1. Circuits Circuits are closed paths that form a loop

2. Circuits There are three basic parts to a circuit: 1.Energy source (battery, etc) 2.Wires 3.Load (light bulb, radio, etc)

3. Circuits What does the load do? ~The load changes electrical energy into OTHER forms of energy Ex: thermal, light, mechanical, etc.

4. Switches ~A switch is used to open and close a circuit ~When a switch is closed, it is “on” ~When a switch is open, it is “off”

5. Series and Parallel Circuits

6. Circuits…  Can either be series or parallel.

7. Series  Current only takes one path for electrons  If there is any break in the circuit, the current will stop flowing

8. Lights in a Series

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

10. If one lightbulb goes out… If you remove a light bulb or one burns out—all go out!

11. If one lightbulb goes out… If your home was wired this way, it would be very difficult! Imagine if your fridge and a lamp were wired in series. When one was off, the other wouldn’t work.

12. Why Do they exist?  They are helpful!  Example: burglar alarms: if the circuit fails, there is no current. When the current goes out, the alarm sounds.

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

14. Voltage in Series  This means, as you add light bulbs, they get dimmer. They are sharing the same current.

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

16. Lights in Parallel

17. Parallel:  Your home is wired in parallel. This school is wired in parallel.

18. Parallel:  Charges in a parallel circuit have more than one path on which they can travel.

19. Parallel:  Charges in a parallel circuit have more than one path on which they can travel.

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

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

22. Removing a Light Bulb You can connect loads that need different currents to the same parallel circuit. Each branch of the circuit can work by itself.

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

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

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!

29. One More FINAL Thing:  Two Types of Current:  DC—Direct Current— produced by solar cells and chemical cells (batteries)  Current only flows in one direction.

30. 2 nd type of current:  AC—Alternating Current  Current flows back and forth (alternates)  Found in homes  Generators produce AC current