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# What factors affect the flow of current through a wire?

Extracts from this document...

Introduction

Sreekar Charlu 1VCB                                                                             14th March 02

Physics Coursework

What factors affect the flow of current through a wire?

## Theory

Current is due to the flow of electrons. The material of the wire consists of layers of atoms whose positive centres (ions) are surrounded by a sea of electrons. These electrons are very mobile (free to move). However, when the electrons start moving, carrying current, they will keep on bumping into the ions. These ions, vibrating in fixed positions, cause obstruction to the free flow of electrons. This obstruction is termed resistance. Resistance opposes current and therefore the higher the resistance, the smaller the current. Therefore the factors that affect the resistance are the same factors that control the flow of current through a wire.

In the above diagram the circle represent the ions and the red line represents the flow of electrons.

The factors affecting the flow of current, which you could investigate, are:

• Area of cross-section of wire

When the area of cross-section of the wire is increased the current through it will increase. This is because the electrons can flow more freely through a large cross-section space available, with the same length of wire, and so avoid colliding

• Length of wire

## When the length of wire is increased the current is expected to decrease.

Middle

0.21

0.16

4.76

0.762

100

0.18

0.16

5.56

0.890

1. Table of Results
 Length (cm) Current (A) Voltage (V) Resistance (ohms) 10 1.63 0.16 0.613 0.098 15 1.29 0.16 0.770 0.123 20 0.91 0.16 1.10 0.176 25 0.71 0.16 1.41 0.2256 30 0.67 0.16 1.49 0.2384 35 0.57 0.16 1.75 0.280 40 0.44 0.16 2.27 0.3632 45 0.42 0.16 2.38 0.3808 50 0.40 0.16 2.50 0.400 55 0.36 0.16 2.78 0.4448 60 0.33 0.16 3.03 0.4848 65 0.31 0.16 2.23 0.568 70 0.28 0.16 3.57 0.5712 75 0.27 0.16 3.70 0.592 80 0.25 0.16 4.00 0.640 85 0.23 0.16 4.35 0.696 90 0.23 0.16 4.35 0.696 95 0.23 0.16 4.76 0.7616 100 0.18 0.16 5.56 0.889
1. Table of Results
 Length (cm) Current (A)

Conclusion

, with the gradient from my graph, a value of was obtained for the specific resistance () of constantan which worked very well with the literature vale (ref. Electricity made simple). These facts clearly show that my investigation was very successful and accurate. However, I did find some anomalous results which I could make more reliable throughout extended investigations.

Nevertheless, there were several areas that could have been improved. Accurate measurement of lengths is one such area and choosing wires of 100% uniform thickness with minimum requirements for straightening would help to increase accuracy and avoid anomalous values in the results. While random errors can be minimised by doing each step extra carefully any systematic errors due to instruments such as the ammeter and voltmeter can be overcome only by calibrating the ones used against accurate instruments.

Repeating each experiment under identical conditions will ensure reproducibility. Both reproducibility and accuracy are required in order to obtain an extremely successful outcome of an investigation. Using different thickness of wire could extend this experiment and also by using different materials, in order to demonstrate the correctness of the relationship  for the resistance of the wire. I could also extend this experiment by using different sets of cross-sections of the wire so I could prove which had the highest resistance and which one had the lowest resistance.

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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