Three plates $A,\;B,\;C$each of area $50\,c{m^2}$ have separation $3\,mm$ between $A$ and $B$ and $3\,mm$ between $B$ and $C$. The energy stored when the plates are fully charged is
Medium
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(b) There are two capacitors parallel to each other.
Total capacitance$ = \frac{{2{\varepsilon _0}A}}{d}$
Energy stored $ = \frac{1}{2}\left( {\frac{{2{\varepsilon _0}A}}{d}} \right)\,{V^2}$
$ = \frac{{8.86 \times {{10}^{ - 12}} \times 50 \times {{10}^{ - 4}} \times {{12}^2}}}{{3 \times {{10}^{ - 3}}}} = 2.1 \times {10^{ - 9}}\,J$
Total capacitance$ = \frac{{2{\varepsilon _0}A}}{d}$
Energy stored $ = \frac{1}{2}\left( {\frac{{2{\varepsilon _0}A}}{d}} \right)\,{V^2}$
$ = \frac{{8.86 \times {{10}^{ - 12}} \times 50 \times {{10}^{ - 4}} \times {{12}^2}}}{{3 \times {{10}^{ - 3}}}} = 2.1 \times {10^{ - 9}}\,J$
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