1. Electric Circuits

2. ► All electrical devices have an electric circuit, also known as a path for electrons to flow. ► All circuits have at least four parts: 1.An energy source 2.An electric load 3.A switch 4.Wires

3. Energy Source ► Provides electrical energy in a circuit ► A simple circuit using a dry cell battery (this is what we will be using)  Electrons flow in one direction leaving the negative end of the battery and returning back to the battery to the positive end ► Other devices such TV`s require more energy for longer periods of time and use electricity from a wall outlet

4. Load ► Examples: Fans, ovens, motors, light bulbs and doorbells ► Without a load to convert the electricity into another form of energy, the wire creates a “short” circuit, which can cause sparks or fires.

5. Switch ► When you turn on a light bulb, the switch closes the circuit that connects the battery to the light bulb. ► This causes the light bulb to glow ► When you turn off the light bulb, the switch opens the circuit ► Now, electrons from the energy source cannot flow through the light bulb

6. Conductors (Wires) ► In your home, conducting wires in the walls connect the energy source to each outlet. ► When you plug a lamp into the outlet, an electric circuit is created with the energy source

7. Drawing Circuit Symbols ► Electrical circuits can be drawn with symbols that are internationally recognized. ► Drawing circuit diagrams before building a circuit will allow you to better understand how to accurately build the circuit.

8. Circuit Symbols

10. Simple Circuit

11. ► When constructing circuits make sure to pay close attention; small amounts of electricity can be very dangerous.  Make sure your hands are dry and that you’re standing on a dry surface.  Do not use batteries (cells) that appear damaged.  Do not use connecting wires if they appear frayed or damaged.  Only operate circuits when instructed by your teacher.  Always build circuits with the switch OPEN.

12. SERIES AND PARALLEL CIRCUITS ► There are two different types of electrical circuits: 1. Series circuits 2. Parallel circuits.

13. Series Circuits  In a series circuit, the electrons only have one path to travel.  Many simple electrical devices are wired in series, such as flashlights and many battery- operated devices.  Most series circuits only have one electrical load, however, more loads can be added.

14. Example ► Simplest circuit:

15. Another Example

16. Series ► Old Christmas lights used to be wired in series. This meant that if one light burned out, the entire strand of lights went out. How could you then figure out which light burned out?

17. Parallel Circuits  In a parallel circuit, the electrons have more than one path that they can take.  Parallel circuits have a very important advantage over series circuits; they allow you to turn off one load while keeping other loads on.  Most houses are wired in parallel with different switches to control different electrical loads.  New Christmas lights are now wired in parallel so that when one light burns out, it is easy to find and replace that light since all the other lights stay on.

18. Example

19. Practice ► Complete the following in class:  Practice circuits Homework: ► Read Section 13.1 (pages 500-503) ► Do Page 503 # 1-4