Circuits

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? Just 10Ω. A B

43. Traffic Report • Some electrons will take Route A, and some will take Route B. A B 30Ω 10Ω

44. Traffic Report • To get our total resistance (the “Traffic Report”), we will add them together like this: A B 30Ω 10Ω

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