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Question: Two positive point charges of \(12\mu C\) and \(8\mu C\) are 10cm apart. The work done in bringing t...

Two positive point charges of 12μC12\mu C and 8μC8\mu C are 10cm apart. The work done in bringing them 4 cm closer is

A

5.8 J

B

5.8 Ev

C

13 J

D

13 eV

Answer

13 J

Explanation

Solution

W=Uf−Ui=9×109×Q1Q2[1r2−1r1]W = U_{f} - U_{i} = 9 \times 10^{9} \times Q_{1}Q_{2}\left\lbrack \frac{1}{r_{2}} - \frac{1}{r_{1}} \right\rbrack

⇒W=9×109×12×10−6×8×10−6[14×10−2−110×10−2]W = 9 \times 10^{9} \times 12 \times 10^{- 6} \times 8 \times 10^{- 6}\left\lbrack \frac{1}{4 \times 10^{- 2}} - \frac{1}{10 \times 10^{- 2}} \right\rbrack

= 12.96 J ≈ 13 J