Tell me more ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.
up vote 0 down vote favorite

Suppose two particles each having charge $q$, are placed at a separation. What charge $Q$ should be placed at the midpoint between them, so that all the three may remain in equilibrium

share|improve this question
2  
This possibly looks like a homework question – Ϛѓăʑɏ βµԂԃϔ Aug 26 '12 at 16:42
Not exactly homework, this is problem from the book I tried to solve but got stuck, please help. – pritam Aug 26 '12 at 16:47
2  
"Homework" does not mean that the problem was necessarily assigned. Merely that the problem is of a pedagogical nature, and as per our FAQ, we don't entertain such questions in their raw form (as here). If you could edit the question to concentrate on what conceptual difficulty is preventing you from proceeding, I (or another mod) can re-open this question. Just flag for attention when you are done. – dmckee♦ Aug 26 '12 at 19:15

closed as too localized by dmckee♦ Aug 26 '12 at 19:15

This question is unlikely to help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet. For help making this question more broadly applicable, see the FAQ.

1 Answer

up vote 0 down vote

This is a standard question asked in pretty much any first course on electrostatics. As such, rather than give the full answer, I'll point out that equilibrium is achieved when there is no net force on any particle. When it comes to forces on static charges, Coulomb's Law is the only equation to choose from. Try balancing the forces using this.

As an added bonus, see if you can prove the instability of the system. Which way does a perturbed force push/pull a particle that has been slightly displaced in this system?

share|improve this answer

Not the answer you're looking for? Browse other questions tagged or ask your own question.