a
(a) The total energy before connection
\( = \frac{1}{2} \times 4 \times {10^{ - 6}} \times {(50)^2} + \frac{1}{2} \times 2 \times {10^{ - 6}} \times {(100)^2}\)
\( = 1.5 \times {10^{ - 2}}J\)
When connected in parallel
\(4 \times 50 + 2 \times 100 = 6 \times V\) \(==>\) \(V = \frac{{200}}{3}\)
Total energy after connection
\( = \frac{1}{2} \times 6 \times {10^{ - 6}} \times {\left( {\frac{{200}}{3}} \right)^2} = 1.33 \times {10^{ - 2}}\,J\)