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EAT118 Electrical Laboratory Exercises – Inductance and
Capacitance
Introduction
This assignment consists of three laboratory exercises which
will allow you to explore the operation of
resistors, inductors and capacitors.
Your work will be submitted in two parts:
1. You will submit a single report though SunSpace DropBox,
covering the three experiments and
including neatly typed experimental results.
2. Your practical construction work and hand written
experimental results should be clearly labelled
with your name and student number and returned in a plastic
wallet to the technician base room.
Task 1 – Resistance and Resistivity
You have been asked to investigate the equation which relates
the resistance of a material to its length,
cross-sectional area and resistivity: -

� =
� �
�
where: -
R = resistance (Ω)
ℛ = resistivity (Ωm)
� = length (m)
A = area (m2)
You will measure the electrical resistance of the ‘pencil lead’ of
a set of HB1 pencils, using your results to: -
a) calculate the resistivity of the graphite-based core of the
pencil, classifying the material as a
conductor, semiconductor or insulator, as appropriate;
b) test whether the resistance of the pencil core varies linearly
with the length of the pencil.
Note: 1 The HB pencil grade refers to a combination of the
hardness of the pencil-lead, and to the darkness
of the line drawn. Modern pencil leads are made from a mixture
of graphite (a form of carbon) and clay,
which has been pressed and heated. The pencil lead is encased
in a wooden outer shell (which is an

electrical insulator).
Equipment Required
For this exercise you will be provided with the following
materials:
sharpener
capacitance (LCR meter) with leads
and ‘crocodile clip’ connectors
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Task 1 – Part A (Resistivity).
Obtain a group of pencils of similar lengths, sharpening both
ends, if required. Use a resistance meter to
determine the resistance of each pencil. To reduce the effects of
random variation in the graphite/clay
mixture, you should calculate the average resistance and the
average length of your group of pencils.

Note: A very high or infinite resistance may indicate a break in
the pencil lead. In this case, remove any
broken or loose pencil lead and re-sharpen the pencil.
Use a suitable measuring instrument (e.g. ruler, Vernier or
micrometer) to find the diameter of the pencil-
lead core, and from this calculate the cross-sectional area
(which is the area of a circle).
Use your experimental results to calculate the resistivity of the
pencil-lead, classifying the material as an
insulator, semiconductor or conductor, justifying your findings.
Task 1 – Part B (Variation of resistance with length)
Obtain a group of pencils of differing lengths sharpening both
ends, if required. Use a resistance meter to
determine the resistance of each pencil.
Plot a graph of resistance against length and determine the
relationship which best describes the data,
commenting on your results.
Note: A useful technique would be to draw a scatter graph in
Excel and plot a line of best fit.
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Task 2 – Inductance of a Solenoid
Your objective is to investigate the equation which describes
the inductance of a long thin solenoid:
� =
�0�� �
2 �
�
Where � is the number of turns, � is the average cross
sectional area (m2), � is the length (m), �0 is the
permeability of free space (4� × 10−7) and �� is the relative
permeability.
Equipment Required
For this exercise you will be provided with the following
materials:
enamelled (insulated) copper wire
capacitance (LCR meter)

Inductor Construction
Begin by wrapping the wire around the nail, as shown in
Appendix A, carefully counting the number of turns.
(Use the table below to identify the required number of turns
based on the last digit of your student
number).
Table 1: Number of required turns of wire, based on your
student number
Last digit of your student number Number of required turns of
wire
0 60
1 65
2 70
3 75
4 80
5 85
6 90
7 95
8 100
9 105

Method and Analysis
Connect a suitable LCR meter and measure the inductance, as
shown in Appendix A, Step 7.
Use a ruler to measure the length of the coil (�) and the average
diameter, converting all lengths to metres.
Calculate the cross sectional area (�) – which is based on the
equation for the area of a circle.
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Rearrange the inductance equation to make �� the subject and
then calculate the value of relative
permeability �� . Compare your result with that expected,
assuming the nail is made from iron.
Vary the length (�) of your inductor by stretching or
compressing the wire coil, noting the effect on the
inductance. Create a table showing the variation of inductance
with length and plot your results on a graph.
Compare your findings with that expected, based on the
inductance equation.

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Task 3 – Capacitance of a Parallel Plate Capacitor
Your objective is to investigate the equation which describes
the capacitance of a parallel plate capacitor:
� =
�0�� �
�
where � is the capacitance (F), � is the area of the plates (m2),
�0 is the permittivity of free space
(8.85 × 10−12), �� is the relative permittivity and � is the
distance between the plates (m)
Equipment Required
For this exercise you will be provided with the following
materials:
s
the sheet of paper
capacitance

Capacitor Construction
A simple parallel plate capacitor may be created by gluing two
sheets of aluminium foil to either side of a
sheet of paper. See Appendix B for details of the capacitor
construction and capacitance measurement
methed.
Experimental Method and Analysis
During the lab session you should do the following:
1. Construct a parallel plate capacitor with the width and height
of the aluminium plates based on your
student number, as given below: -
A B C D E
Width = 1AB mm (e.g. if A = 5 and B = 6, the width = 156 mm)
Height = 1CD mm (e.g. if C = 3 and D = 4, the height = 134
mm)
Note: Digit E was used in Task 1 to select the number of turns
of wire used in the inductor (see Table
1)
2. Use a capacitance meter to measure the resulting capacitance,
and record this information.

3. Use a micrometer to measure the thickness of the five layer
sandwich (foil-glue-paper-glue-foil), and
also the paper and foil separately. hence estimate the distance
between the capacitor plates, d.
4. Rearrange the capacitance equation, hence calculate the
relative permittivity, εr, of your paper
dielectric. Compare your result with that expected for the
dielectric material accounting for any
differences.
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5. Obtain a selection of representative capacitance dimensions
and measured capacitance values from
your classmates. Use this capacitance data, combined with your
own, to plot a graph of capacitance
versus area, and comment on your findings.
Report
You should write a report detailing the results from all three
experiments. Your report should contain the
following information:
each task.

ould
be based on the hand-written results).
relative permeability and relative
permittivity for the resistor, inductor and capacitor respectively.
comparing these with the expected results
according to theory.
and how your analysis technique
minimises these.
Mark Scheme
Data Collection
Evidence of Practical Construction (practical hand-in) /10
Evidence of Correct Data Collection (hand written results) /10
Description of Method /10
Identification of sources of Experimental Error /10
Data Analysis

Explanation of Method of Analysis /10
Estimated values of relative resistivity / permeability /
permittivity
/10
Report Presentation
Graphs /10
Tables (both tables of experimental results and calculations) /10
Overall Presentation /20
TOTAL: /100
Your report should not exceed 7 pages. References are not
required as the report is primarily focused on
your own work. You may, however, use and reference external
materials if you wish.
This electrical lab work contributes 25% of your overall mark.
Hand In Date:
This report should be submitted through SunSpace DropBox by
11:59 PM on Friday 9th December, 2016.
Your practical construction work and hand written experimental
results should be clearly labelled with your
name and student number and returned in a plastic wallet to the
technician base room.

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Appendix A – Inductor Construction and Inductance
Measurement
Step 1: Bend the first end into a loop, leaving about 5 cm of
wire for the first connector. Pass the second end
of the wire through the loop in the direction of the arrow.
Step 2: Pull the loop tight, then begin winding the wire tightly
around the nail in a clockwise direction,
keeping a count of the number of turns. (The required number of
turns is given in Table 1.)
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Step 3: Form a second loop after winding the required number
of turns.
Step 4: Pass the remaining wire through the loop in the
direction of the arrow and pull tight.

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Step 5: Trim off the unwanted wire, leaving two connecting
leads approximately 5 cm in length.
Step 6: Use sandpaper to remove the enamel from the leads,
allowing electrical connection using crocodile
clips.
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Step 7: Connect the meter as shown and read the inductance.
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Appendix B – Capacitor Construction and Capacitance
Measurement

The final result: Measuring the capacitance with the completed
capacitor
Step 1: Draw a rectangle on one side of a sheet of A4 paper,
with the dimensions based on digits A, B, C, D,
as explained on p. 5. Trace the same rectangle onto the opposite
side of the paper.
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Step 2: Create two aluminium rectangles the correct size to glue
into the areas marked out in Step 1. (You
can either use scissors to cut out the shapes or carefully tear the
foil along the edge of a ruler.)
Step 3: Use a glue stick to cover the rectangular area with a thin
layer of glue. Stick the first sheet of foil to
the paper and smooth it down. Turn the paper over and stick-
down the second sheet of foil.
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Step 4: The final step is to create two insulated tabs which will
make it easier to connect the capacitor to the
meter using crocodile clips. Cut around the capacitor leaving a
margin on the lower three sides of
approximately 5 mm. On the upper side, leave two tabs
approximately 2 cm square, as shown below left.
Fold one of the tabs towards you and the other away from you
and then stick them down using the glue
stick.
Step 5: Connect the crocodile clip leads to the capacitor, as
shown above right. Notice that the folded tabs
act as insulators, causing each crocodile clip to be connected to
one of the plates only.