If you have not heard of the term conductivity or of its unit of measurement (mS/cm or µS/cm), we would like to first tell you in simple terms what conductivity is all about.

The electric power generated at a power station is transmitted through an electric wire and reaches your home. When we say we use electric power at home, it means that electric current flows from a distant power station to reach your home. If it were the force of flowing water, the power station would be the high-ground source of a river, and your home would be downstream near the sea. Electric resistance hinders this flow from upstream to downstream, as we have mentioned already. Let's think a little further about electric resistance.

Let's think for a moment of electricity as a man and the substance through which electricity flows (usually electric wire) as a road. There are paved roads, gravel roads and muddy roads. Furthermore, a narrow road hinders the man's passage, causing him to expend much more energy on a long trip.

The difficulty of passage on a bad road may be represented by the following formula:

You may notice that the above formula can be directly converted to a formula for electric resistance:

Think about the resistance of an electric wire. The greater the length and the smaller the cross-sectional area, the greater the resistance. You may also understand that the greater the resistivity with the same length and the same area, the greater the resistance value. Each substance has its own resistivity value. For example, aluminum wire has a resistivity of about 1.6 times the resistivity of copper wire. This means that when an aluminum wire and a copper wire of the same size are compared, the aluminum wire has more resistance against the flow of electric current than the copper wire.

Thus, resistivity becomes an index of difficulty of flow of electric current. And the reciprocal of resistivity (1/resistivity) is conductivity. So, conductivity becomes an index of ease of flow of electric current. Its unit is written S/cm, meaning siemens per centimeter. Also, 1/1000 S/cm is a called millisiemens per centimeter, and 1/1000 of a millisiemens per centimeter is a microsiemens per centimeter.

We hope you now understand what conductivity means. We have two questions to help this gel in your mind:

Question 1: The resistance of a substance with a length of 1 cm and an cross-sectional area of 1 cm2 is 10 Ohms. What is the conductivity of this substance?

Question 2: What is the conductivity of a piece of wire with resistivity of 100 (/cm)? Give your answer in mS/cm.