0
$\begingroup$

Suppose we have a charge $Q$ in deep space (isolated), now suppose another charge $q$ appears instantly (no matter how). Obviously it will feel electrostatic force but the question is how quickly (will the be felt instantly even at large distance). As I mentioned electrostatic, both the charge are stationary

$\endgroup$
  • 1
    $\begingroup$ I'm closing this post (v2) as non-mainstream as a charge $q$ cannot appear instantly. $\endgroup$ – Qmechanic Apr 25 at 20:13
  • $\begingroup$ But it is a reasonable thought experiment? And I'd say reasonable for the concept of the propogation of EM radiation. $\endgroup$ – SamuraiMelon Apr 25 at 21:43
-1
$\begingroup$

The 2nd charge $q$ will be felt (by $Q$) after a time $t$ such that $$ t=\frac{d}{c} \tag{1} $$ Where $d$ is the distance between the charges and $c$ is the speed of light in a vacuum.

The effects of $Q$ on $q$ should be felt instantly (given $Q$ was already present for a sufficient time still given by (1)).

| cite | improve this answer | |
$\endgroup$
  • $\begingroup$ This is plain wrong, the field generated by the first charge will be already present at the position of the second charge (assuming the first charge was present long enough). So the force can be felt instantly (t = 0). $\endgroup$ – Rob Apr 28 at 7:38
  • $\begingroup$ @Rob But the first charge $Q$ won't feel the effects of the second charge $q$ till a time $\frac{d}{c}$? Perhaps I should edit the answer to make it clearer which charge I'm referring to feeling an effect. $\endgroup$ – SamuraiMelon Apr 28 at 12:14
  • $\begingroup$ @Rob Could you remove the down-vote as I have clarified my answer please? $\endgroup$ – SamuraiMelon Apr 28 at 14:19
1
$\begingroup$

Every charge that we have,makes a field that is called electrical field;shown by "E" and this field fills all the space around.if we imagine that there is nothing else in the universe to interact with the charge and the field,field of our charge fills all of the space.now we put a new charge in a random point;what happens is that new charge feels the field of first charge at the first moment that we put it in the space but,in this case a new field will appear that is for our new charge and 2 fields will interact with each other.at last we understand that,new charge will feel the field and force at the first moment, because there was a field before it and we have the equation: F=Eq but the new field and force of the new charge will travel to old particle with the speed of light and after that the old charge will feel the new field and force!

| cite | improve this answer | |
$\endgroup$
0
$\begingroup$

Any change in an otherwise static arrangement of charges and currents will lead to a change in the fields that propagates at light speed away from its origin.

| cite | improve this answer | |
$\endgroup$

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