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Investigate the effects of resistance on a nichrome wire

Extracts from this document...

Introduction

Physics Coursework : Resistance of a wire

Aim:

To investigate the effects of resistance on a nichrome wire

Planning

My planning will begin with providing a background understanding on the theory of resistance and how it participates in the overall process of the electric current. Reistance is simply a force which challenges the flow current. Resistance is like car racers racing round a track, the more friction there is due to the conditions, and the material of the tyres, the more slower the car will move, similarly an electric current with a more resistant material, causes more resistance thus makes the current move slower. The electrons are like the cars, as they move round the circuit they collide with positive ions and the current slows down creating resistance.

The unit of resistance in an electric current is the ohm, (or known as the greek letter omega). The formula for resistance is as follows:

Resistance ( R ) = Voltage(V) / Current (I)

The investigation is split into 3 experiments, the experiment will be on the length of a nichrome wire, the second experiment will be on the length of a copper wire, and finally the third experiment shall be on the cross sectional area of the nicrome wire.

Equipment

  • Nicrome wire, in 3 different cross sectional areas
  • Copper wire
  • Battery
  • Crocodile clips
  • Ammeter
  • Voltmeter
  • Pliers
  • 1 metre ruler
  • Micrometer

These are the constant variables that I will test in the first experiment

  • The wire will be nichrome and will stay as nichrome
  • The voltage
  • Cross sectional area
  • Room temperature

These values must be kept at a constant, to keep the experiement as a fair test.

...read more.

Middle

Obtaining Evidence

Length of the nicrome wire

This is the table for the results of resistance against the length of the nichrome wire, the cross sectional area was 1.11 x 10-06m2

Length of the wire(cm)

Current1 (amps)

Current2 (amps)

Voltage1 (volts)

Voltage2 (volts)

Resistance1 (ohms)

Resistance2 (ohms)

Average Resistance (ohms)

10

0.92

0.90

0.10

0.13

0.11

0.11

0.11

20

0.87

0.87

0.21

0.20

0.23

0.23

0.23

30

0.85

0.85

0.33

0.23

0.35

0.26

0.30

40

0.82

0.80

0.39

0.36

0.48

0.45

0.47

50

0.80

0.75

0.43

0.37

0.57

0.49

0.49

60

0.75

0.71

0.54

0.49

0.67

0.69

0.68

70

0.72

0.67

0.61

0.43

0.83

0.64

0.75

80

0.71

0.67

0.65

0.51

0.93

0.75

0.84

90

0.69

0.66

0.71

0.57

1.01

0.86

0.93

100

0.65

0.65

0.80

0.60

1.23

0.92

1.08

Results of resistance for the length of a copper wire, the cross sectional area was 3.07 x 10-06 m2

...read more.

Conclusion

2I will need to divide the radius by 1000, then use the area of a circle formula , to find out the cross sectional area.

Therefore:

0.595mm / 1000 = 0.000595 m

π(0.000595)2= 1.11 x 10-06 m2

Cross Sectional Area and wire no.

Current1 (amps)

Current2 (amps)

Voltage1 (volts)

Voltage2 (volts)

Resistance1 (ohms)

Resistance2 (ohms)

Average Resistance (ohms)

Wire 1 1.11 x 10-06 m2

0.80

0.75

0.40

0.37

0.50

0.49

0.49

Wire 2

3.7 x 10-07 m2

0.56

0.58

0.72

07

1.28

1.20

1.24

Wire 3

1.0 x 10-07 m2

0.37

0.37

1.60

1.50

4.32

4.05

2.23

Analysis

These are the Graphs for each table of resistance.

image00.png

image01.png

image02.png

Conclusion

In my conclusion, I conclude that the wire with the least length had the least resistance, and this is evident from the graph. You can see that at 10 cm the resistance was about 0.10 or 0.11 ohms,  also the wire with the longest length had the most resistance which in accordance to graph is at the length of 100 cm and at the resistance of 1.5 or 1.8 ohms . This also applies to the copper wire.

In regard to the cross sectional area, the more bigger the cross sectional area was , the lower the resistance was. From the graph and the tables we can see that at the lowest cross sectional area of 1.0 x 10-07 m2

The resistance was 2.23 ohms.

Evaluation

I think that the experiment was a success, the results were correct in accordance to the background knowledge and also the predictions made at the start

I think the few ways that the experiment could have been improved is a longer wire could have been used, about 2m, also I think that if I were to use different materials the theory would have been more accurate. Checking the wire with the micrometer in 10 different places wouldve also helped. However despite these facts I belive that generally the experiment was successful.

...read more.

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