Procedure

5.1 Part 1

Following the instructions for measuring the potential, plot a series of equipotential curves (staying away from the edges of the paper if possible) and draw a full pattern of field lines for the following configurations of charged conductors:

1. Two equal but opposite sign ``point" charges (with each oscillator lead connected to a pin on the bare paper).
2. Two equal and same sign ``point" charges (with one oscillator lead connected in common to two separated pins while the other lead is connected to several pins at the edges of the paper, i.e., ``at infinity").
3. Two parallel straight conductors having opposite sign charges (with a separate oscillator lead connected to each). Leave at least six inches between the conductors.
4. Some other arrangement of charged conductors which you feel is interesting.

5.2 Part 2

Verify the ``Electrostatic Shielding'' theorem described previously. You can test this theorem by painting a closed conducting loop (e.g., a circle) in a region of known electric field and investigating the potential inside this loop. You should use the sheet of conducting paper previously used in Part 1(C) and paint a closed loop in the region between the two parallel straight conductors.

5.3 Part 3

In addition to the null method for plotting equipotentials, the digital voltmeter can be used to make direct quantitative measurements of the potential difference between two points. Recall that for this lab you have set the total potential difference between the electrodes at 150 mV.

Using one of the long strips of conducting paper available in the lab, paint a conducting bar at each end and insert one electrode into each bar. Place one DVM probe on one of the bars, and with the other DVM probe measure the potential difference at some other point on the strip. Verify that the potential varies linearly with position by measuring the potential difference for various distances along the strip. Does this indicate a uniform electric field?

5.4 Part 4

Using the spreadsheet, solve Laplace's equation numerically for each of the electrode configurations you've measured. Have EXCEL graph the potential surfaces in each case. Compare your calculated and measured results.