1. Circuits
Series and Parallel

2. Ohm’s Law In a very isolated situation, we know that: V = IR
But how does this apply to the real world?

3. Circuits Ohm’s Law is the basis for how all circuits function.
Examples of Circuits:

4. Circuits Ohm’s Law is the basis for how all circuits function.
Examples of Circuits:
Playstation

5. Circuits Ohm’s Law is the basis for how all circuits function.
Examples of Circuits:
Playstation
Cell Phones

6. Circuits Ohm’s Law is the basis for how all circuits function.
Examples of Circuits:
Playstation
Cell Phones
Computers

7. Circuits Ohm’s Law is the basis for how all circuits function.
Examples of Circuits:
Playstation Anything that gets
Cell Phones plugged into a wall
Computers or a battery has a circuit

8. Making sense of circuits
The best way to imagine a circuit is to think of traffic!

9. Electricity Terms Electrons Current Resistance If electricity is like
Voltage traffic, what would
Wires the cars be??

10. Making sense of circuits
Electricity comes from moving electrons.
Cars are the electrons on the road. -q

11. Electricity Terms Electrons Current Resistance Cars drive on the
Voltage road. What
Wires represents the road?

12. Making sense of circuits
Wires are the roads that electrons travel along.

13. Electricity Terms Electrons Current Resistance The gas in a car is
Voltage the Potential Energy
Wires that makes it go.
Which is the gas?

14. Making Sense of Circuits
Voltage is like how much gas you have. It determines how far you can go and how long your car can run. V

15. Electricity Terms Electrons Current Resistance The cars are all
Voltage driving at one speed
Wires or another.
What is speed representative of?

16. Making sense of circuits
Current is the speed of the cars going down the road. I

17. Electricity Terms Electrons Current Resistance In traffic there’s
Voltage always construction
Wires that slows the cars
down.

18. Making sense of circuits
Resistance is like roadwork on the road that slows traffic down. Remember: A resistor is anything that uses electricity. R

19. Electricity Terms
Electrons
Current
Resistance
Voltage
Wires

20. Making sense of circuits
Imagine these two trips around the block:
Trip 1
Trip 2

21. Making sense of circuits
Which trip will result in slower traffic speeds?
Trip 1
Trip 2

22. Making sense of circuits
If these were circuits instead of a road map, it would look like this:
Trip 1
Trip 2

23. Making sense of circuits
Everything that applies to the traffic applies to the circuit. Trip 1 is faster, so current is higher too.
Trip 1
Trip 2

24. Making sense of circuits
Which trip has the most amount of slow downs?
Trip 1
Trip 2

25. Making sense of circuits
Which circuit has the most amount of resistance?
Trip 1
Trip 2

26. Series Circuits These kinds of circuit are called Series Circuits.
Trip 1
Trip 2

27. Series Circuits
Series Circuits are like a one lane road. There’s only one way to go, so you have to go that way. If you run into construction, TOO BAD!!

28. Making sense of circuits
Now let’s look at a more complicated road trip:

29. Making sense of circuits
Which path will more cars take, A or B? Why?
A B

30. Making sense of circuits
Compare the current (car speed) and resistance (amount of construction) between A and B.
A B

31. Making sense of circuits
And the circuit would look like this:
A B

32. Parallel Circuits
These circuits are called Parallel Circuits. This is like a highway, where you can change lanes if one gets to slow.

33. Series vs. Parallel Circuits
Let’s take a look at how different kinds of circuits will change things in the real world…

34. Traffic Report
When we’re talking about traffic we want to know the overall delays, not what’s going on in each lane. (We don’t have all day!)
We can describe a circuit by giving it’s overall resistance instead of listing each resistor as well…

35. Traffic Report
If each construction zone takes 10 min to get through, what’s our total delay?

36. Traffic Report
If each construction zone is a 10Ω light bulb, what is our overall resistance?

37. Traffic Report
For Series Circuits, you have to go through all the delays, so we just add them up.
Rtotal = 10Ω +10Ω +10Ω= 30Ω

38. Traffic Report
For Parallel Circuits, we have to handle things a little differently because there’s more than one way to go. Consider this circuit:
A B

39. Traffic Report
What is the total resistance if you take route A? (Each bulb is still 10Ω)
A B

40. Traffic Report
What is the total resistance if you take route A? (Each bulb is still 10Ω)
10Ω + 10Ω + 10Ω = 30Ω
A B

41. Traffic Report
What is the total resistance if you take route B?
A B

42. Traffic Report What is the total resistance if you take route B? A B
Just 10Ω.
A B

43. Traffic Report
Some electrons will take Route A, and some will take Route B.
A B
30Ω Ω

44. Traffic Report
To get our total resistance (the “Traffic Report”), we will add them together like this:
A B
30Ω Ω

45. Traffic Report
To get our total resistance (the “Traffic Report”), we will add them together like this:

46. Practice Find the total resistance for this circuit:
Let each bulb have a resistance of 1Ω.

47. Practice
Find the total resistance for this circuit:

48. Practice Find the total resistance for this circuit:
Let each bulb have a resistance of 1Ω.

49. Practice
Find the total resistance for this circuit:
A=1Ω B=1Ω

50. Practice
Find the total resistance for this circuit:
A=1Ω B=1Ω