Which term defines a capacitor whose capacitance changes by changing the area of its plates?

Which term defines a capacitor whose capacitance changes by changing the area of its plates?

• A. Open Capacitors
• B. Counter EMF
• C. Variable Capacitors
• D. Shorted Capacitors

Answer: (C)

Capacitance changes with physical dimensions, specifically C = εA/d, so increasing the overlapping plate area directly increases the capacitance while keeping the separation and dielectric constant constant. A device designed to vary that area—such as the rotor and stator plates that slide or rotate to change how much area overlap occurs—is a variable capacitor. That’s why this term best describes a capacitor whose capacitance is altered by changing plate area. The other terms don’t describe a tunable capacitor: “Open” capacitors isn’t a standard designation for a tunable device; Counter EMF relates to inductors and changing current in a coil, not a capacitor’s plate area; Shorted capacitors would imply a fault where the plates are effectively connected together, not a means of adjusting capacitance.

Capacitance changes with physical dimensions, specifically C = εA/d, so increasing the overlapping plate area directly increases the capacitance while keeping the separation and dielectric constant constant. A device designed to vary that area—such as the rotor and stator plates that slide or rotate to change how much area overlap occurs—is a variable capacitor. That’s why this term best describes a capacitor whose capacitance is altered by changing plate area.

The other terms don’t describe a tunable capacitor: “Open” capacitors isn’t a standard designation for a tunable device; Counter EMF relates to inductors and changing current in a coil, not a capacitor’s plate area; Shorted capacitors would imply a fault where the plates are effectively connected together, not a means of adjusting capacitance.