator →


Resistor and Conductance
Ohm`s Law
Specific Resistance
Voltage Drop
Power








Is this page helpful?            
Thank you for your feedback!

Sorry about that

How can we improve it?