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This text is meant to accompany class discussions. It is not everything there is to know about uniform circular motion. It is meant as a  prep for class. More detailed notes and examples are given in the class notes, presentations, and demonstrations (click here.)

Click for the questions that go with this reading


Electrostatics is the study of statsionary charges. Charges come in three types, positive, negative and neutral. This unit is about these charges, how they get placed and their effect on each other.


Insulators, Conductors and Semi-Conductors


A material that allow the transfer of charge from one point to another is a conductor.


A material that does not allow the transfer of charge is an insulator.
However, the charges can be part of an atom that can change shape such that one side of the atom is positive and the other side is negative. They just cannot move from point to point.
A semiconductor is a material made of carbon, silicone, and germanium. When mixed properly, a semiconductor is an insulator until you add a little energy, (from a battery,) to it. When enough energy is added, the semiconductor switches from insulator to a conductor. The little red, yellow, green or blue light that tell you when equipment is on are probably LED's. Some flashlights use "white" LED's instead of light bulbs to produce light. Radios, televisions, cellphones, iPods, and probably all the electronic devices you use, have semiconductors in them. Below are 3 examples of a semiconductors.
The rectangular object is a IC chip found in a computer. The little black object with three wires is a transistor. The clear looking device is an LED. LED stands for Light Emitting Diode.



The Charge Model
The charge model says to make a body have a net charge, you can either add like charges or remove opposite charges.


While these two animations who how to make something positively charged, something similar can be done to make a body negatively charged.

Charge Model Rule

This charge model has an important rule:

Opposites attract and likes repel.

In other words, positive charges repel positive charges and negative charges repel negative charges. And, positive charges attract negative charges and negative charges attract positive ones.



by Tony Wayne ...(If you are a teacher, please feel free to use these resources in your teaching.)