Which statement best describes the effect of inserting a dielectric on a capacitor's ability to store charge at a given voltage?

Which statement best describes the effect of inserting a dielectric on a capacitor's ability to store charge at a given voltage?

• A. It allows the capacitor to store more charge
• B. It reduces the stored charge
• C. It has no effect
• D. It causes the capacitor to short

Answer: (A)

Inserting a dielectric increases a capacitor’s ability to store charge at a fixed voltage because it raises the capacitance. Capacitance is C = ε0 εr A / d, so adding a dielectric with a higher dielectric constant εr increases C. With a constant voltage applied, the stored charge is Q = C V, so a larger C means more charge on the plates. The energy stored also grows as (1/2) C V^2. The dielectric does not short the capacitor; it merely polarizes to weaken the internal field for a given charge, allowing more charge to accumulate when the voltage is held steady by the source.

Inserting a dielectric increases a capacitor’s ability to store charge at a fixed voltage because it raises the capacitance. Capacitance is C = ε0 εr A / d, so adding a dielectric with a higher dielectric constant εr increases C. With a constant voltage applied, the stored charge is Q = C V, so a larger C means more charge on the plates. The energy stored also grows as (1/2) C V^2. The dielectric does not short the capacitor; it merely polarizes to weaken the internal field for a given charge, allowing more charge to accumulate when the voltage is held steady by the source.