R is resistance measured in ohms
Hypothesis
It is believed that ‘the longer a wire, the more resistance it will produce’. A portion of this has been explained above, but for further ideas I shall see why it is so. If we had two wires of the same kind and were investigating upon the length; and one of the wires being long as for the other being short, which wire will produce more resistance?
The long wire of course. But how?
If you were to imagine two drinking straw, both of which having same diameter but different lengths. As one being a longer straw than the other. Which straw will be able to suck up the drink faster? The longer straw or the shorter straw?
Logically, the short straw as there being shorter distance from the drink to the mouth. Likewise, the straw can be thought of as the wire and the drink can be thought of as the current.
Apparatus
- Power Supply
- Electronic ammeter
- Electronic voltmeter
- Nichrome wire
- A meter ruler
- Wire with crocodile clips at both ends
Preliminary Diagram
N.B (ref. Preliminary Diagram)
The wire will be placed on the Nichrome wire, including one of the wires of the voltmeter. i.e: if 10cm of Nichrome wire is measured, then one of the wire of the voltmeter as well as the wire which links to the power supply will be placed at 10cm, like this the rest of the range will (from 10-80cn) will be measured.
Method
- The circuit will be set up as shown above preliminary diagram.
- Power supply will be switched on, after adjusting it to exert 6 volts and to adjust it to D.C.
- The wires of the voltmeter and power supply will be placed on 10cm of the Nichrome wire
- Readings will be taken, immediately as shown on the ammeter and voltmeter
- Likewise the method 1-4 will be repeated for 20cm, 30cm, 40cm, 50cm, 60cm, 70cm and 80cm.
- To ensure precise readings, method 5 will be repeated twice more (including 10cm)
Safety
As the mains electricity will be a source for powering our power supply, I must ensure that the socket is kept away from the dangers of water spillage. My hands and the work place must be kept dry whilst using the electrical apparatus. This would ensure that there is no chance of being electrocuted. However, for more assurance, I will consult our teacher to make certain if it is safe and then the investigation can continue.
Variables / Constants
I will keep the following thing as a variable:
The following are a list of what will be kept as constant:
- The thickness/diameter and the material of the wire will remain constant as we will use the same Nichrome wire
- Temperature will be kept at an average room temperature
- The same amount of voltage will be used throughout the experiment
I have to keep one factor variable; in this case it is the length and I shall keep the rest as a constant. This is because; we will be seeing the affect of only length on a Nichrome wire.
In order to ensure that we collect fair results, I shall try as much as possible in not heating the wire as this can cause a tremendous effect on the resistance. This can be overcome by gently tapping the wires on and off the Nichrome wire. The thickness/diameter and the amount of voltage used for the investigation will not be given much care as these are definitely less likely to change during the investigation.
Range
I will be measuring from 10cm-80cm at every 10cm intervals. I believe this will be more than enough for the investigation to be dependable. This investigation will be done three times so that further analysis can be made i.e.: finding the average
OBSERVATION
As mentioned earlier, I will try and obtain as accurate readings as possible. Since electronic ammeter and voltmeter is being used, it should read 0 before any investigation could commence.
The following is what I have collected.
1st Reading:
2nd Reading:
3rd Reading:
ANALYSIS
More or less, the results seem to be quite similar to one another. As I am investigating resistance of a wire, sufficient data has been gathered to find the resistance. As noted earlier that I will be using the formula ‘V=I x R’ (voltage = current x resistance).
Using my mathematical knowledge, I will rearrange the above formula and make resistance the subject. ‘R=V/I’ (resistance = voltage / current).
Now I shall work out the resistance of all three readings.
Resistance of 1st reading:
Resistance of 2nd reading:
Resistance of 3rd reading:
By combining the above three results, I can now work out the average. Using the average, further analysis will be made.
Now that I have found the average resistance of Nichrome wire from 10-80cm, I can present it in a better way; in a scatter graph. By this way, I can draw up a line of best fit to see if any similarities or differences can be observed.
From the above graph, it can be seen clearly that as the length of the wire increases the resistance increases also. Since longer wire means longer distance for the electrons to travel, it can mean that increasing wire increases resistance.
As you can see, I have made a right-angle triangle on the line of best fit.
The value of Y is 0.08 ohms and the value of X is 40cm. Now, in order to find the gradient, I must use the formula Y/X, so in this case it is 0.08ohms/40cm. This equals to 0.002ohms/cm.
I can know easily work out the resistance, if any length (cm) was given to me. For example, if I wanted to find out the resistance of a 1000cm wire, I would multiply it by 0.002ohms, which will give 2ohms. This is more time-efficient, instead of actually investigating the resistance of 1000cm Nichrome wire.
EVALUATION
I think my investigation went correctly, achieving fine results. I say fine with little uncertainty, due to believing that my results were not 100% accurate. It can be seen on the above graph that the points do no lie exact on the ‘line of best fit’.
Throughout my investigation, I didn’t have any anomalous result. The graph above shows the points on the graph are very much close to the ‘line of best fit’, implying that there were no anomalies in my results.
If I was to do this investigation again, I would have improved and attain better results if I had used 4 decimal point, electronic ammeter and voltmeter. This would ensure that I get precise readings and probably increase the chance for my readings to lie exact on the ‘line of best fit’. If I had compared my results with a colleague of mine or repeated the investigation more, it would have proved to be more reliable.
Overall, my results were as reliable as possible and I came to the conclusion that ‘as the length of the wire increases, the resistance also increases’.