Section 1 
1. See the two "From the Lab" links for lab notes.
2. Law of Charges: Likes repel and unlikes attract.
3. Repulsion always indicates that objects are of like sign.
4. Attraction. is not so clear cut. Oppositely charged objects will attract, but a charged object will also attract a neutral object.
1. Ordinary matter is made of atoms, consisting of a tiny nucleus with a positive charge, surrounded by orbiting electrons which carry a negative charge. We call the carriers of this positive charge protons. We now know that the nuclei of all atoms larger than Hydrogen also contain neutral particles which we call neutrons.
2. The proton and electron carry exactly the same amount of electrical charge, the elementary charge, e. The proton has a charge of +e; the electron's charge is -e. The + and - signs refer to the two types of charge we learned about in the lab.
3. An neutral atoms has equal numbers of electrons & protons. Positive & negative ions has a deficiency or excess of electrons, respectively.
4. Currents flowing through wires or any other solids are made up entirely of electrons. Protons & neutrons are bound to the nucleus by very strong forces.
5. Whatever is carrying the charge, we always find that the amount of charge will be some integer multiple of e. We say that charge is quantized.
1. Charging by Friction: Rubbing two dissimilar objects together will always result in their having opposite charges. The electrons will transfer to the object with the greatest affinity for them.
2. When we talk about the charge on a body, we are referring to its net charge. The net charge is the amount of excess of negative or positive charge.
3. The Law of Conservation of charge: Net charge can be neither created nor destroyed.
1. When the leaves of an electroscope are given a net charge, they will spread apart due to the repulsion between like charges. The plate of the scope may or may not be charged, depending on the possible presence of a nearby charged object.
2. Only electrons move through the electroscope.
3. The charge (sign) of an object may be determined by bringing it near a scope with a known charge. If it is of like sign (relative to the scope), the leaves will diverge further. If it is of unlike sign, the leaves will converge.
1. The leaves of a neutral electroscope will diverge if a charged body is brought near the plate, thus polarizing the scope from top to bottom.
2. When charge is distributed so that one part of an body is positive and another part is negative, we say that the body is electrically polarized.
3. Electrical Ground - earth or some other large conductor that can receive or supply charges (usually electrons) without significantly affecting its own electrical condition.
4. Grounding - making electrical contact between a charged body and ground. Charges flow between the body and ground in a direction that "equalizes crowding" thus nearly neutralizing the small body.
1. Charging by Friction: Rubbing two dissimilar neutral objects together will result in their having opposite charges. The electrons will tranfer to the object with the greater affinity for them.
2. Charging by Contact of Conduction: The passage of charge directly from one body to another upon contact.
3. Charging by Induction: Bringing a charged object near a conductor & then grounding the conductor will cause electrons to move on or off the conductor. (The electrons move from or to ground, respectively.) As a result, the two objects will become oppositely charged.
1. A neutral body can have some of its charge redistributed into positive and negative regions if a charged object is brought nearby. We say that the uncharged body becomes polarized by induction.
2. Because of polarization, a neutral body will be attracted to a charged body. For example, a negative rod will polarize a neutral sphere such that positive side of the sphere is closer to the rod. The attraction between that side & the rod is greater than the repulsion between the more distance side & the rod.
3. When an insulator becomes polarized, the charges don't move from one region of the body to another. They stay with the same molecule, but redistribute so that the molecule itself is polarized.