Circuits

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Circuits

• 4/17/10

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Electric Circuits

• Circuit Any path along which electrons can flow
  
• For a continuous flow of electrons, there must be
  a complete circuit with no gaps
• A gap is usually provided by an electric switch
  that can be opened or closed to either cut off or
  allow electron flow

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In Series
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In Series

• Current passing through each electric device is
  the same
• I1 I2 I3
• Total resistance to current in the circuit is the
  sum of the individual resistances along the
  circuit path
• Rtotal R1 R2 R3
• Vtotal IRtotal
• Ohms Law applies across each individual device
• V1 IR1 V2 IR2 V3 IR3
• Sum of the voltage drops across the individual
  devices is equal to the total voltage supplied by
  the source
• Vtotal V1 V2 V3

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In Parallel
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In Parallel

• Voltage is the same across each device
• V1 V2 V3
• Total current in the circuit equals the sum of
  the currents in its parallel branches
• Itotal I1 I2 I3
• Ohms Law applies across each individual device
• V I1R1 V I2R2 V I3R3
• Overall resistance of the circuit is less than
  the resistance of any one of the branches
• 1/Rtotal 1/R1 1/R2 1/R3

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Combining Resistors

• Series Rtotal R1 R2 R3
• Parallel 1/Rtotal 1/R1 1/R2 1/R3

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