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Investigation to determine whether the resistance of a wire increases in proportion to its length.

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Introduction

Investigation to determine whether the resistance of a wire increases in proportion to its length.

Aim: To investigate if the resistance of a Nichrome wire is directly or inversely proportional to the length of the wire. I will determine if the resistance is affected by changing the length of the Nichrome wire between 11cm and 99cm.

Prediction: I predict that the longer the length of wire, the higher the resistance will be. Resistance is a way of saying how easy or difficult it is for electrons to flow through something. The longer the length of the wire the harder it is for Electrons to pass through the wire thus causing a greater resistance. The longer the length of wire, the more chance there is of the electrons colliding with each other as they flow through the Nichrome wire. Therefore decreasing the rate at which they flow, thus causing the resistance to increase. I predict the resistance of the wire will be directly proportional to its length. From this I can also say that if I doubled the length of the wire the resistance would also double this would mean that the number of electrons would double and therefore causing more collisions. If there are more collisions then this means that the resistance of the wire will also increase.

A property of the atoms of all conductors is that they have free electrons in the outer shell of their structure. As a result of the structure of all conductive atoms, the outer electrons are able to move about freely, even in a solid.. When there is a potential difference across a conductive material all of the free electrons arrange themselves in lines moving in the same direction. This forms an electrical current.

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Middle

After takings the readings I turned the power pack off and allowed the wire to cool for 45 seconds. Once it had cooled I decreased the length by moving the power leads (wire) in by 11cm. I turned the power pack on and took the readings of the voltmeter and ammeter.

I continued to do this until I had decreased the length of the nichrome wire to 11cm. I took readings for the following lengths: 99, 88, 77, 66, 55, 44, 33, 22 and 11 cm. I repeated the test for each of these lengths three times in order to achieve a good average.

Diagram:

Results: 1st trial

Length of wire (cm)

Current (A)  (2.D.P)

Voltage (V) (2.D.P)

Resistance (Ohms) (2.D.P.)

99

0.33

4.53

13.72

88

0.37

4.55

12.30

77

0.41

4.48

10.93

66

0.47

4.44

9.45

55

0.58

4.40

7.74

44

0.69

4.27

6.19

33

0.87

4.19

4.82

22

1.22

4.09

3.35

11

2.20

3.67

1.62

2nd trial:

Length of wire (cm)

Current (A)  (2.D.P)

Voltage (V) (2.D.P)

Resistance (Ohms) (2.D.P.)

99

0.33

4.64

14.06

88

0.37

4.65

12.57

77

0.42

4.56

10.86

66

0.48

4.54

9.46

55

0.57

4.50

8.04

44

0.69

4.41

6.39

33

0.91

4.24

4.66

22

1.25

4.07

3.26

11

2.14

3.61

1.69

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Conclusion

If I were to use different equipment it could provide me with more accurate or less accurate results which may mean that I am not able to compare my results from the follow up experiment, with previous results from the length of the wire experiment.

If I were to predict whether the temperature was directly or inversely proportional to resistance I would say it was directly proportional. This is because as the temperature increases it causes the electrons to collide more often and this would result in an increase in resistance making the temperature directly proportional to the resistance.

However if I were to conduct an experiment to see if the thickness of the wire was directly or inversely proportional to the resistance I would predict that it was inversely proportional because as the thickness of the wire is increased the area is also increased this provides the electrons with more room to move around in. If there is more room then this means that fewer collisions will occur. With less collision occurring the resistance of the wire will also decrease making the thickness of the wire inversely proportional to the resistance.

Their were a number of good and bad points in my experiment. The good points included being able to complete the investigation within the time limit and being able to achieve accurate fair results. Other good points included being able to work safely. The bad points included not having very accurate equipment and not being able to use exactly the same equipment each week. Apart from these points I don’t think that their were any other good or bad points that could have been made regarding the experiment.

Overall I felt that the experiment which I conducted was a huge success and the results I received were accurate and reliable.

Omar Jamshad 10S / B1

07-12-03

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