1. 10.3 Series and Parallel Circuits
2.31 Electric Circuits
10.3 Series and Parallel Circuits

2. Recap Amps = rate of electrons flowing through a circuit
Can be measured using an ammeter that’s connected to a circuit in series
Volts (V) = how much energy the electrons are moving with (potential energy or difference in charge between the two ends)
measured by a voltmeter that has to be connected to the circuit in parallel to the load it is measuring

3. 2.4 – Series and Parallel Circuits
Circuits are described by the number of pathways that the electrons (current) are provided
Series circuits only have one pathway
Parallel circuits offer a choice of different pathways that an electron can flow through

4. 2.41 – Series Circuits and Current
When the light switch is off, the whole circuit is off
Because there is only one path for electrons to flow through, the current must flow through each load

5. 2.41 – Series Circuits and Current
Examples of series circuits:
Old Christmas light strands
Do diagram of christmas lights

6. 2.41 – Placement of Ammeter
Ammeters need to be connected to a circuit in series.
Do diagram of christmas lights A

7. 2.41 – Series Circuits and Current
The current is shared between all loads.
Therefore, Itotal = I1 = I2 = I3 etc.
Demo
I1 = 0.5 A
I2 = 0.5 A
I1 = 0.33 A
I2 = 0.33 A
I1 = 1.0 A
I2 = 1.0 A
I3 = 0.5 A
I3 = 0.33 A
Itotal = 1.0 A
Itotal = 0.5 A
Itotal = 0.33 A

8. 2.41 – Placement of Voltmeter
Voltmeters need to be connected to a circuit in parallel.
Remember: parallel circuits offer a choice of different pathways that an electron can flow through
Do diagram of christmas lights V

9. 2.41 – Series Circuits and Current
If more loads are added
each light will grow dimmer. This is because the potential of each load has been reduced.
The voltage of each load adds up to the voltage of the cell/battery
Vtotal = V1 + V2 + V3 etc.
Class demonstration?

10. 2.41 – Series Circuits and Current
The voltage of each load adds up to the voltage of the cell/battery
Vtotal = V1 + V2 + V3 etc.
Demo
V1 = 9 V
V1 = 4.5 V
V2 = 4.5 V
V1 = 3 V
V2 = 3 V
V3 = 3 V
Vtotal = 9 V
Vtotal = 9 V
Vtotal = 9 V

11. 2.42 – Parallel Circuits and Current
Since electrons can choose which path to follow, when one switch is opened (turned off), the lights don’t all go off since there is more than one path for the current to follow.
Change drawing to open switch

12. 2.42 – Parallel Circuits and Current
The current is divided between each pathway
Comparable to the way water flows down a river and is divided between parallel channels
The current of each branch adds up to the total current.
Therefore, Itotal = I1 + I2 + I3 etc

13. 2.42 – Parallel Circuits and Current
The current of each branch adds up to the total current.
Itotal = I1 + I2 + I3 etc
Demo
I1 = 0.6
I2 = 0.6 A A
Itotal = 1.2 A

14. 2.42 – Parallel Circuits and Potential
All electrons leaving the battery have the same “incentive” or energy to bring them back into it, regardless of the path they take to get there.
Analogy:
Water flowing over the Canadian and American falls in Niagara Falls will travel from the same height and end up in the same place. Therefore, the energy is the same.

15. 2.42 – Parallel Circuits and Potential
Adding more paths doesn’t reduce the energy – or brightness of a bulb – it only draws more current – allows more electrons to travel through.
The voltage of each branch is the same as the voltage of the cell/battery
Vtotal = V1 = V2 = V3 etc. V1 V2