Gujarati
2. Electric Potential and Capacitance
medium

A variable condenser is permanently connected to a $100$ $V$ battery. If the capacity is changed from $2\,\mu \,F$ to $10\,\mu \,F$, then change in energy is equal to

A

$2 \times {10^{ - 2}}\,J$

B

$2.5 \times {10^{ - 2}}\,J$

C

$3.5 \times {10^{ - 2}}\,J$

D

$4 \times {10^{ - 2}}\,J$

Solution

(d) $\Delta U = {U_2} – {U_1} = \frac{{{V^2}}}{2}({C_2} – {C_1})$
$ = \frac{{{{(100)}^2}}}{2}(10 – 2) \times {10^{ – 6}} = 4 \times {10^{ – 2}}\,J$

Standard 12
Physics

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