The shape of the lesson
By the end of the lesson, learners can
- Read the symbols: Match each symbol to its component and see how the input transducers respond.
- What each component does: Some components simply pass current; others sense light or heat, or switch and steer the current.
- Meters: ammeter in series, voltmeter in parallel.
- Cell: long line positive, short line negative.
- Diode: current passes only in the direction the triangle points.
One picture every idea returns to
Components are drawn with standard symbols. A light-dependent resistor has a low resistance in bright light, a thermistor has a low resistance when hot, a relay uses a small current to switch a larger one, and a diode allows current in one direction only.
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 language of circuits.. A circuit diagram is a kind of writing, each squiggle a known component. | Whole class, then pairs |
| 5 to 17 min | Teach and check: Read the symbols | Match each symbol to its component and see how the input transducers respond. Project tab 1 of the lab (Circuit builder) and let a student drive it while the class predicts. | Whole class, then pairs |
| 17 to 30 min | Teach and check: What each component does | Some components simply pass current; others sense light or heat, or switch and steer the current. | 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, 13 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 What each component does, 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 |
|---|---|
| An LDR has a high resistance in the dark and a low resistance in bright light. | A thermistor has a high resistance when cold and a low resistance when hot. It is easy to state both the wrong way round. |
Circuit symbols and components: worksheet
6 questions, 13 marks. Written in the style of the papers; no past paper question is reproduced.
Name the component represented by each of these symbols: (a) a circle with the letter A, (b) a circle with a cross inside, (c) a triangle touching a straight bar.
State how an ammeter and a voltmeter should each be connected into a circuit.
Describe how a thermistor and a light-dependent resistor each respond to a change in their surroundings.
A student wants to draw a circuit with a cell, a switch and a lamp connected one after another. Describe the diagram, and state what the long line and the short line on the cell represent.
State the purpose of a fuse in a circuit, and describe what happens to it if the current becomes too large.
A diode is placed in a circuit so that its triangle points from the positive terminal toward the lamp. State whether the lamp lights, and explain. Then state what happens if the diode is reversed.
Answer key and marking notes
- (a) an ammeter. ✓
- (b) a lamp. ✓
- (c) a diode. ✓
- An ammeter is connected in series. ✓
- A voltmeter is connected in parallel (across the component). ✓
- A thermistor: its resistance falls as its temperature rises. ✓
- A light-dependent resistor: its resistance falls as the light gets brighter. ✓
- A single loop with the cell, switch and lamp joined in series by straight lines (wires). ✓
- The long line is the positive terminal and the short line is the negative terminal. ✓
- A fuse protects the circuit from too large a current. ✓
- If the current is too large, the fuse wire melts and breaks the circuit, stopping the current. ✓
- The lamp lights, because the diode is forward (current can pass in the direction the triangle points). ✓
- If the diode is reversed, it blocks the current and the lamp does not light. ✓
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.
The resistance of a light-dependent resistor (LDR) changes with light. What happens to its resistance as the light gets brighter?
- AIts resistance decreases.
- BIts resistance increases.
- CIts resistance stays the same.
- DIt stops conducting completely.
Which circuit symbol represents a fuse?
- AB: a rectangle with a line through it
- BA: a plain rectangle
- CC: a circle with a cross
- Dthey are all fuses
Quiz key
An LDR's resistance decreases as the light intensity increases, letting more current pass. This is why LDRs are used in light-sensing circuits such as automatic street lamps.
Symbol B, a rectangle with a line through it, is a fuse. A plain rectangle (A) is a resistor, and a circle with a cross (C) is a lamp.
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.