How to Calculate Conductance

••• Givaga/iStock/GettyImages

In electronics, conductance is a measure of the current produced through a circuit element for a given applied voltage. Usually denoted by the letter G, conductance is the reciprocal of resistance, R. The unit of conductance is the siemens (S). The conductance of a conductor depends on many factors, including its shape, dimensions, and the material's conductivity—usually denoted by the Greek letter σ.

Conductance from Resistance

Suppose a particular circuit element has a resistance of 1.25 × 103 ohms. Because conductance is the reciprocal of resistance, we can write:



G=\frac{1}{1.25\times 10^3\text{ ohms}}=8\times10^2\text{ siemens}

Conductance when Current and Voltage Are Known

Consider this example: A voltage (V) of 5 volts generates a current (I) of 0.30 amps in a particular length of wire. Ohm's law tells us that resistance (R) can be easily determined. According to the law:




In this case, it's 0.30 amps ÷ 5 volts = 0.06 Siemens.

Conductance from Conductivity

Suppose you have a wire with a round cross-section that has a radius r and length L. If you know the conductivity (σ) of the wire material, you can find the conductance (G) of the wire. The relationship between them is:


and since cross-sectional area is πr2, this becomes:

G=\frac{\pi r^2\sigma}{L}


Find the conductance of a round piece of iron with a cross-sectional radius of 0.001 meters and length of 0.1 meters.

Iron has a conductivity of 1.03 × 107 siemens/m, and the cross-sectional area of the wire is 3.14 X 10-6 m. The conductance of the wire is then 324 siemens.

Related Articles

How to Calculate Ampacity
How to Calculate Electroplating
How to Calculate Volume in a Wire
How to Calculate the Weight of Wire Based on Gauge...
How to Calculate Voltage Across a Resistor
How to Calculate Ampacity
How to Calculate the Field Current in a DC Motor
How to Convert Ohms to Kilowatts
Physical Characteristics of Aluminum Oxide
How to Calculate the Force of an Electromagnet
What Is a Ferrite Clamp?
How to Calculate the Size of a Cable
Aluminum Vs. Copper Conductivity
How to Calculate Ohms
How to Calculate Electroplating
How to Calculate Electrical Winding Wires by Weight...
How to Calculate the Length of Cable on a Drum
How to Measure the Ohm Value for an Inductor
How to Test a Blower Resistor
How to Calculate 30 KW to Amps

Dont Go!

We Have More Great Sciencing Articles!