Question

The insertion of a dielectric between the plates of a parallel-plate capacitor always

• A. increases its capacitance
• B. decreases its capacitance
• C. remains same its capacitance
• D. none of the above

Answer 1

The correct option is A increases its capacitance

The capacitance of a parallel plate capacitor completely filled with a given material of dielectric constant $K$ is given by:

$C=\frac{K{\epsilon }_{0}A}{d}$ .....................eq1

And the capacitance of the same capacitor without the given material is given by:

$C^{\prime }=\frac{{\epsilon }_{0}A}{d}$ .....................eq2

Dividing eq1 by eq2:

$C/C^{\prime }=K$

As $K>1$ always, hence $C>C^{\prime }$ i.e. the insertion of a dielectric between the plates of a parallel -plate capacitor always increases the capacitance.