Four metallic plates of equal surface area \(A\) are arranged, as shown in figure. The equivalent…

Four metallic plates of equal surface area \(A\) are arranged, as shown in figure. The equivalent capacitance between \(A\) and \(B\) is,
  1. \(\frac{\varepsilon_{0} A}{d}\)
  2. \(\frac{3 \varepsilon_{0} A}{d}\)
  3. \(\frac{3 \varepsilon_{0} A}{2 d}\)
  4. \(\frac{2}{3} \frac{\varepsilon_{0} A}{d}\)

Solution

The equivalent circuit for the given combination of plates is shown in figure. The effective capacitance of the series combination of \(C_{1}\) and \(C_{2}\) is


\(\begin{array}{c}
\frac{1}{C_{s}}=\frac{1}{C_{1}}+\frac{1}{C_{2}}=\frac{1}{\frac{\varepsilon_{0} A}{d}}+\frac{1}{\frac{\varepsilon_{0} A}{d}} \\
C_{s}=\frac{\varepsilon_{0} A}{2 d}
\end{array}\)
\(\mathrm{C}_{\mathrm{s}}\) and \(\mathrm{C}_{3}\) are parallel.
\(C_{A B}=C_{s}+C_{3}=\frac{\varepsilon_{0} A}{2 d}+\frac{\varepsilon_{0} A}{d}\)
\(\Rightarrow C_{A B}=\frac{3}{2} \frac{\varepsilon_{0} A}{d}\) *

Asked in: JEE Mains - Capacitance - Chapter Test

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