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What Affects The Resistance Of A Wire??

Extracts from this document...

Introduction

What Affects The Resistance Of A Wire??

Short Prediction

My prediction is that when the length of the wire in a circuit is increased, the resistance also increases.

Apparatus

The Apparatus I will be using is as follows:

• A power pack (at 2 volt)
• Nichrome wire
• Ammeter                     (Digital)
• Voltmeter                    (Digital)
• Crocodile clips

Method (list):

1) Get a power pack, some nichrome wire, an ammeter, a voltmeter leads and some crocodile clips.

2) Connect a lead to the power pack (-) with a crocodile clip.

3) Then connect the lead to the ammeter with a crocodile clip.

4) Then connect the nichrome wire to the ammeter with lead and a crocodile clip keeping it in series.

5) I then connect it to the power pack (+) again to complete the circuit.

6) Then add the voltmeter in parallel round the nichrome wire.

And it should look like the circuit below:

7) Then switch on the power pack.

8) Take a reading from both the ammeter and the voltmeter.

9) Then lengthen the nichrome wire by 5 cm.

11) Repeat this process 5 times and take 5 readings.

12) Then work out resistance R=V/I

Middle

Preliminary Experiment

I have carried out the experiment and it works, and my prediction was correct, but however what I did not know would happen is that the voltage would increase.

Length Of Wire

CM

Voltmeter

(Volts)

Resistance

(Ohms)

20

1.92

0.87

0.45

40

1.40

1.21

0.86

60

1.16

1.46

1.26

80

0.95

1.66

1.75

100

0.86

1.80

2.09

2 volt power

There is a good gap between the results, of which the biggest value is 4X bigger than the smallest value.

So to recap the kit I used in the experiment: a digital voltmeter, a digital ammeter, a voltage of 2 volts from a power pack and 1 metre of nichrome wire.

The reason I have decided to use the digital ammeter is because it is accurate to 2 decimal places, which is very accurate, and also I am using a digital voltmeter because that too can also be accurate to 2 decimal places and this is why I’m not using the needle versions, which could measure to the nearest 0.5 volt or amp.

Conclusion

5">20

0.99

0.88

0.94

0.93

0.98

0.96

0.98

40

1.22

1.20

1.20

0.70

0.68

0.69

1.75

60

1.38

1.38

1.38

0.53

0.53

0.53

2.60

80

1.49

1.50

1.495

0.43

0.43

0.43

3.49

100

1.50

1.55

1.525

0.35

0.36

0.355

4.39

Analysis

when the length of the wire is increased so does the resistance of the wire and so the current decreases. This is caused by the amount of nuclei in the wire. When the electrons pass through the wire they hit the protons and rebound and hit more protons and so this will happen till it gets back to the energy source. This I’d all shown by the diagram below.

Evaluation

Accuracy: the voltmeter and ammeter were accurate to two decimal places, which is very accurate, and the wooden ruler used was also accurate, to the mini meter. The power pack wasn’t accurate and was set to the right voltage using the voltmeter; however I didn’t always use the same equipment so some of my results were a bit out.

Anomalous results:

Reliability:

My results were very close the largest range was 0.11.

Improvements:

1.  Use a more accurate ruler.
2.  Spend more time on actual experiment.

Justify: My results do in deed justify my conclusion.

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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