Resistance of a Wire

Resistance of a Wire
Resistance of a Wire If the length of the wire is increased, then the resistance will
increase. This is due to the electrons having a longer distance to
travel and so more collisions will occur. Due to this, the length
increase should be directly proportional to the increase in
Material: The type of material will effect the number of free electrons, which are able to flow through the wire. The number of electrons depends on the amount of electrons in the outer shell of the atoms, so if there are more atoms then there are more electrons available. If the material has a high number of atoms, there will be a higher number of electrons. This will cause a lower resistance because of an increase in number of electrons Wire diameter: If the wires diameter is increased the resistance will decrease. This is due to the increase in space for the electrons to travel through. Because of this increased space between the atoms, there should be fewer collisions. If the cross-sectional area of the wire were greater, the resistance would be less because more current will be able to flow through the wire -Temperature ? If the wire is heated up, the atoms in the wire will start to vibrate more rapidly. This will cause more collisions between the electrons and the atoms, due to atoms moving into the path of the flowing electrons. This increase in collisions means that there will be an increase in resistance -Wire density ? If the wire has a higher density, the resistance will be higher. This is due to the wire having more atoms in a smaller space, creating smaller and less gaps for the electrons to flow through. Because of the increased lack of space there should be more collisions. help me choose which factor I shall investigate, I am going to consider how I will measure each factor and which factor would be the best to record. ? To measure the wire width, I would use a micrometer to measure the widths of the same length and material of wire e.g. Constantin 22, 23, 23 etc. I would use the same voltage and I would record the resistance for each width of wire. Although these results would be easy to obtain a record, the data graphs that would result from these would not be interesting. For temperature of the wire, I would not be able to conduct a fair test, as it is extremely difficult to control and produce the correct range of temperatures needed without the correct equipment If I chose to measure the difference in the resistance in different materials, I would choose a number of different materials, but using the same voltage. I would record each resistance given by the same length and width. However, this will also produce graphs that will not be interesting and will not produce a connection between the materials and resistance, because of the materials I could test with the equipment available. If I chose to investigate the effect of density on the resistance of wires, I would not be able to do this, as there is no way of measuring different densities of the wiresThe final factor left to consider is the effect of wire length on the resistance of wires. To measure and record these findings for this factor would be simple, and the results should show a connection between the length of wire and the resistance produced by the wire. This is why I am going to investigate this factor: the wire length. -I predict that if the length doubles, then the resistance will increase in direct proportion. I think this because the longer the wire the more atoms, and so there is a greater chance of the electrons colliding with the atoms. So if the length is doubled the resistance should also double. This is because if the length is doubled there are double the amount of atoms, which will result in double the collisions. This will slow down the electron flow and increasing the resistance. The diagrams below explain the prediction more clearly: ? This is a predicted graph. I think this will happen because the resistance should be directly proportional to its length, due to my predictionI have chosen to use Constantin 24, as it offers a high resistance, and any change in resistance will be noticeable, in my main experiment. -Apparatus 1x Power supply (2v) 1x Voltmeter 1x Ammeter 5x Wires (with crocodile clips) to complete the circuit Constantin 24 test wire -Controlled Variables Wire material Wire diameter Density of wire Room Temperature -Dependant variable ResistanceIndependent Variable Wire length -Circuit diagram -Method - First, set up the apparatus as above. To collect results for my graph, I will need at least 5 points. I have chosen a range of 5, so that I am able to plot an accurate graph. I have also chosen to do 3 repeats at each length, and then I will take an average result. This is so I do not get any anomalous results plotted on my graph. The lengths I have chosen are as follows: 20cm, 35cm, 55cm, 60cm, and 75cm. I have chosen these lengths, because give a good range and are easily measured by a meter ruler. I will not use an ohmmeter, but will record results from an ammeter and voltmeter. Then I will work out the resistance using the equation R+AD0-V/I. I have chosen to use a meter ruler, due to the fact that a small ruler has a higher percentage error and the wire is too big for a small ruler. -Risk Assessment I shall stay below 3 amps+ADw-br+AD4- +IB4-h I shall be careful if handling live wires The power supply will be handled carefully+ADw-/p+AD4- ADw-pAD4-Results+ADw-/p+AD4- ADw-pAD4-(See Tables)ADw-brAD4- (See Graphs)ADw-/pAD4- ADw-pAD4-Analysis+ADw-/p+AD4- ADw-pAD4-From my first set of results, I could see that the experiment had not produced the expected outcome. I attributed this to a design error of the circuit. I thought that this could have been due to imperfect connections to the test wire. To overcome this, I replaced the crocodile clips with wire connecting blocks and repeated the experiment.ADw-brAD4- From graph 2 on the previous page, I can see that the resistance of the wire is directly proportional to the length of the wire. I know this because my line of best fit is a straight line, passing through the origin (0,0) showing that if the length of the wire is doubled then the resistance of the wire will also be doubled 0.1 ohms. ADw-brAD4- These results prove my prediction+ADs- +AKEApQ-I predict that if the length doubles, then the resistance will increase in direct proportion.AKEApg- The reason for this isADs- as electrons pass through the wire, the electrons hit the atoms of the wire whilst making the journey from one end to the other, giving opposition or resistance to the electrons. When this happens electrons move an electromotive force such as voltage, and in hitting these atoms, also create heat via friction of the electrons and atoms. When the wire is lengthened, the journey is longer and the resistance changes in proportion. -Evaluation -I feel that my experiment went well, there were no real problems. I took my time and measured as accurately as I could, making our result satisfactory. I had some anomalous results in the first experiment, which could be down to many things such as:The Crocodile clips not put on straight instead they could have been placed on a tilt, as show below, this could mean that the distances in between the clips were incorrect. I could have read the instruments incorrectly. The crocodile clips could have been slightly rusty. There could have been some Parallax error, where I did not read the instruments straight on. I could have rushed and placed the crocodile clips on the wire carelessly and not I think that if I were to do the experiment again then I would use the connecting blocks first time, rather than crocodile clips and I could also use an ohmmeter to give me more accurate results and take less time. The other main thing would be to not rush as much because the first experiment was slightly rushed because I was running out of time. The circuit after the change from clips to connecting blocks would look like this. Overall I am pleased with my effort and am happy that I have supported my theory that when you double the length of the wire, the resistance doubles.

Resistance of a Wire 8.9 of 10 on the basis of 2080 Review.