Conductor or Insulator?
	Topic Area Electric conductors and insulators Introductory Statement Students will test a variety of materials to deterrnine if they are conductors or insulators.   Math Venn diagrams Science Predicting Observing Drawing conclusions   Materials Per group: 15-25 cm wire with ends stripped D cell flashlight bulb tape materials to be tested (see activity sheet) Key Question What materials will conduct electricity? Background Information A direct electric current is a steady flow of electric charges through a rnedium called a conductor. In solid conductors (which include all metals), it is the nega tively charged electrons that flow and make up the electric current. Metals have some electrons that are not tightly bound to any single atom; they are free to move about from atom to atom. These electrons are called conducting electrons. Positive charges do not flow in a solid conductor, since the positively charged protons are bound within the nuclei of atoms. These atoms are locked in the grid like structure of the solid material and are not free to move. Therefore, the current in a solid conductor is caused by the movement of negative electric charges (electrons). In liquids that conduct electricity, the electric charges that flow can be positive, negative, or both. The nega tive charges are provided by either free electrons or negative ions (atoms or molecules with extra electrons). The positive charges are provided by positive ions (atoms or molecules that are missing electrons). Materials that do not nommally conduct electricity are called insulators. Other materials that conduct electricity to a lesser degree than conductors, but more than insulators, are called semiconductors; these are of great importance in electronics. It is important to note that at certain uoltages and temperatures, all materials will conduct electricity to some degree. Even air, which is norrnally an excellent insulator, will conduct electric charges when the voltage is high enough; lightning illustrates this. The only perfect insulator is a vacuum.		Procedure Part 1 1. Distribute materials to each group. 2. Show students how to build a circuit to test the conductivity of materials using the D cell, wire, and light bulb. 3. For the first five objects listed, predict whether or not the object will conduct electricity. Place the object in the circuit and record the results. 4. Have students pick five additional objects to test, and repeat the above process. 5. Discuss the results and write conclusions in the space provided. Make sure that students note that some objects, like the pencil, are both conductors and insulators, depending on what part of the object is placed in the test circuit. Part 2 1. Using Page 1, list the conductors and insulators in the appropriate boxes on Page 2. 2. Discuss common characteristics of the conductors. Record these characteristics in the space provided. 3. Discuss common characteristics of the insulators. Record these characteristics in the space provided. 4. Distribute Page 3. In the appropriate areas of the Venn diagram, write the names of the objects tested. Discuss the results. Discussion 1. How are all the conductors alike? 2. How are all the insulators alike? 3. What distinguishes a conductor from an insulator? 4. Are there any objects that are both conductors and insulators? Ipencil] 5. What other things do you think might be conductors? What other things might be insulators? Why are many wires coated with plastic or some other material? Extensions 1. Test other objects to see if they are insulators of conductors. 2. Build a different circuit to test the conductivity of materials. 3. Build a circuit to test the conductivity of various liquids. Curriculum Correlations Health: Discuss the importance of insulators to health and safety. Identify some of the places insulators are used in the classroom.