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The varying of the resistance of nichrome wire depending on its length

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Introduction

Zaynab Kazi- Yr 11                Physics Coursework

Physics Coursework

The varying of the resistance of nichrome wire depending on its length

Electric current flows when charged particles known as electrons move through a conductor. When the electrons move through a conductor they collide with the atoms of the material of the wire which then causes resistance. The longer a wire is, the more the resistance due to the electrons having to travel further with increased collisions due to increased amount of atoms. However, increasing the thickness of a wire decreases the resistance because the electrons can move about more freely as there is more space for them to manoeuvre around other atoms.

Resistance is measured in ohms (image04.png), therefore the greater the number of ohms, the more the resistance. The name ohm is given due to the fact that in 1826 a German scientist named George Ohm discovered that ‘the current flowing through a metal wire is proportional to the potential difference across it (providing the temperature remains constant).’

When the temperature is constant the graph would be as follows.

image00.png

Current, I

Voltage, Volts

Voltage measures the energy available to drive the force of a current, and this energy is known as potential difference or Electromotive Force (EMF). It is measured using a voltmeter, which is represented by the symbol: image06.png

...read more.

Middle

Intervals in which length will be increased i.e.10cm

Factor which will vary is:

  • Length of nichrome wire

Nichrome Wire

Test 1

Voltage Current

Test 2

Voltage Current

Test 3

Voltage Current

Average

Voltage Current

Resistance

Length

(cm)

Volts

Amps

Volts

Amps

Volts

Amps

Volts

Amps

Ohms

10

1.64

1.59

1.65

1.57

1.65

1.55

1.65

1.57

1.05

20

1.80

0.82

1.83

0.87

1.81

0.84

1.81

0.84

2.15

30

1.99

0.64

2

0.82

1.97

0.64

1.99

0.7

2.84

40

2.03

0.5

2.04

0.99

2.05

0.47

2.04

0.65

3.14

50

2.21

0.42

2.23

0.41

2.24

0.42

2.23

0.42

5.31

60

2.25

0.35

2.27

0.37

2.26

0.36

2.26

1.08

3.34

70

2.28

0.29

2.29

0.32

2.29

0.31

2.27

0.31

7.32

80

2.33

0.26

2.34

0.26

2.12

0.27

2.26

0.26

8.69

90

2.36

0.25

2.38

0.24

2.37

0.23

2.37

0.24

9.88

100

2.40

0.21

2.42

0.22

2.41

0.22

2.41

0.22

10.95

image10.png

Graph Analysis

The graph clearly shows that as the length increases, the resistance does likewise. At the beginning of the experiment, the length was 10cm and the resistance 1.05 ohms. Halfway through, with the length at 50cm the resistance became 5.31 ohms and at the end of the investigation the resistance had increased to 10.95. Therefore, the prediction which I made at the beginning saying that as the length would increase, so would the resistance has been proved to be correct. I think that the results which I have obtained are constant enough to prove my hypothesis correct.

The resistance has increased because although the current was kept the same, it had to travel a longer distance thus slowing it down. Due to the wire being narrow, the electrons could not move about freely and thus their restricted movement also caused slowness. A person trying to walk hurriedly down a crowded street is exactly the manner in which electrons behave when the length is increased.

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Conclusion

Record all results and turn power pack off.

Results for investigation with fixed value resistor

Number

Current (amps)

Voltage (volts)

Resistance (ohms)

1

0.03

0.04

0.75

2

0.41

0.44

0.93

3

1.07

1.14

0.94

4

1.39

1.46

0.95

5

2.47

2.55

0.97

Average

0.91

Results for investigation with filament lamp

Number

Current (amps)

Voltage (volts)

Resistance (ohms)

1

0.1

0.8

8

2

0.11

0.84

7.64

3

0.13

1.69

13

4

0.16

2.7

16.9

5

0.2

3.68

18.4

Average

63.94

image12.png

image05.png

Graph Analysis & Evaluation

The first graph which has the results of the investigation with the fixed value resistor relates in perfect precision to Ohm’s law. The current is directly proportional to the voltage, meaning that my prediction was also correct. There are no anomalies and therefore I have accepted these results as reliable and constant.

The second graph however, does not relate to his law because the temperature was not kept constant. The bulb only glowed after it was heated up and this is obviously changing the temperature. In the background information which I have provided at the beginning, I have also included a graph which shows what would happen when the temperature is not constant. Here, my graph shows the same thing, meaning that although the voltage increases with the current, it is not proportional to it. My results again link to each other fairly well and have a steady consistency in them.

To achieve more accurate results I could have repeated the experiment more. In extending the experiment I could have added additional apparatus such as another resistor or another bulb etc. to understand their effect on resistance.

My investigation overall went smoothly due to a reliable and simple method.

...read more.

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