Static Electricity Box
| Physics: | Electricity |
| Grade Range: | Middle School, High School |
| Format: | Hands-on |
The static electricity box is a small box covered with poly-carbonate that displays some surprising and fun properties of static electricity up close that students can play with themselves.
Materials
- Static electricity box (cardboard)
- Aluminum foil
- 1 cm diameter Styrofoam balls wrapped with aluminum foil
- Small poly-carbonate blast shield
- Roll of duct tape or something of similar height
- Piece of paper towel
Safety Precautions
- Please see the Demonstration Safety Page for General Safety Precautions
Demonstration
Preparation: Place the static electricity box on a table that is within range for students to interact with. Fold up a long strip of aluminum foil so that 4 layers of aluminum foil can fit inside the box. Push the foil all the way to the bottom of the box and try to get it as close to the bottom as possible. Open up small blast shield. Place one half of it on a roll of duct tape or something of similar height to support this side of the blast shield. Lay the other half of the blast shield on top of the static electricity box.
Using this set up, you can perform 2 different actions:
- Place the Styrofoam balls wrapped with aluminum foil inside the box, then place the blast shield on top of the box
- If this is done, rub the blast shield with a piece of paper towel (a circular motion seems to work best). While sometimes the Styrofoam balls can be reluctant, at some point some of them should begin bouncing around and floating inside the box. If you are careful enough, it is also possible to get one or a couple to stick against the bottom of the blast shield. If this occurs, you can put your finger tip close to touching the outside of the blast shield (where the Styrofoam ball is touching on the other side). The ball should move around when this occurs.
- The shorter of the 2 boxes works better with this. If using the shorter box, you can also make the Styrofoam balls jump around by rubbing the tip of your finger on the outside of the blast shield.
- Place the Styrofoam balls wrapped with aluminum foil on top of the blast shield, which is resting on top of the box
- If this is done, prior to placing the Styrofoam balls on the surface of the blast shield, rub the top of the blast shield with a paper towel. Once the Styrofoam balls are placed on top of the blast shield, an instructor or student can bring their finger tip in very close proximity to a Styrofoam ball (or just barely touching it) and the ball should roll around the top of the blast shield.
Why This Works
In static electricity, charges (+ and -) are separated from one another. Due to the properties of the materials these charges are separated onto, some of these charges are not able to disperse, and are "stuck in place" (i.e. if the surface is a nonconductor). One property of charges is that opposite charges attract each other and like charges repel each other. In the case of this demonstration, rubbing the blast shield (made out of polycarbonate, a nonconductor) makes parts of the blast shield + charged. The tin foil-wrapped Styrofoam balls are essentially - charged. When the balls are on the blast shield and they are touched, this changes their charge, the they slide around the blast shield trying to find a spot that is more attracted to their new charge than the place they were previously sitting. When the balls are underneath the blast shield and the blast shield is rubbed by the paper towel, the blast shield is gaining + charge, so the balls are attracted to the places with + charge to them until (with continual rubbing) a new place acquires more + charge, or the place they were attracted to loses + charge, and they bounce to that new area.
Tips and Tricks
- Try to make the blast shield as flat across the top of the box as possible