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…
JEE Main 2009 — Physics Electromagnetism
2009mcqhard
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
Official previous-year question
Held on 30 Apr 2009 · Verified 6 Jul 2026.
Options
A
−22
B
−1
C
1
D
−21
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Solution
Three forces F41,F42 and f43 acting on Q are shown Resultant of F41+F43=2Feach =24πε01d2Qq Resultant on Q becomes zero only when ' q ' charges are of negative nature. F4,2=4πε01(2d)2Q×Q⇒2d2dQ=2d2Q×Q⇒2×q=2Q×Q∴q=−22Q or qQ=−22
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