To find the relationship between the length of the wire and the resistance it gives.

I will carry out a preliminary experiment to check that my method will work. Here are my results:

Wire 1-(Longer)

Wire 2-(Shorter)

I=0.15A

I=0.11A

V=1.23V

V=1.26V

R=8.20?

R=11.46?

While I was carrying out my preliminary experiment I discovered that my experiment worked. However it also hi-lighted the fact that there are other factors which can effect the resistance, other than length. This is because; the longer wire has the smallest resistance according to my results. This is not correct, it is not possible, this means that the wires may have been difference thicknesses, different types of materials or even different temperatures. This is why I must take all aspects into consideration in order to make my experiment a fair test.

Although, my experiment appeared to work, I have seen in the past that results do not always do as expected, for example when I carried out and experiment to find the relationship between potential difference and current I predicted that as the ammeter reading went up, so would the resistance. After carrying out this experiment, I discovered that the resistance was very close to each other, mainly going up by a small amount however in one case this did not happen, the resistance went up but for the next two readings they went back down before going back up again. Because of this, I have decided to use a variable resistor to make it possible for me to carry out the experiment five times on each length of wire, therefore making it possible for me to work out an average and improving my experiment overall.

Here is a diagram of my new circuit I will use for this experiment:

While carrying out this experiment there will be no potential safety hazards.

Prediction: I predict that the longer the wire the greater the resistance. I predict this because there will be more atoms for the travelling electrons to collide with therefore there will be more electrical resistance. The electrons are negative charges which are sent around the circuit. These charger are measured in bundles of 6 million million million called coulombs. When working out the resistance of a circuit you use the potential difference and current. This will tell you how difficult it is for current to flow through the circuit. As the wire is longer, there will be more atoms making up the wire waiting to collide with the electrons travelling in the current therefore creating more resistance. As the wire is shorter there will be less atoms making up the wire waiting to collide with the electrons travelling in the current therefore creating less resistance.

Results:

Length (cm)

Voltage (volts)

Current (amps)

Resistance (V/I) (ohms)

Average resistance

50

2.16

0.22

9.81818181818

0.08777922

.58

0.16

9.875

.17

0.12

9.75

0.86

0.08

0.75[H1]

0.72

0.07

0.24571429

40

2.22

0.28

7.928571429

8.135714286

.19

0.15

7.933333333

0.84

0.10

8.4

0.66

0.08

8.25

0.49

0.06

8.1666666667

30

2.02

0.32

6.3125

6.407936509

0.99

0.16

6.1875

0.61

0.09

6.777777778

0.52

0.07

7.428571429

0.32

0.06

5.333333333

20

.76

0.44

4

4.194444444

0.74

0.18

4.111111111

0.49

0.12

4.083333333

0.37

0.09

4.111111111

0.28

0.06

4.666666667

0

.61

0.81

.987654321

.968439955

0.43

0.22

.954545454

0.26

0.14

2

0.19

0.10

.9

0.14

0.07

2

Analysis: My graph is showing that as the length or wire increases, so does the resistance. This is showing that my prediction was correct meaning my theory was also correct, see prediction theory. There is a steady increase in resistance as the wire steadily increases in length.

Evaluation: From my graph I can tell that the accuracy of my experiment was generally very good. All the points are on the line, apart from one. However this one result is not far off my line telling me my results are very accurate. This one result has been circled and is slightly anomalous. This may be because there may have been some rounding up errors, due to me using a volt meter and ammeter which only read up to two decimal places, not the three decimal places I had planned. This is because the resources were not available for my use. If I used an ammeter or volt meter which read to more decimal placed there would have been less room for rounding errors. Another reason may have been that one of my results was very inaccurate. There are many explanations as to why this happened. One of these is, one of the wires may not have been plugged in properly for this reading, or the switch was not closed properly for this reading, both creating more resistance. The result which I feel may have been causing this problem was the result which read 7.428571429. Therefore, I should have ignored this result when calculating the resistance for this reading. This was one mistake I made. I feel that my line of best fit is the only way of drawing the line of best fit. I feel this as my results are more or less in a straight line, showing a straight line graph. There is no other obvious way of drawing the line. My results were very reliable, if someone was to repeat this experiment with the same equipment, their results should not be much different to mine. This is because the experiment was a straight forward experiment and there is nothing that could really go wrong.

Improvements that I could make to this experiment are I could as I planned use appliances (volt meters and ammeters) which read to three decimal places to prevent rounding errors even more. You could also obtain more results but the accuracy of my results are that as such that this should not make much difference i.e. they are very accurate.

Overall I feel my experiment was very successful.

[H1]From here on I will not take account of the last two readings as they are too small a current and there will be more room for rounding errors.

By Hannah Ridley