Static Electricity Box

Physics:	Electricity
Grade Range:	Middle School, High School
Format:	Hands-on

The static electricity box is a small box covered in plastic and contains aluminum foil balls. This quirky box displays some surprising and fun properties of static electricity up close that students can play with.

Materials

• Static electricity box:
  • Aluminum foil
  • 1 cm diameter Styrofoam balls, wrapped with aluminum foil
  • Small clear plastic dome with base (Such as a cookie platter tray)
  • Small cardboard boxes, cardboard strips, or similar
• Piece of paper towel, cloth, or fur

Safety Precautions

• Please see the Demonstration Safety Page for General Safety Precautions

Demonstration

Preparation

Assemble the Static Electricity Box

1. Rinse out the plastic platter tray and dry. Stack the small cardboard boxes, strips, or similar until they nearly touch the lid of the tray when inside. Tape them together.
2. Line the top cardboard box (or cover the top of the stack) with an aluminum foil sheet. Cut two additional sheets to then fold and stack on top, pressing them in and leaving the edge elevated.
3. Place some of the Aluminum-wrapped styrofoam balls inside the aluminum lined box. Close the lid on top, ensuring it is a snug but sturdy fit.

Presentation

Style A:

1. Rub the plastic lid with your cloth (a circular motion work best). Some of the balls inside the box should begin bouncing around and floating. It is also possible to get a couple to stick against the bottom of the lid.
2. Put your finger tip close to touching the outside of the lid, above where the Styrofoam ball is sticking. The ball will move around!

Style B:

1. Rub the plastic lid with your cloth (A circular motion works best), then place the extra Styrofoam balls wrapped with aluminum foil on top. They will shift around a bit, then stick into place.
2. Once the Styrofoam balls are in place, bring your finger tip close to one of the balls (or just barely touching it) and the ball should roll and jump around the top of the lid!

Why This Works

Static electricity is when charges (+ and -) are separated from one another. This separation is often due to materials which are insulators, meaning materials that are good at preventing charges from moving, rub against each other. While this happens, the charges are separated onto the surfaces, and are "stuck in place" (i.e. the charges cannot be dispersed). A major property of charges is that opposite charges attract each other, and like charges repel each other. That is, - attracts +, but - repels -. However, anything that has a neutral charge will be attracted to either - or +.

In this demonstration, rubbing cloth on the plastic, an insulator, makes the lid - charged. The aluminum foil-wrapped Styrofoam balls are attracted to the charged surface, and will jump to it! The styrofoam balls are neutral charge, and are attracted to the - charge on the surface. The aluminum foil is a conductor, or a material that is good at letting charges move through it, so the - charge of the surface never reaches the styrofoam ball. Instead, the charge stays on the aluminum surrounding it!

When you try to poke the balls, you can see that they move away. This is because, when your hand touches the plastic, it removes the - charge on the surface. With the charge gone, there is nothing attracting the balls to that spot anymore, so the balls will either fall back down, or slide around the lid to another spot that is charged.

Tips and Tricks

• Be sure to discharge the surface completely after use. Otherwise, the balls can pick up a - charge, and then they will no longer be attracted to the charged spots.
• This demonstration goes well with the Van de Graaff generator and other static electricity demonstrations.