A charge of 8mC is located at the origin. Calculate the work done in taking a small charge of `-2 xx 10^(-9)C` from a point P (0,0,3 cm) to a point Q(0,4cm,0), via a point F (0.6 cm, 9cm).

Explanation

q=8mC `=8 xx 10^(-3)C q_(0)=-2 xx 10^(-9)C`
Work done =change in PE
`U_(1)=(1)/(4pi epsi_(0)) (q_(1)q_(2))/(r_(1)r_(2))=(9 xx 10^(9) xx 8 xx 10^(-3) xx (-2) xx 10^(-9))/(3 xx 10^(-2))`
`U_(2)=(9 xx 10^(9) xx 8 xx 10^(-3) xx -2 xx 10^(-9))/(4 xx 10^(-2))`
`U_(2)-U_(1)=(9 xx 10^(9) xx 8 xx 10^(-3) xx 2 xx 10^(-9))/(10^(-2)) {1/3-1/4}=9 xx 8 xx 2xx 10^(-1) xx 1/(12)=1.2J`