Question 138 of 180

A $60pF$ capacitor is fully charged by a $20V$ supply. It is then disconnected from the supply and is connected to another uncharged $60pF$ capacitor in parallel. The electrostatic energy that is lost in this process by the time the charge is redistributed between them is (in $nJ$ ) ________

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Answer: 6

${V}_{0}=20V$
Heat loss $={U}_{i}-{U}_{t}$
$=\dfrac{1}{2}C{v}_{o}^{2}-2\left[\dfrac{1}{2}C{\left(\dfrac{{V}_{0}}{2}\right)}^{2}\right]$
$=\dfrac{C{V}_{o}^{2}}{4}$
$=\dfrac{\left(60\times {10}^{-12}\right){\left(20\right)}^{2}}{4}J$
$=6\times {10}^{-9}J=6nJ$