Charges Q are placed at the ends of a diagonal of a square and charges q are placed at the other two corners. The condition for the net electric force on Q to be zero is

Options

A. `Q = - 2sqrt(2q),q` being negative
B. `Q = - (q)/(sqrt(2)),q` being negative
C. `Q = 2sqrt(2q),q` being negative
D. Q = 2q ,q being negative

Explanation

Net force on D due to A and B `R=(Ksqrt(2)Qq)/(a^(2))`

Force on D due to B `=(KQ^(2))/(2a^(2))`
For net electric field on D to be zero
`K[(Q^(2))/(2a^(2))+(sqrt(2)Qq)/(a^(2))]=0`
`rArr " " (Q)/(2) + sqrt(2)q = 0`
`Q = - 2sqrt(2)q`
`therefore` q should be negative.