p7 electrical power and energy
4 detailed 50-minute lessons with teaching scripts, worked examples, parent guides, and assessment criteria.
Lesson Overview
Total Lessons: 4
Tier: Foundation and Higher
Duration: 50 minutes per lesson (200 minutes total)
Exam Boards: AQA, Edexcel, OCR, Eduqas, CCEA
Tier: Foundation and Higher
Duration: 50 minutes per lesson (200 minutes total)
Exam Boards: AQA, Edexcel, OCR, Eduqas, CCEA
Learning Objectives
- Explain the key ideas of p7 electrical power and energy
- Apply p7 electrical power and energy to exam-style questions
- Develop independent study skills
- Build cross-topic connections
Prerequisites
- Read the revision notes for p7 electrical power and energy first (GCSE Revise summary)
- Key vocab to pre-teach: Power, The National Grid, Transformer
- Basic skills: reading the summary notes and answering the practice questions there
Materials & Equipment
- Exercise book, coloured pens
- Scientific calculator
- Ruler
- Printed revision notes (link below)
- Internet for videos (see Resources)
Lesson 1: Introduction: p7 electrical power and energy
Duration: 50 minutes
Starter Activity (5 minutes)
Quick Recall
Write down everything you already know about p7 electrical power and energy. Then check against the key terms: Power, The National Grid, Transformer. Use a mini-whiteboard or paper.
Main Content (35 minutes)
Parent/Teacher Guide:
Before lesson: Read the script below. Pre-teach key vocab: Power, The National Grid, Transformer.
If stuck: Re-read the revision notes (link above), then break the content into smaller steps.
Extension: See the Stretch & Challenge ideas in Lesson 4.
Before lesson: Read the script below. Pre-teach key vocab: Power, The National Grid, Transformer.
If stuck: Re-read the revision notes (link above), then break the content into smaller steps.
Extension: See the Stretch & Challenge ideas in Lesson 4.
Teaching Script (35 mins):
Mins 0-5 - Hook: "Today: p7 electrical power and energy. By the end you will be able to answer exam questions on it unaided. It connects to the rest of Physics because the ideas here recur across the spec."
Mins 5-20 - Direct Instruction: Work through the core ideas below one at a time; after each, ask your student to explain it back in their own words.
Mins 20-30 - Guided Practice: Model the worked example together, then let your student attempt the first practice question with guidance.
Mins 30-35 - Independent Practice: 2-3 practice questions from Lesson 3 below, with immediate feedback.
Mins 0-5 - Hook: "Today: p7 electrical power and energy. By the end you will be able to answer exam questions on it unaided. It connects to the rest of Physics because the ideas here recur across the spec."
Mins 5-20 - Direct Instruction: Work through the core ideas below one at a time; after each, ask your student to explain it back in their own words.
Mins 20-30 - Guided Practice: Model the worked example together, then let your student attempt the first practice question with guidance.
Mins 30-35 - Independent Practice: 2-3 practice questions from Lesson 3 below, with immediate feedback.
First Look
Start with the revision notes summary, then attempt: Foundation A hair dryer has a power of 1200 W and is connected to a 230 V supply. Calculate the current it draws.
Plenary (5 minutes)
Check Out
Your student states one thing they learned and one question they still have about p7 electrical power and energy.
Lesson 2: Core Concepts: p7 electrical power and energy
Duration: 50 minutes
Starter Activity (5 minutes)
Review Previous Lesson
Quick recap: write 3 key points from Lesson 1 on p7 electrical power and energy. Check them against the notes below.
Main Content (35 minutes)
Power: The rate at which energy is transferred. Measured in watts (W). 1 watt = 1 joule per second.
The National Grid: A network of cables and transformers that connects power stations to consumers (homes and industry) across the UK.
Transformer: A device that changes the voltage of an alternating current (AC). Step-up transformers increase voltage; step-down transformers decrease voltage.
The National Grid: distributes electricity from power stations to consumers. To reduce energy loss in the cables, electricity is transmitted at very high voltage and low current.
UK mains supply: 230 V AC (alternating current) at 50 Hz. AC means the current changes direction 50 times per second.
Fuses: A thin wire that melts and breaks the circuit if the current gets too high. The fuse rating should be slightly above the normal operating current. Fuses are always placed in the live wire .
| Term | Meaning | Example |
|---|---|---|
| Step-up | Increases | Decreases |
| Step-down | Decreases | Increases |
| Live | Brown | Carries alternating current from the supply (230 V) |
| Neutral | Blue | Completes the circuit (0 V) |
| Earth | Green/yellow | Safety wire — connects metal casing to ground |
| Fuse | Wire melts when current is too high | Cheap, simple, reliable |
| Circuit breaker | Switch trips when current is too high | Can be reset, faster reaction |
| Earth wire | Provides path to ground if fault occurs | Protects against electric shock from metal cases |
Practice (10 minutes)
Q: Foundation A hair dryer has a power of 1200 W and is connected to a 230 V supply. Calculate the current it draws.
Answer: I = P / V = 1200 / 230 = 5.22 A.
Plenary (5 minutes)
Explain Back
Your student teaches the key points back to you without looking. Fill any gaps immediately.
Lesson 3: Application: p7 electrical power and energy
Duration: 50 minutes
Starter Activity (5 minutes)
Quick Recall
Recall the key terms: Power, The National Grid, Transformer. Define each in one sentence.
Main Content (35 minutes)
Parent/Teacher Guide: Let your student attempt each question alone first, then compare with the model answer. Award method marks for correct working even if the final answer is wrong.
Q1: Foundation A hair dryer has a power of 1200 W and is connected to a 230 V supply. Calculate the current it draws.
Answer: I = P / V = 1200 / 230 = 5.22 A.
Q2: Foundation Explain why the National Grid uses step-up transformers at power stations.
Answer: Step-up transformers increase the voltage and decrease the current. Lower current means less energy is wasted as heat in the transmission cables (since power loss = I squared x R). This makes the National Grid more efficient.
Q3: Foundation State the colour and function of each wire in a three-core mains cable.
Answer: Live wire = brown, carries the 230 V current from the supply. Neutral wire = blue, completes the circuit at 0 V. Earth wire = green/yellow, safety wire that connects the metal case to the ground to protect against electric shock.
Q4: Higher A 1500 W electric heater is used for 30 minutes. Calculate the energy transferred in (a) joules and (b) kWh.
Answer: (a) Time = 30 x 60 = 1800 s. E = P x t = 1500 x 1800 = 2 700 000 J = 2.7 MJ. (b) E = 1.5 kW x 0.5 h = 0.75 kWh.
Q5: Higher A 10 Ω resistor has a current of 4 A flowing through it. Calculate the power dissipated using two different power equations and verify they give the same answer.
Answer: Using P = I x I x R = 4 x 4 x 10 = 160 W. Using P = V x I: first find V = I x R = 4 x 10 = 40 V. Then P = 40 x 4 = 160 W. Both give 160 W, confirming the equations are consistent.
Plenary (5 minutes)
Error Review
Review any questions answered incorrectly. Identify whether the error was knowledge, method, or reading the question.
Lesson 4: Exam Practice: p7 electrical power and energy
Duration: 50 minutes
Starter Activity (5 minutes)
Command Words
Review what these command words require: state (one point), describe (say what happens), explain (say why), compare (both sides), evaluate (judgement).
Main Content (35 minutes)
Extended Answer
Extended question: Extended Answer 6 marks: Explain how the National Grid transmits electricity efficiently using step-up and step-down transformers. Refer to power, current, voltage and energy loss. <div class="
Electricity is generated at power stations at around 25 000 V. A step-up transformer at the power station increases the voltage to 400 000 V for transmission through the National Grid cables. Since power = voltage × current, increasing the voltage means the current is reduced proportionally for the same power transmitted. Lower current is crucial because the energy lost as heat in the transmission cables depends on P = I²R — even a small reduction in current causes a large reduction in power loss because the current is squared. This means less energy is wasted and more reaches the consumer. Near homes and industry, step-down transformers at substations reduce the voltage to 230 V for safe domestic use, which increases the current back to the level needed by appliances. Using transformers makes the grid efficient by minimising energy loss during long-distance transmission while delivering safe voltages to consumers. Mark scheme: 1 mark — step-up transformer increases voltage at power station, 1 mark — current is reduced, 1 mark — P = I²R explains energy loss in cables, 1 mark — lower current means much less energy wasted as heat, 1 mark — step-down transformer reduces voltage to 230
Exam Tips: Know all four power equations — P = E/t, P = VI, P = IIR, P = VV/R — and when to use each one. | For energy calculations, always convert time to seconds if using joules, or use hours for kWh. | When asked about the National Grid, always mention: high voltage reduces current, which reduces energy loss as heat (P = IIR) . | Know the wire colours : brown = live, blue = neutral, green/yellow = earth. | Fuse choice: the fuse rating should be slightly above the normal operating current. | When explaining earthing: live wire touches metal case → large current flows to earth → fuse blows → circuit is disconnected → user is safe. | AC (alternating current) is used in mains; batteries supply DC (direc
Common Errors: Watch Out! 1. Wrong: Power and energy are the same thing Correct: Power is the rate of energy transfer (watts); energy is the total transferred (joules or kWh). P = E/t — they are related but not the same 2. Wrong: A higher power appliance always uses more energy Correct: Energy depends on power AND time. A 3 kW heater on for 10 minutes uses less energy than a 1 kW heater on for 1 hour 3. Wrong: Fuses "use" electricity Correct: Fuses do not consume energy — they are safety devices that melt and break the circuit if the current exceeds their rating
AO3 - Reasoning & Interpretation: Analysis and Evaluation The table shows the power ratings and typical daily use of three household appliances on a 230 V supply. Electricity costs 28p per kWh. Appliance Power Daily use Kettle 2.2 kW 12 minutes Fridge 150 W 24 hours Tumble dryer 2.5 kW 45 minutes (a) Calculate the daily energy consumption in kWh for each appliance. Which uses the most energy per day? (b) Calculate the daily cost of running the fridge and the weekly cost (7 days). Why might the fridge's actual consumption be lower than calculated? (c) A student claims "the tumble dryer costs the most to run because it has the highest power." Evaluate this claim using your calculations. Answers: (a) Kettle: 2.2 × (12/60) = 0.4
Stretch & Challenge (Grade 8-9):
- Synoptic links: explain how p7 electrical power and energy connects to another Physics topic you have studied
- Real-world: research one real-world use or example of p7 electrical power and energy
- Critical: "What are the limitations of the models used in p7 electrical power and energy?"
Plenary (5 minutes)
Assessment Criteria
- Got it: Confident explanation + correct worked examples
- Getting there: Main points OK, needs support with detail
- Not yet: Confused on key concepts - re-run Lesson 2
Homework & Consolidation
- Consolidation: Re-answer any Lesson 3 practice questions answered incorrectly (20 mins)
- Retrieval: Write flashcards for the key terms: Power, The National Grid, Transformer (10 mins)
- Exam practice: One past-paper question on p7 electrical power and energy from the board websites (15 mins)
- Extension: Explain p7 electrical power and energy to someone else in your own words (10 mins)