Alternating Current · SHS3 Physics

Lesson notes

Learning Objectives

Indicator: 3.3.2.LI.1 - Discuss the characteristics of alternating current/voltage.

By the end of the lesson, learners can:

Define alternating current (AC) and alternating voltage in their own words, distinguishing them from direct current (DC).
Explain the terms peak current (Io), peak voltage (Vo), root mean square current (Irms) and root mean square voltage (Vrms) with reference to a sinusoidal waveform.
State the mathematical relationships between peak and rms values for both current and voltage, and use them to solve simple numerical problems at Level 3 (strategic reasoning) depth.
Sketch and label a sinusoidal AC waveform showing the peak value, time period and one complete cycle.
Justify why the rms value, rather than the peak value, is used when specifying AC quantities in homes and industry.

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Curriculum details

Strand: Electric Field, Magnetic Field and Electronics (Strand 3)
Sub-strand: Alternating Current (3.2)
Content standard: 3.3.2.CS.1 - Demonstrate knowledge and understanding of Alternating Current Theory. 3.3.2.LO.1 Describe alternating current and utilise the associated mathematical relationships
Indicator: 3.3.2.LI.1 - Discuss the characteristics of alternating current/voltage.
Suggested placement: Semester 2, Week 3 (Week 23 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. 178

Exemplars (from the NaCCA curriculum)

Collaborative learning: Using the videos and simulation as well as internet/reference books let learners research to find the meaning of the following (i) Peak current Io, (ii) Peak voltage Vo, (iii) Root mean square value of alternating current I rms (iv) root mean square value of alternating voltage Vrms terms.
Provide equitable access to resources and opportunities.
Assessment (3.3.2.AS.1). The document marks these depth-of-knowledge levels for this indicator: Level 3 Strategic reasoning.
Teaching and Learning Resources:
- Audio-visuals
- Internet
- Projectors
- YouTube
- Interactive
- Reference virtual laboratory books