Isolated Power Supply — FRCA Primary MCQ
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Correct answer: E — Providing no earth reference so that a single fault does not complete a circuit through the patient to earth
An isolated power supply (transformer with no earth reference on the secondary winding) means that a single fault (patient touching one live wire) does not complete a circuit to earth — current cannot flow through the patient. A line isolation monitor detects current leakage to earth and alarms if it exceeds a safe limit (usually 2-5 mA).
Reference: Al-Shaikh Stacey 2019 Essentials of Anaesthetic Equipment