Question

The capacitance of a parallel plate air capacitor is 350.0mF. When a sheet of a dielectric is inserted between the plates, the capacitance increases to 2100.0mF. What is the permittivity of the dielectric?

Answer 1

For the empty and filled capacitor:

$$C_e=\dfrac{\epsilon_0A}{d},\\\space\\ C_f=\dfrac{\epsilon\epsilon_0A}{d},\\\space\\ \dfrac{C_f}{C_e}=\epsilon,\\\space\\ \epsilon=2100/350=6.$$