Method:
- Collect equipment
- Measure out 50cm of each wire
- Attach the circuit together as it is showing the diagram above
- Attach the wire to the circuit
- Measure the voltage and amps that are present when using different wires
- Repeat experiment at different voltages and using the different wires.
Results for pre-test:
Conclusion for pre-test
From our results we can see that the Constantine is the best wire that we tested as it gave us a slightly smaller range of results, which can be improved by simply changing the voltage in the main test, to get a shorter range. Also Constantine will not overheat, like copper would. If it did over heat this could possibly affect the resistance in our results, making them unfair. After looking at our graph we can confirm this by looking at the steady increase of amps in Constantine unlike the rapid increase when using copper and then it overheated tripping out. This tells us that the results from the Constantine are easier to use as we can test it with higher amps with it not tripping out or overheating. Constantine is the best wire for this as it is the best Conductor of electricity for the test that we need.
Main test
Equipment
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Battery pack-This will be used to supply power to the circuit
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Leads-These connect up components in the circuit
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Constantan wire-This is our test wire and is our independent variable with different lengths
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Volt meter-This measures the volts in the circuit
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Ammeter-This measures the amps in the circuit
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Meter ruler-Used to measure length of wire used
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Invariable resister-used to allow our charge to be the same in each experiment
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Crocodile clips-to attach the independent variable to the circuit
Method
- Collect equipment
- Attach Constantan wire to a meter ruler
- Set circuit up as shown above
- Turn battery pack on
- Adjust the rheostat to give a current of 0.28amps
- Attach crocodile clips to where you want to the measure
- Measure the voltage for each different length in 10’s
- Repeat for all measurements up until 100cm three times
Scientific explanation for main test
Resistance of a wire depends on several factors:
- Material,
- Length,
- Thickness,
- Temperature.
Resistance=voltage/current
Controlled factors
There are some factors that may have affected our experiment. We controlled these by trying to keep them the same for each different test that we completed. We tried to keep the diameter of the wire and faeces the current passing through the wire the same. If we were to change the diameter of the wire then the resistance would differ to the true readings, this may have affected our results in a negative way. This is why we controlled this factor.
Results for main test, current is 0.28=amps
Conclusion for main test
From our results we can see that as the length of the wire increases, the resistance increases. This is because, as you increase the length of the wire you increase the amount of electrons in which the current has to pass through. This increases the resistance through the wire. We can see this by looking at our table of results; at a length of 30cm the voltage is 0.93v and the resistance is an average of 3.64 Ώ, when you compare this to a higher.
From our results we can see that when you change the length of a wire within an experiment, the resistance increases as the length of the wire increases. We can explain this with ohms law, which tells us that, the more particles that the current must pass; the quicker the current takes to occur as there are fewer collisions within the wire.
We can tells this by looking a t our results table; When the wire was at its shortest (10%) it only took an average of 1.36 Ώ resistance, this has a low voltage of 0.38, whereas looking at the longest length of Constantine wire (100%) it took, on average, 11.21Ώ resistance for a current to go through a circuit, which has a larger resistance than the length of wire at its shortest.
Evaluation:
From our experiment we now know that the length of the wire does affect the resistance of a circuit. Although some of the parts In our experiment may have not been entirely correct we do know that our results are relatively accurate and reliable; we know this by looking at the size of our error bars in our graph, we notice here that every error bar is small with all three tests concluding in a similar result for each different length of wire. This meant that our averages in our results table should be very close to each different test that we completed, which they are. We notice also in our error bars that none of our results on our graph overlap, this increases our experiments reliability. From this we can say that we completed our experiment to a high standard of accuracy. This is confirmed through our line of best fit which runs in a perfect line directly in the centre of the error bars on our graph. In our experiment we didn’t have any outliers; we know this by again looking at our graph. We notice have no results which look out of the ordinary or different to the general pattern of results. We have no result which is either too high or too low compared to the average of each set of results; this tells us that our experiment was effective, reliable and accurate.
If we were to do the experiment again however, we would change some things to improve our experiment to ensure that our results were in fact “perfect”. Firstly we would test all of the components in our circuit to make sure that all of them were working noting the efficiency of each component making sure that they were of the correct power and resistance. We would do this to restrict the amount of ways in which our experiment could go wrong making our results more reliable. We would also measure out our length of wire at full extension, as we did our experiments the wire was not fully straight and so there could have been millimetre variations in our results and lengths of wires were not measured to a high degree of accuracy. This would improve our accuracy of our experiment and our results would be much more accurate.
Within our experiment we made some mistakes, these may have affected the accuracy of our experiment and the reliability of our conclusion. These mistakes may have affected our results and thus our conclusion; we know that our experiment was reliable and fairly accurate by looking at our graph and error bars this shows that our conclusion must be reliable and account for our experiment with great accuracy.
So overall we know that our experiment and results were of high accuracy and reliability this is confirmed by looking at our graph and averages. This also tells us that our conclusion was reliable but we also do know that we did make some small mistakes and we could have completed the experiment better if we were to do it again.