Diagram
Equipment
I will need the following equipment:
- A battery pack
- Copper wire
- 110cm of constantan wire
- Some crocodile clips
- Volt meter
- Amp Meter
- One small variable resistor
Key Points
I could change one or two thing during this experiment. A few examples of these could be the thickness of the wire, the type of wire for example copper and gold and also how hot the wire gets. I am changing the length of the constantan wire. The variable will be the voltage, and then I will calculate the resistance, also as I have said I will keep the amperage the same.
Hypothesis
I predict that the longer the wire the greater the resistance will be.
Justification
As the length of the wire increases, so do the chances for the electrons to collide with a positive ion. The chances increase because there is a bigger distance for the electrons to travel. A rule is that energy is always given out from a collision in the form of heat.
Results
I have used ‘Ohm’s law’ which is a formula, to get a resistance for my results. R= V/I
The anomalies are in red.
Accuracy of my results
I did the experiment five times to make sure the results are accurate and I had enough results. I was only given a certain amount of time to do the experiment in so I couldn’t do the experiment more than 5 times. Because I have used an average result it makes them more reliable.
Analysis
These results support the prediction I have made before hand. My prediction “I predict that the longer the wire the greater the resistance will be”. My results support my prediction that as the wire gets longer; the resistance also gets larger.
My line graphs show that the resistance readings are more or less the same, in relation to the length of the constantan wire, and the current was keep at a constant level. This proves that the voltage is a dependent variable and that the current running through the wire causes the resistance. My graph also tells us that the length of wire does affect the resistance. This is because, as the length of constantan wire increases, so does the average reading for each of the five resistance readings. The length of the wire is directly proportional to the resistance. This means that as the length of wire triples, the resistance also triples. This is because in 3x the amount of wire, electrons are 3x as likely to collide with positive ions. They will be slowed down by these collisions and lose some of their heat energy.
The Evaluation
The accuracy that I achieved was very high even though I had very little time. Also I got lots of results to make a good analysis. The level of accuracy in this investigation was as high as I could get.
Any Anomalies?
The time I had been allocated made it very difficult to achieve 100% accuracy for my experiments, as I said above. This meant that there was an unavoidably that there is always going to be some anomalies. Ideally, we would want all of the resistance’s for each length of wire to be the same but that is nearly impossible. Because of factors such faulty equipment, like amp meters that half work and only measure through sight, rather than computer measuring tools. Anomalies can been seen easily because they are too close to the one in front or the behind it. From the graphs, the readings taken at 30, 50 and 70cm all contain anomalies. If we look at the charts we can see that all of these anomalies were in the fifth experiment. This could be because of a change in the wire length or type of wire.
Improvements
If I were to do the experiment again, I could make some improvements to make the level of accuracy better. For example, I could make sure that the joints/connections were jointed properly and would have to make sure I use the same equipment every time. I could also get a machine to measure the length of the constantan wire and do it in a larger team. I could also try to do the experiment several more times. This would improve my accuracy greatly; also I would check the wire and make sure it is perfect because this would affect amount of collisions.
Further work
If I was to do this experiment a different way I would simply change on of the key points I have listed above.
