Physics Demo Number: 042

Approximate Run Time: 10 min

Basic Electrostatics With Rods, Furs, Silk and Electroscopes

Demo Description

Rub silk on a glass rod to create a positive charge on the rod.

Rub fur on a plastic rod to charge the  rod negatively.

Scientific Principles

  • Electric charges may be separated by rubbing materials together.
    ( One may display evidence of this charge separation  by using an electroscope.)

Equipment

  • Silk

  • Fur

  • Plastic Rod

  • Glass Rod

  • Electroscope for overhead

  • Soda Can

Equipment Location

The pictured items reside in Kit (042) on [B-1-4].

Instructions

The greenish cloth on left is silk and can be used with the glass rod to make the rod positive. The furs on right can be used to leave a negative charge on the black plastic rod.

(Alternate silk cloth includes brown burlap-looking and rough-feeling , but pure silk cloth.)

The electroscope can be used on the overhead projector or document camera to display charges on rods. One simply lays a charged rod on the black disc and swipes the rod along its entire length against the disc, perhaps repeating the swiping process a few times for maximum deflection of needle.

Alternatively one may leave the charged rod laying on the black disc, if the first method does not yield a satisfactory deflection of the needle.

One may also lay a soda can on its side on the lecture table and set it into rolling motion by attraction from a negatively charged black rod.

With all the electrostatics demos, there is  an option for reducing the effects of excessive humidity.

Simply warm the components with the dedicated heat gun.

The gun normally resides on the repair bench I .

 The bench is on the wall next to the Science Library  just before the [H] columns.


The heat gun is the object on the right in the second picture.

Please note, this is a Heat Gun, not a hairdryer!

Use sparingly and carefully to avoid burning yourself , setting something on fire ,or ruining the demonstration components!!
  
Writeup created by David A. Burba
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