Investigation Of Factors That Affect The Resistance

Of A Wire Essay, Research Paper

Introduction In this piece of coursework, I have been set the task of

investigating factors that affect the resistance of a wire. There are many

things that affect the resistance of a wire but I have only got the chance to

do one of these. The one I will choose will depend on it being the most

effective and on its ease to do. ???? Firstly, I will give an explanation of how

resistance works. Resistance is when travelling electrons in a wire collide with

the atoms of the wire. The collisions between the electrons and the atoms cause

the electrons to move slower, which in effect causes resistance. So, resistance

is how hard it is to move electrons through a wire. ???? Now, the factors that affect the resistance

of a wire are going to be described. ???? Firstly, temperature is a factor. If the

wire is heated, the atoms will move around more because there will be an

increase in energy. This would cause more collisions between the atoms and the

electrons. The increase in collisions would cause the resistance to rise. ???? This would be very hard to do, because the

equipment needed to do this experiment effectively has not been given to us. ???? Secondly, the width of the wire is a

factor. This will cause resistance to decrease

because of the increase in space in the wire. The increase in space means

that there is more space for the electrons to flow freely because there would

be fewer collisions with atoms. ???? I could do this by using different widths

of a wire; for example thin, medium, or thick copper could be used. ???? Thirdly, the material used would be a

factor. If the material being used contains atoms with a large number of

electrons on the outer shells, then this means there are more electrons

available. So, in theory, if the material has a large number of atoms, there

should be less resistance, because of the higher number of electrons .If the

atoms in the wire are closely packed, then this will cause an increase in resistance, due to frequent

collisions. ???? To do this I would use the same length and

width of many different wire materials, using the same amount of voltage each

time. ???? Finally, the length of the wire is a

factor. The longer the wire, the longer it will take electrons to get to the

end of the wire. This is because there will be more collisions between

electrons and atoms. So, in theory, the length of the wire should be directly

proportional to the resistance. ???? This would be very easy to do, and give

accurate results. Because of the length being proportional to the resistance, I

could link the length of a wire with the resistance of the wire, which would

make my graph more interesting. ???? Due to the effectiveness of this method, I

have decided to use the length of the wire as the factor that I am going to

use.Prediction I predict that, the longer the wire is, the more

resistance there will be due to more collisions between the electrons and

atoms. The length of the wire should be approximately proportionally the same

as the resistance. In theory, if the wire is doubled, then so will the

resistance. If the length is twice as much, then there will be twice as much

collisions, which would increase the resistance.Method Apparatus ·

Crocodile

clips ·

Ammeter ·

Voltmeter ·

Power

supply ·

Meter

ruler ·

Connecting

wires ·

sticky

tape ·

Thin

Constantine wire Diagram The reason I have chose to use Constantine wire is

because of its high resistance. This makes it a lot easier to record the

results, as it gives me higher numbers to work with. ???? The resistance

is going to be recorded at nine different lengths. I have chosen to record the

results at this amount of lengths, as it will give me a much more accurate

result at the end of the experiment. ???? As you can see

in the diagram, I have chose to use a digital voltmeter instead of a

conventional analogue voltmeter, as this can give me a much more precise result

than an analogue meter. This is because the needle on an analogue meter could

be bent and give me the wrong reading, but a digital meter does not involve

needles, so would give a much clearer reading. ???? The way to

calculate the Resistance relies on this formula: ??????????????????????????????? Resistance =

Voltage/current I will use the Voltmeter provided to get the voltage, and

the ammeter provided to get the current (in amps).ResultsHere

is a result table from my main experiment:?????? 20 cm V I R 1 0.27 3.70 1.5 0.39 3.85 2 0.52 3.85 2.5 0.60 4.17 3 0.70 4.29 3.5 0.80 4.38 4 0.91 4.39 ?????? 30 cm V I R 1 0.17 5.88 1.5 0.25 6.00 2 0.33 6.06 2.5 0.41 6.09 3 0.48 6.25 3.5 0.55 6.36 4 0.71 6.67 ???? ? 40

cm V I R 1 0.14 7.14 1.5 0.21 7.14 2 0.28 7.14 2.5 0.34 7.35 3 0.40 7.50 3.5 0.46 7.61 4 0.52 7.69 ??? 50 cm V I R 1 0.11 9.09 1.5 0.16 9.38 2 0.21 9.52 2.5 0.25 10.00 3 0.29 10.34 3.5 0.33 10.61 4 0.37 10.82 ??? ??60 cm V I R 1 0.09 11.11 1.5 0.13 11.54 2 0.18 11.11 2.5 0.21 11.91 3 0.25 12.00 3.5 0.29 12.07 4 0.33 12.12 ????? 70 cm V I R 1 0.08 12.50 1.5 0.12 12.50 2 0.16 12.50 2.5 0.20 12.50 3 0.23 13.04 3.5 0.26 13.46 4 0.29 13.79 ???? ?80 cm V I R 1 0.07 14.29 1.5 0.10 15.00 2 0.13 15.38 2.5 0.16 15.63 3 0.19 15.79 3.5 0.22 15.91 4 0.26 16.00 ???? 90 cm V I R 1 0.06 16.67 1.5 0.09 16.67 2 0.12 16.67 2.5 0.14 17.86 3 0.16 18.75 3.5 0.18 19.44 4 0.20 20.00 ?? 100 cm V I R 1 0.05 20.00 1.5 0.07 21.43 2 0.09 22.22 2.5 0.11 22.73 3 0.13 23.08 3.5 0.15 23.33 4 0.17 23.52 Average resistance Length of wire (cm) Average resistance (ohms) 20 4.09 30 6.19 40 7.37 50 9.97 60 11.69 70 12.89 80 15.43 90 18.01 100 22.33 Conclusion In conclusion, I have found that my prediction was

correct. I said that the resistance will increase approximately proportionally

to the length, and as you can see from the graph, this was correct. This is

emphasised because the line of best fit is a straight line, which means the

resistance is proportional to the length. This proves the fact that the longer

the wire is, the more collisions there are between atoms and electrons. So if

the wire increases in length, so does the resistance. If the wire decreases in

length, so does the resistance. This can be shown in the diagram below:As you can see in the diagram, the wire on the top is

twice as big as the one below it, so it has twice the electrons too.EvaluationThis experiment has gone satisfactory, but there have

been certain things in the experiment that I have not been pleased with. ???? Some of my

results have turned out anomalous. This mainly being:60cm???????? ??????????????????? ?Anomalous V I R 1 0.09 11.11 1.5 0.13 11.54 2 0.18 11.11 2.5 0.21 11.91 3 0.25 12.00 3.5 0.29 12.07 4 0.33 12.12 I have probably ended up with this anomalous result

because of an error in recording my results. ???? However, as you

can see from my average resistance graph, the results are roughly on the same

line, so this anomalous result did not do much harm when the results are

averaged. ???? I have noticed,

now that I have finished my coursework, that there are a number of things I

could have done to get more accurate results. ???? Firstly, I

would do the experiment using the width and the material used as a factor too,

just to make sure that my averages are as correct as possible. ???? The next thing

I would have done is to use pointers instead of the crocodile clips which I

used. This is because pointers are a lot more accurate, because they have a

smaller surface area on their tips than crocodile clips. This in effect would

give much more accurate measurements.

381