Why Does Aluminum Foil Conduct Electricity?

Instructor: Damien Howard

Damien has a master's degree in physics and has taught physics lab to college students.

Explore the electrical properties of aluminum by learning about what makes it a conductor of electricity. Then, discover what effect, if any, there is on aluminum's conductivity when it's in foil form.

Insulator Confusion

When it comes to aluminum foil, there seems to be some confusion out there about the properties of the material. You'll see people wondering about how aluminum foil can be a conductor when it's used for insulation at the same time. It turns out these two words, while seeming related, are actually being used to talk about two very different situations. Aluminum foil is useful for insulation in building construction due to its reflective properties. For conduction, we aren't talking about home insulation, but instead the material's electrical properties.

In this lesson, we'll learn about the electrical properties of aluminum foil. We'll discover what it is about aluminum that allows it to conduct electricity.

Conductors vs. Insulators

Before we learn what makes aluminum foil a conductor, we need to learn what makes any material conductive. As far as electrical conduction goes, materials can generally be split into two categories: conductors and insulators. Conductors are materials that allow electrons to move freely through them when a charge is applied. The insulators in this case are not the type that keeps your home warm, but materials that do not allow electrons to move freely through them when charge is applied. In other words, electricity flows easily through conductors but not through insulators.

This chart shows some examples of different conductors and insulators.
examples of insulators and conductors

So what determines whether or not the electrons flow through a material when that charge is applied? It has to do with the outermost electrons in the atoms of the material. Solid materials are made of atoms bound to each other, forming a pattern called a lattice. Each atom consists of a single nucleus surrounded by a cloud of electrons. The outermost electrons are known as the valence electrons. Whether a material is a conductor or an insulator depends on how well they hold onto these valence electrons.

This diagram of an aluminum atom shows the location of its valence electrons.
aluminum atom valence electrons

Insulator valence electrons are bound strongly to their parent atom. When a charge is applied to an insulator, the valence electrons hold their positions. Since the charge has nowhere to go, electricity cannot flow through the material. In a conductor, the valence electrons are not bound strongly to their parent atom. When a charge is applied to a conductor, it knocks a valence electron off of its parent atom. That newly free electron then knocks off a valence electron from another atom and so on. This creates a chain reaction of moving electrons called electric current in a conductor.

Aluminum Foil Conduction

So now that we know how conductors work, what makes aluminum foil a good conductor? It turns out it's not just aluminum foil, but it's what makes all metals good conductors. When metallic bonds are created, they set the valence electrons loose from their parent atoms. These _free electrons flow through the metal's lattice in random directions.

The red circles represent the free electrons in aluminum flowing in random directions around the atoms represented by blue circles.
free electrons in aluminum

When a charge is introduced to a metal, the free electrons immediately go from flowing in random directions to a single direction. This creates an electric current in the metal. Like all other metals, aluminum is a great conductor because of this. In fact, it is the fourth best conductor behind only gold, copper, and silver.

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