To calculate resistance, which is measured in Ohms ( ), you would have to connect all the series components first and lastly add a voltmeter parallel to the resistor.
As the sliding contact moves, it varies the length of wire in the circuit.
‘Moving through a resistor, electrons keep bumping into atoms. This makes the resistor hotter’
The number component also changes the resistance in the circuit. As the components increase, the resistance increases as well. As the resistance increases, the current decreases.
Prediction: After looking and researching about how resistance is affected by the thickness of the wire, I predict the thinner the wire the greater the resistance. This is because fewer electrons are able to pass through the thin wire; therefore the wire is resisting the flow of electrons. The thin wire has less space for the electrons tot ravel, therefore the resistance tends to be high.
Apparatus: Power pack, Nichrome 36 SWG, Connecting wires, Crocodile clips, Ammeter, Voltmeter, Ruler, Wire cutter and Bulb.
Method: Firstly I will set up the circuit as shown. I will then be starting with the thinnest piece of Nichrome of 36 SWG and measuring the volts and amps at four different positions on the rheostat.
I will then replace the piece by doubling the wire. The similar recordings and readings will be carried out for the wire piece being doubled up to 5 layers.
Diagram:
Fair test:
To make this experiment a fair test the power pack will be kept at the same voltage (6V), the length of the connecting wires will be kept the same and the ammeter and voltmeter will be kept in the same place. The positions of the reading on the rheostat will be kept the same (5cm apart) this is because the readings would be more accurate.
Accuracy: I will be repeating the whole experiment twice and will record the results in a results table. To get the readings accurate, I found out the averages between the 4 different rheostat positions for each layer. I then repeated the experiment, found out the averages of the positions again, and them found the final averages between the averages of the two experiments.
Safety: I will be careful and insuring that no water will be in contact with the apparatus (circuit) and that the wires that are fully insulated. I will avoid touching the nichrome wire that is being tested, as it will be hot and may cause the skin to burn
Results
2nd Experiment
Conclusion:
After looking at my results, I have come to the conclusion that, the thinner the wire the greater the resistance. In this case as the layers of nichrome increase the amount of resistance decreases, as the piece of nichrome is getting thicker. So therefore the electrons have additional paths to travel through, as the cross- sectional area is increased. So the layers that are added are making the resistance weaker, and so this is why the resistance decreases.
My results show that at 1 layer of nichrome, which is 36 swg, average resistance caused is 7.29 in comparison to 5 layers the resistance is lower, as it is 1.36.
My graph does show that as the thickness increases the resistance decreases. I noticed that there is a sharp decrease at first, but the line starts to level off. This maybe because
Therefore my results and graph do support my original prediction, which was that as the thickness increases the resistance would decrease. My results also match the known scientific theory of how thickness of wires affects resistance, which is stated in the PFY book as “As the cross-sectional area increase the resistance decreases.”
From working out the gradients or the tangent of the line, I can see that as the layers of the wire increase the steepness of the line decreases, showing that the thicker the wire the less resistance there is. Even though I can conclude that the resistance decreases as the layers increase, I can see from the tangents I cannot give a firm law that there is a solid relationship between the two factors in the sense that my results does not show that as the wire doubles the resistance drops twice as much. I think that for me to obtain this result I would have to explore the investigation in more depth. By this I mean that I should test more layers and then analyse my results to see that whether or not they show that as the layer doubles the resistance drops twice as much.
Evaluation:
During the course of this investigation, there were difficulties, as well as easy straightforward parts to carry out. I found that getting the length of the wire the same when doubling the wire was incredibly hard at first and it needed me to be patient, in order for me to carry out the procedure accurately. Changing the positions on Rheostat was a bit difficult, as it was very firm, but after practising it did become slightly easier.
If I were to extend this experiment, I would take readings of more layers, by this I mean, instead of readings up to 5 layers, I would extend to 10 layers. This is because I would get more results to analyse, and to see any trends within the layers. I would also change the voltage of the power pack, which was initially 6V, which I would increase to 8V. This is because I would like to see what effect the initial voltage would have on the readings. I may also decrease or increase the length of nichrome wire used through out the whole experiment. By this I mean that instead of using 15cm for every layer, I may increase the length or decrease to 10cm. However I could also change the original thickness of the nichrome wire used in the experiment, by this I mean instead of 36 swg, I could replace it by 32, or 30 swg, and see the effect it would make on the resistance, and how I matches the theory of resistance and cross-sectional area.
Even though my results and graph support my prediction, I discovered that there are two anomalies, when I drew line of best fit, because in this case the line can also be a curve.
I think that the anomalies also known as freak results for layers 1 and 3 have occurred, because there may have been a mistake when the readings were taken of the ammeter or the voltmeter before the averages were calculated. They may also have occurred due to the fact that the positioning of the rheostat might have been slight out of place, for the readings, as it would then affect the final average. The result for layer three is not so much of a anomaly, it’s quite close to the norm.
To improve the quality of my results and to avoid obtaining anomalies, I would try being more accurate when reading the results of Amps or Volts from the meters and I would consider repeating the whole experiment three times instead of twice. This is because it would help make my final averages more accurate.
Investigations that I may carry out related to resistance, are the other factors, which effect resistance.
I would carry out an investigation of how the length of nichrome wire would affect resistance. I would do this by placing different sized nichrome wire into a similar circuit to this investigation and would record and analyse the results, and to see if there are any other patterns or trends that I could identify. I would also like to see whether or not the results of my experiment would obey the scientific theory of the effect of the size and resistance. The science theory of effect of size on resistance is “As the length of the wire increases, the resistance increases.” (PFY)
By Kajal Patel 10mh
Preliminary experiment.
Aim: To find out a material to use for the resistance investigation
Prediction: I think that the nichrome wire will be the best material to use for the investigation.
Apparatus: Power pack, ammeter, connecting wires, nichrome and copper wire.
Method: We connected the circuit with an ammeter. We replaced a gap with different types of wire, of the same length, and two thicknesses. We then read the readings of amps on the ammeter, and recoreded them in a table.
Diagram:
Results:
Conclusion:
From my results, I conclude that nichrome is a better resistor than copper, and therefore it would be ideal for me to use nichrome in the investigation. Copper allowed more current to pass through, and so was less resistant than the nichrome, as it resisted the flow of electrons.