Comparing Lab Results to Theory: Equipotential Lines Analysis

[cy19861126]

Okay, we are supposed to do a lab in class and compare it to the real results. However, for some reason, my lab result is very different from my theoretical value.

The lab is like this: I put a sheet of conductive paper with the dipole electrodes, one positive and one negative, of course. I connected the two electrodes to a battery by clip-leads. Also, I connected the Voltmeter to the two pins on the electrodes, I connected one of the wires from Voltmeter to the negative electrodes and one another (positive) to various places on the conductive sheet. In the lab, the two electrodes are points. Therefore, this is a situation of two point charges.

After I placed the positive probes on various places and measured the voltage on a 0.5V increments, I drew the lab result. The shape of the result is fine; it is almost exactly like what you would fine on a topography, but what I'm concerned about are the numbers. The voltage numbers all came out to be positive, while from the theory, only half of the equipotential lines are positive (the half that is close to the positve side).

If you want to know what the theory would look like, you can go to: http://www.colorado.edu/physics/phet/simulations/chargesandfields/ChargesAndFields.swf. The way to use this is to drag 1nC to the top of the page and -1nC to the bottom of the page. And on the lower left hand corner, try and plot different equipotential lines. Remember to click on "show numbers" on the lower right hand corner

 

[member 553083]

before plotting the lines. There could be a couple of factors that could explain why this might be the case. The first could be that the battery I used in the lab wasn't powerful enough to create a larger potential difference, thus the numbers all appeared to be positive. The second is that the conductive paper I used in the lab wasn't thick enough, or it wasn't made out of material that allows for a large potential difference. It would be helpful to have some guidance from my professor or TA in order to understand why this discrepancy is happening and what I can do to solve the problem.