Lab 3: Ohm’s Law
Jacob Derr
Lab Partners: Evan Reid, Sierra Johnson
TA: David Weisberger
PHY 132
Room: 366 Group #: 1
Wed: 12:00-1:50
Abstract:
The purpose of this lab was to find the electric resistance and resistivity of
many different samples. For portion 3 of this lab, a cylindrical conductor (graphite)
was used. 5 data points for voltage and current were found for each of 5 different
lengths, measured with a caliper between two alligator clips. The cross-sectional
area (0.3456cm^2) was found by using the diameter (0.22cm) of the piece of
graphite. The electric resistance (5.85
Ω
) was calculated from the slope after
constructing a graph of current vs. voltage. Another graph was then made, this time
plotting electric resistance vs. length. From this, the resistivity of the graphite was
determined to be 0.57698
Ω.
The final graph also showed a non-zero intercept of
1.618 +/-0.07892. The meaning of this non-zero intercept is that anything below the
length of 1.618 will have no resistivity.

Objective:
The purpose of this lab was to experiment with the concepts of resistivity
and electric resistance. A key component of this lab was using Ohm’s Law, which can
help determine the voltage drop across a resistor, as it is proportional to the current
flow. If a sample obeys Ohm’s Law, it is said to be ohmic. For each of the three main
portions in this lab, data consisting of current and voltage was calculated, limiting
the voltage to a certain range. Afterwards, this data was used to find the electric
resistance of each sample.