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Electricity

Electricity. What is electricity? The flow of charge Mostly, we focus on the flow of electrons in “normal” matter With static electricity, we get a good “zap” But we cannot stand around all day with Fluffy trying to keep the lights on. Sources of electric charges Chemical Batteries

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Electricity

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  1. Electricity

  2. What is electricity? • The flow of charge • Mostly, we focus on the flow of electrons in “normal” matter • With static electricity, we get a good “zap” • But we cannot stand around all day with Fluffy trying to keep the lights on

  3. Sources of electric charges • Chemical • Batteries • Mechanical • Generators • Hydro, thermal, nuclear (thermal) • Solar • Solar cells • In every case, the source provides electrons with a “push” that makes it run around in a path (“circuit”)

  4. What is “voltage”? • Batteries • 1.5V • 6V • 12V • AC electricity • 120V • 240V • 7500V • 115000V • Voltage is the “push” electrons have in a circuit

  5. What is a circuit? A circuit has three elements A conductor A potential difference or “voltage” A closed loop

  6. An electric circuit is composed of what 3 elements? • Conductor, potential difference, closed loop The “push” is called voltage, and is measured in Volts. The flow of electrons is called current, and is measured in Amperes or Amps. The flow of electrons is hindered by resistance, measured in Ohms.

  7. Ohm’s Law Mnemonic

  8. Ohm’s Law: Ohm's Law …says that, for many materials under a wide range of conditions, the voltage, V, and current, I, are linearly related, which implies resistance, R, is independent of V and I. When does it not apply? (Most important case) • https://www.youtube.com/watch?v=u4FpbaMW5sk • https://www.youtube.com/watch?v=m4jzgqZu-4s

  9. Questions When a battery is connected to a complete circuit, charges flow in the circuit almost simultaneously. Why?

  10. Examples How does this work? http://www.youtube.com/watch?v=0dLTEOM3qQc&feature=related

  11. Electrical Power • P= IV “Poison Ivy”

  12. Electrical Energy • Hand Generator

  13. Resistance and Ohm’s Law • Resistance is the impedance to the flow of charge • Resistance is defined as the ratio of potential difference to current • R = V/I Unit is the Ohm, Ω • A device is said to obey Ohm’s Law of its resistance is independent of the Voltage

  14. Find Resistance of a material • Depends on four factors • R ∞ Temp • R ∞ RHO (ρ) resitivity • R ∞ Length • R ∞ A-1 (cross-sectional Area)

  15. Low resistance • Short • Fat • cold

  16. High Resistance • Long • Thin • Hot

  17. Diagramming circuits

  18. Series Diagram

  19. Parallel Circuit • More than one path for the flow of charge • More room for the flow of charge so Resistance goes down • Voltage must stay the same since all charges have the same drop

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