Direct Current · SHS3 Physics

Lesson notes

Learning Objectives

Indicator: 3.3.1.LI.2 - Describe and demonstrate the types of variable resistors i.e., potentiometers and rheostats and their working principles.

By the end of the lesson, learners can:

Identify potentiometers and rheostats from their physical appearance, circuit symbols, and terminal arrangements.
Describe the working principle of a variable resistor, explaining how the position of a sliding contact changes the effective resistance in a circuit.
Distinguish between a potentiometer (three-terminal device used as a voltage divider) and a rheostat (two-terminal device used to control current), giving at least two uses of each.
Demonstrate, using a virtual circuit simulator or physical components, how adjusting a variable resistor changes the brightness of a bulb or the reading on a meter.
Select the appropriate type of variable resistor for a given application and justify the choice based on the circuit requirements.

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Curriculum details

Strand: Electric Field, Magnetic Field and Electronics (Strand 3)
Sub-strand: Direct Current (3.1)
Content standard: 3.3.1.CS.2 - Demonstrate knowledge and understanding of the structure and working principles of resistors. 3.3.1.LO.2 Characterise resistors through calculation, identification and propose suitable resistors for a given electrical circuit.
Indicator: 3.3.1.LI.2 - Describe and demonstrate the types of variable resistors i.e., potentiometers and rheostats and their working principles.
Suggested placement: Semester 1, Week 20 (Week 20 of the year)
Our suggestion, laid out in curriculum order across three terms of twelve weeks. NaCCA does not fix the week, so follow your school's scheme of learning.
Curriculum reference: NaCCA curriculum document, p. 174

Exemplars (from the NaCCA curriculum)

Collaborative and Experiential learning:
- In pairs, learners identify the types of variable resistors.
- Learners describe how variable resistors are used in electrical circuits.
Ensure that the teaching materials, examples, and illustrations reflect diverse perspectives.
Assessment (3.3.1.AS.2). The document marks these depth-of-knowledge levels for this indicator: Level 2 Skills of conceptual understanding; Level 3 Strategic reasoning.
Teaching and Learning Resources:
- Audio-visuals
- Internet
- Projectors
- YouTube
- Interactive laboratory,
- Connecting virtual wires
- Ammeter
- Galvanometer
- Voltmeter
- Resistance
- Rheostats
- Standard box resistors