Download The Effect of the Length of Wire on the Current and Voltage of Series

The Effect of the Length of Wire on the Current and Voltage of
Series and Parallel Circuits
Eleanor Cook
Takoma Park Middle School 2011-2012
Abstract
The purpose of this experiment was to determine how the length of wire in different electrical circuits
affects the voltage and current of those circuits. The hypothesis was that if the length of the wire increases, the
current and voltage will decrease. Also, if the circuit is changed from parallel to series, then the current and
voltage will decrease. This is because increasing the length of the wire and changing to a series circuit both
increase resistance, which decreases current and voltage. First, a series circuit was set up with 3 light bulbs, 3 D
batteries and 1 foot of copper wire and a light bulb between the middle light bulb and the batteries. The voltage
was measured and Ohm’s law was used to calculate the current. This was repeated with 5 feet and 25 feet of
wire. Then a parallel circuit was set up with 3 D batteries, 3 light bulbs, and 1 foot of copper wire between the
batteries and the middle bulb. The voltage was measured and Ohm’s law was used to calculate the current.
This was repeated with 5 feet and 25 feet of wire. The hypothesis was supported because the parallel circuits
had more voltage and current than the series circuits, and as the length of the wire increased, the current and
voltage decreased. The results show that electricity companies should have more than one power source along a
power line so that not too much electricity is lost by the end of the circuit.
Key Terms: current, voltage, resistance, parallel circuit, series circuit, Ohm’s law, wire, length
Introduction & Review of Literature
The testable question for this experiment is
“How does the length of wire affect the current and
voltage of electricity at its destinations in series and
parallel circuits?”
This experiment was to
demonstrate the difference that the length of wire
and the type of circuit can cause in the electrical
voltage, current, and resistance of a circuit. This
experiment was to find how circuits and electricity
work and to see whether series circuits or parallel
circuits were more efficient.
I do not have much previous experience
with electricity, but I got the project idea because
we learned a bit in fifth grade about series and
parallel circuits. I decided to learn more about these
circuits.
TPMS Journal of Science
Page 1 of 7
The independent variables are the type of
circuit and length of the wire. The dependent
variables are the current, voltage, and resistance in
the circuit.
This experiment could be analyzed in the
future by an electrical engineer especially, but also
architects and other types of designers because it
demonstrates whether parallel or series circuits
should be used. It shows that if one were to build a
building, it would be better to have more sources of
power that are scattered because this way, there is
not as much electricity lost through the shorter wire
connections. The experiment also tells whether it
would be best to configure light fixtures and other
power sources in series or parallel circuits.
In this experiment, the first hypothesis is if
the length of the wire increases, then the resistance
will increase, while the voltage and the current
The Effect of the Length of Wire on the Current and Voltage of Series
and Parallel Circuits
decreases. This is because as the length of the wire
increases, there are more atoms in it, and therefore
more electrons. The electrically charged electrons
from the power source therefore have more
electrons with which it is possible to collide when
moving through the wire, which means that the
resistance has increased. When the resistance
increases, more electricity that was previously
traveling through the wire is converted into heat
energy, and therefore heating the wire. This means
that there are less electrically charged electrons at
the end of the circuit, and therefore the current and
voltage decrease. This was similar to the third
previous study, in which the current decreased
while the resistance and length of wire increased. It
also agrees with common sense because as the wire
gets longer, there is more space for electricity to get
lost along the way.
The second hypothesis is if the circuit is
changed from a series circuit to a parallel one, then
the resistance will decrease, and the current and
voltage will increase. The resistance will decrease
because in a series circuit, although the distance is
the same between the electricity source and the
destination as in a parallel circuit, there is a light
bulb between the middle one and the batteries. In a
parallel circuit, however, there is not this
obstruction, so there is less resistance and less loss
of electricity. In parallel circuits, the voltage and
current will also increase because of the decrease in
resistance, and because in parallel circuits, there are
more routes for the electricity to go through, and
therefore, more electricity is capable of reaching
each individual light bulb because the electricity
does not need to be distributed to each light bulb.
This is very similar in “Bright Lights,” the first
previous study, except that it changed the circuit
type in the power source, while I am changing it in
the components. This resulted in the data trends
being opposite. This also relates to some of my
previous knowledge, which was that one can
remove a component from a parallel circuit and it
will still work, but this is not true with series
circuits. This supports my hypothesis because it
shows how parallel circuits connect individually to
each component, and that the failure of one
component does not affect the rest of the circuit. It
TPMS Journal of Science
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demonstrates how each component is individual in
parallel circuits, and so they do not affect each
other, but that it is the opposite with series circuits.
The first previous study was from a book
called Shocking Science, published in 1999 and was
called “Bright Lights.” The experiment tested
whether batteries arranged in series or parallel
circuits would light a light bulb brighter. In the
experiment, first a battery was attached to a light
bulb. Then, two other batteries were attached to the
first in series and parallel configurations. The
experiment proved that the circuit with the series
arrangement made the light brighter. This was
because each individual battery provided about 1.5
volts, and in the series, each of the three batteries
provided 1.5 volts, for a total of 4.5. With the
parallel circuit, the three batteries in total provided
1.5 volts. This study relates to my experiment
because it tests the differences between series and
parallel circuits, similar to mine, except for this
study did the opposite of mine.
The second study was in a book called
Electricity, published in 2001, and was called “Fast
or Slow.” It tested how good conductors different
materials were. A circuit was set up with one light
bulb in a socket. One of the terminals was
connected with one wire that had metal clips on the
end, and on the other side, with two of the same
type wires. The two wires were not connected.
First, the wires were connected to complete the
circuit. Then, an eraser, a wooden ruler, a metal
ruler, a plastic ruler, a lead pencil, and scissors were
clipped one by one between the two unconnected
clips so that the material in between completed the
circuit. The study found that the objects made of
wood or rubber produced dim light because they
have the greatest resistance, and therefore lowest
current. It also found that thinner or longer
materials had greater resistance, and therefore less
current, and a dimmer light. This study relates to
mine because in both studies, the main scientific
principle is resistance.
The third study was called “The Effect of
Length on Resistance of a Wire.” In this study, the
scientist investigated the effect of the length of wire
on the current, voltage, and resistance in a circuit.
The Effect of the Length of Wire on the Current and Voltage of Series
and Parallel Circuits
First, the experiment used a 12-volt power pack,
which was plugged into an outlet, which was the
power source. A lead was plugged into the power
pack on the positive side and was connected to an
ammeter. Then, a lead was connected going out of
the ammeter. Wire was clipped onto this lead so
that the wire also got electricity. A ruler was
attached parallel to the wire so that it could be
measured. Another lead was clipped to the power
pack and then to the wire so that the circuit was
complete. Then, on each end of the wire, a
voltmeter was attached.
The scientist took
measurements of amps and volts at 0, 10, 20, 30,
40, 50, 60, 70, 80, 90, and 100 centimeters, and
calculated the resistance. It was found that as the
length of the wire increased, the current decreased.
Also as the length of the wire increased from 0 cm
to 60 cm, so did the resistance and voltage.
However, after 70 cm, the voltage stayed the same.
This study relates to my own because both studies
test how length affects current, voltage and
resistance.
In this experiment, two types of circuits are
use. These two types of circuits are series circuits
and parallel circuits. Series circuits are circuits
where the power source is connected through one
wire to two or more components which are all in
one line. If one component of the circuit fails, or if
one part of the circuit breaks, it is impossible for the
circuit to function. Parallel circuits are circuits
where the power source directly connects to two or
more components; there is more than one wire.
Each component has its own mini circuit, so if one
component fails, none of the other components are
affected.
Voltage and current are the two key
measurements in this experiment. Voltage is the
measurement of the electromotive force in the
circuit. Electromotive force is the force which
causes electricity to move and flow in a circuit. The
current in an electric circuit is a measurement of the
movement of the flow of electricity through the
circuit.
The scientific principle of this experiment is
resistance. Resistance is when electrically charged
electrons bump into the electrons of the wire while
TPMS Journal of Science
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traveling to the destination. The longer a wire gets,
the more electrons there are to bump into over time,
and therefore the resistance increases decreasing the
current and voltage. Resistance is also why in a
series circuit, the voltage and current decrease. In a
series circuit, in order for the electricity to reach the
middle light bulb, it must first pass through another
light bulb.
Light bulbs create light through
resistance in the tungsten filament. Tungsten is a
metal with many more electrons than the copper
that is in the standard copper wire, and therefore the
resistance is greater in tungsten. Because of this, in
a series circuit, components do not get as much
power. Electricity that is lost due to resistance is
turned into heat energy.
Materials & Methods
“How does the length of wire affect the
current and voltage of electricity at its destinations
in series and parallel circuits?” To test this
question, parallel and series circuits with copper
wires of different lengths were created, to see which
circuits and lengths had the most voltage. These
were the independent variables. The dependent
variables were the current and voltage of the
electricity at its destination. In this experiment, the
width and type of wire were kept the same, because
these can affect the resistance in the wire, which
affects the current and voltage.
The same
destinations for the electricity were also used, which
was 3.7 volt, incandescent light bulbs. The bulbs
were spaced equidistantly so that the resistance was
not affected. There were 3 bulbs in each circuit.
The same brand, size, and strength (D) batteries
were also used, which were the source of electricity
in the circuit.
To begin the experiment, make a series
circuit. Put three 3.7 volt light bulbs into three
separate sockets. Then measure two 8 inch and two
4 inch lengths of 24 gauge copper bell wire. Strip
the insulation off of the ends of each of the wires.
Connect one end of the first 8 inch wire to the first
socket, and tape the other end to the positive side of
a D battery. Next, connect the first 4 inch wire to
the other terminal of the first socket and a terminal
of the second. Connect the other 4 inch wire to the
other terminal of the second socket and a terminal
The Effect of the Length of Wire on the Current and Voltage of Series
and Parallel Circuits
of the third socket. Also connect one end of the
other 8 inch wire to the last terminal of the third
socket, and the other to the negative end of a D
battery. Between the two D batteries connected to
the sockets (one connected to the first, the other to
the third), add another D battery so that the three are
lined up negative end to positive end. (See Figure 1
in appendix) Make sure that the light bulbs light
up. Attach the positive lead of the voltmeter to
where the wire on the positive side connected with
the second socket, and the negative lead where the
wire on the negative side connected to the second
socket. Set the voltmeter to 20 millivolts and read
and record the number of millivolts. Calculate the
current by using Ohm’s Law which is V=IR where
V is voltage, I is current, and R is resistance. This
means that V/R=I. The resistance of 24 gauge
copper wire, the wire which is being used, is .0302
ohms per foot. Multiply this by the length of the
wire (in feet) and find the resistance. Divide the
voltage by the resistance to find the current.
Disassemble and reassemble the circuit, then
rerecord the voltage 4 more times to ensure
accuracy. Repeat this again with 56 inch and 296
inch long wire instead of 8 inch.
line up positive end to negative end. Make sure that
the light bulbs light up. Connect the positive lead
of the voltmeter where the middle socket (the one
that was connected to the 12 inch wire at 8 inch) is
connected to the positive wire. Connect the
negative lead of the voltmeter to the place where the
wire on the negative side connects to the middle
socket. Set the voltmeter to 20 millivolts and read
and record the number of millivolts. The resistance
of 24 gauge copper wire, the wire which is being
used, is .0302 ohms per foot. Multiply this by the
length of the wire (in feet) and find the resistance.
Find the current by using Ohm’s Law which is
V=IR where V is voltage, I is current, and R is
resistance. This means that V/R=I. Divide the
voltage by the resistance to find the current.
Disassemble and reassemble the circuit 4 more
times, then reread and record the data to ensure
accuracy. Repeat this again except with 60 inch and
300 inch wire instead of 12 inch. When using
longer wire, keep the same distance between the
three places where the wire was stripped to be
connected to the other wire or sockets (4 inches).
For the parallel circuits, measure two
lengths of 12 inches of wire and four lengths of 4
inches wire. Strip the ends of each of the wires.
Also strip about an inch of insulation off both 12
inch wires towards the middle at 8 inches and 4
inches. The two 12 inch should wires line up so
that the places where they are stripped are next to
each other. Put three 3.7 volt light bulbs into three
different sockets. Connect the first 4 inch wire to
the terminal of the first socket and the other end, to
the part of the wire at 8 inch which is stripped. Do
the same on the other wire and terminal of the first
socket. Do the same with the second socket and
light bulb, but connect the wires to the 4 inch
(instead of 8 inch) area that is stripped. Connect the
end of the first 12 inch wire to the positive end of a
D battery, and the other end to a terminal on the
third socket. Connect the other 12 inch wire to the
negative side of a D battery, and the other end of the
wire to the other terminal of the third socket. Put
another D battery between the two batteries which
are connected to wires. Do this so that the batteries
The parallel circuits had much greater
voltage and current than the series circuit.
Although all of the circuits had the same voltage at
the beginning, 3 D batteries for a total of 4.5 volts,
the longest lost the most electricity. This is
demonstrated by the data collected, and a
comparison of the means. The circuit with the most
current and voltage was the 1 foot parallel circuit,
with 3.97 volts and 131.46 amperes, which was
much more than the 1 foot series circuit with 1.53
volts and 50.79 amperes. The circuit with the least
current and voltage was the 25 foot series circuit
with 1.42 volts and 1.88 amperes.
The
corresponding parallel circuit, which was also 25
feet, had 3.02 volts and 4 amperes. With the 5 foot
circuits, the series had 1.5 volts and 9.91 amperes,
while the parallel had 3.85 volts and 25.5 amperes.
TPMS Journal of Science
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Results
The Effect of the Length of Wire on the Current and Voltage of Series
and Parallel Circuits
the 25 foot series circuit current and voltage, 1.42
volts and 1.88 amps, which were 0.11 volts and
48.91 amperes.
Discussion & Analysis
The current and voltage had a negative
correlation to the length of the wire. Based on this,
The hypotheses were, first of all, when the
I concluded that as the length of wire increases, the
length
of the wire increased, the resistance
current and voltage decrease. Also, although the
increased, while the voltage and the current
parallel circuits had greater current and voltage than
the
Wire
series
Length &
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
Mean
Resistance
Series
1 foot
0.0302
ohms
5 feet
0.151 ohms
25 feet
.755 ohms
Parallel
1 foot
0.0302
ohms
5 feet
0.151 ohms
25 feet
.755 ohms
1.53 volts
1.55 volts
1.53 volts
1.53 volts
1.53 volts
1.53 volts
50.66 amps
51.32 amps
50.66 amps
50.66 amps
50.66 amp
50.79 amps
1.5 volts
9.93 amps
1.4 volts
1.85 amps
1.5 volts
9.93 amps
1.42 volts
1.88 amps
1.46 volts
9.67 amps
1.45 volts
1.92 amps
1.51 volts
10 amps
1.42 volts
1.88 amps
1.51 volts
10 amps
1.43 volts
1.89 amps
1.5 volts
9.91 amps
1.42 volts
1.88 amps
3.99 volts
132.12
amps
3.86 volts
25.56 amps
3.09 volts
4.09 amps
3.99 volts
132.12
amps
3.87 volts
25.63 amps
3.04 volts
4.03 amps
3.94 volts
130.46
amps
3.84 volts
25.43 amps
2.93 volts
3.88 amps
4.03 volts
133.44
amps
3.83 volts
25.36 amps
3.04 volts
4.03 amps
3.9 volts
129.14
amps
3.85 volts
25.5 amps
3.01 volts
3.99 amps
3.97 volts
131.46
amps
3.85 volts
25.5 amps
3.02 volts
4 amps
Table 1: The effect of the length of wire on the current and voltage in series and parallel circuits.
circuits, their current and voltage were affected
much more by the
length of the wire
Length of Wire and
than
the
series
circuits. The 1 foot
4.5
parallel circuit had an
4
average of 3.97 volts
3.5
and 131.46 amps,
3
while the 25 foot
2.5
2
parallel circuit had an
1.5
average of 3.02 volts
1
and 4 amps. The
0.5
difference of voltage
0
was 0.95 volts and
1
5
25
the difference in
Length of Wire (ft.)
current was 127.46
Voltage (volts)
decreased.
The
second hypothesis
Voltage
was if the circuit
changed from a
series circuit to a
parallel one, then
the
resistance
would
decrease
and the current
and voltage would
Voltage of Series
increase.
These
Circuit (volts)
were
both
supported. With
Voltage of Parallel
voltage, there was
Circuit (volts)
a large difference.
The
25
foot
amperes. These values were both Graph 1: The effect of the length of wire on
parallel circuit had an average
greater than the differences
of 3.02 volts, which was
the voltage in series and parallel circuits.
between the 1 foot series circuit
much greater than the voltage
current and voltage, 1.53 volts and 50.79 amps, and
TPMS Journal of Science
Page 5 of 7
The Effect of the Length of Wire on the Current and Voltage of Series
and Parallel Circuits
of the 1 foot series circuit, which had an average of
1.53 volts. With current, the difference was not as
great, but still, the parallel circuit had a greater
current every time. When the 25 foot series
circuit’s current was 50.79 amps, the 25 foot
parallel’s was 131.46 amps. When the 5 foot series
circuit’s current was 9.91 amps, the parallel one had
25.5 amps. The 1 foot series had 1.88 amps, while
the 1 foot parallel had 4 amps.
There were several sources of error in this
experiment. The main source of error in this project
was that the current was calculated, instead of
measured because there was no ammeter to measure
the current.
This calculation, however, was
inaccurate because the resistance of the light bulbs
that were used could not be found, which affected
the current of the series circuit, which required the
electricity to pass through a light bulb before
reaching the light bulb at which measurements were
taken.
When
calculating the
Length of Wire
current for the
series
circuit,
140
the resistance of
120
the light bulb
100
was left out,
80
making
the
60
current less than
40
it should have
20
been.
Some
0
other,
more
1
5
minor, sources
Length
of
Wire (ft)
of error were,
skewed. Another source of error in this experiment
was that the same batteries were used throughout
the experiment, which may have led them to
weaken over the course of the experiment. Finally,
the measurements were rounded when the current of
the circuit was calculated, which caused slight
inaccuracy.
This experiment proves that the resistance
has a strong effect on voltage, and subsequently, on
current. It supported most of the third previous
study in which the current decreased as the wire
lengthened, and so did the voltage, until the wire
was 70 cm, where the voltage stayed the same. It
also relates to my research because it proved it
correct by showing that series circuits have more
resistance than parallel ones.
Current (amps)
In the future, these results could assist urban
developers or architects and electrical engineers
because these people would need to know to place
electricity sources
not too far from
and Current
each other so that
the current and
voltage of the
electricity do not
decrease
too
Current of series
much overtime,
circuit (amps)
leaving the user
Current of parallel
of the electricity
circuit (amps)
less
electrical
25
power far away
from the source
than
nearby.
for example, when measuring Graph 2: The effect of the length of wire on
Further related experiments are
the wire, it was impossible to the current in series and parallel circuits.
“What is the effect of the width
get exactly the length that
of wire on the current and
desired, so the length of the wire may not have been
voltage in series and parallel circuits?” or “How
exactly the length intended. Plus, when attaching
does the length of different types of wire affect the
the wires to the terminals or to each other, they
current and voltage in series circuits?” The effect
could not be connected in exactly the same place,
of type of circuit on the current and voltage could
which would have made some wire a bit longer or
also be tested on different types of electricity such
shorter than others. Also, when measuring the
as solar, wind, alternating current, and direct.
voltage in the circuits, the leads of the voltmeter
Finally, through this experiment I learned a lot,
could not be placed in exactly the same places,
including many new vocabulary terms about
potentially making the readings slightly different.
electricity, such as resistance and current, and more
In addition, the
voltmeter may not have been
about simple electricity.
completely accurate, making the results a bit
TPMS Journal of Science
Page 6 of 7
The Effect of the Length of Wire on the Current and Voltage of Series
and Parallel Circuits
Acknowledgements
Appendices
Thank you to my mom, Mr. Goehring, and
those who peer edited my paper.
References
Alley, P. W. (n.d.). Electric Circuit.
Retrieved October 17, 2011, from World Book
Student database.
circuit. (2002). In The american heritage
student science dictionary (p. 70). Retrieved from
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Copper wire figures- Wire gauge resistance
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Communications Ltd. website:
http://www.radiolocman.com/shem/ shemcache.html?di=18899
Current and Resistance. (2006). Retrieved
October 17, 2011, from Science Reference Center
database. (21987007)
The effect of the length on resistance of a
wire. (n.d.). Retrieved January 2, 2012, from
123helpme.com website:
http://www.123helpme.com/ view.asp?id=122088
Farndon, J. (2001). Fast or slow. In
Electricity (pp. 26-27). New York: Benchmark
Books.
Levine, S., & Johnstone, L. (1999). Bright
lights. In Shocking science: fun & fascinating
electrical experiments (pp. 40-41). New York:
Sterling Publishing Co., Inc.
Resistance and Ohm's Law. (n.d.). Retrieved
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http://library.thinkquest.org/10784/phys7.html
Taylor, K. (2002). How to Measure Voltage
& Current. Retrieved October 10, 2011, from
http://www.sciencebuddies.org/mentoring/project_i
deas/ Elec_HowToMeasure.shtml
TPMS Journal of Science
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The Effect of the Length of Wire on the Current and Voltage of Series
and Parallel Circuits