2. Make a Switch





Overview


This lesson begins with a review of the Switch Hunt students have done for homework. Then they discuss reasons for including a switch in a circuit, so they can turn it off without disconnecting wires. Then they design and create their own switches, based on the types they have found, such as rotary, slide, pull, toggle and pushbutton switches.


Advance Preparation

  • Make four sample switches (see a video for each one): a) rotary, b) slide, c) toggle and d) pushbutton
  • Photocopy worksheet and assessment (downloadable at bottom of page)
  • Post a sheet of chart paper with title "Switch Hunt" and headings, "Where it was Found," "What it controls" and "How to Operate it" (see Procedure, step 1, below).
  • Post a sheet of chart paper with title "Troubleshooting" and headings "Issue" "Cause" and "Fix" (see Procedure, step 5)

Materials

  • LEDs, buzzers and coin batteries (as in Lesson 1)
  • Materials for making switches: cardstock, tape, paper clips, paper fasteners, mini-binder clips, scissors, wire
  • Sample home-made switches

Procedure

1. Switch hunt: Conduct a class discussion of the outcomes of the switch hunt . Then use these results to review the major types of switches (click on each link to see a video).

2. What does a switch do? Lead a discussion about why switches are used and what they do. If a circuit doesn't have a switch, the only way to turn it off would be to disconnect a wire. This can be very inconveneint, because turning the circuit on again will require reconnecting the wire in the right place. Nobody would want to use that method to turn the lights in their home off and on. A switch provides a very convenient way to stop and start the flow of electricity. 

3. Make a switch: Ask students to think about how they could create their own switches. These could work in a similar way to the switches they found in the Switch Hunt: they could be activated by turning, pushing, pulling, sliding or flipping something.
  • What materials could they use?
  • What action would they have to take to turn the switch on or off?
Provide materials and challenge students to make their own switches. If they have difficullty, share the sample switches you have made (see diagrams and videos).

4. Add your switch to a circuit: Challenge students to add the switch to a circuit so it controls a LED or buzzer. When the switch is closed, electricity can flow through it and the LED or buzzer should turn on. When the switch is open, it should block the flow of electricty and turn the circuit off. Opening a switch is like removing a segment of the ramp from the Penguin Toy -- the penguins won't be able to get back to the top of the stairs.  See a diagram and video.

5. Troubleshooting chart: A switch is working if the LED or buzzer comes on only when the switch is closed, and turns off only when the switch is open. Engage the class in a discussion about their switches:
  • What problems came up?
  • What caused each one?
  • How did they fix it?
Use this information to create a class troubleshooting chart, with the columns "Issue," "Cause" and "Fix," and leave it poseted for future reference.

Troubleshooting


If students have difficulty making basic switches, you can review simple ways of making the four basic types:
 Often, a switch is not added to a circuit correctly. Here are some common prolbems and how to deal with them: If both the switch and the circuit design are good, but the circuit still doesn't work, the fault probably lies in: A good way to test a switch or a battery is to use the Digital Multimeter. More information about the Digital Multimeter is available in the Appendix to this unit. Cick on the items below for some videos and drawings showing to use the Multimeter to:

Worksheet

Make a Switch.doc
Download



Assessment

Assessment of Lesson 2.docx
Download