# Electric Field in a wire - creation

#### dobry_den

Hi! My exams are coming up soon and I'm revising some of the notions of electromagnetism. What intrigues me is the way electric field is created/distributed within a wire. I've been thinking about it for some time and have come up with the following "hypothesis", idea:

When a conducting wire is connected to a positively charged body, the nearest free electrons of the wire will "jump" on the body (due to the force of the charged body acting on them) and thus "uncover" the positive charge of several nuclei in that part of the wire. These positively charged nuclei will attract electrons situated further along the wire, making them to move and "uncover" another set of nuclei. This process goes on and on until the end of the wire is reached. If this end is connected to a negatively charged body, the process is even more intensified.

What is your approach to this problem? Any help would highly appreciated, since it bothers me quite a lot :)

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#### dobry_den

Well, the question is how the electric field is created in a wire when it connects two bodies with different potentials. In the first post a described the way I think it might be, but I'm quite unsure about it.

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#### ranger

Gold Member
Well, the question is how the electric field is created in a wire when it connects two bodies with different potentials. In the first post a described the way I think it might be, but I'm quite unsure about it.
A electric field is created by uneven charge distribution. Or in the case of the conductor, a difference in voltage (potential difference). Basically when a body is electrically charged,we say that it has small or great concentrations of electron. In your situation, a potential difference exists between the oppositely charge objects. Therefore we can associate this electric field with a difference of potential.

In your description are you trying to describe the motion of charge?

#### robb_

The part of your statement that I have been staring at is
If this end is connected to a negatively charged body, the process is even more intensified.
I am not sure exactly what you are asking or stating but if you are sustaining a current in the conducting wire, there should be a closed path for the charge carriers, generally.

#### dobry_den

In your description are you trying to describe the motion of charge?
Yep, I tried to. The electric field created in a wire is always tangential to the wire, in the direction from the point of higher potential to that of lower potential - this field drives free electrons along the wire (in the opposite direction). What I am unsure about is the "mechanism" how this electric field is created - whether it is the way I described it in my first post or any other?

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#### ranger

Gold Member
Well since one end of your conductor is connected to a positively charged body and the other to a negatively charged body. This creates an electric field. The "mechanism" that creates the E field here would be a potential difference.

#### atat1tata

This question troubles me too.

How can the field be created if some parts of the wire are going in the opposite direction than needed, that is if they go from lower potential to higher potential? IFor example, let's say I have a generator and a wire connecting the two terminals making a sort of omega-shape. Some parts of the wire are in the "wrong" direction, namely those closer to the terminals. When this wire is connected to the generator, how does the electric field inside it establish?

#### MHD93

Up up..

Because I, too, have the same problem.

I know that voltage = E.Field times the distance in the case of uniform electric field
But I ain't able to comprehend how we're allowed to use this in the case of bent wire [like in the picture in post #8]

#### Papikoss

It is falsely believed that the source of the Electric Field within a wire carrying a constant current is the charges that are accumulated in the terminals of a battery.

If that was true, the internal Electric Field could not adjust to any change in the geometry of the wire, which is a remarkable attribute.

We should seek elsewhere for the sources and that is on the surface of the conductor. It seems that a linear distribution of surface charges along the wire is responsible not only for the internal Field (of constant magnitude and tangential direction), but also for some Electric Field outside the wire. The role of the battery is to sustain such a charge distribution.

When we bend the wire the surface charges rearrange themselves so that the internal Field remains tangential to the new path.

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#### iera wan

If I have a wire and use a battery to apply a potential difference between the two ends, do I get an electric field inside the wire?

Absolutely! Why would the electrons move through the wire in the absence of a force. After all, the resistance of the wire can be looked at as being similar to the force of friction in that the interactions between the electrons and the atoms around them inhibits their movement. In order for the electrons to move they would have to have some external force applied to them in order to balance out the resistance. If you multiply the electric field in the wire by the charge you get the electrostatic force acting on the electron: F = E*q.
Roughly speaking, the electric field within the wire can be determined by dividing the potential difference V across the wire by the length d of the wire: E=V/d.

i dont understand well the explanation..can anybody help me to explain more to me??

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