IGCSE Physics: Fuses and Circuit Breakers | Edexcel Modular | Unit 2 | L12

This lesson covers spec points 2.2 and 2.3 — explaining the heating effect of
current, describing how fuses and circuit breakers work, and selecting
appropriate fuse ratings using P = IV.

PowerPoint includes:
• Retrieval starter reviewing plug wiring and safety from L11
• Direct Instruction (I Do) — heating effect of current explained qualitatively;
fuse mechanism described step by step; fuse selection using I = P/V modelled;
circuit breaker mechanism described (electromagnet or bimetallic strip);
advantages of circuit breakers over fuses; RCCB introduced as protecting
against electric shock
• Guided Practice (We Do) — three tasks: explain how a fuse works; select the
correct fuse rating for a given appliance; state one advantage of a circuit
breaker over a fuse
• Independent Practice (You Do) — fuse mechanism; fuse selection calculations;
circuit breaker vs fuse comparison; heating effect as hazard and safety feature
• Review and Reflect — 3 MCQs and exit ticket

Activity Sheet includes:
• Formula box: P = IV
• 10 exam-style questions covering the heating effect, fuse mechanism, fuse
selection calculations, circuit breaker advantages and the RCCB
• Stretch question: oven — calculate operating current, justify fuse rating,
explain fault protection and suggest why modern homes use circuit breakers
• Full mark scheme for teacher use