Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: Electric Field Mapping



Tina
First a clarification of the configuration
One terminal is a circle, the other is a point
which is not at the center of the circular
terminal? Something like?

-
- -
- + -
_ -

- -
- -
-

The circular terminal is connected to one side of
the power supply and the point is connected to the
other? Good electrical contact is being made at
these connections at the paper? We use small
washers on the banana plugs that connect to the
paper to help make better contact.

The ring is boldly painted on with the conductive
paint?

Use an ohmmeter to measure the resistance between
different points on the ring. For example set and
leave one probe at the bottom of the circle and
probe every 30 degrees. The variation should be
"small." Here small is relative to the resistance
across the same distance on unpainted field
mapping (resistor) paper. If the resistance of
the ring is of the same order of magnitude as the
that of the paper, the situation quickly gets
quite complex.

Thanks
Roger Haar




****************************************************************





Tina Fanetti wrote:

Hi all
Today's physics lab was using the Pasco field mapper kits to map the Electric field and lines of equipotential.

Okay so my students were given a point charge with a guard ring around it. It just wouldn't seem to work.
One problem was that the potential difference on the guard ring wasn't constant. The farther you got from the point where the electrode was connected, the lower the potential difference got. Shouldn't it be the same?

What's going on?
Tina (user error...lots of it)

Tina Fanetti
Physics Instructor
Western Iowa Technical Community College
4647 Stone Ave
Sioux City IA 51102
712-274-8733 ext 1429