Final answer:
It is true that a relay uses a small input current to control a large circuit current. Relays employ electromagnetic principles to allow low-power signals to switch larger currents safely and efficiently. They are essential in various applications for controlling power and ensuring circuit protection.
Step-by-step explanation:
A relay uses a small input current to control a large circuit current, which is true. Relays are electromagnetic devices that allow a small current flowing through one circuit to control the on/off status of another, typically larger, circuit current. This principle is critical in various applications, allowing for safe and efficient control of high-power devices by low-power signals.
In terms of circuit protection, relays play an essential role. For instance, circuit breakers rely on the principle of using a small trigger current to interrupt a potentially dangerous circuit current during faults or overloads, ensuring safety and preventing damage to equipment.