2. Make a Switch





Overview

Students share the results of their home Switch Hunt. They looked for electrical switches and what they control. They categorized the action needed to operate them:  push button, slide, toggle and rotary switches. Students discuss the reasons for including a switch in a circuit. They then design and create as many types of switches as they can. Each student places a switch in a circuit so that it controls a motor.


Advance Preparation

  • Drawing of a circuit with a battery and motor to discuss switch location
  • Photocopy worksheet Lesson 1, Part 2: Switch Hunt.   Download below.
  • Photocopy worksheet Lesson 2: Make a Switch. Download below.

Materials

  • AA batteries, motors , and student-made battery holders (as in Lesson 1)
  • Materials to make switches: cardboard, paper clips, paper fasteners, aluminum foil, scissors, tape,  wire

Procedure

1. Switch hunt: The class reviews the Switch Hunt worksheets they completed at home.  Here are ideas for this review.  Ask students:

  • What is a switch?
  • Where can you find one?
  • What is the advantage of having a switch over touching two wires together?

Develop the idea that a switch lets you turn a motor (or light) on or off without touching any wires.

2. How does a switch work?  In order for a switch to work, it has to be in one position for the motor to be ON and in another position for the motor to be OFF.  A switch stops the flow of electricity to a load when it is off. It allows electricity to flow through the load when it is on. This means the switch must be placed in a circuit in such a way that all the electricity that flows through the load must also flow through the switch. See this video.  On a drawing of a circuit with a battery and motor, ask:

  • Where could you place a switch in this circuit so it can turn the motor on and off?

3. Make a switch: Explain that students will make their own switches. Ask:

Then engage students in thinking what they could use to make a switch:

Provide materials and time for students to make and test their own switches. If necessary, provide sample homemade switches. Here are some samples

4. Add your switch to a circuit:   The next challenge is:

  • Put your switch inside a circuit so it controls the lmotor.

To meet the challenge, students need to connect the motor and switch to a battery. Here is one way to make a battery holder and connect it to a motor. Students use the Make a Switch Worksheet to draw what they have made, and record the results of testing their switches.

5. Sorting switches by action needed to operate them: After students have made switches and gotten them to work, gather the class to think about types of switches, according to the action you take to operate them. The most common types are rotary, toggle, pushbutton and slide. Ask students

  • What kind of switch have you  made?
  • How would you make one of the other types?

Outcomes

  • A switch is a reliable way to control a circuit. Touching wires together is not reliable, and could even be dangerous.
  • A switch can be made from common materials. It requires two metal contacts where it is connected in the circuit.  It also requires a conductor that can touch both contacts to turn the circuit ON and a way the conductor can be moved so it doesn’t touch both contacts, which will turn the circuit OFF.
  • Switches can be operated by sliding, turning, pushing, pulling, or holding something down temporarily.
  • Word-wall words open circuit, closed circuit, contacts, connections, switch, rotary switch, pushbutton switch, toggle switch, slide switch, control, troubleshooting.




Troubleshooting


Most of the problems students have is with bad connections. These are connections that do not allow current to flow from one circuit element to the next. Here are videos of two common problems.

Here are videos of how to make better connections.

Here are analyses and solutions to other common problems.

Here is what to look for if the connections are all good and the motor still doesn’t run.


Worksheet

Lesson 2 - Make a Switch.doc
Download



Assessment

Assessment of Lesson 2.doc
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