University of Virginia
Physics Department

## Conductor or Insulator?

A Physical Science Activity

2003 Virginia SOLs
• PS.1
• PS.11

Objectives

Students will

• see how a light bulb works;
• build a three-wire electrical tester;
• classify a group of items as conductors or insulators of electricity based on whether the items complete a circuit or not.

Motivation for Learning

Discrepant Event: Demonstration of How a Light Bulb Works

Materials

• Two nails
• 6" piece of nichrome wire
• Bottle or jar
• Cork that fits the bottle/jar
• At least 4 "D" size batteries or a 6-volt lantern battery
• 5 Pieces (each no more than 12 inches long) of copper wire if you are only using four batteries. You will need more wire if you use more batteries. The ends need to be stripped of insulation.

Assembly

1. Stick the nails into the cork with the heads of the nails above the cork
2. Wrap the one piece of copper wire around the top of each of the nails. Leave some length of wire free to attach to the batteries (see figure).
3. Attach the picture frame wire near the two nail points as shown in the figure below. The wire can hang down and can be coiled as long as it does not touch itself. You can coil it around a pencil before attaching the lose ends to the nail points.
4. Put the cork in the bottle making sure that the nail points with the wire are inside the bottle.
5. Connect the batteries to the ends of the wire. You should now have 2 pieces of wire that are not attached. These two pieces will attach to the nail heads when you are ready to do the demonstration.

NOTES: The thin picture frame wire will get hot and glow. The wire gets so hot that it burns the air in the bottle. The wire breaks and the lamp goes out. You will have to use more picture frame wire each time you want to do the demonstration.

Have an electric lamp ready to show the students. There is no light bulb to this demonstration so the students usually do not believe that you can make the wire glow (the glow is brief but bright).

### Student Activity

Materials

• One "D" size battery with a battery holder
• One light bulb holder
• One light bulb (6.3 volts)
• Three pieces of bell wire about 8 inches long each piece (ends stripped)
• A bag full of items that are conductors and insulators
Examples of conductors: aluminum foil, paper clips, metal screws, steel nails, metal washers
Examples of insulators: popsicle sticks, toothpicks, bark, plastic utensils, plastic cups, rubber bands, straws, rulers.
• Wire cutters/strippers
• Wire (wire with alligator clips are easy for students to use)

Procedure

1. Do in groups of two to three students.
2. Have the students use the equipment at their station to make an electrical tester. If students need a hint tell them that two ends of two different wires will not attach to anything. (This is where the items to be tested will be inserted, and the light bulb will light when the item is a conductor).
3. Have them draw and label their electrical tester before they construct it.
4. *PREDICT FIRST?* Once they have constructed their tester, they should begin to test all objects in the bag and record on data sheet.

Data Sheet

List the materials from the baggie as either conductors or insulators.

In the Baggie:

 Conductors Insulators _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________

In the classroom:

 Conductors Insulators _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ _______________________

1. What is an insulator?

2. What is a conductor?

3. Tell whether the following objects are conductors or insulators. Write C for conductors and I for insulators.

_____ Wood-dry _____ Plastic _____Silk _____Gold

_____ Brass _____Chalk _____Fur _____Glass

_____ Clothes _____ Copper _____ Rubber _____Water

4. What should the light do if there is an insulator placed between the two wires?

5. During this experiment, can the tips of your stripped wires cross each other and touch while trying to test whether an object is a conductor or an insulator? Explain your answer.

Extensions

Let the students walk around the classroom and test different objects in the classroom.

 WARN them about sockets and fuse boxes. Do not test these items.

Students with Special Needs

Some children will need help to actually hook the wires to the battery and the light. I recommend alligator clips for those children who have physical disabilities with their hands. If they can not carry the set-up around the room, you can place it in a plastic box for easier carrying. Have your resource teacher help you but give them advance warning that you will need their assistance this day.

Click here for further information on laboratories with students with special needs.

Assessment

Data sheet to be completed during the laboratory.