Final answer:
The presence of an indicator light for the parking brake in vehicles is a safety feature that operates based on the principles of electrical systems, where a significant current draw, like starting a car engine, might cause other lights to dim momentarily.
Step-by-step explanation:
The question pertains to the behavior of electrical systems in vehicles, specifically the dimming of lights when heavy electrical loads start up. This is due to the fact that starting the engine or a compressor in a refrigerator requires a large amount of current, which can cause a temporary voltage drop in the electrical system. This phenomenon can be noticed when the lights, such as the passenger compartment light or refrigerator light, dim momentarily. It's a clear example of how resistance and current draw in an electrical circuit can impact the performance of other components connected to the same power source. The same principle can explain the function of the indicator light for the parking brake in vehicles. The light will come on when the vehicle is started and will remain on as long as the parking brake is engaged, serving as an important safety feature.