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Primary Science · Year 4Chapter 10 · Switches, conductors and insulators
Year 4 Science · Switches, conductors and insulators · Lesson 10.5

Year 4 Science: Switches use both conductors and insulators

Part of the Year 4 Science switches, conductors and insulators chapter. Chapter overview · whole chapter on one page

10.5

Switches use both conductors and insulators

Year 4
E4 and E5: a switch uses a conductor to complete the loop and an insulator to keep the user safe
Story. Leo looks inside a simple switch. “There is a metal part that touches to close the loop,” he says. “And the handle I press is plastic.” Ms Chen says, “Good. The metal conducts, and the plastic insulates. A switch needs both.”

A switch has metal contacts inside. When the switch is closed, the metal contacts touch, and they are conductors that complete the loop. The handle that you press is usually made of an insulator, such as plastic, so that the person using it is kept safe.

Choosing a material means thinking about what the material must do. A conductor is chosen where the electricity must flow, and an insulator is chosen where it must not.

Key ideas

  • The metal contacts of a switch are conductors.
  • The plastic handle of a switch is an insulator.
  • A conductor is chosen where the electricity must flow.
  • An insulator is chosen where the electricity must not flow.
Worked example 10.5.1
In a switch, which part completes the loop: the metal contacts or the plastic handle? Write the words.

Method. Think about the loop.

  1. Think about the contacts. When the metal contacts touch, the loop is complete.
    touch
  2. Name the part. So the metal contacts complete the loop.
    metal contacts
  3. Write the answer.
    the metal contacts

Check. The metal contacts are conductors. ✓

Worked example 10.5.2
Is the plastic handle of a switch a conductor or an insulator? Write the word.

Method. Think about the material.

  1. Think about plastic. Plastic does not let electricity flow through it.
    does not let
  2. Name the kind. So the plastic handle is an insulator.
    insulator
  3. Write the answer.
    insulator

Check. Plastic is an insulator, which keeps the user safe. ✓

Worked example 10.5.3
Should the handle of a switch be made of metal? Write yes or no.

Method. Think about safety.

  1. Think about the handle. A metal handle could carry electricity to the hand.
    carry electricity
  2. Decide. So the handle should not be metal, and the answer is no.
    no
  3. Write the answer.
    no

Check. The handle is an insulator, so the user is kept safe. ✓

Watch out

Watch out: a conductor is not always the best choice. In a circuit, the wires need a conductor, but the covering of the wires must be an insulator.

Try it at home or school (with a grown-up). Look at a switch on a torch or a toy, with a grown-up. Find the part you press, and say whether it is an insulator. Do not open any mains switch or socket.

Exam tip

Grown-up tip. Ask: “Which part do you press? Which part lets the electricity through?” Let your child name the conductor and the insulator in the switch.

Exercise 10E  Switches use both conductors and insulators

1
FIn a switch, which part completes the loop when it is closed? Write the words: metal contacts or plastic handle.
2
FIs the plastic handle of a switch a conductor or an insulator? Write the word.
3
FShould the handle of a switch be made of metal? Write yes or no.
4
FFill in the gap: a conductor is chosen where the electricity ___ flow. Write the word: must or must not.
5
FFill in the gap: an insulator is chosen where the electricity ___ flow. Write the words: must or must not.
6
FWhich material is better for a wire: copper or plastic? Write the word.
7
FWhich material is better for the covering of a wire: copper or plastic? Write the word.
8
FFill in the gap: a good conductor for a wire is a ___. Write the word.
9
PSSam says a plastic handle keeps the hand safe from electricity in a switch. Is Sam right? Write yes or no.
10
PSA wire has a metal core and a plastic cover. Which part carries the electricity? Write the words.
11
PSWorking scientifically. Predict which material will make the lamp light: a steel paper clip or a plastic ruler. Write the name.
12
RExplain why a switch needs both a conductor and an insulator. Write one sentence.

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