Two capacitors, each having capacitance 40 μ F are connected in series. The space between one of the…

When a dielectric is inserted between the sheets of a capacitor, its capacitance becomes $KC$.

Now the equivalent capacitance in series combination will be,

$$\begin{gathered} C_{\mathrm{eq}}=\frac{C\times KC}{C\left(1+K\right)} \\ \Rightarrow 24=\frac{40K}{1+K} \\ \Rightarrow K=1.5 \end{gathered}$$