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Lesson Explainer: How Switches Work Science

In this explainer, we will learn how to describe how a switch works in a series circuit and identify problems when using switches.

If you have ever turned a light on or off, you have used a switch.

A switch is a component that can be added to a circuit.

Let’s start by recapping what we already know about circuits and their components.

Electric charge is a property that particles can have. Electricity is the energy resulting from the movement of charged particles.

An electric circuit is a path that allows electric charge to flow through it.

When a switch is added to a circuit, we can use it to control the components of the circuit. We can turn components on and off by making or breaking the circuit with the switch.

Definition: Switch

A switch is a component of an electric circuit that makes or breaks the circuit, turning the components on and off.

Here is a diagram of a circuit with a switch in it.

Switches do not all look the exact same, and they can be drawn in a number of different ways.

Example 1: Recognizing a Switch

Identify the switch in the electric circuit shown.

Answer

We can see that this circuit has four different components: 1, 2, 3, and 4.

Component 1 is a battery that provides electrical energy to the circuit.

Component 2 is a switch that is open.

Component 3 is a pair of bulbs that will light up if the circuit is working (closed).

Component 4 is a wire that is used to connect all the components together.

So, component 2 is a switch.

Many electrical appliances that we use in daily life have switches built into them, including

  • toasters,
  • vacuums,
  • televisions (remote control),
  • irons,
  • kettles.

Example 2: Identifying Everyday Appliances Containing Switches

Which of the following electrical appliances have a switch built into them? Select all that apply.

  1. All of the above

Answer

When you push down the switch on the side of a toaster to toast your bread, you are turning a switch from off to on and completing a circuit. So, option A is true.

This is also true when you switch a lamp on or press the power button on a cell phone. So, options B and C are also true.

So, the correct answer is option D: all of the above electrical appliances have a switch built into them.

A switch can be either open or closed.

Example 3: Identifying Open and Closed Switches

Look at the diagrams shown. In which of the circuits would the bulb light up?

Answer

We can see that the switch in circuit A is open.

When switches are open, the circuit is broken with a gap, so electric charge cannot flow. This means that the circuit will not work, and the bulb will not light up.

We can see that the switch in circuit B is closed.

When switches are closed, there is no gap in the circuit, so electric charge can flow. This means that the circuit will work, and the bulb will light up.

So, the bulb in circuit B will light up.

Switches allow us to turn things on and off, but why is this useful?

Turning electrical devices off using a switch when we are not using them can help us

  1. save energy and money, since wasting electricity costs money and is also harmful to the environment;
  2. keep safe, because if you left a hot iron on when you are not using it, this could be a hazard and burn somebody.

Example 4: Identifying the Importance of Switches

Why are on/off switches important to build into electric circuits? Select all that apply.

  1. To save electricity when we do not need to use it
  2. Because a circuit cannot work properly without a switch
  3. To make electrical appliances safer to use
  4. Switches are not important to build into electric circuits.

Answer

Turning off our electrical appliances using switches allows us to save electricity, so answer A is correct. Saving electricity helps us to save money and also to protect the environment.

Answer B is incorrect because a circuit can work without a switch. The minimum components required to make a working circuit are a battery or cell and a wire.

Answer C is correct because turning off appliances using a switch can keep us safe. For example, leaving a hot iron switched on could cause somebody to burn themselves.

Answer D is incorrect because switches are important to build into electric circuits.

So, the correct answers are option A and option C: switches allow us to save electricity and make electrical appliances safer to use.

Did you know that a switch can be made out of household materials?

This circuit has a switch made out of a metal paperclip, metal pins, and a piece of cardboard.

In order for a switch to work, it needs to be made out of an electrical conductor.

As we already know, an electrical conductor is a material that allows electric charge to flow through it easily. All metals, and some nonmetals, conduct electricity.

If a switch is made out of an electrical conductor, it will allow electricity to be transferred through it when it is closed.

Rule: The Material of a Switch

A switch must be made out of an electrical conductor so that electric charge can flow through it when it is closed.

Example 5: Choosing Materials to Make a Switch

Switches can be made from a variety of materials, including household objects. Which of these objects do you think would make a good homemade switch?

  1. Plastic spoon
  2. Metal fork
  3. Wooden pencil

Answer

A switch needs to allow electric charge to flow through it when it is closed. Therefore, a switch needs to be made from a material that allows electric charge to flow through it, also known as an electrical conductor.

Metal does conduct electricity, but plastic and wood do not.

So, option B is the correct answer: only the metal fork would make a good homemade switch.

In this explainer, we have learned how to describe how a switch work in a series circuit and identify problems when using switches.

Here is a summary of all that we have learned.

Key Points

  • A switch is a component of an electric circuit that makes or breaks the circuit, turning the components on and off.
  • Many electrical appliances we use every day have switches built into them.
  • Switches can be open or closed:
    • When the switch is open, a gap is created in the electric circuit, which breaks the flow of electric charge, and the bulb does not light up.
    • When the switch is closed, there is no gap in the electric circuit, electric charge can flow, and the bulb lights up.
  • Switches help us save money and electricity and stay safe.
  • Switches must be made out of a material that conducts electricity.

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