1. Series and Parallel Circuits

2. Circuits
Can either be series or parallel.

3. Series Current only takes one path for electrons
Current flows through every part of the circuit

4. Lights in a Series

5. Series If you add a resistor (like another light):
Total resistance goes UP since all the current must go through each resistor.

6. Adding Resistors to Series:
Current in the circuit will go DOWN (lights will dim)
If you remove a light bulb or one burns out—all go out!

7. Current in Series Current is the same at all points
Use Ohm’s Law to find current using resistance and voltage

8. Calculating Current Example:

9. Voltage is reduced by each resistance – voltage drop
Voltage in Series
Voltage is reduced by each resistance – voltage drop

10. Calculating Voltage Example

11. Resistance in Series Add up all resistors to get total
Total resistance will go up because all of the current must go through each resistor.

12. Calculating Resistance Example:

13. Sample Problem #1
Draw a series circuit with two 1.5 V batteries, 3 resistors, and a current of 0.5 A.
What is the total voltage of the circuit?
What is the resistance of each resistor?
What is the voltage drop across each resistor? Label on your circuit.

14. Parallel Circuits Has at least one point where current divides
More than one path for current to flow
Paths are also known as branches

15. Lights in Parallel

16. Parallel: Total resistance goes down
If you add a resistor:
Total resistance goes down
Total current goes up when you add another path

17. Removing a Light Bulb
If you remove a light bulb or one burns out, the others stay on because the circuit is still closed.

18. Current in Parallel
Current flows into a branching point, the same total current must flow out again
Current depends on resistance in each branch

19. Calculating Current Example:

20. Voltage in Parallel
Voltage is the same across each branch – because each branch is on the same wire

21. Calculating Voltage Example:

22. Resistance in Parallel
Calculate current in each branch based on resistance in each branch by using Ohm’s Law

23. Calculating Resistance Example:

24. Practice problem #2
Draw a parallel circuit with two resistors (one on each branch) and a 12 V battery.
What is the voltage through each resistor?
What is the current flowing through each branch?

25. Toll Road—Circuit Analogy

26. Toll Booth Explanation
Adding toll booths in series increases resistance and slows the current flow.
Adding toll booths in parallel lowers resistance and increases the current flow.

27. Batteries in Series and Parallel:

28. In series—The voltage is increased.
In parallel—No change in voltage; these batteries will last longer!