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investigating the relationship between the diameter and the current in a wire at its melting point

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Introduction

Investigation Report

Aim

Theory

Electrical resistance is a measure of the degree to which an object opposes the passage of an electric current. The SI unit of electrical resistance is the ohm. Its reciprocal quantity is electrical conductance measured in siemens.

Resistance is the property of any object or substance of resisting or opposing the flow of an electrical current. The quantity of resistance in an electric circuit determines the amount of current flowing in the circuit for any given voltage applied to the circuit.

Some formulae for resistance are

image00.png

where

R is the resistance of the object / Ω

V is the potential difference across the object / V

I is the current passing through the object / A

(Ref. http://en.wikipedia.org/wiki/Electrical_resistance)

image01.png

where

...read more.

Middle

wires(image05.png)Voltmeter(image09.pngV)Ammeter(image09.pngA)Variable resisterPower supply

Result

SWG

d/mm

Voltage/V

14

0.195

0.199

0.196

0.002

0.005

0.008

0.01

16

1.11

1.03

1.06

0.024

0.046

0.067

0.089

18

0.12

0.199

0.122

0.005

0.01

0.02

0.03

20

0.95

0.91

0.96

0.008

0.016

0.024

0.031

22

0.76

0.73

0.76

0.013

0.026

0.04

0.052

24

0.055

0.055

0.056

0.538

1.03

1.56

2.07

29

0.033

0.032

0.032

2.63

5.03

7.51

10.14

35

0.027

0.027

0.026

4.93

10.22

14.85

19.88

SWG

Current/A

Resistance/Ω

14

0.251

0.502

0.751

1.003

0.007968

0.00996

0.010653

0.009973

16

0.254

0.5

0.728

1.009

0.094488

0.092

0.092033

0.088206

18

0.254

0.506

1.001

1.501

0.019685

0.019763

0.019987

0.02008

20

0.246

0.503

0.756

1.003

0.03252

0.031809

0.031746

0.030907

22

0.252

0.501

0.757

1.003

0.051587

0.051896

0.05284

0.051845

24

0.255

0.497

0.753

1.003

2.109804

2.072435

2.071713

2.063809

29

0.246

0.494

0.75

1.003

10.69106

10.18219

10.01333

10.10967

35

0.248

0.501

0.754

1.005

19.87903

20.3992

19.69496

19.7811

SWG

Range in d

...read more.

Conclusion

image14.png

The gradient of the line should be image03.png.

image15.png

     = 0.621Ωmimage10.png

SWG

R

1/d^-2

y = mx + c

% difference between data point and best fit line

14

0.009638

25.85

-0.2078

-105

16

0.09168

0.8789

-0.5410

-117

18

0.01985

46.28

0.06466

-69

20

0.03175

1.132

-0.5376

-106

22

0.05204

1.778

-0.5290

-110

24

2.079

326.6

3.804

-45

28

10.249

956.5

12.21

-16

32

19.94

1406

18.21

10

The worst case difference between the data point and the best fit line is -117%.

Evaluation

The % uncertainty in R should be about ±14% according to the calculation. However, the worse difference is –117%.

Sources of error:

  1. 1% error during the measurement of length of wire.
  2. 27% error during the measurement of diameter of wire.
  3. 14% error when reading the ammeter and voltage.

Improvement to the method:

  1. Use longer wires.
  2. Measure the thickness of the wire at as many places as possible.
  3. Use as many significance as the ammeter and voltmeter can use.

The final uncertainty for the experiment is 100%.

...read more.

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Here's what a star student thought of this essay

4 star(s)

Response to the question

This is a good report but a lack of conclusion and some significant errors in analysis of uncertainties have let it down somewhat.
The writer initially makes clear what the task is and how they approach it. The explanation of ...

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Response to the question

This is a good report but a lack of conclusion and some significant errors in analysis of uncertainties have let it down somewhat.
The writer initially makes clear what the task is and how they approach it. The explanation of the equations are good but the full derivation and rearrangement isn't required in this type of report. For a final report, the full results before averages are taken should be relegated to an appendix. The biggest problem is that the results are actually OK and the final graph reasonable. The actual uncertainty is approximately 10% rather than the 100% quoted. This can be determined from your graphing software, which usually has a value for this.

Level of analysis

The physical concepts aren't discussed in particular detail but it is largely accurate, with some relevant physics discussed.

Quality of writing

The layout is good with good spelling, punctuation and grammar in general. The appropriate scientific terms are spelt correctly.
Overall, a good report with some room for improvement.


Did you find this review helpful? Join our team of reviewers and help other students learn

Reviewed by k9markiii 08/03/2012

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