Question

I'm trying to find the direction and magnitude of electric fields from power lines, given specific parameters. Can anyone point me to good resources that might help?

Answer 1

Are you looking for a reference to quote or a book to learn about field structure?

Answer 2

I'm actually looking for a website resource that will give formulas and some diagrams to relate them to

Answer 3

I found the hyperphysics site - it's great - but it doesn't help with the problem I'm stuck on.... http://230nsc1.phy-astr.gsu.edu/hbase/hframe.html (click on the bubbles for specific info)

Answer 4

The Hyperphysics site is really good. I use it a lot. What is your problem specifically?

Answer 5

You were looking for help with Electric Fields, direction and magnitude. Try this:
.... http://230nsc1.phy-astr.gsu.edu/hbase/electric/elefie.html#c1
I'm not sure how to make it a link - I'm somewhat new here.

Answer 6

Oh, it did link...

Answer 7

I will attach a file....it's so hard to explain, otherwise:

Answer 8

First, check out this response I did about 9 days ago to help you understand the direction of the electromagnetic field:
http://openstudy.com/updates/5443212de4b0e38f7ad17de9
Also, you will need to know the current (in amperes) flowing trough the 4 cm diamter (is that right?) conductor from A to B, and which direction the current (conventional or electrons) is flowing. It is assumed that the electric field will be produced by a constant Direct Current (DC) flowing, otherwise it will get Ugly.

Answer 9

Ooops - yes, the V-AB is 440V. and I will look through the notes....yes, that would be a 4cm conductor. I believe it would be DC.

Answer 10

If you give me the voltage, but no current, I assume that the conductor has a static charge on it (of 440 volts) and no current flowing. Is that right?

Answer 11

Sorry. If this is a static charge (no current flow or loss) the link I sent you won't be of much use.

Answer 12

I may have misread the problem... V-AB is the potential difference

Answer 13

There will be at least one (1) electric charge produced by this "Power Line", that is the static electric charge. It is present with no current flow and with. If you click on the image of the cylinder in the first box of the hyperphysics link I sent above, you will go to the following:
http://230nsc1.phy-astr.gsu.edu/hbase/electric/elecyl.html#c2
This will give you the information you need to calculate the field magnitude and direction of the Static Charge.
Now, If there is current flowing, then The static charge may vary along the conductor (by the amount of voltage loss per unit of length), but in practicality, the Static Charge difference will be very small.
If there is current flowing, we will need to know that.

Answer 14

Just saw - Potential difference of 440 Volts?

Answer 15

yes, that's how the problem originally was worded....my shorthand notes weren't great, sorry

Answer 16

Is one end 0 volts and the other 440 volts? If so, which end is 0?
Or is there a drop of 440 volts along that section of the line? If so, one will have to know the total voltage at some point as that will be a factor in the magnitude.

Answer 17

there is a difference of 440 volts between them....and the lines are parallel, not connected. They are saying to use the midpoint between them as an origin, so I guess plotting the field symmetrically over that midpoint?

Answer 18

Ohhhhhhh! That makes a difference. Lets back Way up.

Answer 19

Does it say which line (A or B) has the larger potential?

Answer 20

no...I guess that's why they want us to use the midpoint, because it would be assumed to be roughly half, all other things equal, right?

Answer 21

sorry to sound confusing, the prof was going really fast on this one
and didn't give us any examples of how to solve it

Answer 22

Follow the following three links,
Takes you to Gauss's laws:
http://230nsc1.phy-astr.gsu.edu/hbase/electric/gaulaw.html#c4
Clicking on Electric Field Concepts on the bottom box take you to this bubble page
http://230nsc1.phy-astr.gsu.edu/hbase/electric/efiecon.html#c1
Clicking on Parallel Lines takes you to
http://230nsc1.phy-astr.gsu.edu/hbase/electric/elewor.html#c1

From this point on, I'm afraid that I can only provide evaluation of you answers.
But, if A is 440 Larger than B, pt 1 will have a an electric field with a larger magnitude than pt 2. And the electric field at the midpoint between A and B will also have a direction and magnitude that is effected by which conductor has the larger (440 v) potential.

I really think there is not enough information to solve this unless one knows that one of the points has X volts and the other is X-440. If A was 0, and B was 440 v, A would not have any effect on the filed whatsoever and the field of B would extend beyond A to the left. Once A starts to have a field, always 440 v less of course, the dynamics of teh interacting fields becomes very important and will change tremendously. Example: If A was 10,000 volt, and B was 10,440 volts, the difference in potential between pts 1 and 2 would be very small.

Does that make sense?

Answer 23

it does....but I realize that there must be a hole in my notes somewhere. I really appreciate your help and insights! I am going to try to go in and talk with the prof tomorrow and see if they can help me work this one out.

Answer 24

Good idea. Showing interest in understanding is better than just doing what will get you by. Most professors love what they teach and want everyone to realize how "simple (??)" this stuff is if they could only understand it.

Answer 25

New day, new thought.
I mentioned this to my friend and she said that the example probably was for a balanced power distribution system. Why didn't that occur to me?
In a balanced power distribution, the power going down one power line is the same power coming back the other line. This means that there would be +220 volts on one of the power lines and -220 volts on the other. That simplifies a lot.
The fields would cancel exactly at the center, along a vertical line. If A were + and B were - , then pt 1 would be + by a voltage smaller than +220 and pt 2 would be - by the same magnitude as pt 1 but with an opposite charge (-).
The hyperphysics links will definitely help you determine the magnitude values.

Answer 26

thanks so much!