Which Materials Conduct Electricity?
Electricity powers many of the devices you use every day. Those devices are made up of circuits, ranging from very simple (like in a lamp with a single light bulb) to very complex (like in a computer). Try this project to build your own simple circuit and use it to test which common household materials conduct electricity.
This activity is not appropriate for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.
You probably hear the word "electricity" a lot, but what does it actually mean? In everyday use, electricity typically refers to electrically charged particles (called electrons) moving through metal wires. The flow of electricity is called current. Metals are generally very good conductors, meaning they let current flow easily. Materials that do not let current flow easily are called insulators. Most non-metal materials, like plastic, wood, and rubber, are insulators. You will notice this if you have ever plugged something into a wall outlet. The prongs on the plug, and the wire inside the cord, are metal, but they are surrounded by plastic insulation so you do not get shocked when you touch the cord!
Electricity requires a complete "loop" for current to flow. This is called a closed circuit. That is why wall outlets have two prongs and batteries have two ends (positive and negative) instead of just one. You connect both of them to a circuit and that creates a complete loop. If the loop is broken at all, that is called an open circuit and no current will flow.
In this project you will build your own simple circuit by disassembling a flashlight. You will use your circuit as a tester to determine whether household materials are conductors or insulators. When you connect the circuit to a conductor, you will create a closed circuit and the flashlight bulb will turn on. If you connect the circuit to an insulator, you will still have an open circuit so the bulb will stay off.
Caution: electricity from wall outlets is very dangerous. Never cut into a wire or open an electronic device while it is plugged into a wall outlet.
Extra: can you find any non-metal conductive materials in your home?
Observations and Results
It may take a bit of work to reverse-engineer a flashlight once you have taken it apart. However, you should be able to get the flashlight to function without its power switch by connecting the battery compartment directly to the bulb using two wires. Adding a third wire allows you to create a "tester." When you touch a metal object with the free wire ends, the bulb should light up just like it would as usual. This works because the metal objects are conductors, so they create a closed circuit. When you touch insulating materials like plastic, rubber, and wood, the circuit is still open, so the bulb stays off because no current can flow.
Non-metal conductive materials can be difficult to find. A graphite pencil core may work for some flashlights, but graphite has a very high resistance compared to metals, so the bulb may appear very dim or not light up at all.
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Ben Finio, PhD, Science Buddies
Science Buddies |
Electricity, conductor, insulator
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