As a guideline, energize solenoids through ______, if possible.

• A. Direct power
• B. Control relays
• C. Battery power
• D. Pushbutton switches

Answer: (B)

Solenoids draw a fairly large current when they energize, and you want that heavy current handled by a device designed for it, while the control side stays safe and low‑power. A control relay is exactly that intermediary: its coil is driven by a small, safe control signal, and its contacts switch the higher current to the solenoid from the proper supply. This provides electrical isolation between the control circuitry and the power circuit, protects the control equipment from voltage spikes or arcing, and lets you control the solenoid from logic, sensors, or remote controls. Pushing current directly through a pushbutton or powering the solenoid directly from a battery is risky and impractical for control purposes—it can overload the switch, wear it out, and remove the needed isolation. So energizing through a control relay is the correct, reliable approach.