Switch in live wire ensures safe isolation

Steps:

• Identify the live wire as the one carrying current from the supply to the load.
• Recognize that switching the live wire disconnects the supply voltage to the lamp.
• Understand that this isolates the lamp, preventing shock even if touched.
• Confirm this aligns with electrical safety practices for lighting circuits.

Why A is correct:

• Isolating the lamp from the live supply prevents electric shock, per electrical safety standards like IEC 60364, which require switches to break the live conductor.

Why the others are wrong:

• B: Fuse placement in live wire is for protection, unrelated to switch position.
• C: Switches function in any wire but are placed in live for safety isolation.
• D: Earth wire carries minimal current under normal conditions, irrelevant to switch placement.

Final answer: A