Stephanie Clarke 11W/MA
Investigating how the number of coils on a C Core affects the Voltage produced
Diagram
Voltmete
r
Power supply
Crocodile clips
and wires
Primary C-Core with
20 coils of wire
wrapped around it.
Secondary C-Core
with a changing
number of coils of
wire around it.
Method
o Twenty coils of wire were wrapped around the primary core; this number of coils
remained constant throughout the experiment to ensure a fair test.
o Crocodile clips were connected to the ends of the coils of wire, and connected to
the voltmeter.
o The secondary core had five coils of wire wrapped around it and the ends of this
wire were connected to an alternating power supply.
o The power was switched on and the voltage produced with five coils of wire on
the secondary core was recorded.
o The numbers of coils of wire were changed to produce a table of results in order
to draw a conclusion as to how the number of coils affects the voltage produced.
o The number of coils increased by 5 each time because this gave a gradual increase
in voltage each time, therefore allowing a graph to be plotted accurately.
Stephanie Clarke 11W/MA
Results
Number of
coils
0
5
10
15
20
25
30
35
40
Voltage
0
0.2
0.6
0.9
1.4
1.9
2.5
2.9
3.5
Graph
Graph to show how the Number of
coils affects the Voltage
4
3.5
3
Voltage
2.5
2
Voltage
Linear (Voltage)
1.5
1
0.5
0
-0.5 0
20
40
Number of Coils
60
Stephanie Clarke 11W/MA
Conclusion
The primary coil is connected to an alternating power supply, the iron core becomes
magnetised due to the current in the coil changing frequently. The magnetic field also
changes because the current is constantly changing, therefore a voltage is induced in the
secondary core because it is within the magnetic field.
The results show that the
voltage increases as the number of coils are increased. This is because the formula for
calculating the volatege in transformers is :
Vp
Vs
=
Np
Ns
If there are more coils on the secondary core than the primary, Vs is greater then Vp
therefore this produces a STEPUP transformer. Whereas if there are less coils on the
secondary core than there are on the primary core, Vp is greater than Vs hence a
STEPDOWN transformer is produced. Therefore, the transformer in this experiment is a
step up transformer when there are more than 20 coils on the secondary coil because
there are more on the secondary than there are on the primary at this time.
The graph shows that the
number of coils and the voltage are proportional because a straight line is produced as the
line of best fit. This is because when one of the values in the equation is altered, the other
is altered by the same ratio/proportion.
Evaluation
In order to improve this experiment, more reading could have been taken, however there
was not time or enough equipment to perform a greater experiment. The number of coils
on the secondary could have been increased further to see if the same pattern occurs or if
there is a limiting factor.
The number of coils on
the primary core could also have been changed in order to see if the same results and
conclusions can be drawn when there are more or less coils on this core.
Another variable that
could have been changed is the power connected to the transformer; this could have been
increased or decreased to see the effect on the voltage produced.
There are no obvious
anomalies shown on the graph because all points fall almost on the straight line. However
they are not exactly on the line of best fit. In order to improve the accuracy and reliability
of the results, the experiment could have been repeated two more times as this would
identify any anomalous results.