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A parallel plate capacitor with width 4 \mathrm{~cm}, length 8 \mathrm{~cm} and separation between the plates of 4 \mathrm{~mm} is connected to a battery of 20 \mathrm{~V}. A dielectric slab of dielectric constant 5 having length 1 \mathrm{~cm}, width 4 \mathrm{~cm} and thickness 4 \mathrm{~mm} is inserted between the plates of parallel plate capacitor. The electrostatic energy of this system will be___________ \mathrm{\epsilon_{0} J}. (Where \mathrm{\epsilon_{0} } is the permittivity of free space)

Option: 1

240


Option: 2

-


Option: 3

-


Option: 4

-


Answers (1)

best_answer

\mathrm{Area=length\times width=32\times 10^{-4}m^{2}}

\mathrm{C_{eq}=C_{1}+C_{2}}

\mathrm{C_{eq}=\frac{7A\varepsilon _{0}}{8d}+\frac{A\varepsilon _{0}k}{8\left ( d \right )}}

        \mathrm{=\frac{A\varepsilon _{0}}{d}\left ( \frac{7}{8}+\frac{5}{8} \right )}

        \mathrm{C_{eq}=\frac{3A\varepsilon _{0}}{2d}}

Eletrostatic energy of the system is

\mathrm{U=\frac{1}{2}C_{eq}V^{2}}

\mathrm{\frac{3}{4}\times \frac{32\times 10^{-4}\varepsilon _{0}}{4\times 10^{-3}}\times 400}

\mathrm{U=240\varepsilon _{0}J}

The electrostatic energy of this system will be \mathrm{240\varepsilon _{0}J}

Posted by

Kuldeep Maurya

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