What role do circuit relays serve in electrical systems?

Circuit relays play a crucial role in electrical systems by enabling the control of high-power circuits using a low-power signal. This functionality is essential for various applications, especially in situations where direct control of high voltage or high current devices might be dangerous or impractical.

When a low-power control signal energizes the relay, it activates the magnetic coil within the relay, which then closes or opens the connection in the high-power circuit. This allows for the safe operation of devices that require significantly more power without risking damage to the control circuit or operator safety. The use of relays enhances system automation and provides a reliable method for controlling various electrical devices from a distance.

With this understanding, it's clear why the other options do not accurately describe the primary function of circuit relays. Preventing electrical shock, for instance, is more related to safety measures such as Ground Fault Circuit Interrupters (GFCIs) rather than the control function of relays. Storing back-up power is typically the role of batteries or capacitors. Measuring electrical voltage is a function performed by voltmeters or measurement devices, not relays. Therefore, the focus on control through low-power signals accurately encapsulates the essential purpose of circuit relays in electrical systems.