A focused three-component revision and exam practice pack for SP10i, covering the complete Edexcel Separate Science Physics specification for mains wire functions, earth wires, fuses, circuit breakers and the danger of live-to-earth connections (P10.37–P10.41).

Topic Mastery Sheet covers the three mains wires in a reference table (colour, potential difference, function); the mechanism by which the earth wire prevents electric shock - live wire touches metal case → large current flows through earth wire (low resistance path) → blows fuse → circuit broken → case no longer live; a comparison of fuses and circuit breakers (fuses are cheaper but must be replaced; circuit breakers can be reset); and a specific explanation of why switches and fuses must be in the live wire, not the neutral wire - if in the neutral wire, the appliance remains connected to the live 230 V when switched off, making any contact with it potentially fatal. The common misconception that current normally flows through the earth wire is addressed directly.

Student Exam Practice Sheet includes a three-row mains wire table completion (colour and p.d. per wire); a two-mark explanation of why switches and fuses go in the live wire; a three-mark earth wire function explanation; and a one-mark circuit breaker advantage question. Question format matches the Edexcel Higher test style.

Teacher Answer Key provides a complete mark scheme noting that the wire table requires both colour and p.d. per row for the mark, that the earth wire explanation requires the three-step causal chain (fault current → blows fuse → circuit broken) for full credit, and that “can be reset / does not need replacing” is the accepted circuit breaker advantage.

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