Question

A parallel plate air capacitor has capacity $C$ farad, potential $V$ volt and energy $E$ joule. When the gap between the plates is completely filled with dielectric

• A. both V and E increase
• B. both V and E decrease
• C. V decreases, E increases
• D. V increases, E decreases

Answer 1

Answer: (B)

A parallel- plate capacitor with a dielectric.
The electric field is reduced between the plates because the dielectric material is polarized, producing an opposing field.
When there is a dielectric, the potential is also reduced because potential is inversely proportional to dielectric
$V^{\prime }=\frac{V}{K}$ where $K$ is dielectric constant.