IIT JEE , AIEEE Forum - Chemistry , Physical Chemistry

ssbrightstar1

Four identical free charges each of value q are located at the four corners of

the square of side a.What charge must be placed at the center for the

system to be in equilibrium?

krishnagn

for the charges to be in equilibrium consider anyone charge q placed at one corner.let it be placed at the top right corner.
(draw as the steps proceed)
then a force of (kqq/a*a) acts along right(repulsive).
same magnitude force acts downwards.
a force of (k*q*q)/(2*a*a) acts towards along the diagonal but opp. in dirn. to the charge placed at bottom left corner.
also a force of (2*k*Q*q/a*a) acts due the charge Q placed ar centr.
resolve these, add and equate to 0

sagarvaze

have already answered check http://www.goiit.com/posts/list/electricity-four-52896.htm

rate me if it helped you

krishnagn

i got the answer as (root2+1)*q/4

please rate if the answer was helpful

krishnagn

but i don't think the answer given in that link is right.
it is force and needs to be resolved.
u can't simply add.
also there can't be attractive force since all are of same sign