Question

A point charge of $20$MC is situated at a point O. A and B are points $0.05$m and $0.15$m away from this charge. Calculate amount of work done to move an electron from B to A.

Answer 1

$Workdone=q\Delta V$--------(1)

Potential difference between A and O,$V_1$=$e\times r$

$V_1=\frac{kq}{r}$

$=\frac{k\times 20\times {10}^{-6}}{0.05}$

$V_1=0.0004kV$

Potential difference between B and O

$V_2=\frac{kq}{r}$

$=\frac{k\times 20\times {10}^{-6}}{0.15}$

$V_1=0.00013kV$

Work done in bringing an electron from A to O

${W}_{1}=q{V}_{1}$

Work done in bringing an electron from O to B

${ W }_{ 1 }=q{ V }_{ 1 }$

$W_{net}=W_1+W_2$

$=q(V_1+V_2)$

$=9\times {10}^9\times 1.6\times {10}^{-19}\left(0.00053\right)$

$W_{net}=7.632\times {10}^{-13}J$

Here $k=9\times {10}^9$ which have been taken common from the values of V