Red Seal Instrumentation and Control Technician Practice Exam

What is the purpose of a relay in control circuits?

1. To store information temporarily

2. To amplify weak signals

3. To control a high-power device with a low-power signal

4. To filter out high-frequency noise

The correct answer is: To control a high-power device with a low-power signal

The purpose of a relay in control circuits is fundamentally about controlling high-power devices with a low-power signal, which is exactly what is achieved when using a relay. A relay functions as an electromechanical switch that allows a low-voltage signal to control the operation of a higher voltage and current circuit. This capability is crucial in many applications where it is unsafe or impractical to control high power directly with a low-power input, as it ensures isolation between the control and the load circuits. By utilizing a low-power signal to energize the relay coil, the relay then activates the switch to either make or break the connection in the high-power circuit. This allows for greater safety and flexibility in circuit design, particularly in industrial and automation processes. The other options provided do not accurately describe the primary function of a relay in control circuits. While relays can indirectly impact signal integrity (as in filtering), the primary role they serve is in the safe and effective control of power devices through minimal signal inputs.