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JEE Mains · Physics · STD 12 - Electric potential and capacitance
  • JEE Mains 2020
  • Medium
  • Numerical

A \(5\, \mu F\) capacitor is charged fully by a \(220\,V\) supply. It is then disconnected from the supply and is connected in series to another uncharged \(2.5\;\mu F\) capacitor. If the energy change during the charge redistribution is \(\frac{ X }{100} \;J\) then value of \(X\) to the nearest integer is\(.....\)

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Answer & Solution

Correct Answer

(A) \(4\)

Step-by-step Solution

Detailed explanation

\(u _{ i }=\frac{1}{2} \times 5 \times 10^{-6}(220)^{2}\)

Final common potential

\(v=\frac{220 \times 5+0 \times 2.5}{5+2.5}=220 \times \frac{2}{3}\)

\(u _{ f }=\frac{1}{2}(5+2.5) \times 10^{-6}\left(220 \times \frac{2}{3}\right)^{2}\)

\(\Delta u = u _{ f }- u _{ i }\)

\(\Delta u =-403.33 \times 10^{-4}\)

\(\Rightarrow-403.33 \times 10^{-4}=\frac{ X }{100}\)

\(X=-4.03\)

or magnitude or value of \(X\) is approximate \(4\)

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