What is Electrical Conductivity? - Definition & Measurement

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  • 0:01 What Is Electricity?
  • 1:48 Electrical Insulators
  • 2:27 Electrical Conductors
  • 3:28 Lesson Summary
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Lesson Transcript
Instructor: Betsy Chesnutt

Betsy teaches college physics, biology, and engineering and has a Ph.D. in Biomedical Engineering

Why do some materials allow electricity to pass through them while others do not? In this lesson, we will learn what determines whether a material will conduct electricity or not, a property known as electrical conductivity.

What is Electricity?

When you flip on a light switch, the light comes on immediately and you can see! Have you ever thought about what is happening inside your walls to make that happen? If you could go inside the walls, you would see that a copper (or other metal) wire connects the switch to the light bulb, and when you flip the switch to the 'on' position, it makes a complete circuit and allows electricity to flow through the wire and the bulb, causing it to heat up and emit a bright light.

What's so special about the copper wire that makes it possible for electricity to flow through it and make your light come on? Copper allows electricity to pass through it because it has a high electrical conductivity, which is basically the ability of electric current to flow through a material. To further understand what that means, we first need to step back and think about what electricity actually is.

Everything in the known universe, including you, is made up of very tiny atoms. Inside each atom are even smaller particles called electrons, protons, and neutrons. Protons and neutrons are a lot bigger than electrons and are stuck together in the center, or nucleus, of an atom. They're always stuck within an atom and don't have much ability to move around. Electrons, however, are in the space surrounding the nucleus and are free to move around much more than protons and neutrons.

Electrons are also charged particles. Each electron has a tiny negative charge that it carries with it wherever it goes. Because electrons can move around easily within an atom, they can also sometimes move from one atom to another. When many electrons are moving from atom to atom in the same direction, charges flow just like water can flow in a pipe. This flow of charged electrons through a material is what we call electric current. Electric current flowing through a light bulb is what causes it to heat up and emit light.

Electrical Insulators

So why is it that electric current can flow easily through some materials (like copper and other metals), and not through others (like plastic or rubber)? Again, we have to look at what is going on inside the atoms of each material.

Materials like plastic and rubber have electrons that are more tightly bound to the nucleus of each atom. It's very hard for electrons in these types of materials to move from one atom to another. Because electric current cannot easily pass through them, they have low electrical conductivity and are called insulators. In addition to plastic and rubber, some other common insulators are air, glass, dirt, and paper.

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