In a series circuit, there is only one path for electrons to flow through each component in the circuit. As more components are added in series, the total resistance increases and the current decreases. In a parallel circuit, there are multiple pathways for current to flow simultaneously through different branches. As more components are added in parallel, the total resistance decreases and the current remains the same. Key concepts are that series circuits represent resistance similar to boulders blocking water flow, while parallel circuits offer additional pathways like stream branches carrying more water. Total resistance in series circuits is calculated by adding the resistance of each component, while resistance in parallel is calculated using reciprocal sums.

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 it’s own separate branch
Current goes through each of the branches at the same
time

6. • How will the brightness of the bulbs change
as we add more in parallel?
• What does this imply about the current in the
circuit?
Predict, Test and Explain
+ + +

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 Ω (ohms)

9. Calculating Resistance in Series
Circuits
Add up the values of
each individual in the
series.
R1 + R2 + R3…
10 + 20 + 10
40 Ω (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
20
 1
-- = 1
Rt
 1
-- = Rt
1
 Rt = 1 Ω (ohms)

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
20
• 1
-- = Rt
.016
• Rt = 62.5 Ω
(ohms)
100 200 1000