Lab Report 1

1. + -
Ethan Vanderbyl
Title: Electric Fields and Electric Potentials
Date: 2/21/14
Lab partners: Christian Houck, Anthony Mendez
Purpose:
The purpose of this lab is to find the equipotentials experimentally, define the electric field lines,
and to calculate the electric field.
Procedure:
Initially we set up our apparatus which included: a power supply, resistive paper, two alligator
clips, and two pins. First we put the two pins at the center of the conducting ink in order to make
a good connection directly with the ink. Then we attached the alligator clips from the power
source to the two pins that were strategically placed. Next we attached probes to our
multimeter and set it to the 20v scale. Then we were able to achieve our desired voltage
measurements by putting the negative probe of the multimeter on the negative pin and then we
searched for various voltages with the positive probe. Then we found 9 equipotentials for 3
different cases that each had a different shape made of the conducting ink.
Diagram:

+ + + + + +
+ + + + + +
+ + + + + +

Data:
Graph: V1 (volts) V2 (volts) ∆V (volts) ∆x (meters)
A 2V 3V 1V .08m
B 7V 8V 1V .06m
C 4V 5V 1V .05



Resistive Paper
Power Supply

2. Results:
Graph: Electric Field (N/C)
A: Irregular object near straight line 12.5 N/C
B: Circle Between 2 parallel lines 16.7 N/C
C: 2 Small Electrodes 20 N/C

Calculations:
1. ??????=−
∆??????
∆??????

Sample Calculations:
1. ??????=
−(1??????−2??????)
.08??????
=
12.5??????
??????

Questions: (None)
Conclusion:
Over the duration of this lab we successfully mapped the potential by drawing
equipotential surfaces. In this lab we proved that field lines are directly related to equipotentials
and we also revealed the validity and usefulness of the equation: =−
∆??????
∆??????
. We used this equation
to identify the electric field by calculating the difference in voltage and distance in two
equipotentials. The graphs clearly represent the symmetrical qualities of the equipotential
surfaces and they express the fact that the electric field lines are perpendicular to the
equipotential surfaces. This lab successfully identifies and proves the purpose of the experiment
because both our data and graphs were very accurate to what the intended readings should be.
Our graphs express the correct symmetry throughout and our calculated E is very standard
because the field strength should be low. Our E field calculations were from 12 to 20 N/C, which
infers the validity of all three trials because the variance is very low.
Over the course of this lab minor errors were experienced due to various issues such as:
inaccurate equipment, discrepancy in measuring ∆x, and inaccurate voltage readings throughout
the high resistance-paper. In particular we had a discrepancy issue with our multimeter which
may have been caused by a faulty meter, a bad circuit, or a bad connection. In addition we also
had issues measuring ∆x because of the limitations of a common ruler and the inaccuracy of the
lines of symmetry. Finally we also experienced error while measuring each individual voltage,
which was induced by the sensitivity of the multimeter and the fact that the paper was not
infinite. This experiment could have been improved by using a more accurate mulitmeter, a
better circuit with better connections, freshly applied silver conducting ink, an even larger sheet
of resistant paper, a better ruler to measure ∆x, and various other things. The overall procedure
could have incurred less error by using better equipment with more consistent readings and a
more accurate circuit that introduced 0 resistance. Overall this experiment introduced various
errors, but expressed the correct symmetry of the equipotential surfaces.