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Electricity Physics

Electricity Physics. Potential difference=Voltage . Cell Covert chemical energy to electrical energy AA, AAA, D batteries have the same voltage + end Max Volts -end Zero Volts. A voltage sets charges in motion “voltage supplies electrical pressure”.

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Electricity Physics

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  1. ElectricityPhysics

  2. Potential difference=Voltage • Cell • Covert chemical energy to electrical energy • AA, AAA, D batteries have the same voltage • + end • Max Volts • -end • Zero Volts

  3. A voltage sets charges in motion“voltage supplies electrical pressure” • Moving electrons (negative to positive) • Current • Rate the charges move through a conductor • Unit = amp • In metals, moving electrons make up the current • In gases or liquids, both + and – charges are in motion WHY? Battery = direct current

  4. Current • The flow of electric charge

  5. Inside your body • Current is mostly positive charge movement • Nerve signals are in the form of changing voltage across the cell membrane • Na+ and K+ move across the cell membrane changing the charge

  6. Ohm’s Law • Voltage - V • Volt • Battery • Potential difference • Current - I • Amps • Rate of flow • Resistance - R • Ohms • As resistance , current I=V/R

  7. Resistance • Compare a 40 watt bulb to a 100 watt bulb – different resistance • Different amount of current running through it • Due to internal friction • Slows down conduction; slows down current (rate of flow)

  8. Resistance • The resistance of the filament determines the brightness of the bulb

  9. Low resistance Moderate resistance High resistance Conductor……Semiconductor……Insulator • Different resistance • Depends on how tightly packed the electrons are held • Remember transition metals? • What are the electrons doing?

  10. Superconductor • Explain how a metal can change from a conductor to a superconductor?

  11. Moving electrons • Random movement if circuit is off • Marching analogy • Where do the electrons come from in a circuit? • Free electrons in the wires • Why do the wires become hot when a current is flowing through them? • Transfer of kinetic energy due to electron speed

  12. Electric circuit • An electrical device connected so that it provides one or more complete paths for the movement of charges • Batteries add the energy for the electrons to move • Electrons move – to + • Conventional Current moves + to – • Explain an open and closed circuit.

  13. Circuit Breakers and fuses • Safety device • Respond to an overloaded circuit by opening the circuit • Acts like a switch • Reset • Fuses: • Must replace

  14. Electric power • Current x voltage • Unit • Watts • Kilowatt-hour • Energy delivered in 1 hour at the rate of 1 kW

  15. Series Circuit Parallel Circuit • One path • Resistors share voltage • Current the same throughout circuit • More than one path • Each path receives maximum voltage • Current could be different in different branches

  16. Kirchoff’s Current Law • All current flowing into a branch point must flow out

  17. Energy Transformations • Motor • Electrical Energy Mechanical Energy • Generator • Mechanical Energy Electrical Energy • Hydroelectric Power Plant http://www.fwee.org/walktour/ • Mechanical Energy (Water flowing and turning the turbines) • Electrical Energy

  18. How does electricity get to your house? • THE SPINNING SHAFT turns magnets inside a stationary ring of copper, moving electrons to produce electricity • STEP-UP TRANSFORMERS increase the voltage of electricity produced by the generator. • TRANSMISSON LINES carry electricity to substations in our communities. The voltage is decreased and the power is distributed to homes and businesses

  19. How does electricity get to your house? • THE SPINNING SHAFT turns magnets inside a stationary ring of copper, moving electrons to produce electricity • STEP-UP TRANSFORMERS increase the voltage of electricity produced by the generator. • TRANSMISSON LINES carry electricity to substations in our communities. The voltage is decreased and the power is distributed to homes and businesses

  20. Calculate resistance using the graph.

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