Physics Quality of Measurement Coursework

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Quality of measurement Write Up


This diagram shows how we carried out our experiment, by connecting 2 wires to the ohmmeter and attached the wires to the samples we used in our experiment.

Preliminary Experiment

At first in our preliminary experiment my group and me decided to use an ohmmeter instead of a multimeter. We did this as we thought it would make it easier for us to record our results. These are the results we got from our preliminary experiment:

Length (mm) +/- 1mm| Diameter (µm) +/- 1 µm| Resistance (Ω) +/- 0.1 Ω| 200| 30| 1.2|
200| 45| 0.8|

There were uncertainties in our experiment.

Diameter = 3.3% for 30 µm2.2% for 45 µm
Length = 0.5%
Resistance = 8.3% for 1.2 Ω12.5% for 0.8 Ω

Evaluation of our Preliminary Experiment

The whole point of our preliminary experiment was to see after doing it, what improvements could be made for the main experiment. The results we gathered show that there must have been some sort of error as there was a different resistance for the same material. From our preliminary experiment, it was clear that there were improvements to be made for our main experiment.


One of the main things that we could improve was getting an average of our results. As we only got one set of results this meant that our results were not very reliable, as we had not repeated the experiment. In our main experiment we had to make sure that we repeated our experiment at least 3 times so that we could calculate the average for the results.

Another way that we could improve is that we could have used measuring apparatus with a more precise scale , resulting in not only increasing the quality of our measurements but also the precision.

One more way in which we could have improved was that, we could check whether the electronic equipment we were using were not faulty and fully functioning, we could do this by doing the experiment using different equipment and see what results come from it.

Errors in our investigation

One of the main sources of error was due to our ohmmeter not being able to give more precise results, these more precise results being to more decimal places. If our ohmmeter was able to give the reading to more decimal places it would have made our results much more precise.

Another error was that the wires was not fully stretched out when we were measuring their lengths, meaning the uncertainties could be even higher than what they are.

The smaller the scale that was used, the closer our result would be to the true value.

Main Experiment

Diagram of circuit used in our main experiment:

What was used in our experiment:

* Ohmmeter – So that we could measure the resistivity of the wire, as this was the whole point of our experiment. Had an uncertainty of +/- 0.1 Ω.

* Micrometer – We used the micrometer to measure the diameter of the wires. Had an uncertainty of +/- 1 µm

* Copper wire with a diameter of 29 +/- 1 µm (worked out using micrometer)

* Copper wire with a diameter of 43 +/- 1 µm (worked out using micrometre)

* Ruler – This was used to measure the length of the wires. Had an uncertainty of +/- 1 cm

Step by step instructions:

* First of all, gather up all the equipment listed above, and connect them how it is in the diagram below.

* Measure the Diameter of the wires using a micrometer

* Measure the resistance of each wire.

* By using the wires length, cross sectional area, and now also the resistance, the resistivity of the wire was measured.

Results For the Main experiment conducted

Wire with Diameter 29 µm (+/- µm)
Length (mm) +/- 1mm| Resistance (Ω) +/- 0.1Ω|
280| 2.2|
280| 1.1|
280| 1.1|
Average Resistance of Wire with Diameter 29 µm (+/- µm) = 2.1 Ω ±0.1Ω

Wire with Diameter 43 µm (+/- µm)

Length (mm) ±1mm|...
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