Circuit breakers protect circuits via electromagnetic switching in the live wire

Steps:

• Identify the device: A circuit breaker replaces a fuse to interrupt excessive current safely.
• Determine connection: It is wired into the live wire to break the circuit from the power source.
• Understand mechanism: High current activates an electromagnet, which opens a switch to disconnect the circuit.
• Compare to fuse: Unlike fuses, circuit breakers reset after tripping, without melting.

Why A is correct:

• Circuit breakers connect to the live wire, and excess current causes an electromagnet to open a switch, per standard electrical safety design.

Why the others are wrong:

• B: Describes a fuse's melting wire, not a circuit breaker's electromagnetic action.
• C: Fuses or breakers go in the live wire, not neutral; melting describes a fuse.
• D: Incorrectly places it in the neutral wire, which doesn't isolate the fault effectively.

Final answer: A