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Electrical Engineering Topic 1: Energy, Power, Information, Current, Voltage

Electrical Engineering Topic 1: Energy, Power, Information, Current, Voltage. EGR 1301. Information iPod / music Digital cameras Radio/Television Internet/Computers Cellular telephone Satellites Embedded systems Fiber optics, lasers. Power Lighting/Appliances Motors Heating RADAR

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Electrical Engineering Topic 1: Energy, Power, Information, Current, Voltage

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  1. Electrical EngineeringTopic 1: Energy, Power, Information, Current, Voltage EGR 1301

  2. Information iPod / music Digital cameras Radio/Television Internet/Computers Cellular telephone Satellites Embedded systems Fiber optics, lasers Power Lighting/Appliances Motors Heating RADAR Welding & manufacturing On grid / off grid EMP Information and Power

  3. Electricity Basics • Charge • The smallest unit of charge is that of an electron • Flowing charge is “Current” • Accumulated charge produces “Voltage”

  4. Electrical Conductors • Metallic bond • Electrons are shared • Valence electrons form “cloud” or “sea” of electrons • Electrons are free to flow • Causes metals to be good conductors

  5. Electrical Insulators • Covalent bond • Valence electrons are shared • BUT have to break bond in order for electrons to flow • Ionic bond • Valence electrons are transferred • Charge must be transferred by movement of entire ion

  6. Electric Current • Current  flow of positive charge “Free” electron Atom Electron Flow Current

  7. Electric Current • Hole  concept used to explain current flow • Hole = absence of an electron • An electron (-) removed from a neutral atom leaves behind a “hole” (+) A B C D E

  8. Electric Current • 1 “Coulomb” of charge is 6,241,506,360,000,000,000 electrons • If 1 Coulomb flows through a wire in 1 second, we say the current is 1 ampere or 1 “amp” • Current always “flows through”

  9. Current Magnitudes • Brain cell synaptic currents 10-13 A • Integrated circuits currents 10-4 A • Threshold of human sensation 10-3 A • Causes ventricular fibrillation 10-1 A • Household appliances 10 A • Large industrial equipment 100 A • Lightning bolt 1000 A

  10. Electrostatic Forces • Electrostatic force gives rise to stored energy • Stored energy mental images • Stretched rubber bands • Compressed springs

  11. Energy • “It is important to realize that in physics today, we have no knowledge what energy is.” – Richard Feynman, Nobel Lauriat physicist • Energy is the “stuff” that gets work done • Units of Joules, or foot pound, or calorie, or BTU, or kilowatt hour, or horsepower, etc. • “For those who want some proof that physicists are human, the proof is in the idiocy of all the different units which they use for measuring energy.” Richard Feynman • Can be thought of as a unit of exchange like money

  12. Power • Power: the rate at which energy flows from one place to another • Units: Joules/second (also called a Watt) • Helpful to think of a Watt as an energy unit per time unit • Like “mach one” is a certain number of miles per hour • Kilowatt = 1000 watts • 1 horsepower = 745.7 watts

  13. Electrostatic Force Example • Example: Calculate the force on each handful of electrons that “electric man” is holding. F F q1 q2 q1=q2=-1C r=1m r

  14. Voltage • Voltage arises from accumulated charge being separated • Opposite charges attract • Positive likes negative • Energy is required to separate them • Like the ends of a stretched rubber band • Rubber bands can be stretched to different lengths • “Voltage” is a measure of how much energy each coulomb of charge contains

  15. 120 VAC Voltage • 1 “volt” means each Coulomb of charge can release 1 Joule of energy • A 12 Volt battery will produce 12 Joules of energy for every coulomb of electrons delivered

  16. Voltage • Voltage exists between two points, • NOT at an individual point • The earth is a common reference point • “Ground” • Voltages with respect ground are like rubber bands with one end on the ground

  17. Power • Remember, power is the rate at which energy is transferred • Electric Power is found by multiplying voltage and current

  18. Power • Question: How much power is supplied to a belt sander that draws 15 amps using “wall” voltage? • Answer: 120 Volts x 15 Amps = 1800 Watts • 1800 W = 1.8 kW

  19. AC, DC, and all that • DC stands for “direct current” and means the voltage and current are constant • All batteries supply DC power • “Cigarette Lighter Power” is DC • AC stands for “alternating current” and means that the voltage and current “alternate” back and forth • Grid-supplied electric power is AC, cycling 60 times every second, or at 60 Hz.

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