Two equal, positive charges, q=2 microC are located on the xaxis one at +0.3m and the other at -0.3m. A third charge Q=4 microCis located on the y axis at +0.4m.

a.) Find the magnitude and direction of resultant (net force)on Q.

b.) find the electric field and potential at the point(0.0,-0.4m)

## Answers ( 1 )

y= +0.4 m,x= 0. The third chargeQ=4.0 uC is placed at this point, D.q(placed atat A) isgiven byF_{Q1}=kq.Q/AD^{2}along thedirection AD outward.q(placedatat B) is given byF_{Q2}=kq.Q/BD^{2}along thedirection BD outward.^{-1}1.333 = 53.1^{o}Fcos ? on either side are equal andopposite; so they cancel each other.Fsin ? add up, beingalong the same direction.F_{c}=2.Fsin ? = 2kq.Q/AD^{2}; AD =0.5 mF_{c}=2x9x10^{9}x2x4x10^{-12}/x0.5x0.5 =0.346NF_{c}is along theyaxis(x= -0.4m)V_{P}=V_{P1}+V_{P2}+V_{P3}V=kq/rk= 9x10^{9}SIunits,r= 0.1m, 0.7 m an ?(0.4^{2}+ 0.4^{2}) =?0.32 = 0.566 m respectivelyE=kq/r^{2}whererhas theabove values.E_{1}andE_{2}are are the same along the -ve x axis. Theyadd up.E=?[(E_{1}+E_{2})^{2}+E_{3}^{2}+2.(E_{1}+E_{2}).E_{3}cos 45]