Electroscope

Purpose:
To demonstrate the attractive and repulsive nature of the electrostatic force and charging by induction.

Equipment:
Electroscope glass rod rubber rod silk cloth rabbit fur

Equipment Location:
Mara_Right

Procedure:
There are many different things you can do. Here is a suggested procedure. 1. Momentarily touch electroscope to ground it. 2. Rub glass (real glass) rod with silk (real silk). The glass rod should become positive. 3. Move glass toward/away from electroscope and observe needle's deflection. 4. Rub glass on electroscope so that electroscope becomes charged. 5. Rub rubber rod with rabbit fur. 6. Move rubber toward electroscope. Needle should reduce deflection, since negative rubber attracts excess charge away from needle. Charging by Induction 1. Momentarily touch electroscope to ground it. 2. Move a charged rod near to, but not touching the electroscope. 3. With rod near electroscope (needle deflected), again momentarily touch the scope with your "ground hand" to ground the electroscope. 4. Move the rod away from the electroscope. 5. Move rod toward the electroscope and notice that the needle's deflection decreases, indicating a charge opposite to the rod.

Hints:
Triboelectric series in order of decreasing ability to loose electrons (i.e., increasing negativity when rubbed by something above it in the list). From T. Moore, Six Ideas Unit E. Air human skin (if dry) rabbit Fur glass human hair nylon wool lead silk aluminum paper cotton stell wood amber hard rubber nickel, copper brass, silver synthetic rubber gold, platinum polyester styrene (styrofoam) saran wrap polyethylene (used in scotch tape) polyporpylene vinyl silicon teflon silicone rubber