Science lesson plan · 11th grade (Year 12 in England) · 45 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 · 5 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.
- Why is an electromagnet useful in a scrapyard crane? (It can be switched off to drop the iron and steel / It never needs electricity / It picks up all metals including aluminium / It is always on) → It can be switched off to drop the iron and steelPrompt: What happens when the current stops?
- The north pole of one magnet is brought near the south pole of another. What happens? (they attract / they repel) → they attractPrompt: Like poles behave differently from unlike poles.
- An electromagnet picked up these numbers of paper clips: 5 turns: 2 clips 10 turns: 4 clips 15 turns: 6 clips 20 turns: 8 clips If the pattern continues, how many clips would 30 turns pick up? → 12Prompt: How many more clips for every 5 extra turns?
Hook · 5 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 · 10 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 · 10 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 4 A sits at right angles to a magnetic field of 0.5 T. What is the force on the wire, in N? → 0.2 NPrompt: F = B × I × l
- A 0.2 m wire carrying 4 A at right angles to a magnetic field feels a force of 0.3 N. What is the magnetic flux density, in T? (Give 2 decimal places.) → 0.38 TPrompt: Rearrange F = B I l to find B.
You do: independent practice · 10 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 · 5 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- A 0.5 m wire carrying 2 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.) → 0.5 TPrompt: Rearrange F = B I l to find B.
- In Fleming's left-hand rule, what do the first finger, second finger and thumb represent? (motion, current, field / current, field, motion / voltage, resistance, power / field, current, motion (force)) → field, current, motion (force)Prompt: "FBI": Field (First finger), current (seCond finger), thrust (thumb) is one way to remember.
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