Case : Read the passage and answer the question(s).

An empty 20 pF capacitor is charged to a potential difference of 40 V. The charging battery is then disconnected, and a piece of Teflon with a dielectric constant of 2.1 is inserted to completely fill the space between the capacitor plates.

What are the energy stored in the capacitor with and without dielectric?

7.6 nJ, 16 nJ

All the options are different so we need to calculate just one. Let's calculate the energy stored without capacitance.

U = \(\frac{1}{2}\) C V²

C = 20 x 10^-12 F ; V = 40 V

U = 16 nJ