Which device trips when there is leakage current to protect a person from electric shock?

Which device trips when there is leakage current to protect a person from electric shock?

• A. Residual current devices (RCDs)
• B. Circuit breakers
• C. Fuses
• D. Outer insulation

Answer: (A)

Protecting a person from electric shock relies on detecting leakage of current to earth and quickly cutting the power. A residual current device monitors the current in the live and neutral conductors and looks for any imbalance. Normally, the same amount of current flows in both wires. If some current leaks away—through a person or moisture to the earth—the current returning in the neutral is less, creating an imbalance. The RCD detects that difference and trips the circuit within milliseconds, removing the supply before a dangerous shock can occur. This is why it’s the device designed for leakage protection. Other devices work differently: a circuit breaker trips when there is too much current overall (overcurrent) or a short circuit, protecting wiring from overheating but not specifically addressing leakage to earth. A fuse also responds to excessive current by melting open, which stops the current but requires replacement. Outer insulation is simply a insulating material; it doesn't actively trip or disconnect—its job is to reduce the chance of contact with live parts, not to protect against leakage.

Protecting a person from electric shock relies on detecting leakage of current to earth and quickly cutting the power. A residual current device monitors the current in the live and neutral conductors and looks for any imbalance. Normally, the same amount of current flows in both wires. If some current leaks away—through a person or moisture to the earth—the current returning in the neutral is less, creating an imbalance. The RCD detects that difference and trips the circuit within milliseconds, removing the supply before a dangerous shock can occur. This is why it’s the device designed for leakage protection.

Other devices work differently: a circuit breaker trips when there is too much current overall (overcurrent) or a short circuit, protecting wiring from overheating but not specifically addressing leakage to earth. A fuse also responds to excessive current by melting open, which stops the current but requires replacement. Outer insulation is simply a insulating material; it doesn't actively trip or disconnect—its job is to reduce the chance of contact with live parts, not to protect against leakage.