Question

A parallel plate air capacitor of capacitance $C$ is connected to a cell of emf $V$ and then disconnected from it. $A$ dielectric slab of dielectric constant $K,$ which can just fill the air gap of the capacitor, is now inserted in it. Which of the following is incorrect?

• A. The energy stored in the capacitor decreases $K$ times.
• B. The change in energy stored is $\frac{1}{2}CV^{2}\left(\frac{1}{ K} - 1\right)$
• C. The charge on the capacitor is not conserved.
• D. The potential difference between the plates decreases $K$ times.

Answer 1

Answer: (C)

Battery disconnected then charge is constant.