3. Resistance: friction that impedes flow of current through the circuit (rocks in the river) How you should be thinking about electric circuits:

4. Current: the actual “substance” that is flowing through the wires of the circuit (electrons!) How you should be thinking about electric circuits:

5. circuit diagram cellswitchlampwires Scientists usually draw electric circuits using symbols.

6. What is the difference between open and closed circuits?

7. Circuit: A closed-loop path of conduction through which an electric current flows

8. Open circuit: An incomplete path that will not permit an electric current to flow

9. Closed circuit: A complete path for electric current

10. Open circuit? Closed circuit? What kind of circuit is this?

11. Open circuit? Closed circuit? What kind of circuit is this?

12. How Do You Make Electricity Do What You Want?

13. Insulator: a substance through which electricity cannot flow readily Examples… woodplasticrubber sulfur glass

14. Conductor: a material through which electrons can move easily Examples… brassaluminumcopper graphite water

15. Which of these items are conductors?

16. Which of these items are insulators?

17. What ’ s the Best Pathway for Electrons?

18. There are two main types of circuits: ParallelSeries and

19. Parallel circuits are circuits with more than one pathway through which electrons can flow. Series circuits are circuits with only one pathway through which electrons can flow.

20. Series and Parallel Circuits

21. Comparison Series CircuitParallel Circuit Definition Resistance Examples Only one path for current to flow Multiple paths for current to flow Total resistance increases Total resistance stays same -Holiday lights-Household Current

22. 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!

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

24. Flashlight What type of circuit is shown here? Parallel? Series?

25. What type of circuit is shown here? Parallel? Series?

26. Home lighting What type of circuit is shown here? Parallel? Series?

27. Holiday lights What type of circuit is shown here? Parallel? Series?

28. Car headlights What type of circuit is shown here? Parallel? Series?

29. Series Duracell Open or closed circuit?

30. Series Duracell Open or closed circuit?

31. Series Duracell Open or closed circuit?

32. Series Duracell Open or closed circuit?

33. Series Duracell Open or closed circuit?

34. Series Duracell Open or closed circuit?

35. Parallel

36. Duracell

37. Parallel Duracell

38. Parallel Duracell

39. Parallel Duracell Two complete circuits

40. Toll Road—Circuit Analogy

41. 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.