In the long wire, if there is high resistance then you need more potential difference (volts) to push the current through the wire so electrons can pass through.
The resistance is calculated by using a formula,
Resistance= Potential Difference (v)
Current in wire (I)
The formula comes from ohms law when the current flowing through a metal wire is proportional to the potential difference across it, providing that the temperature is constant.
DIAGRAM:
APPARATUS:
- Crocodile clips
- Connecting wires
- Selotape
- Wire
- Power terminal
- Voltmeter
- Ammeter
METHOD:
1. First I set up all my equipment and attached all my components together. I built my circuit with all the apparatus above and started the experiment.
2. I then wrote down the readings off the voltmeter and ammeter so I could calculate the resistance using the formula RESISTANCE= Potential Difference
Current
3. Then I changed the size of the wire from 100cm to 80cm and did the whole experiment again and calculated the resistance again for this length of wire and then started onto another length of wire like 60cm, 40cm, and 20cm.
4. Once I calculated and recorded my five lengths of wire and its resistance, I did the whole experiment again using and 100cm wire and this time I stuck the two ends down with selotape making sure the crocodile clip was still attached, to see whether there was more resistance in a straighter wire or non-straight wire.
RESULTS:
CONCLUSION: By looking at my graph and my results table I can see that as I increased the voltage, the resistance increased too. My prediction was that the longer the wire will be, the greater the resistance will occur. My prediction was correct because as I decreased the length of the wire the resistance and the voltage decreased too. This shows there was high resistance and the particles and the atoms inside the wire were colliding and caused higher pressure that the smaller lengths of wire.
If you look at my graph, you can see that for the wire that was held down with selotape had three anomalous points for each type of voltage supplied by the power terminal. The graph clearly shows three different voltage supplies in a straight line that go up in the same direction and have one anomalous point each. The lines of best-fit show that there is a pattern being formed. The pattern is that as you increased the length of the wire, the resistance increased because there was not much current could pass through and the electrons were struggling to get into the wire. Once they got into the wire they started to collide with the atoms which then resistance occurred and high pressure within the wire occurred too.
But if you look at my graph without selotape holding the wire down, it shows there are many anomalous points. This could be because of various reasons to do with the way the wire was and because the wire would loose energy from electrons traveling and moving round the wire and vibrating with the atoms and heating up the wire and making it hot to use burn the wire. This doesn’t mean that there was not much resistance. There was resistance as the length of wire increased but there was more resistance in my second graph where there was only one anomalous point for each type of voltage supplied by power terminal.
Overall I can say that the length of the wire is affected to the resistance of a wire because if you change the length of the wire then you would be changing the resistance, to either increasing it(if you increase length of wire) or decreasing it(if the wire is shorter).
EVALUATION: If you look at my graphs you can see that all my points are on a line of best fit. They show the pattern, as you increase the length of wire you are increasing the resistance.
On the graphs you can see many anomalous points in graph one. These could have occurred because the wire was not straight and nothing held it down so when I was recording the results on a table I realized that some of my results for the volts section became increased at one point and then in the next section after the voltage had decreased and then increased again. Significantly this shows me if I were to do this experiment again I would have to get a straighter wire that does not curl up into knots so it makes my experiment more efficient. This shows that this experiment I did for this graph was not reliable because the readings off the voltmeter and ammeter were changing constantly and no pattern was really shown.
I think these anomalous points occurred for graph one because the wire was not straight, the voltmeter and ammeter readings were not in a pattern and constantly changing, and finally, because I might have not cut the wire to a correct length and could of put down the wrong results by mistake.
Whereas in graph two I can say the results were more accurate but you can still see anomalous points but less of them unlike graph one. These anomalous points show me that somewhere in the experiment I might have gone wrong, but because I used selotape to stick down the wire as straight as possible I had an advantage to keep this experiment more accurate.
These anomalous points could have occurred because I might have not stuck down the selotape properly and this might of allowed the wire to move about and not stay straight. Also these anomalous points could of occurred because I might have not calculated the resistance properly and may have forgotten to put down the wrong answer.
If I could do this experiment again I would make it a fair test by doing each experiment three times so its more accurate and I will make sure I cut the wire at the appropriate length. I will also use a reliable voltmeter and ammeter so I can read the readings off the meters and calculate the resistance more accurately. Finally, next time I do the experiment again, I will use maybe an even thicker wire to see whether there was a difference between the amounts of resistances in the wire and also increase the length even more to see if the results differ in any way.
Significantly, I could also change the components used. For instance instead of using a long wire I could have used a variable resistor because it does the same job as the wire. For example, when I decrease the length size of the wire I could be doing the same thing easily and more accurately on a variable resistor, because when you turn move the connector at the top of the variable resistor it changes the resistance to either high or low resistance. This prevents heat loss from the normal wire when the wire reached up to high resistance, and also prevents the wire getting knotted together because the variable resistor has a coil of wire, which is already attached to the resistor.
As you can see, from my graphs, that I got a number of anomalous points. This can be avoided if I had a specific time difference between each time I recorded the resistance of the wire for each length of wire. This is because when I did my experiment I recorded all the resistances one after the other, and the wire got quite hot because there was high resistance flowing across it. If I waited for about 5 minutes between each recording of resistances, I could see a difference between the temperatures of the wire and how high or low the resistance would be. This is because as you increase the temperature you get high resistance and if you don’t leave a time gap in between the next recording you do of the resistance, the wire would still be hot and this would effect on how high the resistance would be and it would not show you a variety of results because they would all be similar to one another, because the wire would be hot and would still have its previous resistance adding to the new resistance of the wire. As for low temperature, it would result to low resistance and this would be more efficient because it gives a more clear picture of the way resistance increases and decreases, but also reduces the amount of anomalous points.
