Students will work in cooperative learning groups to discover how Gauss's law applies to conductors and dielectric materials. This lesson is appropriate for grades 6-8 as a part of an introduction to electrostatics and can be completed in approximately 30 minutes.

The student knows that the action of forces on matter is understood and can be explained using specific laws.

• To discover Gauss's Law.
• To use an electroscope to detect electrostatic charge.
• To determine location of charges during static charge.

• Scotch tape
• Van deGraaff electrostatic generator
• Styrofoam chips (cut up plates, cups, etc. or use packing peanuts)
• metal container (such as large tuna can)
• plastic container (such as margarine tub)
• electroscope (These can be made; see Teaching Suggestions)

1. Focus: Each student will obtain two strips of scotch tape and stick them to the desk. then each student should quickly strip each piece of tape from the desk so that they do not touch. Students will slowly bring tape pieces together to observe the results. Discuss and Analyze. Note: Pieces of tape develop like charges and thus repel.
2. Laboratory Activity:
   a. Place Styrofoam chips inside plastic container (dielectric material). Test container and chips with coke can electroscope to determine charge.
   Obs: no charge
   b. Place plastic container on top of Electrostatic Generator. Turn on EG and observe results. Test container and chips with the coke can electroscope to determine charge. Discharge properly.
   Obs: Chips fly out due to induced positive charges and subsequent repulsion.
   c. Place Styrofoam chips inside metal container. Test container and chips with coke can electroscope to determine charge.
   Obs: no charge
   d. Place metal container on top of Electrostatic Generator. Turn on EG and observe results. test container and chips with the coke can electroscope to determine charge. Discharge properly.
   Obs : Chips do not fly out since charge accumulates outside of can.
3. Questions to investigate:

• What was the manipulated variable? Ans: material of containers.
• What was the responding variable?  Ans: motion of the Styrofoam chips.
• What caused the chips to act as they did?
• Contrast the charges on the chips in the two different containers.

Communicate results:
Working in cooperative groups, students will produce a graphic which locates the charges and clarifies the reason for the actions observed. Each group will explain the graphic to the class.

Making an electroscope:

• Cut and smooth a 0.5cm x 8cm strip  of aluminum foil. (Do not use heavy duty foil.)
• Drape it through the extended pull tab of a soda can. the tab will need to be parallel to the floor when in use.
• Tape a Styrofoam cup to the side of the can.
• Test the electroscope strips by bringing a charged object close to the foil.

Gauss's Law: Like charges accumulate on the outside surface of a conductor. On the metal container, electrons accumulate on the outside of the container and do not pass to the chips inside. The negatively charged Van de Graaff generator induces positive charges on the plastic container and on the chips causing the repulsion of the chips.

Dielectric- a non conducting material that can acquire and induced charge.

Be certain to discharge Van de Graaff Generator after each use!