🔍 Key Concepts

• Basic principle of how a solenoid works • Relationship between electromagnets and motion of valves • Difference between mechanical, electrical, hydraulic, and pneumatic (air) systems

💭 Think About

• Think about what actually creates the magnetic field inside a solenoid that pulls or pushes the valve stem. • Ask yourself: which of these options is commonly used to energize coils on starters, relays, and remote-operated valves on ships? • Consider which option can be switched on and off quickly from a control panel to operate a valve at a distance.

✅ Before You Answer

• Recall that a solenoid is essentially a coil that becomes a magnet when energized—what energizes that coil? • Eliminate options that describe what the valve might control (like fluid) instead of what powers the solenoid itself. • Check your marine engineering basics: what power source is usually wired to solenoid coils on engines, fuel shutoffs, and control systems?