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Investigating How the Cross-Sectional Area of a Conductor Affects the Resistance of Current Passing Through it

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Investigating How the Cross-Sectional Area of a Conductor Affects the Resistance of Current Passing Through it


I will investigate how the cross sectional area of a conductor which in this case will be a length of nichrome wire will affect its resistance.


I predict that as the cross sectional area of the nichrome wire increases the resistance will decrease. I know that on an atomic level the more free electrons there are in a substance the less resistance there will be. This is because there will be more free electrons that are able to travel through the substance.

Background Knowledge:

A circuit is a flow of electrons flowing from negative to positive. The electric current flowing through a circuit is measured in amperes. This flow of electrons is pushed around a circuit by an electrical pressure called electromotive force or e.m.f. Across any resistor such a lamp or wire there is an electrical pressure difference called potential difference of voltage. It is measured in volts.

        Resistance is the term given to resistance of the flow of electrons in a circuit. A lamp in a circuit applies a level of resistance to the current in a circuit as does the wire. Resistance is affected by four factors.

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Variable rheostat                                                                x 1

Results 1:

WireCurrent: ampsVoltage: voltsResistance: ohms

Yellow                        0.50                        1.39                        2.78

Green                        0.50                        3.38                        6.76

Blue                        0.50                        4.84                        9.68

Red                        0.50                        6.68                        13.36                

White                        0.50                        9.06                        18.12

Orange                        0.44                        11.15                        22.30

Results 2:

WireCurrent: ampsVoltage: voltsResistance: ohms

Yellow                        0.66                        1.28                        1.94    

Green                        0.94                        6.08                        6.47

Blue                        0.75                        7.34                        9.79

Red                        0.67                        8.76                        13.07                

White                        0.51                        9.40                        18.43

Orange                        0.40                        9.98                        24.95

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        My results for both experiments were quite close which proves that my experiments were fair. I complied with all the regulations I set for this experiment which would make the experiments fair under ideal circumstances. The results that I produced are reliable and I believe them to be easily reproduced.

        I did notice that the wire SWG 34 produced anomalous results. I believe this to be down to its small surface area which makes it quite fragile. This makes them easily damageable which affects the surface area. If I were to repeat the experiment I would perhaps exclude wires with including or smaller that SWG 34. I believe that the variables used in this experiment produced reliable results and I would use the same variables if I were to attempt this experiment again.

        If I were to extend this experiment I would perhaps experiment on how other factors influence resistance such as temperature or length. If I were to extend this experiment using the same variables I would test out more types of wire with different SWG values and wires made of different materials such as copper. If I had more time to carry out the experiment I would use a wider range of wires and would vary the current passed through the resistor.  

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