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review_exam6 - Review Notes For Exam 6 SAR Physics AM...

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Review Notes For Exam 6 SAR Physics AM Kolchin I. Electrostatics : study of interactions between charged ob- jects that don’t move. 1. Charge : an intrinsic property of a particle. There are two types called (+) and (-). The S.I. fundamental unit of charge is the coulomb (C). 2. Charged Objects : Objects can be charged atoms (ions) or objects com- posed of atoms. Objects can be (+) due to having fewer electrons than protons or (-) due to having more elctrons than protons. 3. Like charges repel; opposite charges attract. 4. Charge Transfer : How objects gain or lose electrons. (a) Friction : Electrons transferred by contact (b) Induction : Polarization of atoms (dipoles induced) in an insulating material or polarization of an ob- ject as a whole in a conducting material. (c) Conduction : Electrons move freely through con- ducting objects. Polarization of a conducting ob- ject occurs as a whole, in that electrons are induced to move towards one side or the other by a charged object nearby. (So the whole object gets polarized as opposed to individual atoms within it getting polarized.) 1

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5. Conservation of Charge : Charge can be neither cre- ated nor destroyed, only transferred, usually by a trans- fer of electrons. 6. Quantization of Charge : charge comes in multiples of a basic amount. This amount is called ” e ” and e = 1 . 6 * 10 - 19 C . All charged objects have a charge that is some whole number times e . 7. Electronic Properties of Materials : (a) Conductors : Outer electrons move almost freely through them. Most metals are good conductors. (b) Insulators : Outer electrons are tightly bound to atoms in bonds and cannot move easily. Most non- metals are good insulators. (c) Semiconductors : Outer electrons are bound, but not so tightly to their atoms. Semiconductors can be made to conduct electricity in a controlled way via i. Doping : adding or subtracting outer electrons by putting in impurities. ii. Photoelectric Effect : Exciting electrons (us- ing light) enough so that they can escape their atoms, but not so much that they can escape the material.
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