1. Aug 17, 2007

stmartin

I just want to ask you something. If the electrons are surround by force around them, why that force is not neutralizing its self like on this picture.
http://img150.imageshack.us/img150/9632/untitledxm4.jpg [Broken]

Last edited by a moderator: May 3, 2017
2. Aug 17, 2007

ZapperZ

Staff Emeritus
Where did you get the idea that "electrons are surrounded by force around them...."? When you solve for the Hydrogen atom, for example, there's only ONE force, and that's the coulombic central force from the nucleus. So where are all these other forces that you are referring to?

Next time, as a hint, when you try to ask something, it would be a lot more complete if you if you also clearly cite your sources.

Zz.

3. Aug 17, 2007

Nesk

Do I understand your question correctly if I assume that by force you mean the electrical field of the electron?

The electrical field is not a force in itself. If a charge q is placed in the field E it is affected by a force determined by F=qE. The field is caused by charges, i.e. it is radiated by positive charges and terminates in negative charges, like your illustration suggests. Thus the electrical field does not act upon itself, except that the field from a charge distribution is the superposition, i.e. the vectorial sum, of the fields caused by each individual element of charge.

4. Aug 17, 2007

stmartin

But look at the electrical force lines. They are opposite. Make an experiment with opposite forces, you'll see that they neutralize.

5. Aug 17, 2007

ZapperZ

Staff Emeritus
So? It doesn't mean it is like that ALL THE TIME!

In classical E&M, a charge CAN be in equilibrium if there are no other charge around, because it experiences no net electrostatic force. This is not E&M, it is basic mechanics.

But put another charge nearby and you don't get that anymore. So I am not sure what exactly is the problem here.

Zz.

6. Aug 17, 2007

Staff: Mentor

No, they don't neutralize because they represent forces acting on different objects.

More explicitly, a single arrow on your diagram represents the direction and magnitude of the electric force that the charge shown on the diagram would exert on another charge if that second charge were placed at the location of the arrow.

So in order to get two forces in opposite directions, you need to place two new charges at the locations of two properly-chosen arrows. These forces do not neutralize because they act on two different objects.

This is just like if you place two balls on the floor and you push on them in opposite directions so they roll towards each other. The forces don't neutralize in this case either.

7. Aug 17, 2007

stmartin

Like this?
Man look on the picture again, the forces are opposite, acting on the electron.

8. Aug 17, 2007

arron

But i think the force has already been neutralized. you see , if an electron is far from other charges, it does not move itself. why? you can think that the force act on the electron itself on opposite directions has already neutralize each other.
and i think the most important thing to accept this explanation is to accept the force (or the electric field) stay where it is, it does not get through the electron and then arrives at another side to neutrolize its counterpart,but exerts and only acts on the the electron.

9. Aug 17, 2007

stmartin

I think the both (protons and electrons) act with their electric forces on each other.

10. Aug 17, 2007

malawi_glenn

But as others have told you already in this thread, the arrows are not representing forces, they are field lines...

11. Aug 17, 2007

Staff: Mentor

In any particular diagram of the electric field produced by a given set of charges, the field arrows do not indicate the forces that currently act on those already-existing charges. They represent the electric force that would be exerted on a new charge that you add to the system.

Of course, adding a new charge to the system changes the pattern of the total electric field, but this affects only what happens to the next new charge that you add to the system.

The rule is that the electric force on a charge is determined by the net electric field produced by all the other charges in the system. You don't include the field produced by the charge in question.

12. Aug 17, 2007

stmartin

But lets say there are 2 charged particles, like on the picture, again the forces around the electron are opposite..

13. Aug 17, 2007

ZapperZ

Staff Emeritus
Force on 1 DUE to 2 is equal to force on 2 DUE to 1. But the force on 1 due to 2 is certainly NOT balanced if you simply look at 1 alone. 1 doesn't care that 2 is there. All it cares about is that it is seeing the field due to 2. That is what is causing it to experience a net force.

The same is true for 2. It is only when you look at BOTH particles as the whole system do you not have any net external forces.

Zz.

14. Aug 17, 2007

Staff: Mentor

But jtbell was talking about your latest picture, showing the combined field from two separated point charges. As he explained, the arrows show the field due to those two charges that would be experienced by a third charge brought nearby.

Note that the diagram shows the combined field created by both charges, not the force that each charge exerts on the other.