What is the role of protective devices such as MCBs and RCBOs in circuits?

• A. They measure energy consumption
• B. They interrupt fault currents to prevent damage, fire, and electric shock.
• C. They provide a constant current source
• D. They reduce voltage to appliances

Answer: (B)

Protective devices like MCBs and RCBOs are there to stop damage and danger by cutting off power when something goes wrong in a circuit. An MCB trips if the current gets too high, such as during an overload or short circuit, so the circuit is opened before wires overheat. An RCBO adds an extra protection layer by also watching for leakage current to earth; if current escapes to the earth (which can indicate a shock hazard or insulation fault), it trips to prevent electric shock and reduce fire risk. In short, they interrupt fault currents to keep people safe and protect wiring and equipment.

These devices don’t measure energy consumption (that’s what meters do), they’re not a constant current source (they don’t supply power), and they don’t reduce voltage to appliances (that’s handled by transformers or regulators).