Electricity Physics

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ElectricityPhysics
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Potential differenceVoltage

• Cell
• Covert chemical energy to electrical energy
• AA, AAA, D batteries have the same voltage
• end
• Max Volts
• -end
• Zero Volts

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A voltage sets charges in motionvoltage
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
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Current

• The flow of electric charge

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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

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Ohms Law

• Voltage - V
• Volt
• Battery
• Potential difference
• Current - I
• Amps
• Rate of flow
• Resistance - R
• Ohms
• As resistance , current

IV/R
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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)

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Resistance

• The resistance of the filament determines the
  brightness of the bulb

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ConductorSemiconductorInsulator
Low resistance
Moderate resistance
High resistance

• Different resistance
• Depends on how tightly packed the electrons are
  held
• Remember transition metals?
• What are the electrons doing?

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Superconductor

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

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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

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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.

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Circuit Breakers and fuses

• Safety device
• Respond to an overloaded circuit by opening the
  circuit
• Acts like a switch
• Reset
• Fuses
• Must replace

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Electric power

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

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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

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Kirchoffs Current Law

• All current flowing into a branch point must flow
  out

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Energy Transformations

• Motor
• Electrical Energy Mechanical Energy
• Generator
• Mechanical Energy Electrical Energy
• Hydroelectric Power Plant http//www.fwee.org/walk
  tour/
• Mechanical Energy (Water flowing and turning the
  turbines)
• Electrical Energy

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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

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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

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Calculate resistance using the graph.