# Generating an E-Field

Discussion in 'The Projects Forum' started by dtow1, Jan 20, 2011.

1. ### dtow1 Thread Starter New Member

Apr 27, 2010
24
0
Hello all,

I am working on generating an efield that I can measure with an antenna. I wanted to see if anyone had any feedback on what I am going to try or any pitfalls I can avoid, or even a better technique.

I am going to build a solenoid to generate the e-field. I was going to use the outer case of a "Dvd" tower since it is large and round and the E-field will be proportional to the area, I'm using thin wire(ripped from an ethernet cable I dont need, one strand out of it) to get a decent number of turns per meter. Does this seem like a decent approach, does anyone know another? Im trying to use a source that I can calculate the approximate field strength I would expect which is why Im not just going to just use electronics. Any input would be apprciated.

Thanks.

2. ### wayneh Expert

Sep 9, 2010
13,607
4,408
So you're going to wind wire around a plastic tube that's ~4" in diameter to create an air-core solenoid? I'm not really sure what you're trying to accomplish, but the magnetic field inside will be proportional to the number of turns of wire (I recommend counting them) and the current passing through the wire. More wire gives more turns, but will reduce current as the total resistance increases. Also, be sure you don't overcurrent your wire. It'll turn into a quick-blo fuse.

dtow1 likes this.
3. ### dtow1 Thread Starter New Member

Apr 27, 2010
24
0

To clarify, that is what I will be building, but Im not looking at the magnetic field inside, Im using it to check the e-field outside of the coil, which is a function of μ n(number of terms) the area of the coil, and the time rate of change of the current. It should drop off at 1/(2*pi*d), d being distance from the coil.

The reason I chose it is because it should give me an estimate of the e-field that I can use to test the sensor plate I am working with.

Im curious if there is a better way to generate an efield of a known size or if anyone has done this and knows any pitfalls that I may encounter with this approach. According to the physics Ive taken it should work, but I still thought I would ask. Thank you again for replying, I hope that clarifies it.

4. ### dtow1 Thread Starter New Member

Apr 27, 2010
24
0
Oh, also about the current, I am going to measure the resistance of this when its built and put it in series with a resistor to cap the current at 1/2 amp.

5. ### wayneh Expert

Sep 9, 2010
13,607
4,408
Hmmm... Beyond my expertise. But I do know that predicting is harder, or should I say less certain, than measuring. I think if you really care about the value, maybe a gauss meter or such would be helpful.

Are you sure the wire can take that current? If it's just one layer of windings (so the heat can get out), it's probably OK if the gauge is 22 or less, but there are charts for such things.

dtow1 likes this.
6. ### dtow1 Thread Starter New Member

Apr 27, 2010
24
0
Thanks for the reply. I believe it should be able to but I will look it up to be on the safe side, thank you for the caution. I appreciate the feedback. If I get good results Ill reply with the details. Thank you again for taking the time to reply!