In a variable resistance type fuel contents gauge, what component moves to vary resistance?

• A. A dielectric.
• B. A float.
• C. A coil.
• D. A vacuum tube.

Answer: (B)

The moving part is the float. In a variable resistance fuel contents gauge, the float sits on the fuel surface and is connected to a rod or linkage that carries a sliding contact along a resistive element. As the fuel level rises or falls, the float moves correspondingly, shifting the contact and thus changing the resistance in the circuit that feeds the gauge. The gauge then indicates the fuel level based on this resistance change. Other options don’t serve as the active moving element in this type of gauge: a dielectric is a non-moving insulating material in a capacitor, a coil isn’t the moving component for this mechanism, and a vacuum tube isn’t used in this application.