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(2)`q ,q being- ve
B. (b) Q = -`q/2` , q be -ve
C. (a) Q = ` 2sqrt(2)`q ,q being- ve
D. q = 2q , q be -ve

Answer

(a)

Explanation

Electric field,` E = 1/4 pi epsilon_(0)[Q^(2)/2a^(2) + sqrt(2) xx Qq/a^(2)]`
`:.1/4 pi epsilon_(0)[Q^(2)/2a^(2) + sqrt(2) xx Qq/a^(2)]` = 0
`:. Q/2 + sqrt(2)q = 0`
Q =` -2sqrt(2)q`
q is negative