Science lesson plan · 11th grade (Year 12 in England) · 60 minutes
The motor effect (F = B I l) and Fleming's left-hand rule
Electricity and magnetism
CCSS NGSS.HS-PS2-5England: GCSE Combined Science: Magnetism and electromagnetism (Higher: motor effect)
Objective and success criteria
Students will: The motor effect (F = B I l) and Fleming's left-hand rule.
- 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: Electromagnets; Magnetic poles, fields and compasses
Leads to: Transformers and the National Grid
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 · 6 min
- Quick retrieval from earlier learning (Electromagnets; Magnetic poles, fields and compasses). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- A wire carrying a current has… (a magnetic field around it / no effect on a compass / a static charge / a gravitational field only) → a magnetic field around itPrompt: Place a compass near a wire and switch on.
- The north pole of one magnet is brought near the north pole of another. What happens? (they attract / they repel) → they repelPrompt: Like poles behave differently from unlike poles.
- An electromagnet picked up these numbers of paper clips: 10 turns: 3 clips 20 turns: 6 clips 30 turns: 9 clips 40 turns: 12 clips If the pattern continues, how many clips would 50 turns pick up? → 15Prompt: How many more clips for every 10 extra turns?
Hook · 6 min
- Show a circuit with a gap and ask why the bulb doesn't light.
- Share the objective: The motor effect (F = B I l) and Fleming's left-hand rule. Read the success criteria together.
I do: model it · 12 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: A wire 0.05 m long carrying 5 A sits at right angles to a magnetic field of 0.5 T. What is the force on the wire, in N?
- Step 1: 0.5 × 5 × 0.05 = 0.125
- Step 2: So the answer is: 0.125 N
- Answer: 0.125 N
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 12 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- A wire 0.1 m long carrying 3 A sits at right angles to a magnetic field of 0.1 T. What is the force on the wire, in N? → 0.03 NPrompt: F = B × I × l
- A 0.2 m wire carrying 5 A at right angles to a magnetic field feels a force of 0.2 N. What is the magnetic flux density, in T? (Give 2 decimal places.) → 0.2 TPrompt: Rearrange F = B I l to find B.
You do: independent practice · 17 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 8 questions are on the student sheet below, with answers in the key.
Exit ticket · 7 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- Why does the coil of a simple dc motor keep spinning in the same direction? (The magnets swap poles / The battery turns over / Friction pushes it / A split-ring commutator reverses the current every half turn) → A split-ring commutator reverses the current every half turnPrompt: Without a change, the forces would reverse the coil back.
- A 0.5 m wire carrying 4 A at right angles to a magnetic field feels a force of 0.5 N. What is the magnetic flux density, in T? (Give 2 decimal places.) → 0.25 TPrompt: Rearrange F = B I l to find B.
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: Electromagnets.
- 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
- Move on to: Transformers and the National Grid.
- 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-11.
Free lesson plan from eurekami.com/lesson-plan-builder