Which change will directly increase the amount of charge stored on a capacitor if the voltage across it remains fixed?

• A. Increasing distance between plates.
• B. Increasing plate area.
• C. Decreasing plate area.
• D. Replacing with a dielectric of lower permittivity.

Answer: (B)

When the voltage across a capacitor is kept constant, the amount of charge stored is Q = C V. So increasing the capacitance C directly increases the stored charge because V is fixed. For a parallel-plate capacitor, C is proportional to the plate area A (C ∝ ε A / d). Increasing the plate area raises C, which in turn increases Q at the same voltage. The other changes would either increase plate separation (which lowers C), reduce plate area (lower C), or use a dielectric with lower permittivity (lower C). Thus, increasing the plate area is the change that increases the stored charge when voltage stays fixed.