The shape of the lesson
By the end of the lesson, learners can
- Magnetise, then let go: Compare how soft iron and hard steel hold or lose their magnetism.
- The right metal for the job: Soft for cores that switch on and off, hard for magnets that must stay magnetised.
- Soft iron (temporary): magnetises easily, loses its magnetism easily. Used for electromagnet cores.
- Steel (permanent): harder to magnetise, keeps its magnetism. Used for permanent magnets.
- Pick by the job: if the magnetism must switch off, choose soft iron; if it must stay, choose steel.
One picture every idea returns to
Magnetically soft materials such as iron magnetise and demagnetise easily, ideal for electromagnet cores. Magnetically hard materials such as steel keep their magnetism, ideal for permanent magnets. The magnetic materials are iron, steel, cobalt and nickel.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, Iron forgets, steel remembers.. Stroke a steel needle with a magnet and it stays magnetic for years. | Whole class, then pairs |
| 5 to 17 min | Teach and check: Magnetise, then let go | Compare how soft iron and hard steel hold or lose their magnetism. Project tab 1 of the lab (the simulation) and let a student drive it while the class predicts. | Whole class, then pairs |
| 17 to 30 min | Teach and check: The right metal for the job | Soft for cores that switch on and off, hard for magnets that must stay magnetised. | Jigsaw |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 17 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in The right metal for the job, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Jigsaw
Split the content into expert pieces. Expert groups master one piece each, then regroup so every home team has one expert per piece, and each expert teaches their piece to the team.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| Magnetically soft does not mean physically soft. | It means easy to magnetise and demagnetise, like iron. Steel keeps its magnetism, which makes it a good permanent magnet but a poor electromagnet core. |
Magnetic materials, soft and hard: worksheet
6 questions, 17 marks. Written in the style of the papers; no past paper question is reproduced.
From the list below, state which materials are magnetic and which are not.
iron, copper, steel, plastic, nickel, brass
Compare soft iron and steel by stating, for each, how easily it is magnetised and whether it keeps its magnetism.
An electromagnet is made by winding a coil around a core. The electromagnet must release whatever it is holding the moment the current is switched off.
(a) State the best material for the core.
(b) Explain why that material is chosen.
State the most suitable material, soft iron or steel, for each of the following, and give no explanation.
(a) A permanent bar magnet for a laboratory.
(b) The core of the electromagnet in an electric bell.
A student says, "A permanent magnet must be stronger than a temporary one, because it lasts longer." Explain why this reasoning is wrong.
Two identical coils are wound, one around a soft iron core and one around a steel core. The same current is passed through each for a short time and then switched off. Describe and explain the difference in the magnetism of the two cores after the current is switched off.
Answer key and marking notes
Magnetic: iron, steel, nickel. ✓
Not magnetic: copper, plastic, brass. ✓
Soft iron: magnetised easily; loses its magnetism easily. ✓✓
Steel: magnetised with difficulty; keeps its magnetism. ✓✓
(a) Soft iron. ✓
(b) It magnetises strongly while the current flows, and loses its magnetism as soon as the current stops, so the load is released. ✓✓
(a) Steel. ✓
(b) Soft iron. ✓
- Lasting longer and being stronger are different properties. ✓
- While the field is applied, soft iron (a temporary magnet) can be magnetised just as strongly, or more strongly, than steel. ✓
- Permanent only means the magnetism is kept after the field is removed, not that the magnet is stronger. ✓
- The soft iron core loses almost all of its magnetism. ✓
- The steel core stays magnetised (it becomes a permanent magnet). ✓
- Soft iron is easily magnetised and demagnetised, while steel retains the alignment once it is magnetised. ✓
The lesson's own checks as a quiz
The quick-check and exam-style questions from the student lesson, printable with the key.
A permanent magnet is best made from...
- ASteel
- BSoft iron
- CCopper
- DPlastic
The core of an electromagnet is best made from...
- ASoft iron
- BSteel
- CAluminium
- DWood
A magnetically soft material...
- ALoses its magnetism easily
- BKeeps its magnetism for years
- CCannot be magnetised
- DIs always a permanent magnet
Which list contains only magnetic materials?
- AIron, steel, cobalt, nickel
- BCopper, brass, wood
- CAluminium, plastic, glass
- DGold, silver, tin
An electromagnet must switch its magnetism on and off quickly. Its core should be...
- ASoft iron, because it loses magnetism easily
- BSteel, because it keeps magnetism
- CCopper, because it conducts
- DPlastic, because it is light
A fridge magnet needs to stay magnetic for years. It is made of a magnetically...
- AHard material such as steel
- BSoft material such as iron
- CNon-magnetic material
- DMaterial that demagnetises easily
An unmagnetised iron nail is held near a strong magnet and picks up paperclips. This is an example of...
- AInduced magnetism
- BPermanent magnetism
- CElectric charge
- DFriction
Quiz key
Steel is magnetically hard, so it keeps its magnetism.
Soft iron magnetises and demagnetises easily, ideal for a switchable core.
Soft means easy to magnetise and demagnetise.
The common magnetic materials are iron, steel, cobalt and nickel.
A soft iron core magnetises and demagnetises with the current, so the magnetism switches cleanly.
A permanent magnet needs a magnetically hard material that retains its magnetism.
The nail becomes a magnet while in the field, which is induced magnetism.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.