The shape of the lesson
By the end of the lesson, learners can
- Trace the field with a compass: Move the compass around the magnet and watch the needle line up with the field at each point.
- Reading the pattern: The spacing of the lines tells you the strength, and the arrows tell you the direction.
- Direction: field lines point from N to S outside the magnet, the way a compass north end points.
- They never cross: the field has one direction at each point.
- Spacing shows strength: closer lines mean a stronger field, so lines bunch near the poles.
One picture every idea returns to
A magnetic field is the region around a magnet where a magnetic force acts. Field lines run from the north pole to the south pole outside the magnet, never cross, and are closest together where the field is strongest, near the poles. A compass needle points along the field line.
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, Mapping the invisible.. Scatter iron filings around a bar magnet and a pattern of curves leaps into view. | Whole class, then pairs |
| 5 to 17 min | Teach and check: Trace the field with a compass | Move the compass around the magnet and watch the needle line up with the field at each point. 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: Reading the pattern | The spacing of the lines tells you the strength, and the arrows tell you the direction. | Corners |
| 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, 14 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 Reading the pattern, 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.
Corners
Put one answer or viewpoint in each corner of the room. Students move to the corner they agree with, justify the choice to a partner there, then hear one voice from each corner before the reveal.
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 |
|---|---|
| Outside the magnet the arrows on the field lines point from north to south. | The lines never cross, and where they crowd together, near the poles, the field is strongest. |
Magnetic fields and field lines: worksheet
6 questions, 14 marks. Written in the style of the papers; no past paper question is reproduced.
State what is meant by a magnetic field, and state how the direction of the field at a point is defined.
State three rules that must be followed when drawing the magnetic field lines around a bar magnet.
A bar magnet has its north pole on the left. A plotting compass is placed directly above the middle of the magnet. State the direction in which the red north-seeking end of the compass points, and give a reason.
Describe how a small plotting compass can be used to plot one magnetic field line around a bar magnet.
On a field diagram, the lines are drawn much closer together near the poles than in the middle of the sides. State what this spacing tells you, and explain why the lines are never drawn crossing.
A student draws field lines around a bar magnet with the arrows pointing from the south pole to the north pole, outside the magnet. State what is wrong, and give the correct rule.
Answer key and marking notes
- A magnetic field is the region around a magnet where a magnetic force acts. ✓
- Its direction at a point is the direction of the force on a north pole there (the way a compass north end points). ✓
- Lines point from the north pole to the south pole outside the magnet. ✓
- Lines never cross one another. ✓
- Lines are closer together where the field is stronger (near the poles). ✓
It points to the right, toward the south pole. ✓
Above the magnet the field runs from the north pole round to the south pole, and the needle lines up with the field. ✓
- Place the compass near the magnet and mark a dot at each end of the needle. ✓
- Move the compass so the tail sits on the last dot, and mark the new tip. Repeat across the paper. ✓
- Join the dots with a smooth line and add an arrow pointing from N to S. ✓
- Closer lines show that the field is stronger there, so the field is strongest near the poles. ✓
- The lines never cross because the field has a single direction at each point, so a compass there can only point one way. ✓
- The arrows are reversed. ✓
- Outside the magnet, field lines point from the north pole to the south pole. ✓
2 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
In which direction do the magnetic field lines outside a bar magnet point?
- Afrom the north pole to the south pole
- Bfrom the south pole to the north pole
- Cfrom both poles toward the middle
- Dthere is no particular direction
Where is a magnetic field strongest around a bar magnet?
- Aat the poles, where the field lines are closest together
- Bin the middle of the magnet, where the lines are farthest apart
- Cequally everywhere around the magnet
- Donly on the north side
Quiz key
Outside the magnet, field lines run from north to south, the direction a compass north pole points. Inside the magnet they run south to north, completing the loops.
The field is strongest at the poles, shown by the field lines being most closely spaced there. Where the lines spread apart, the field is weaker.
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.