NB. When each wire was added, the power was turned off to prevent overheating.
Preliminary Experiment
A week before I did the experiment, I did a preliminary experiment in which I could investigate the conditions I could introduce to my experiment and decide upon the variables and things that should remain consistent and how I could make it a fairer test. In this experiment, I identified: the voltage, the wire type, the wire length and revised the best way to set up my experiment. I discovered that anything above 7V was very hot and caused the wire to heat up which would affect the resistance, I decided the resistance should be 5V and the time the power was on should be minimal to prevent the wire heating up and affecting the results. The wire type was chosen at random, although I was aware that different wire types would give different results, I just chose one at random - Nickel Chrome, which I measured at for the cross section. The wire length mattered as the only variable I wanted was the wire thickness and wire length might affect the resistance, I decided to use wire of length 30cm. This was small enough to not get wound up and keep straight but long enough to prevent over heating and affecting the resistance. I had no problems with setting up the experiment, but it helped having set it up before and putting the voltmeter into parallel with the wires and the ammeter in series. I took a few practice results to aid predicting the outcome, which helped with hypothesizing.
Circuit Diagram
Measures to ensure a fair test
Certain measures were taken to ensure that the results were as accurate as possible. Therefore, the wire was kept consistent, it was always Nickel Chrome which had the presumably had the same cross section width and was cut into the same length to prevent the length affecting resistance. The same equipment was used and the same voltage (5 volts) was used for each. Therefore the only variables were the number of wires and the position on the variable resistor. The crocodile clips have to keep the wire at the same length and hold all the wire at the same point to make it a fair test.
Hypothesis
The resistance will be lower the thicker the wire (more wires) because resistance is lower with a cross sectional surface area.
This is as, as the wire gets thicker the electrons in the wire have more room to flow, resistance will become lower and current will flow more easily. If the wire is a good conductor the resistance will be lower. The higher the resistance, the lower the current. I already know that the when the cross sectional area of the wire is increased, the resistance decreases as in a previous experiment involving a bulb, the bulb brightened when I doubled over the wire (increased the cross sectional area). I know that altering the variable resistor would vary the current and voltage. Resistance will be greater the greater the current.
ANALYZING
As predicted, the resistance decreases the thicker the wire (the larger the cross - sectional area). This is because as the wire gets thicker the electrons in the wire have more room to flow, resistance will become lower and current will flow more easily.
There appears to be an almost directly proportional link between 1/cross sectional area and resistance as the line of best fit goes through the origin.
EVALUATING
Though these results show a definite link that the resistance decreases the thicker the wire, it is possible that they could be more accurate in that a few factors may have been overlooked. For example the distances along the variable resistor were not definite and the position in the middle was not definite and quite rough so if I repeated this experiment I would probably mark the point for the middle of the variable resistor so it could be consistent.
The second point was that the wires might not have been completely accurate in that the length or position of the crocodile clips may have been slightly off each time. The wires may also have got warmer due to the power or even room temperature, which may alter the results. They may have got twisted and would have been curly anyway due to the fact that they had been coiled around the wire reel. The wire’s cross-section was only measured once and that may have been wrong because the wire thickness could have changed over the wire. If I was to repeat this experiment, I would measure it several times and work out an average for the wire instead of assuming the wire would keep a consistent thickness throughout.
The experiment works in that it identifies any basic link between the thickness of wire and resistance. To receive more detailed results, an ammeter or voltmeter with more digits or in analog form would help.
The voltage, though it stayed consistent could have been higher to create a wider range of results, less intricate and to less decimal places. When practiced, a number of voltages were tried and five was decided as being powerful enough, however it was overlooked that a higher voltage may have been needed to ensure larger results. If I was to repeat this experiment, I would use a voltage of 7 or 6 volts, this would not be too much to heat the wire dramatically but may give larger results.
The evidence, though it gives the basic link between the thickness of wire and resistance, it is not always reliable as certain elements cannot be controlled such as room temperature which may not remain constant during the experiment (especially if, as I did the results were gathered on different days and at different times on those days) and overlooking things which may in some way alter the results. For example, the cross sectional area of the wire was just measured once and is quite likely to be inconsistent along the wire. The conclusion is likely to be correct though could be more detailed if the investigation was taken further.
There are roughly no anomalies and I have received incredibly accurate results, allowing me to form an excellent line of best fit..
To further the investigation
To further the investigation, these results could just be seen as a starting point and other variables could be changed to investigate the effects of different conditions on the resistance. Temperature (of room), length of wire, types of wire (instead of using just nickel chrome, the experiment could be repeated each time but with different wires and investigate their resistance in relation to mass or thickness), voltage etc. could all be changed to investigate the effects and they could all be recorded as the effects on resistance.