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Factors affecting Resistance of a wire

Extracts from this document...

Introduction

Factors affecting Resistance

In preliminary work, I wanted to find out which factors affect resistance. In some research I found that there were four factors. The four factors of resistance are:

  • Temperature: If the wire is heated up the atoms in the wire will start to vibrate because of their increase in energy. This causes more collisions between the electrons and the atoms as the atoms are moving into the path of the electrons. This increase in collisions means that there will be an increase in resistance.
  • Material: The type of material will affect the amount of free electrons, which are able to flow through the wire. The number of electrons depends on the amount of electrons in the outer energy shell of the atoms, so if there are more or larger atoms then there must be more electrons available. If the material has a high number of atoms there will be high number of electrons
    causing a lower resistance because of the increase in the number of electrons. Also if the atoms in the material are closely packed then the electrons will have more frequent collisions and the resistance will increase.
  • Wire length: If the length of the wire is increased then the resistance will also increase as the electrons will have a longer distance to travel and so more collisions will occur. Due to this the length increase should be proportional to the resistance increase.
  • Wire width: If the wires width is increased the resistance will decrease. This is because of the increase in the space for the electrons to travel through. Due to this increased space between the atoms there should be fewer collisions.

This can be explained using the formula:

R=V/I

Prediction

I predict that the longer the wire, the higher the resistance.

...read more.

Middle

0.289617486

40

0.74

0.72

0.71

0.72

1.9

1.8

1.8

1.83

0.393442623

50

0.92

0.89

0.89

0.90

1.9

1.8

1.8

1.83

0.491803278

60

1.09

1.10

1.07

1.09

1.9

1.8

1.8

1.83

0.595628415

70

1.30

1.27

1.25

1.27

2.0

1.8

1.8

1.87

0.679144385

80

1.44

1.41

1.44

1.43

1.8

1.8

1.8

1.80

0.794444444

90

1.58

1.59

1.60

1.59

1.8

1.8

1.8

1.80

0.883333333

100

1.86

1.75

1.76

1.79

1.8

1.8

1.8

1.80

0.994444444

[Hand drawn graph here]

Table & Graph for 26 SWG

Length (cm)

26 SWG volts

26 SWG amps

Average

Resistance (Ω)

Test 1

2

3

Average

Test 1

2

3

Average

Measured in seconds

Measured in seconds

10

0.35

0.28

0.30

0.31

0.4

0.4

0.4

0.4

0.775

20

0.56

0.54

0.55

0.55

0.4

0.4

0.4

0.4

1.375

30

0.91

0.84

0.87

0.87

0.4

0.4

0.4

0.4

2.175

40

1.21

1.06

1.15

1.14

0.4

0.4

0.4

0.4

2.850

50

1.52

1.32

1.40

1.41

0.4

0.4

0.4

0.4

3.525

60

1.82

1.59

1.70

1.70

0.4

0.4

0.4

0.4

4.250

70

2.15

1.88

2.00

2.01

0.4

0.4

0.4

0.4

5.025

80

2.43

2.17

2.30

2.30

0.4

0.4

0.4

0.4

5.750

90

2.73

2.44

2.60

2.58

0.4

0.4

0.4

0.4

6.450

100

3.0

2.66

2.88

2.85

0.4

0.4

0.4

0.4

7.125

image01.png

Table & Graph for 28 SWG

Length (cm)

28 SWG volts

28 SWG amps

Average Resistance (Ω)

Test 1

2

3

Average

Test 1

2

3

Average

Measured in seconds

Measured in seconds

10

0.29

0.30

0.30

0.30

0.2

0.2

0.2

0.2

1.50

20

0.60

0.60

0.59

0.60

0.2

0.2

0.2

0.2

3.00

30

0.89

0.92

0.88

0.90

0.2

0.2

0.2

0.2

4.50

40

1.15

1.24

1.21

1.20

0.2

0.2

0.2

0.2

6.00

50

1.39

1.53

1.50

1.47

0.2

0.2

0.2

0.2

7.35

60

1.78

1.84

1.82

1.81

0.2

0.2

0.2

0.2

9.05

70

2.10

2.14

2.11

2.11

0.2

0.2

0.2

0.2

10.55

80

2.37

2.45

2.45

2.42

0.2

0.2

0.2

0.2

12.10

90

2.73

2.76

2.75

2.75

0.2

0.2

0.2

0.2

13.75

100

2.97

3.04

3.03

3.01

0.2

0.2

0.2

0.2

15.05

image02.png

...read more.

Conclusion

The only way we would be able to solve the problem of the bends and twists in the wire is to use a brand new piece of wire and look after it very carefully. We could solve the length problem by using a brand new piece of wire, which starts off at 1m in length, and we would cut it down to size for each result. This would make our observations closer to the exact length.

Our results were also made more accurate by the fact that we used a fairly wide range. Using just one or two increments is not reliable enough to draw a valid conclusion, so we used 10 increments. This way we would have been able to cope with any anomalous results using a line of best fit.

Anomalies could have been because the temperature became too high, creating an extra variable to make the test unfair. If the temperature did get too high it would have decreased the current, increasing the resistance. Similar to this idea, the wire could have had some impurities in it, varying the resistivity and increasing/decreasing the resistance. Any of the remaining three (I say this because we have already used one in our experiment - length) factors affecting resistance could have been varied - temperature, resistivity and thickness, leading to unreliable readings. The other reason for an anomaly could simply be that we misread the voltmeter/ammeter.

We could use an even wider range of results to increase the reliability of out results, or we could repeat the results more times. For further work, we could think about which material, length, width and temperature wire has the highest/lowest resistance. We could also use different kinds of resistors in the circuit, for example thermistors, so we could see how resistance varied with heat and that resistor, or we could instead use a light dependant resistor, to see how resistance would vary with that.

...read more.

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