Electrostatics · SHS2 Physics

Lesson notes

Learning Objectives

Indicator: 2.3.1.LI.5 - Calculate the energy stored in a capacitor.

By the end of the lesson, learners can:

State the formula for energy stored in a capacitor as E = 1/2 QV, E = 1/2 CV², and E = Q²/2C, and recall the units of energy (joules).
Calculate the energy stored in a capacitor given any two of the three quantities (charge Q, capacitance C, potential difference V).
Convert between the three forms of the energy formula using the relation Q = CV.
Explain, using practical reasoning, why the energy stored in a capacitor depends on the square of the voltage, not just the voltage itself.
Solve multi-step problems that require finding the energy stored after calculating capacitance or potential difference first.

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Curriculum details

Strand: Electric Field, Magnetic Field and Electronics (Strand 3)
Sub-strand: Electrostatics (3.1)
Content standard: 2.3.1.CS.2 - Demonstrate knowledge and understanding of the structure and operation of capacitors. 2.3.1.LO.2 Explain and analyse the structure and working principles of capacitors and calculate capacitance.
Indicator: 2.3.1.LI.5 - Calculate the energy stored in a capacitor.
Suggested placement: Semester 2, Week 5 (Week 25 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. 121

Exemplars (from the NaCCA curriculum)

Project-Based learning: Learners in mixed groups present the mode of operation and principles of applications that depend on energy stored in a capacitor. Learners calculate the potential difference and capacitance using the relation Q=Cv
Ensure that the teaching materials, examples, and illustrations reflect diverse perspectives.
Assessment (2.3.1.AS.5). The document marks these depth-of-knowledge levels for this indicator: Level 1 Recall; Level 3 Strategic reasoning.
Teaching and Learning Resources:
- Science experimental kit with capacitors and connectors