Two metal plates A. increase

B. decrease

C. remain the same

D. become zero

Dielectric constant of a substance is the factor>1) by which the capacitance increases from its vacuum value, when the dielectric is inserted fully between the plates of the capacitor

∴

Where,

C=capacitance in presence of dielectric

C₀=capacitance in presence of vacuumK=1)

The electric field between the plates of a capacitor when the space between the plates is filled with a dielectric of dielectric constant K is given by

Where,

Q=charge on the capacitor

A=area of metal plates

K=dielectric constant

ϵ₀=permittivity of vacuum

When dipped in oil tank value of K>1

When oil is removed there is air between the plates with K~1

∴ the value of K decreases when oil is pumped out

By the formula,

So as K decrease from greater than 1 to 1 , the electric field increases.

Therefore, after pumping out oil, the electric field between the plates increases.