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Science lesson plan · 9th grade (Year 10 in England) · 30 minutes

Mains electricity, AC/DC and plug safety

Electricity and magnetism

CCSS NGSS.HS-PS3-3England: GCSE Combined Science: Electricity (domestic uses and safety)

Objective and success criteria

Students will: Mains electricity, AC/DC and plug safety.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: Current, voltage and resistance (V = IR)

Leads to: the next skill in this area.

Materials: Circuit kits (cells, wires, bulbs), Circuit symbol cards, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 4 min

  • Quick retrieval from earlier learning (Current, voltage and resistance (V = IR)). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. A current of 1.5 A flows through a 12 Ω resistor. What is the potential difference (voltage) across it, in V? → 18 VPrompt: V = I × R
  2. A 20 V supply is connected across a 20 Ω resistor. What current flows, in A? → 1 APrompt: Rearrange V = I R to find I.
  3. A 6 V battery drives a current of 2 A through a lamp. What is the resistance of the lamp, in Ω? → 3 ΩPrompt: R = V ÷ I

Hook · 3 min

  • Show a circuit with a gap and ask why the bulb doesn't light.
  • Share the objective: Mains electricity, AC/DC and plug safety. Read the success criteria together.

I do: model it · 7 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: In a UK three-pin plug, which wire is this: completes the circuit at about 0 V?
  • Step 1: The neutral wire (blue) completes the circuit and is at about 0 V.
  • Step 2: So the answer is: neutral wire
  • Answer: neutral wire
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 6 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. In a UK three-pin plug, which wire is this: carries the alternating potential difference? (live wire / neutral wire / earth wire) → live wirePrompt: Brown, blue, green-and-yellow.
  2. What does a fuse do? (It increases the current / It melts and breaks the circuit if the current is too high / It changes ac into dc / It stores charge) → It melts and breaks the circuit if the current is too highPrompt: It is a thin wire in the live side of the circuit.

You do: independent practice · 7 min

  • Students work on the student sheet. Circulate and check the first two answers of every student early.
  • Students who finish: write a question of their own for a partner, with the answer.

The 6 questions are on the student sheet below, with answers in the key.

Exit ticket · 3 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. What does a fuse do? (It stores charge / It increases the current / It melts and breaks the circuit if the current is too high / It changes ac into dc) → It melts and breaks the circuit if the current is too highPrompt: It is a thin wire in the live side of the circuit.
  2. In a UK three-pin plug, which wire is this: completes the circuit at about 0 V? (live wire / neutral wire / earth wire) → neutral wirePrompt: Brown, blue, green-and-yellow.

Watch out for

  • Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
  • Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

  • Review first: Current, voltage and resistance (V = IR).
  • Use concrete materials: circuit kits (cells, wires, bulbs).
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-9.

Free lesson plan from eurekami.com/lesson-plan-builder

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Mains electricity, AC/DC and plug safety

Name

Date

Score/ 6

  1. Question 1

    Mains electricity: which statement is NOT true?

    • A. The earth wire only carries current when there is a fault.
    • B. The fuse is connected in the live wire.
    • C. The neutral wire is at 230 V.
    • D. Mains electricity in the UK is alternating current.

  2. Question 2

    In a UK three-pin plug, which wire is this: stops a metal case becoming live?

    • A. live wire
    • B. neutral wire
    • C. earth wire

  3. Question 3

    What does a fuse do?

    • A. It stores charge
    • B. It increases the current
    • C. It changes ac into dc
    • D. It melts and breaks the circuit if the current is too high

  4. Question 4

    In a UK three-pin plug, which wire is this: green and yellow stripes?

    • A. live wire
    • B. neutral wire
    • C. earth wire

  5. Question 5

    In a UK three-pin plug, which wire is this: carries the alternating potential difference?

    • A. live wire
    • B. neutral wire
    • C. earth wire

  6. Question 6

    What is the difference between ac and dc?

    • A. ac comes from batteries
    • B. there is no difference
    • C. dc is used in mains sockets
    • D. ac keeps reversing direction; dc flows in one direction only

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Answer key: Mains electricity, AC/DC and plug safety

  1. 1. C. The neutral wire is at 230 V.

  2. 2. C. earth wire

  3. 3. D. It melts and breaks the circuit if the current is too high

  4. 4. C. earth wire

  5. 5. A. live wire

  6. 6. D. ac keeps reversing direction; dc flows in one direction only