Data Analysis of the Resistance of a Piece of Wire

Data Analysis
The investigation I did was to find the resistance of a piece if wire. The piece of wire is my dependent variable throughout the investigation. I changed the length of the wire in order to measure the resistance of each length.
Plan
In this investigation, a simple circuit will be set up to read the voltage and current when the length of the wire changes. The length will range from 10cm-80cm with intervals of 10cm. The length of the wire will be changed by moving the crocodile clip across the wire and checking the measurements with a ruler.
The circuit should be set up as in the circuit diagram (as attached). The voltmeter should be set up parallel to the ammeter. The readings from the ammeter and voltmeter will be used to work out the resistance. This can be done using the formula: R = V/I (V is the potential difference in volts, I is the current in amperes (amps), R is the resistance in ohms, Ω)
Safety
In order to perform a safe experiment, a low voltage of 4v was chosen so that it won’t over heat and to avoid electrocution. The power pack must be turn off between readings/ when moving the wire. If the wire gets hot or if there’s a smell, the plug should be turned off immediately.
Fair test To ensure that the investigation is carried out in fair way, the wire must be measured as accurately as possible and the same circuit and power supply must be used throughout as different power supplies may have different voltages. The experiment will be repeated three times for each length of wire, with low, medium and high resistor. Also, an average should be taken to enable that the test results are reliable.
Apparatus used * 2 crocodile clips * Power pack * Voltmeter * 6 wire * A meter ruler with attached wire * A variable resistor * A calculator

Method
1. We set up the circuit as drawn on the circuit diagram.
2. Then starting with 10cm, we measured the wire with the metre stick and place the crocodile clips at the appropriate places on the wire and connect the resistance wire into the circuit.
3. When done setting up the circuit, we switched the power supply on, made sure the resistor is at low and recorded the ammeter reading and the voltmeter reading in a table (as shown below).
4. After that we changed the resistor to medium to get a second reading, and changed it again to high to get the third and recorded the readings on the ammeter and voltmeter in a table.
5. Then we did the same to different lengths of wire. E.g. 20cm, 30cm...etc
6. When we’ve finished recording up to 80cm, we used the formula R=V/I to get the resistance of the results. When all three results have been calculated, we got the mean resistant and recorded this data in a table. Results Length | Voltage (V) | Current (A) | Resistance (ohm) | Mean resistance (ohm) | 10cm | 20.20.1 | 2.430.260.13 | 0.820.770.77 | 0.79 | 20cm | 2.350.370.2 | 1.50.240.13 | 1.571.541.54 | 1.55 | 30cm | 2.470.50.24 | 1.10.230.12 | 2.252.172 | 2.14 | 40cm | 2.570.630.36 | 0.860.220.12 | 2.992.863 | 2.95 | 50cm | 2.630.760.44 | 0.70.20.12 | 3.763.83.67 | 3.74 | 60cm | 2.690.840.51 | 0.60.190.11 | 4.484.424.64 | 4.51 | 70cm | 2.710.950.65 | 0.50.180.11 | 5.425.285.9 | 5.54 | 80cm | 2.751.040.65 | 0.450.170.11 | 6.136.126 | 6.08 |
-Please turn to the last page for my graph-

INTERPRETING DATA
Evaluating data
My results are reliable because the repeats are very close to each other. The trend is accurate with the exception of the one mistake at 40cm on the third reading. Also, the sizes of the bars are small and there are no over laps. However, there are two results on the graph at 30cm and 70cm are outliers, which brings down the accuracy of the test.
Conclusion
Resistance is measured in ohms. It can be calculated from the potential difference across a component and the current flowing through it. The total resistance of a series circuit is the sum of the resistances of the components in the circuit. I predicted that the longer the piece of wire, the greater the resistance will be. This is due to the idea of the free moving electrons being resisted by the atoms in the wire. So the longer the wire, the more collisions there will be and this loses more energy, which gives a greater resistance.
The result from the graph gives a clear indication of how the resistance compares to the wire length. When there is no wire, there is no resistance so the line of best fit passes through the origin. Also, there is a positive correlation. The line of best fit shows that the change in length of wire is nearly proportional to the resistance which means that as the length increases so does the resistance. When the length of the wire doubles, so does the resistance. For example, the resistance at 20cm is 1.55 and at 40cm is 2.95 which is just over double. Furthermore, if we double 40cm, we get 80cm and at 80cm the resistance is 6.08 which is just over double of the resistance at 40cm. This is due to the number of atoms in the wire being proportional to the length.
The error bars are 80% reliable because of the two outliers. I think this might be a human mistake because we gave the voltmeter reading as it was still going up and down and didn’t get the result if it has stopped.
Problems and Improvements
There were quite a lot of problems collecting the data because,
-The voltmeter changes all the time so it was hard to know what the result was
-The wire wasn’t so straight; it was a bit wiggly which might affect the actual length.
Apart from that, I think the rest of the apparatus was very reliable.

To improve, we could:
-Do the experiment again to make sure the results were reliable.
-Use a very straight wire

Reliability of conclusion
In my prediction I said “If the length increases then the resistance will also increase in proportion to the length”. From my graph I have shown that my prediction was correct as the line of best fit is a straight line proving that the resistance of the wire is proportional to the length of the wire. I think my conclusion is reliable because the technique we used is accurate and the data is accurate and reliable. However further data would make it more secure such as increasing length of wire to 100cm instead of 80cm. Or decrease the length of wire when increasing such as measuring 5cm each time instead of 10cm to get a more accurate result.