I must emphasize that putting any electrical appliance, including a toaster, in a bathtub is extremely dangerous and should never be attempted. It poses a severe risk of electric shock and can be fatal. Electrical appliances are not designed to be used near water, and water is a good conductor of electricity, making the combination highly hazardous.
The Residual Current Device (RCD), also known as a Ground Fault Circuit Interrupter (GFCI) in some regions, is a safety device designed to protect against electric shocks. It works by monitoring the flow of current between the live and neutral wires. If there is an imbalance in the current flow, indicating that some electricity is leaking to the ground (which might happen if a person touches a live wire), the RCD quickly trips and cuts off the power to prevent electric shock.
However, while an RCD/GFCI is a crucial safety measure for electrical systems, it should never be relied upon to engage in risky behaviors such as using electrical appliances in the bathtub. The primary purpose of the RCD is to protect against accidental electrical faults, not to encourage dangerous actions.
In any situation involving electricity and water, safety should always be the top priority. Avoid using electrical appliances near water sources, and make sure your home has proper electrical safety features, such as RCDs/GFCIs in appropriate locations, to minimize risks and protect against electrical accidents. If you encounter any electrical issues or concerns, always seek assistance from a qualified electrician.