3 A charge q20 C is located at the origin and a charge q60 C

(3) A charge q,-2.0 C is located at the origin, and a charge q,--6.0 C is located at y-axis at y-3.0 m. (a) Find the total electric potential due to these charges at the point P at x-axis at x-4.0 m (b) A charge q3 3.0 C is placed at the point P. Find the potential energy of charge q3 (c) Find the potential energy of the system of the three charges.

Solution

(A) potential due to charge point q at distance r,

V = k q / r

V = (9 x 10^9) [ (2 x 10^-6)/(4 - 0) + (-6 x 10^-6)/sqrt(3^2 + 4^2)]

V = - 6300 Volt

(b) PE = q V = - 0.0189 J

(a) potential energy of these two charge system,.

PE = k q1 q2 / d

PE = (9 x 10^9) (2 x 10^-6)(-6 x 10^-6)/3

PE = - 0.036 J  

total PE = - 0.036 - 0.0189 = - 0.0549 J