Red Seal Industrial Electrician Practice Exam

What type of protection does a Residual Current Device (RCD) provide?

1. Protection against voltage surges

2. Protection against overloads in circuits

3. Protection against electrical shock by detecting current imbalances

4. Protection against electromagnetic interference

The correct answer is: Protection against electrical shock by detecting current imbalances

A Residual Current Device (RCD) is designed specifically to protect individuals from electrical shock by detecting imbalances between the live (phase) and neutral conductors within a circuit. When a fault occurs, such as a person accidentally coming into contact with a live wire, the amount of current flowing through the live wire will differ from that returning through the neutral wire. The RCD senses this difference, known as a residual current, and rapidly disconnects the circuit, minimizing the risk of electric shock. This type of device is particularly important in preventing serious injuries or fatalities caused by electric shocks and is commonly used in residential and commercial electrical installations to enhance safety. The rapid disconnection can happen in milliseconds, providing a crucial layer of protection. In contrast, devices that protect against voltage surges are meant to manage spikes in electrical energy, such as those caused by lightning strikes or power surges, but they do not provide shock protection. Similarly, protection against overloads refers to devices like circuit breakers or fuses that prevent overheating from excessive current but do not detect imbalance in current flow. Lastly, protecting against electromagnetic interference deals with issues related to radio frequency interference and does not involve electrical shock protection. All other options address different aspects of electrical safety and circuit protection