ElectrostaticsHard

Question

A charge Q is placed at each of the opposite corners of a square. A charge q is placed at each of the other two corners. If the net electrical force on Q is zero, then the Q/q equals

Options

A.-2√2
B.-1
C.1
D.

Solution

         
Three forces F41, F42 and f43 acting on Q are shown
Resultant of F41 + F43
= √2 Feach

Resultant on Q becomes zero only when ′q′ charges are of negative nature.
F4.2 =
⇒    
⇒     √2 × q =
∴     q = - or = - 2√2

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