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# GCSE Physics Coursework - Investigation of the resistance of a wire

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Introduction

GCSE Physics Coursework – Investigation of the resistance of a wire

AIM:

To investigate what affects the resistance of a wire.

VARIABLES:

The material of the wire – e.g. iron has greater resistance than copper.

The length of the wire.

The cross-sectional area of the wire – e.g. the width of the wire.

The temperature of the wire.

PREDICTION:

I have chosen to base my investigation on the length of the wire. I predict that as the length increases, the resistance increases too.

HYPOTHESIS:

I hypothesise that the length of the wire affects its resistance. This is because from in-depth research from encyclopaedias and the internet I have found out that the electric current is the flow of charged particles around a circuit of conducting material. In solid metal conductors, current is a flow of negatively charged electrons; in an electrolyte it is a flow of positive and negative ions.

The energy given to electrons to push them around an electric circuit is transferred from an electrical source, such as a power supply, a battery, solar cells or a generator, to components in the circuit, such as resistors, lamps bells, LED’s and buzzers; the energy transferred makes things happen in the circuit, e.g. light, heat, sound.

In an electrical circuit, the cell or the battery provides the electrons with electrical potential energy.

Middle

To make my experiment as reliable as possible I will repeat it 3 times and then find an average result using the ‘arithmetic mean’.

Arithmetic Mean =           ∑ x

n

Where:

‘∑’ is a capital Greek letter (sigma). ‘∑x’ means the sum of all the terms and ‘n’ is the number of terms.

I will use this formula to calculate my ‘Average Resistance’ and for the ‘mean of graph’ (this allows me to work out the exact point where the line of best fit runs straight through).

Graph – Line of Best Fit:

To calculate the line of best fit we need to use the formula:

Y =  mx + c

Where:

‘Y’ is the y-axis, ‘m’ is the gradient (y/x), ‘x’ is the x-axis, and ‘c’ is the y-intercept.

Here are examples of 3 main types of correlation:

RESULTS:   Width of Wire:  0.55mm

 Length (cm) Volts (V) Amps (A) Resistance Average Resistance 1st          2nd           3rd 1st           2nd          3rd 1st           2nd          3rd 5 0.60        0.64        0.62 0.20         0.20       0.20 0.33         0.31       0.32 0.32 10 0.54        0.56        0.55 0.25         0.30       0.30 0.46         0.54       0.55 0.52 15 0.51        0.52        0.54 0.30         0.35       0.40 0.59         0.67       0.74 0.67 20 0.46        0.48        0.47 0.40         0.40       0.40 0.87         0.83       0.85 0.85 25 0.44        0.42        0.43 0.45         0.45       0.45 1.02         1.07       1.05 1.05 30 0.40        0.40        0.42 0.50         0.50       0.50 1.25         1.25       1.19 1.23 35 0.38        0.38        0.40 0.53         0.50       0.50 1.45         1.32       1.25 1.34 40 0.35        0.34        0.37 0.60         0.60       0.60 1.71         1.76       1.62 1.7 45 0.33        0.35        0.34 0.60         0.60       0.60 1.82         1.71       1.76 1.76

Conclusion

R = the overall resistance of nichrome wire, the crocodile clips, and the connecting wires.

C = the overall resistance of crocodile clips and connecting leads.

Overall, I believe that the data provides sufficient evidence to support my theory and conclusions.

I could have improved my investigation to support my analysis by doing other experiments such as the following – I have also added a prediction for each factor from my own scientific knowledge:

The diameter (cross-sectional area) of the wire:

I believe that as the diameter of the wire increased, the resistance would decrease. This is because there are more space for the electrons to travel through, therefore less collisions.

The temperature of the wire:

I think that if the wire is heated up, the atoms in the wire will start to vibrate faster because of their increase in energy. This will cause greater collisions between the electrons and the atoms. So, there would be higher resistance.

The material of the wire:

I think that the type of material of the wire would affect the amount of free electrons. This is because the number of electrons depends on the amount of electrons in the outer shell of the atoms. If the material has a high number of atoms there will be high numbers of electrons causing a lower resistance because of the increase in the number of electrons. Also if the atoms in the material are closely packed then the electrons will have more recurrent collisions and the resistance will increase.

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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