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We have been asked to investigate how the length of two different pieces of wire, Nichrome and Constantin effects the resistance. These are both metal alloys and they both conduct electricity. Metals conduct electricity because the atoms in them don't hold on to their electrons very well, so allowing electrons to move carrying a negative charge along the wire. Resistance occurs when it is difficult for the electrons to be released from their nuclei to continue along the piece of wire.

Some variables that could have an effect on the resistance of the piece of wire is the thickness of the piece of wire, the length, the temperature, what the wire is made from, whether or not there is a kink or bend in the wire, and if the wire is short circuiting its self.

Straight

Not Straight

Kinked

Short Circuiting

If the piece of wire is thin then it will have a higher resistance because the current will not have as many different paths to go down making the electrical flow slower.

If the piece of wire is thick then the electric current will have many paths to go down making the resistance lower. If the piece of wire is longer then the electrons will have further to travel down the wire and they will come into contact with more electrons that wont move. This increases the resistance.

As the temperature of the wire increases the resistance increases this is because the thermal vibrations make the electrons scatter and therefore slow them down creating more resistance.

Another thing that might effect the resistance in the piece of wire is what it is made from. The wire might be made from a substance where the nuclei in the atoms hold on to their electrons quite well, on the other hand the nuclei might not hold on very well at all. If there is a kink or bend in the wire then that could effect because the wire will not quite be the length it is measured as. If the wire is short circuiting then the electrons will have a short cut making the resistance less than it should be.

We will be investigating the effect the length has on the resistance.

Prediction

I think that the longer the piece of wire is the greater the resistance will be. This is because the electrons will have further to travel down the wire and will come across more nuclei where the electrons are not free moving.

Method

For this experiment I will need: One piece of Constantin wire and one piece of Nichrome wire, a voltmeter, an ammeter, a power pack, cables and crocodile clips.

This is a diagram to show how I will set up my apparatus.

I set up the equipment as shown and then measured the wire to be 1 meter long. We put 5 volts around the circuit and measured the voltage and the current. We did this 3 times for each piece of wire, Nichrome and Constantin, and for each length 1, 0.8, 0.6, 0.4, and 0.2 meters. Once I had got all the results I worked out the resistance for each result using the formula -

Resistance = Voltage ï¿½ Current or R = V ï¿½ I

Then we worked out the average for each set of 3 results using the resistance. After that we worked out the resistivity for each of the averages. I did this using the formula -

Resistivity = Resistance * Cross Sectional Area ï¿½ Length

Ways in which we can make this experiment accurate is - by making sure that the Crocodile clips at right at the end of the wire; that when the wire is measured it is pulled tort on the ruler so there is no kinks or bends in it; that when we are doing the experiment the wire doesn't short circuit its self; that we keep the voltage the same, that the surface we are working on isn't wet; that we use the same pieces of wire for each of the three experiments and that we keep the rest of the equipment the same.

To keep this experiment safe we are not going to use a high voltage so that the wire doesn't get too hot.

Results (Constantin)

Length

Voltage

Current

Resistance

1 meter

2.75 Volts

0.66 Amps

4.2 Ohms

1 m

3.14 v

0.67 a

4.7 Ohms

1 m

3.16 v

0.68 a

4.6 Ohms

0.8 m

3.02 v

0.81 a

3.7 Ohms

0.8 m

2.98 v

0.80 a

3.7 Ohms

0.8 m

3 v

0.80 a

3.8 Ohms

0.6 m

2.92 v

1.05 a

2.8 Ohms

0.6 m

2.98 v

1.03 a

2.9 Ohms

0.6 m

2.95 v

1.06 a

2.8 Ohms

0.4 m

2.85 v

1.55 a

1.8 Ohms

0.4 m

2.80 v

1.52 a

1.8 Ohms

0.4 m

2.79 v

1.50 a

1.9 Ohms

0.2 m

2.45 v

2.71 a

0.9 Ohms

0.2 m

2.42 v

2.70 a

1.2 Ohms

0.2 m

2.40 v

2.69 a

1 Ohms

Results (Nichrome)

Length

Voltage

Current

Resistance

1 meter

2.45 Volts

2.20 Amps

0.9 Ohms

1 m

2.65 v

2.22 a

1.2 Ohms

1 m

2.36 v

2.10 a

1.1 Ohms

0.8 m

2.25 v

2.40 a

0.9 Ohms

0.8 m

2.17 v

2.26 a

1 Ohms

0.8 m

2.32 v

2.40 a

1 Ohms

0.6 m

2.13 v

2.70 a

1 Ohms

0.6 m

2.10 v

2.80 a

0.8 Ohms

0.6 m

2.12 v

2.76 a

0.8 Ohms

0.4 m

1.91 v

3.50 a

0.5 Ohms

0.4 m

1.73 v

3.40 a

0.5 Ohms

0.4 m

1.84 v

3.70 a

0.5 Ohms

0.2 m

1.36 v

5.20 a

0.3 Ohms

0.2 m

1.32 v

5.19 a

0.3 Ohms

0.2 m

1.40 v

5.47 a

0.3 Ohms

Averages (Constantin)

Length

Voltage

Amps

Resistance

1 Meters

3.03 Volts

0.67 Amps

4.514 Ohms

0.8 m

3 v

0.80 a

3.734 Ohms

0.6 m

2.29 v

1.04 a

2.787 Ohms

0.4 m

2.81 v

1.52 a

1.849 Ohms

0.2 m

2.42 v

2.7 a

0.897 Ohms

Averages (Nichrome)

Length

Voltage

Amps

Resistance

1 Meters

2.49 Volts

2.1 Amps

1.075 Ohms

0.8 m

2.45 v

2.35 a

0.955 Ohms

0.6 m

2.12 v

2.75 a

0.769 Ohms

0.4 m

2.83 v

3.53 a

0.517 Ohms

0.2 m

1.36 v

5.95 a

0.258 Ohms

Resistivity (Constantin)

Length

Resistivity

1 Meters

0.000000564 Ohms/m 2

0.8 m

0.000000538 Ohms/m 2

0.6 m

0.00000058 Ohms/m 2

0.4 m

0.000000577 Ohms/m 2

0.2 m

0.00000056 Ohms/m 2

Resistivity (Nichrome)

Length

Resistivity

1 Meters

0.000000843 Ohms/m 2

0.8 m

0.000000937 Ohms/m 2

0.6 m

0.000001006 Ohms/m 2

0.4 m

0.000001014 Ohms/m 2

0.2 m

0.000001012 Ohms/m 2

The results highlighted in Red means that they are odd so something might have happened to make them go wrong. Either a something was miss-read or miss calculated.

Conclusion

The results I got formed a straight lined graph with a positive gradient. This is because as the length of the wire doubled so did the resistance. This made my graph steadily increase. These results agree with my prediction "I think that the longer the piece of wire is the greater the resistance will be." However we can be more specific by saying that when the length of the wire is doubled so does the resistance.

Evaluation

Most of the results from this experiment are quite accurate. There is the odd result here and there which is not quite in place for one reason or another. Maybe I miss calculated it when I was working out the average or the resistance. Other than that most of them are quite accurate. I took the necessary precautions to make sure that the experiment was as accurate as it could be and that it was safe. I am afraid I am unable to explain the odd results in my tables. There is one that is quite shocking and that is the resistivity result. Unfortunately I am not sure why it is out of place. Read also does length of wire affect current essay

The only problem I had with the original method was trying to keep the wire straight and not letting it short circuit its self.

In all I think I produced some good quality results that are fairly reliable. If I were to do this experiment again I would use more lengths that just 0.2, 0.4, 0.6, 0.8, and 1 meter. I would use measurements in between like: 0.3 and 0.5 meters as well. I would do this so that I would have a better idea of the shape of the graph and where to put the best fit line.

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