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. 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…
20 Ω (ohms)

9. Calculating Resistance in Series Circuits
Add up the values of each individual in the series.
R1 + R2 + R3…
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
-- =   Rt
-- = 1 1
-- = 1 Rt
-- = Rt
Rt = 1 Ω (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      -- =   Rt  100   200     1000 1
-- =   Rt
-- = .016 1
= Rt
.016
Rt = 62.5 Ω
(ohms)
1000
100
200 20