Aim:
To test different materials to see what their resistivity is
which ultimately gives us the resistance of the material which can then be used
in formulas such as V = IR
Equipment:
·
3 different resistive material
·
Cables
·
Power Pack
·
Multimeters
Procedure:
1.
Set up a circuit such that the material is
connected to power pack and an ammeter in series while a voltmeter has to be
connected to the material in parallel.
2.
Write down the reading from both the ammeter and
voltmeter.
3.
Calculate the resistance of the material
4.
Calculate the resistivity of the material using
the formula R = (p x L) ÷ A where R is the resistance, p is the resistivity, L
is the length of the material and A is the circular area of the material.
5.
Repeat with the other 2 materials
Results:
|
Material
|
Thick Graphite
|
Thin Graphite
|
Standard Lead Pencil
|
|
Current
|
1.95
|
1.95
|
1.95
|
|
Potential Difference
|
0.04
|
0.32
|
0.19
|
|
Resistance
|
48.8
|
6.09
|
10.3
|
|
Resistivity
|
1.83 x 10-3
|
7.80 x 10-5
|
4.92 x 10-5
|
Discussion:
From the results above we can see that the thin graphite as
the lowest resistance while the thick graphite has the highest. These graphites
are basically carbon bonds which have a giant lattice structure. However, these
structures are layered meaning that the strong structure is only in layers, and
not throughout the whole piece of graphite. This is because in graphite, every
carbon is bonded to three other carbons meaning that there is a delocalised
electron. This weak intermolecular layer allows the graphite to rub off on
materials such as paper. Therefore, it is used in common pencils that we use
every day.
Graphite itself is actually very soft making it very hard to
write with. This is why in 1795, Nicholas Jacques Conte, a French chemist came
up with a new process which involved mixing graphite with clay and water in
resulted in the graphite hardening up and creating a more stable and rigid
writing experience. From this process, they can also create different hardness
levels of “lead pencil” which is to mix more clay with the graphite resulting
in it to become harder.
The process by the French chemist was a revolution to the
pencil industry which allowed cost to drop significantly because of the mixture
of clay and water instead of the conventional pure graphite in hollowed wood.
This made manufacturing much simpler because the hardened pencils did not
deform while they were being put in the hollow wood casing.
Conclusion:
To conclude, we can say that the thick graphite has a higher
resistivity than the thin graphite which means less power going through the
thick graphite. We also know that the “lead” in pencils are actually graphite
mixed with clay and water.
