Series and Parallel Circuits

1
Series and Parallel Circuits
2
Circuits

• In order for electricity to flow we need
• Power source
• Closed circuit
• There are two type of circuits we will explore
• Series circuit
• Parallel circuit

3
Series Circuit

• In a series circuit there is only one path for
  the electrons to flow
• In other words all the components are in series
  with each other
• Because there is only one path each charge will
  go through each resistor

4
Predict, Test and Explain

• How will the brightness of the bulbs change as we
  add more in series?
• What does this imply about the current in the
  circuit?

5
Parallel Circuit

• In a Parallel circuit there are multiple pathways
  for charge to flow
• Each device is placed on its own separate branch
• Current goes through each of the branches at the
  same time

6
Predict, Test and Explain

• How will the brightness of the bulbs change as we
  add more in parallel?
• What does this imply about the current in the
  circuit?

7
Key Concepts

• Bulbs in series represent a source of resistance
  to current flow, similar to boulders in a stream
  which can block the flow of water
• Bulbs in parallel offer additional pathways for
  current flow, similar to branches of a stream
  which can carry more water.

8
Calculating Resistance in Series Circuits

• The rule for calculating Series Circuits is to
• Add up the values of each individual in the
  series.
• R1 R2 R3
• 5 5 10
• 20 O (ohms)

9
Calculating Resistance in Series Circuits

• Add up the values of each individual in the
  series.
• R1 R2 R3
• 10 20 10
• 40 O (ohms)

10
20
10
Calculating Resistance in Series Circuits

• The rule for calculating Series Circuits is to
• Add up the values of each individual in the
  series.
• 1    1     1   1  -- -- -- -- 
  Rt   R1   R2   R3
• 1    1    1    1  -- -- -- --  Rt   4   
  4     2
• 1
• -- .25 .25 .5 
• Rt
• 1
• -- 1
• Rt
• 1
• -- 1
• Rt

• 1
• -- 1
• Rt
• 1
• -- Rt
• 1
• Rt 1 O (ohms)

20
11
Calculating Resistance in Series Circuits

• The rule for calculating Series Circuits is to
• Add up the values of each individual in the
  series.
• 1    1     1   1  -- -- -- -- 
  Rt   R1   R2   R3
• 1    1    1 1  -- -- --
  --  Rt  100   200     1000
• 1
• -- .01 .005 .001 
• Rt
• 1
• -- .016
• Rt
• 1
• -- .016
• Rt

• 1
• -- Rt
• .016
• Rt 62.5 O
• (ohms)

1000
100
200
20