Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

Can there be a charge configuration in space such that at any instant of time I can change the electric field at one and only one point?

share|improve this question
    
Electric fields propagate at the speed of light--so if you can stop time you can change the electric field at only one point. –  JoeHobbit Aug 17 '11 at 8:41
    
How would you be changing the electric field? –  David Z Aug 17 '11 at 9:01
add comment

1 Answer

The electric field obeys Maxwell's equations and in particula the Gauss's law. This means that $\rm div E \sim \rho$. If you change the field at only one point, this will introduce an infinite divergence and consequently infinite density. In other words, you'd have to introduce a point charge. But then the field $E$ itself will diverge at that point. So the answer is no, you can't do this.

In general, the allowed configurations are continuous except at boundaries of objects (where $E$ has to jump to account for charges in the material) and at point charges (where the field diverges).

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

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