PHY-104 Lab Report Tips for the Coulomb’s Law Investigation
Charge Separation RCorrected, cm
Format
Title Page
1. Introduction
a. Statement of Purpose or the goal of the investigation
b. Brief description of Coulomb’s Law including a brief biography of August Coulomb (See Wikipedia).
This section need be only 10 or so sentences long.
c. A brief description of the experimental set up, including a labeled diagram that identifies the data
parameters A0, A and B, and a derivation demonstrating that we can use the distance D as a proxy for the
electrostatic force.
2. Data
3. Analysis
a. A Graph (#1) of D (y-axis) versus R (x-axis) with a power law trend line.
b. A Graph (#2) of D (y-axis) versus RCorrected (x-axis) with a power law trend line where RCorrected represents
a reasonable “correction” for the effect of polarization on the two charged spheres as they approach each
other.
4. Discussion and Conclusion
a. Discuss Graph #1 and relate it to your purpose or goal.
b. Discuss the phenomena of polarization and describe how you reasonably “corrected” the R values to
account for polarization.
c. Discuss Graph #2.
d. A summary statement that addresses the purpose or goal of the investigation.
Tip on correcting for polarization of the two spheres.
1. A reasonable correction to include the effect of polarization of the two conducting charge-carrying spheres would
assert that
a. There is no polarization when the spheres are farthest apart. (This probably is not completely true but it is
a good starting point.)
b. The degree of polarization increases as the two charged spheres get closer (i.e. R gets smaller). A
reasonable starting point is that the polarization increases linearly as the separation decreases.
c. The maximum polarization occurs when the spheres are closest. At this minimum separation the center of
charge on each conducting sphere is shifted away from the geometric center of the sphere by an amount
no more than the radius of the sphere. The shift from the geometric center may be less, but not more than
the radius of the spheres.
d. You must
determine how to
Experiment on Coulomb's Law
14.0
“correct” the
12.0
separation of the
10.0
spheres to model
the separation of
8.0
charges. You will
6.0
Charge Separation
find Wikipedia’s
4.0
Sphere Separation
Two-Point Form of
2.0
a Linear Equation
0.0
helpful. The result
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
Sphere Separation R, cm
you are looking for
is illustrated