Resistors in Series and Parallel Circuits

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Resistors in Series and Parallel Circuits
Physics 12
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JOKE OF THE DAY
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Resistors in circuits

• To determine the current or voltage in a circuit
  that contains multiple resistors, the total
  resistance must first be calculated.
• Resistors can be combined in series or parallel.

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PARALLEL CIRCUITS
SERIES CIRCUITS
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Resistors in Series

• When connected in series, the total resistance
  (Rt) is equal to
• Rt R1 R2 R3
• The total resistance is always larger than any
  individual resistance.

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Sample Problem
Calculate the total current through the circuit.
Rt 15 O 10 O 6 O
Rt 31 O
I V/Rt
10 V/ 31 O
0.32 A
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Resistors in Series

• Since charge has only one path to flow through,
  the current that passes through each resistor is
  the same.
• The sum of all potential differences equals the
  potential difference across the battery.

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Resistors in Parallel

• When connected in parallel, the total resistance
  (Rt) is equal to
• 1 1 1 1
• RT R1 R2 R3
• Due to this reciprocal relationship, the total
  resistance is always smaller than any individual
  resistance.

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Sample Problem
Calculate the total resistance through this
segment of a circuit.
1/Rt 1/12 O 1/4 O 1/6 O
1/12 O 3/12 O 2/12 O
1/Rt 6/12 O ½ O
Rt 2 O
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Resistors in Parallel

• Since there is more than one possible path, the
  current divides itself according to the
  resistance of each path.
• smallest resistor more current passes
• largest resistor least current passes

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Resistors in Parallel

• The voltage across each resistor in a parallel
  combination is the same.

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Calculate the total resistance in the circuit
below
Rtot 3 1/3 O
1/Rtot 2/10 O 1/10 O 3/10 O
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Try it ?

• Electric Circuits MC Worksheet
• Page 719
• 27-31
• Page 724
• 32-35
• Challenge Try
• Page 728 36