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ELECTRICITY

ELECTRICITY. Part 1: Overview and Electrostatics. Exam # 1 was. Too hard About right Too easy fubared. One of the three basic energy use sectors. We will study all aspects of generating electricity, but first and overview and some basic physics. Electric Power Generation 1950-2005. Graph.

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ELECTRICITY

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  1. ELECTRICITY Part 1: Overview and Electrostatics.

  2. Exam # 1 was • Too hard • About right • Too easy • fubared

  3. One of the three basic energy use sectors. • We will study all aspects of generating electricity, but first and overview and some basic physics.

  4. Electric Power Generation1950-2005

  5. Graph

  6. Have you studied Electricity before this class? • Yes • No

  7. Electrostatics • Study of charges that are NOT moving. • What is Charge? • A new property of matter. Similar to mass. • Mass creates and responds to gravitational fields • Charges create and respond to electric fields. • (Moving charges generate and respond to magnetic fields….more later)

  8. There are two types of charges: positive (+) and negative (-). • Common symbols for charge are q and/or Q. • Rubber/fur and glass/silk demo • Units of charge: Coulomb (C) • A Coulomb is a lot of charge. Usually deal in micro coulombs and less in electrostatics. • Fundamental charge: Magnitude of the charge on an electron or proton. • e=1.6x10-19C • Like charges repel, Unlike charges attract. • Van de Graff demo 1

  9. Definitions • Conductor: Material that charges are free to move around in. Examples: metal (silver is best but copper is almost as good) • Insulator (Dielectric): Material that charges are NOT free to move around in. Examples: glass, quartz, wood. • Semiconductor: Can behave as either depending on conditions: Silicon, Germanium, Gallium-Arsenide. • Van de Graff demos continued

  10. Forces on electric charges • Gravitational force on a mass: • F=mg • Electric force on a charge: • F=qE • E: electric field =F/q is the force per unit charge that a given charge experiences. (vector) • Note: In general E changes in space and time.

  11. If we move a charge in an electric field, we do work on it. • W =Fd =qEd • Define Voltage as V=Ed (Not exact, but it will do.) • Note V=W/q: work done per unit charge in moving it through an electric field. (Or potential energy per unit charge.) • Equivalent to raising mass up in a gravitational field.

  12. UNITS OF E & V • V=PE/q (Joule/Coulomb=Volt) • E =F/q (Newton/Coulomb) OR • E=V/d (Volt/meter)

  13. CAPACITOR • Device for storing charge • Two conductors separated by an insulator. • Battery moves charge from one plate to another.

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