A positive charge q is kept at the mid point of two charges each of magnitude -q .then it is in?

a) stable equilibrium

b)unstable equilibrium

c) neutral equilibrium

d) none

It will be in stable equilibrium since the forces on the charge q are equal and opposite

it wiil b in neural equilibrium....... since it lie at the neutral point .

It will be in stable equilibrium as the forces exerted by the two charges(-q) will be equal and opposite.

it is in UNSTABLE EQUILIBRIUM because even if it is going to be moved by avery small amount the electricfield of one particular charge will predominate and the +q charge starts moving in that direction.

Surely in unstable equilibrium...as the two electric field vectors equalises each other and angle between them is 180 degrees..

This is a tricky question.

If you displace the positive charge slightly along the line joining the two negative charges the pull of the closer negative charge starts to dominate over the other negative charge's pull. So the positve charge doesn't return to the equilibrium position.

But if you displace the positive charge slightly in a direction perpendicular to the line joining the negative charges the positive charge will return to its equilibrium position(it will actually oscillate).

So the answer depends on how one defines stable & unstable equilibrium(please dont think that this is neutal equilibrium. Contrary to popular belief neutral equilibrim is not an intermediate between stable & unstable equilibrium). I think according to usual definition this is a case of UNSTABLE EQUILIBRIUM.

P.S. :  I've heard a physics teacher say that every equilibrium in electrostatics is unstable equilibrium. Take any case of equilibrium in electrostatics and you will be able to find atleast one direction in which a displacement of the body in equilibrium will lead to the body moving away from equilibrium position. This trick might save time your JEE.

ALL THE BEST FOR YOUR JEE 20XX

due to the osscillation of the charge to its position, it will be in unstable equlibrium

i think ,the answer should be unstable equilibrium because the point charge is moving in oscilliation so.answer is b

its unstable eq

i think if we displace the +ve charge along the line joining the 2 -ve charges,then it will unstable equillibrium.

but in the perpendicular direction it will be stable as it returns back to its original position due to electrostatic attraction of 2 other charges

it will be unstable equilibrium