Question

in the figure if net force on q is zero then value of Q/q is

Answer 1

please send the picture first

Answer 2

your question is incomplete ,
Well, I attached figure as mentioned in figure .

net force on Q is zero , it means Q and q are in opposite nature .
Let Q is positive nature and q is negative nature 
Then, force between Q and Q will be repulsion, 
And force between Q and q will be attraction, 

Now, net force act on Q =net force act by q - net force act by Q on Q = 0
net force act by q on Q = net force act by Q on Q 

$\sqrt{[\frac{kqQ}{r^2}]^2+[\frac{KqQ}{r^2}]^2}=\frac{KQQ}{(\sqrt{2}r)^2}\\\\\sqrt{2}\frac{KqQ}{r^2}=\frac{KQQ}{2r^2}\\\\2\sqrt{2}qQ=Q^2\\\\2\sqrt{2}=\frac{Q \cancel{Q}}{q \cancel{Q}}\\\\2\sqrt{2}=\frac{Q}{q}\\\\\\hence,\bold{ \frac{Q}{q}=2\sqrt{2}}$