What device converts electrical energy into a magnetic field to operate a valve?

• A. solenoid
• B. motor
• C. transformer
• D. relay coil

Answer: (A)

A solenoid is a coil of wire that creates a magnetic field when current flows. This magnetic field pulls or pushes a metal plunger, directly opening or closing the valve in a linear, controlled way. That direct electromagnetic actuation is what makes a solenoid ideal for valve operation.

A motor provides rotational motion, which isn’t as straightforward for opening/closing a valve. A transformer is about transferring energy between circuits using magnetic fields and doesn’t move mechanical parts. A relay coil also produces a magnetic field to switch contacts and can indirectly control a valve by driving a relay, but the device that directly moves the valve is the solenoid.