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Electricity

Electricity. The flow of charges. Atoms. Made up of: Nucleus: Protons and neutrons Electrons: negative charge orbit nucleus. Current. Flow of electrons Measured in Amperes (Amps) Electrons passing per second. Circuit. Must have complete, unbroken path for current to flow 3 Parts:

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Electricity

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  1. Electricity The flow of charges

  2. Atoms • Made up of: • Nucleus: Protons and neutrons • Electrons: negative charge orbit nucleus

  3. Current • Flow of electrons • Measured in Amperes (Amps) • Electrons passing per second

  4. Circuit • Must have complete, unbroken path for current to flow • 3 Parts: • Load: device run by electricity • Wires: path for electron flow • Source: moves the electrons through the wire • Battery, generator, wall socket (power plant)

  5. A break in the circuit stops electricity from flowing

  6. Conductors • Materials allowing electrons to flow • Examples: • metals: electrons loosely held, move easily • Copper is one of the best

  7. Insulators • Do not allow electricity to flow • Examples: rubber, plastic • Electrons held tightly, will not move easily

  8. Voltage • Measures the force “pushing” electrons • Volt (v) as unit • Higher voltage is higher potential to push electrons through circuit

  9. Water dam Lower Potential energy =Low voltage Higher Potential energy=high voltage

  10. Resistance • Force working against (“resisting”) the flow of electrons • Measured in Ohms (Ω) • All parts of circuit “slows the flow”

  11. V I = R Ohm’s Law • Tells how current, voltage, resistance are related • Current = voltage resistance

  12. Practice Ohm’s Law • A 9 volt battery is used to light 3 bulbs with a resistance of 0.5 Ω each. Wires and a switch add another 3 ohms of resistance. How much current (amps) is flowing through the circuit? • Plan • What information is given? • 9 volts, 3 bulbs x 0.5 ohms = 1.5 ohms plus 3 ohms for total of 4.5 ohms. • What formula do I use? • I = v / r • I = 9 v / 4.5 Ω • Solve • I = 2 amps • Check:Does it make sense? • The current is less than the voltage because the resistance is reducing the flow

  13. Circuits and Current Direction

  14. Series Circuit • Only one path for electricity to flow • What happens if one bulb goes out? • Will the bulbs be dimmer or brighter than a parallel? Load (bulb) Switch

  15. Parallel circuit • More than one path for electricity to flow • Each load on separate circuit • What happens if one bulb goes out? • Compare series/parallel to water supply

  16. Current Direction • Current always flows in one direction: From negative to positive AC vs. DC

  17. Direct CurrentDC • Charges always flow in same direction, from negative terminal to positive terminal • Battery (cells)

  18. anode collector plastic seal plastic sleeve anode steel jacket Case sleeve Cell straps cathode Negative terminal cathode collector electrolyte Positive terminal Cells and Batteries 9 Volt Battery • Convert chemical energy to electrical energy • Potato clock Electron acceptor Electron donor

  19. Other sources of DC • Thermocouple: convert heat to electricity • Solar cells: convert solar energy to electricity

  20. Alternating CurrentAC • Charges flow from negative to positive but switch directions back and forth (alternate) • House current

  21. Producing AC current • Induction: Coil of wire and magnet produce electricity • It’s electro-magnetism! • Generator: converts mechanical energy to electrical energy • Motor: converts electrical energy to mechanical energy

  22. Electromagnetism • Magnetism and Electricity are closely related • Electric current causes magnetic fields • Cell phones, television, light • Magnets can cause an electric current to flow • Generators

  23. Power • Measures how fast energy is transferred from one form to another • Measured in Watts • Power = voltage x current • P= V I • A 100 watt light bulb changes or uses electrical energy to light energy twice as fast as a 50 watt bulb • Brainpop on current

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