Q 12-02-211JEE MainJEE Main 2025 (4 Apr, Shift 2)Easy
Three parallel plate capacitors $C_1$, $C_2$ and $C_3$, each of capacitance $5\ \mu\text{F}$, are connected as shown in the figure ($C_1$ and $C_2$ in series, together in parallel with $C_3$). The effective capacitance between points A and B, when the space between the parallel plates of capacitor $C_1$ is filled with a dielectric medium having dielectric constant 4, is:
Answer: (C) $9\ \mu\text{F}$
With the dielectric, $C_1 = 4\times5 = 20\ \mu\text{F}$; $C_2 = C_3 = 5\ \mu\text{F}$.
$C_1$ and $C_2$ in series: $\dfrac{20\times5}{20 + 5} = 4\ \mu\text{F}$. In parallel with $C_3$:
$$C_{AB} = 4 + 5 = 9\ \mu\text{F}$$
Solution by Sreeraj P, M.Sc Physics