You have told equilibrium and not Stable equilibrium.At the centre INTENSITY is 0.so ABCD should be the answer
If a charge q is placed at the centre of line joining two equal like charges Q,the system will be in equilibrium if q is
a)-Q2
b)-Q4
c)+Q2
d) +4Q
Plz explain yur ans ......
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12 Answers
Ok If I change the question to stable equilibrium,then what would be the answer and why?
only positive charge can attain stable equilibrium,(CD)
check by giving the charge Qmid a small displacement of x .
Then check which force dominates to restore it in orignal position.
Only an unlike charge can balance the system.Lets calculate the value of charge and we can guess the sign from options(since nothing given in ques)
Q q Q
Balance force on Q,because its no use of trying it on q
kQ2/x2=4KQq/x2
so,q=Q/4
hence option b)
I can promise you that this was the exact question( in words ) which was given to me in the test.
B is the correct ans....( dont take the language of the quesn too seriously!!!:P)