The shape of the lesson
By the end of the lesson, learners can
- Map the field around charges: Place charges and plates and watch the field lines and the force on a small positive test charge.
- Two patterns to know: A single charge gives a radial pattern, parallel plates give a uniform field.
- Direction: the field is the direction of the force on a positive charge, so lines leave + and enter −.
- A negative charge feels a force opposite to the field.
- Parallel plates: the field between them is uniform, drawn as straight, evenly spaced lines.
One picture every idea returns to
An electric field is a region where an electric charge experiences a force. Field lines point in the direction of the force on a positive charge, so they point away from a positive charge and toward a negative one. Around a point charge the field is radial; between parallel plates it is uniform.
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, The reach of a charge.. A charge does not need to touch another to push it. | Whole class, then pairs |
| 5 to 17 min | Teach and check: Map the field around charges | Place charges and plates and watch the field lines and the force on a small positive test charge. Project tab 3 of the lab (Electric fields) and let a student drive it while the class predicts. | Whole class, then pairs |
| 17 to 30 min | Teach and check: Two patterns to know | A single charge gives a radial pattern, parallel plates give a uniform field. | Cooperative Concept Mapping |
| 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 Two patterns to know, 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.
Cooperative Concept Mapping
Teams receive the key terms on cards and arrange them on a large sheet, drawing and labelling the links. Compare maps between teams before showing the model map.
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 |
|---|---|
| Field lines show the direction of the force on a positive charge, so they leave a positive charge and enter a negative one. | They never cross, and where they are closer the field is stronger. |
Electric fields: worksheet
6 questions, 14 marks. Written in the style of the papers; no past paper question is reproduced.
Define an electric field, and state how the direction of an electric field at a point is defined.
Describe and sketch in words the electric field pattern around a single isolated negative point charge.
Two parallel metal plates are connected so that the left plate is positive and the right plate is negative.
(a) State the direction of the electric field between the plates.
(b) State one feature of the field that shows it is uniform.
A negative charge is placed at a point in an electric field where the field points to the left. State the direction of the force on the charge, and explain.
Describe the electric field pattern produced by one positive and one negative point charge placed a short distance apart.
On a field diagram for a single positive charge, a student draws the field lines getting closer together far away from the charge. State what is wrong and give the correct description.
Answer key and marking notes
- An electric field is a region in which an electric charge experiences a force. ✓
- Its direction at a point is the direction of the force on a positive charge placed there. ✓
- The field is radial: straight lines along the radii. ✓
- The arrows point inward, toward the negative charge (the force on a positive charge is toward it). ✓
(a) From the positive (left) plate to the negative (right) plate, so the field points to the right. ✓
(b) The field lines are straight, parallel and evenly spaced. ✓✓
- The force is to the right. ✓
- The field direction is the force on a positive charge, so a negative charge feels a force in the opposite direction. ✓
- Field lines start on the positive charge and end on the negative charge. ✓
- They curve across the gap from + to −, with arrows pointing from + to −. ✓
- The lines are most closely spaced (field strongest) close to each charge. ✓
- It is wrong because the field gets weaker with distance, not stronger. ✓
- The lines should be closest together near the charge and spread further apart with distance. ✓
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.
What is the direction of the electric field around an isolated positive charge?
- Aradially outward, away from the charge
- Bradially inward, toward the charge
- Cin circles around the charge
- Dthere is no field around a single charge
What does the electric field look like in the region between two oppositely charged parallel plates?
- Aa uniform field, with parallel, evenly spaced lines from the positive to the negative plate
- Ba radial field spreading out from the centre
- Ccircular field lines between the plates
- Dno field, because the plates cancel out
Quiz key
The electric field points the way a positive test charge would be pushed, so it points radially outward from a positive charge. Around a negative charge the field would point inward instead.
Between parallel plates the field is uniform: the lines are parallel, equally spaced, and run from the positive plate to the negative plate. A radial pattern belongs to a point charge, not parallel plates.
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.