Introduction The purpose of this investigation is to expose the factors responsible for affecting the resistance of a wire in an electrical circuit. Many factors will have to be investigated prior to experimentation. A prior knowledge of electrical circuits and the factors of resistance will be required. The conclusive objective will be that research on the subject matter is proven by experimentation. Resistance The standard opinion of resistance when electricity is concerned is the ability of a substance to resist the flow of electricity through it. Good conductors are associated with low resistance and poor conductors are associated with high resistance.
As resistance is responsible for the current that flows, a high resistance will be responsible for a low current and a low resistance will be responsible for a higher current. This is definition of resistance given by Hutchinson’s Encyclopaedia:’ In physics, that property of a conductor that restricts the flow of electricity through it, associated with the conversion of electrical energy to heat; also the magnitude of this property. Resistance depends on many factors, such as the nature of the material, its temperature, dimensions, and thermal properties; degree of impurity; the nature and state of illumination of the surface; and the frequency and magnitude of the current. The SI unit of resistance is the ohm (Ω ).
Electricity has three features that include current, voltage and resistance. Current is the flow of electrons round a circuit that is measured by ... the investigation there will be many factors that will affect the resistance in a wire. These factors include: . Length of wire - ... of wire - Different materials may affect the resistance of the wire. This factor relies on the material on whether the wire ...
Resistors are devices, as a coil or length of wire, used in a circuit primarily to provide resistance.’ ; Resistor In physics, any component in an electrical circuit used to introduce resistance to a current. Resistors are often made from wire-wound coils or pieces of carbon. Rheostats and potentiometers are variable resistors. Prior knowledge and Internet research indicates that a Georg Simon Ohm was one of the forefathers of research into electrical resistance.’ Ohm, Georg Simon Ohm, Georg Simon, 1789-1854. German physicist best known for Ohm’s Law, the basic law of current flow. Educated in science by his father, a master locksmith, he worked as a schoolteacher before deciding to devote himself to research in physics.
He began the studies leading to the formulation of his law in 1825 and discovered that the force of a current traveling through a conductor is a measure of the current. The resulting Ohm’s Law was the earliest theoretical study of electricity. The unit of resistance (ohm) and unit of conductivity (mho — ohm spelled backward) are named for him.’ ; (Extracted from Compton’s Home Library 1998) E = Electromotive force (Volts) I = Current (Amps) R = Resistance (Ohms) Figure 1-1 The most common definition of Ohms Law. The most common definition of Ohms Law is given in Figure 1-1. Actually, it is not an expression of Ohm’s Law; it simply defines resistance. Starting from any section of the triangle, this can be read in any direction – clockwise, anti-clockwise, top to bottom or bottom to top – and it will always provide the calculation you require.
If the horizontal lines are treated as divide signs and the short vertical line as a multiply sign, and the calculation is started with whatever quantity that is looked for, i. e. ; ‘V = ‘, ‘I = ‘ or ‘R = ‘ all possible formulae based on this particular Ohms law will be attained. That is; V = IxR, I = V/R, R = V/I. It should be apparent that the formula works the other way too, that is; IxR = V, Ri = V, V/I = R and V/R = I. Ohms Law is defined as; ‘Provided that the temperature remains constant, the ratio of potential difference (p.
... the current decreased. Ohm came up with a formula to state these findings. It is V = IR, whereas V = Voltage, I = Current, and R = Resistance. Ohm ... study of heat conduction. This is also known as Ohm's Law. Ohm's Law, which is Georg's greatest accomplishment, started as an ...
d. ) across the ends of a conductor (R) to the current (I) flowing in that conductor will also be constant’. Or… the current passing through a wire at constant temperature is proportional to the potential difference between its ends.
From this, we conclude that; Current equals Voltage divided by Resistance (I = V/R), Resistance equals Voltage divided by Current (R = V/I), and Voltage equals Current times Resistance (V = IR).
The important factor here is the temperature. If calculations based on Ohms law are to produce accurate results this must remain constant. In the ‘real’ world it hardly ever does, but shall not prove a significant threat to result accuracy if precautions are taken.
Ohm’s Law only applies to metallic conductors. A more useful demonstration of Ohms Law is given below in Figure 1-2. Figure 1-2 A grid demonstrating how to calculate resistance It enables many more equations to be applied for calculating electrical resistance but still only applies to materials that obey Ohms Law (metals).
The circle below in figure 1-3 is another example. Figure 1-3 A resistance calculating Crop Circle Formation produced by E.
T. Figure 1-3 demonstrates how complex as the calculating with resistance becomes. The chart above gives the formulas for many equations for making calculations about resistance. However, it is not suspected that many or even several of these formulas will be required in this investigation. The triangular series of formulas featured earlier is the most probable method to be used as it simple and easy to calculate. This is how Ohm’s Law would be applied into this hypothetical equation.
Metal wires usually obey Ohm’s Law. If a potential difference of 1. 5 V causes 3 A of current to flow in a wire, how much current will flow when 6 V is applied? Voltage and current are proportional — – the voltage is multiplied by a factor of 4 so the current is also multiplied by 4: 12 A of current will flow. Find the electrical resistance of a light bulb, which passes 2 A of current when a potential difference of 120 V is placed across it. R = V/I = (120 V) / (2 A) = 60 Suppose a bulb passes 3 A of current when 120 V is put across it, what then is its resistance? R = V/I = (120 V) / (3 A) = 40 It is a very simple but effective method of calculating electrical resistance. However, all physical conditions need to remain constant.
... the current and resistance of a wire. Variables The variables that could change resistance are: o Length of the wire Cross section area (thickness) o Changing material ... . 07 2. 09 Conclusion: the thicker the wire, the lower the resistance Changing Materials Material Voltage (V) Current (A) Resistance ( ) Constantan 5. 51 0. 48 ...
The resistance of some conductors alters if they are bent or placed under tension or if they are placed at right angles to a strong magnetic field (magnetic fields induce current).
Factors affecting the resistance of a wire at constant temperature Resistance in Different-sized Conductors A thicker wire offers less resistance to current than a thinner one of the same material. This is because current consists of electrons flowing through the metal of the wire. The electrons jump from atom to atom in the metal in response to the electric field in the circuit.
A conductor with a larger cross section allows more electrons to interact with the field. Because there is more current with a given voltage, a conductor with a larger cross section has lower resistance. The resistance of a wire is inversely proportional to its cross section width. If the area / cross section of the wire is doubled, the resistance will be halved.
R “u 1 A R = resistivity (Ω ), A = area of cross-section of specimen (m) Length of the wire is also a factor in resistance. If the length of a wire is doubled, the resistance is doubled. This is because twice the length of wire is equivalent to two equal resistances in series. Resistance in series circuits is calculated using this equation = r + rR = resistivity (Ω ), r = hypothetical resistor, r = hypothetical resistor Resistances are just added together in a series circuit so having a long length of wire will just be the same as having 2 lengths of wire half the size, etc…
Resistance will increase with length. Resistance is proportional to length. R “u LR = resistivity (Ω ), L = length of specimen (m) Effect of Temperature on a Conductor In turn, heat in metals reduces conductivity, or increases resistance, slightly. More vibration makes atoms ‘get in the way’ of the electrons more often. The electrons then must spend extra time on deflected courses instead of going straight ahead. This cuts down current slightly.
In modern theory, the atoms scatter the electron waves carried by the electrons. Current can sometimes cause the wire to get hot; this would increase the resistance. Different Materials Different materials have different resistances. That is why metals have specific purposes in electrical circuits. Copper is primarily used in electrical circuits because of its low resistance.
... faults in my results. Temperature cannot be controlled. It causes the resistance to increase. I could increase the number of times I ... work out the resistance by using the equation resistance = Voltage/Current, R = V/IResultsResult number Length (cm) Current (A) Voltage (V) Resistance (R) Ω ... electrons to travel to the end, making the resistance of the wire longer. A. 8 aMy conclusion does support ...
It is energy efficient and is second only to silver, which is too expensive for national use. Materials with high resistances have their purposes in some electrical circuits too. Nichrome, an alloy of 80% Nickel and 20% Chromium is often used as a heating element in electrical devices. The differences in resistivity in materials are caused by the number of free electrons that the material has. If there are more free electrons, less energy is needed to be spent. There is no way that this can be calculated with the available level of equipment other than experimentation.
The other factors in consideration such as impurities in the wire, thermal properties and the state of illumination at the surface will be negligible in this investigation because there is no possible way they can be taken into account. There is no way they can corrupt the results because conditions will be the same for each experiment. The frequency of the alternating current is not a factor because only a direct current will be used. Experiment Plan If all of the experiments to be practiced could be based on a single setup it would be very useful because this would save time and make the results easier to relate to. This experiment set up would have to be able to test the following factors for differentiation of resistance in a wire. Material Length Cross Section width variance of material will have to be tested to confirm that resisting capacities are different with different materials.
The only wires that can be accessed are made from copper and nichrome. The results given by these wires should be interesting because copper is renowned for its low resistance as it is primarily used for electrical cabling. Nichrome however, is renowned for its high resistance as it is primarily used as a heating element. With this prior knowledge of these two materials it will help making an accurate hypothesis and it should also be obvious when problems occur. Wires of differing lengths will have to be tested to confirm that resistance is in proportion to length.
This should simply involve testing different lengths of one type of wire. There is no range limit to how long the lengths could be but it is doubtful that they will exceed 1 m for practicality. Wires with different diameters or SWG (standard wire gauge) need to be tested to prove that the resistance of a wire is inversely proportional to its area. The only widths of wire that can be accessed are SWG 26, SWG 32 and SWG 36 The experiment will obviously require an electrical circuit as the resistance of a wire in an electrical circuit is being calculated. To calculate the resistance of the wire using Ohms Law, both an ammeter and a voltmeter will be required: Voltage / Current = Resistance The wire in question will have to be attached in this circuit in series so that the current flows directly through it. Power will need to be supplied through a DC power pack that enables the power to be changed easily and accurately.
... graph of the results showing Current Vs. Resistance and Current Vs. Voltage. The Conclusion The results that I have obtained from the experiment are relatively near ... way may be to work out the resistance of the wire that I am using. The resistance of a material varies with temperature ...
Figure 1-4 shows the required circuit: Figure 1-4 The required circuit. It does not matter about the power being supplied because voltage or current does not affect resistance. The voltage supplied by the power pack cannot be regarded as accurate, that is also a reason why a voltmeter is used. It may be necessary to alter the power supplied if problems arise with temperature.
As was noted earlier, resistance in conductors rises with temperature. This would give inaccurate results. Results of the highest accuracy are required because the conclusion will be based on the results mainly in graphical format. Numbered Plan for Experiment Number 1 a. This first experiment is to test the accuracy and practicality of the experiment itself. It also has the purpose of demonstrating that temperature does have an effect on resistance.
A 20 cm long strip of nichrome wire SWG 32 will be attached to the circuit as shown in the diagram above and the current will be raised and recordings taken at various levels. Attach 20 cm Nichrome SWG 32 wire in the position shown. Turn on the power supply and raise the current to 0. 05 A.
Take reading from the Voltmeter Continue raising the power recording voltmeter readings at 0. 1 A, 0. 2 A, 0. 3 A, 0. 5 A, 1 A and 1.
5 A. Hypothesis. Nichrome is supposed to have a high resistance so will heat reasonably easily when a current is passed through it. As the current through the nichrome increases the temperature of the nichrome should also increase. As the temperature of the nichrome increases the resistance of the nichrome will increase as resistance increases with temperature. The resistance should increase as the current increases which means that the nichrome will not be obeying Ohm’s Law because the temperature is not at a constant.
... how the length of a wire affects the resistance. Resistance: is a force that resists the flow of the current in a wire. Resistance = Voltage / Current R = V ... will vary is the length of wire. Prediction: I predict that as the length of the wire increases, so will the resistance. I think this ...
When applied to graph format it should produce a curve showing voltage increasing as current increase. The current and voltage should not be in proportion because the temperature is not constant. Results. The results are given in Table 1-5. I (Current in Amps) V (Voltage in Volts) W (Resistance in Ohms) 0.
050. 2550. 10. 525.
20. 21. 055. 250. 31. 595.
30. 52. 945. 8816. 906. 901.
513. 619. 07 Table 1-5 the results. A graph can now be constructed using the information from Table 1-5.
Graph 1-6 The line of Graph 1-6 indicates that he resistance in the nichrome SWG 32 wire increases according to current. It is clearly seen that the resistance rises as the current rises. Voltage is not an issue here because it is the current that causes temperature rise. Graph 1-6 clearly shows that temperature has an important effect on resistance. Temperature is responsible for raising resistance because voltage is increasing at a higher proportion to current as was predicted in the hypothesis. The reasons for this are explained earlier in the investigation.
More vibration makes atoms ‘get in the way’ of the electrons more often. The electrons then must spend extra time on deflected courses instead of going straight ahead. This cuts down current slightly. Temperature is the only factor responsible for nic home disobeying Ohm’s Law.
The resistance should not rise when power is increased. Temperature Control is clearly going to be an important factor in determining the accuracy of this investigation. Steps need to be taken to ensure that the results from this investigation are not corrupted. Temperature control should not be as large a problem with copper as it is with nichrome because copper is renowned for low resistance so will not generate heat as easily.
It does not matter what temperature the wire is at, as long as it does not change in the experiment enough to alter the results. As long as the current is kept extremely low, the wire will not become hot. When there is a low current the wire does not get as hot as it would in a higher current so the atoms in the wire do not vibrate as much so the electrons move more freely. Another method of keeping the temperature of the wire under control would be to keep the wire submerged under water in a beaker. This would keep the wire at a near constant temperature. The wire could not simply be put into a beaker as no part of the wire can touch any other part of the wire because it would disrupt the circuit and the results would be corrupted.
The basis of the experiment itself was very effective. It was simple in principal but gave everything required. It was a very effective method of calculating resistance. This experiment will be the basis for all of the following experiments unless there is reason for exception.
Plan of experiments 1 = Length An experiment will be required to confirm that resistance increases in proportion to length. Only one wire material will be necessary as this test is solely for testing the effects of length. Although there is no scientific judgment behind this, copper SWG 32 wire will be used in this experiment. Resistance recordings will be taken on the wire whilst the circuit is flowing through 10 – 60 cm of the wire. To attain an average, the experiment will be conducted twice for more accurate results. It does not matter about the power output whilst calculating the resistance, as voltage or current do not affect resistance.
However, the recordings will be taken at a current of 0. 22 A so any problems in will be easily noticed whilst conducting the experiment and because it will demonstrate how the resistance was calculated. Attach 10 cm length of the copper SWG 32 wire in the correct position. Apply current. Record readings from voltmeter and ammeter. Calculate resistance.
The same steps will be applied for the following lengths: 10 cm, 20 cm, 30 cm, 40 cm, 50 cm, and 60 cm. Hypothesis It is expected that the resistance should increase in proportion to the length. The resistance should be considerably higher for the 60 cm length than it is for the 10 cm length. Theoretically the resistance for the 60 cm length should be 6 times that of the 10 cm length. The reason for this was explained earlier. Resistances are just added together in a series circuit so having a long length of wire will just be the same as having 2 lengths of wire half the size, etc…
Resistance will increase with length. Resistance is proportional to length. If these suspicions are correct then this experiment will also confirm that copper obeys Ohm’s Law. ResultsLengthExperiment 1 Experiment 2 AverageCmIVWIVWIVW 100. 220.
080. 3640. 220. 090. 4090.
220. 850. 386200. 220. 140. 6360.
220. 180. 8180. 220.
160. 727300. 220. 231. 0450. 220.
251. 1360. 220. 241. 091400.
220. 321. 450. 220. 331. 50.
220. 3251. 477500. 220. 41. 8180.
220. 421. 9090. 220. 411. 864600.
220. 472. 1360. 220. 512.
3180. 220. 492. 227 Table 1-7 the resultsA graph can now be constructed using the information from table 1-7 Graph 1-8 A line of best fit is not required in Graph 1-8 because the points are in near perfect correlation. The level of resistance is clearly increasing as the length of the wire increases. It is also clear because the line is practically straight that resistance is in proportion to length.
If they were not in proportion the line connecting the points would not be nearly as straight as it is. The graph also shows that copper has a very low resistance. The results shown in Graph 1-8 are exactly what were expected to happen as stated in the hypothesis. The resistance increases in proportion to length.
Also, the level that the resistance has increased is as was also stated in the hypothesis. If the results of table 1-7 are examined, it is noticed that the resistance has acted exactly as it would if it did obey Ohm’s Law. Although the results are not perfect, most probably due to the limited usability of the equipment provided the results are in proportion to length. This is because: The resistance in 10 cm of wire should be 50% of the resistance of 20 cm of wire. According to table 1-7 the average resistance of the 10 cm length of copper SWG 32 is 0. 386.
The average resistance of the 20 cm wire is 0. 7270. 3860. 727 = 0. 5353% is very close to 50 % and that is significant enough to say that this experiment was a success. If other readings are compared, a closer percentage may be found.
The resistance of the 20 cm wire should be 1/3 of the resistance of the 60 cm wire. This is because 20 is 1/3 of 60. 0. 7272. 227 = 0. 326 This is extremely close to 0.
33 (1/3) and confirms the success of this experiment. Resistance is proportional to length. R “u L 2 = Cross Section An experiment is required to confirm that the resistance of a wire is inversely proportional to its diameter. For the success of this experiment, one material will be required.
Several different diameters for this wire will also be required. As was noted earlier, the only available diameters are SWG 26, 32 and 36. These will limit a fuller in ves into this factor of resistance but the results should still show a good insight. The material chosen for this test will again be copper. There is a scientific reason behind this choice. In the primary experiment that investigated the effects of temperature it was noted that the nichrome wire did get extremely hot with a reasonably low current.
To get an accurate result using nichrome wire without temperature interference the current would have to be kept very low. When the current is lower it is more difficult to get an accurate reading from the ammeter. This is due to the level of the equipment. A would help in this situation Therefore copper SWG 26 and 32 will be used in this experiment. Copper SWG 36 will not be tested, as it is not deemed necessary. It will be easier to contrast the resistances of two materials.
They will all be tested on lengths of wire from 10-60 cm so that a graph can be drawn for evaluating. There is no need to test copper SWG 32 again so the results from experiment 1 will be used. Again, everything will be performed twice to achieve an average for more accurate results. Attach 10 cm length of wire to the correct position in the circuit.
Apply Current Record readings from ammeter and voltmeter Calculate Resistance Repeat steps 2, 3 and 4 for the following lengths of wire: 10 cm, 20 cm, 30 cm, 40 cm, 50 cm, and 60 cm. Hypothesis. These are the diameters of the 2 wires in use: 26 SWG = 0. 45 mm diameter 32 SWG = 0. 28 mm diameter It is expected that the thinnest wire (32 SWG) will have the highest resistance because a thicker wire offers less resistance to current than a thinner one of the same material.
This is because current consists of electrons flowing through the metal of the wire. The electrons jump from atom to atom in the metal in response to the electric field in the circuit. A conductor with a larger cross section allows more electrons to interact with the field. Because there is more current with a given voltage, a conductor with a larger cross section has lower resistance. ResultsLengthWSWG 26 SWG 32 CmExp 1 Exp 2 AvgExp 1 Exp 2 Avg 100. 1360.
1360. 1360. 3640. 4090. 386200.
2730. 2730. 2730. 6360. 8180. 727300.
3640. 4550. 4091. 0451.
1361. 091400. 5450. 5450. 5451. 451.
51. 477500. 6360. 6820. 6591. 8181.
9091. 864600. 7730. 8180.
7962. 1362. 3182. 227 Table 1-9 the resultsA graph can now be constructed using the information from table 1-9: Graph 1-10 It can clearly be seen from Graph 1-10 that length is an important factor in affecting resistance by the way both lines go up indicating that resistance is increasing. The main focus of this graph however, is that it clearly shows that the two wires which are both made from copper have extremely different resistances and as the length of each wire is increased the resistivity of each wire spreads even further apart.
This is noticed because the lines interpreting the two wires have resistances of 0. 136 ohms and 0. 386 ohms respectively when 10 cm long. This is a difference of 0. 25 ohms. When the wire length is increased to 60 cm the two wires have resistances of 0.
796 ohms and 2. 227 ohms respectively. This is a difference of 1. 433 ohms. It does appear that this test has confirmed that resistance is inversely proportional to length as the results are exactly what were predicted in the hypothesis except for a negligible margin of inaccuracy that would undoubtedly have been caused by the level of equipment. This margin of inaccuracy can be seen in any irregularities on the line.
They should both be perfectly straight to indicate the proportion. The theory that resistance is inversely proportional to area has not yet been fully confirmed. To confirm that resistance is proportional to area a simple test must be carried out on the results from table 1-9. The percentage difference between the resistance of the two wires in question (Copper SWG 26 and 32) should not differ no matter what the length the resistances were calculated at. At 10 cm the resistances of the wires were 0. 136 and 0.
386 for the SWG 26 and 32 respectively. At 60 cm the resistances of the wires were 0. 796 and 2. 227 for the SWG 26 and 32 respectively. 0.
1360. 386 = 0. 3523 = 35. 2 %0. 7962. 227 = 0.
3574 = 35. 7%With only a percentage difference of 0. 5% it is correct to say that resistance is inversely proportional to length. This is because a thicker wire offers less resistance to current than a thinner one of the same material. This is because current consists of electrons flowing through the metal of the wire. The electrons jump from atom to atom in the metal in response to the electric field in the circuit.
A conductor with a larger cross section allows more electrons to interact with the field. Because there is more current with a given voltage, a conductor with a larger cross section has lower resistance. The resistance of a wire is inversely proportional to its cross section width. If the area of the wire is doubled, the resistance will be halved. R “u 1 A 3 = Material It has yet to be confirmed that resistance changes with material. An experiment is required to prove that different materials have different resistances.
For this experiment both copper and nichrome will have to be tested against each other. Lengths of nichrome and copper wire of the same SWG will have to be put in the circuit in the correct position and their resistances will have to be taken for lengths from 10-60 cm. The wires tested must be of exactly the same length and SWG because these factors are not wanted to affect this experiment. If the lengths or the SWG’s were different the experiment would not solely be testing the materials. The results would not be true. The resistances will be recorded from 10-60 cm so that a graph can be constructed.
Again, each experiment will be conducted twice to attain an average for more accurate results. SWG 32 wire will be used, as the results are already available for that SWG copper wire. Only nichrome SWG 32 will need to be tested. 1 Attach 10 cm length of Nichrome SWG 32 in the correct position in the circuit. 2 Apply current. 3 Record readings from ammeter and voltmeter.
4 Calculate Resistance. Repeat steps 2, 3 and 4 for the following lengths of wire: 10 cm, 20 cm, 30 cm, 40 cm, 50 cm and 60 cm. Hypothesis. The prediction of this hypothesis is based solely on the knowledge that both of these wires have completely different purposes in electrical circuits because they are both known to have very different levels of resistance. This experiment is now only for statistical purposes. If the nichrome wire does not have a larger resistance than the copper wire then there is clearly a problem with the experiment.
It cannot be said that copper will have a lower resistance than nichrome because it has more free electrons because that is not known although it must be a reality. The only thing that is being changed in this experiment is the material; the dimensions are not being changed at all to demonstrate a ‘fair test’. Nichrome is used as a heating element because it supposedly has high resistance. Copper is used as the standard wiring system in electrical circuits because it supposedly has low resistance.
This will be evident in the results. LengthΩ Nichrome SWG 32Ω Copper SWG 32 CmExp 1 Exp 2 AvgExp 1 Exp 2 Avg 102121210. 3640. 4090. 3862041. 6740.
6741. 170. 6360. 8180. 727306061. 6760.
831. 0451. 1361. 0914077. 3380. 3378.
831. 451. 51. 47750102. 67103. 67103.
171. 8181. 9091. 86460126126.
67126. 332. 1362. 3182.
227 Table 1-11 the resultsA graph can now be constructed from the information from Table 1-11. Graph 1-12 It can clearly be seen when concluding the lines of best fit from Graph 1-12 that there is a large difference in the resistances of copper and nichrome. Nichrome has a much larger resistance than copper. This can be seen by examining the line interpreting nichrome.
The line begins much higher than the line interpreting copper and the gap extends widely as length increases. The difference in resistance it gives the impression of a poor graph, as it is barely noticeable that the resistance of copper rises at all when compared to the rate at which the resistance of nichrome increases. From evaluating the Graph 1-12 it is definitively confirmed that nichrome has a higher resistance than copper. Its resistivity must be many times the resistivity of copper. To calculate how many times more resistive it is a simple calculation will have to be made. For 10 cm, the average resistance of the nichrome wire was 21.
For the copper, the resistance was 0. 386. 21. 0000. 386 = 54. 4 For 60 cm, the average resistance of the nichrome wire was 126.
33. For the copper, the resistance was 2. 227126. 3302. 227 = 56. 754.
4 + 56. 7 = 55. 55 / 2 = 55. 55 Nichrome’s resistance is approximately 55. 55 times greater than the resistance of copper.
It can also be confirmed that copper does have more free electrons than nichrome, which was also predicted in the hypothesis. This is simply because copper has a lower resistance than nichrome. The differences in resistivity in materials are caused by the number of free electrons that the material has. If there are more free electrons, less energy is needed to be spent. There is no way that this can be calculated with the available level of equipment other than experimentation It would have been better for scientific purposes if more materials could have been tested but sadly, these were the only available.
At present it is not known whether the difference between the resistivity of nichrome and copper is exceptional or not. It is not known whether these two materials represent the boundaries of resistance in conductors. Although copper is known for its very low resistance which has also been proven here, it is already known that silver has an even lower resistance although it is not known how much lower. Nichrome is known for its high resistance but it is not known whether it actually is that high.
It looks like it has a very high resistance but only compared to copper, which has a low resistance. Other materials could have a much higher resistivity. Resistivity Resistivity simply defines the resistance of a material. It has been included in this investigation only to prove that work on resistance can be taken much further.
This is merely basic physics. Combining these two dimension equations made the resistivity equation further below. R “u 1 & R “u L This is the equation for calculating resistivity. ρ = RA / Where R = resistance (Ω ), ρ = resistivity (Ω m), L = length of specimen (m), A = area of cross-section (m) This equation will enable the resistances of copper and nichrome to be found To calculate the resistivity of nichrome the following statistics would be required. The resistance of the nichrome is required with a certain area and length. It does not matter what length or area as long as all the readings are accurate which cannot be guaranteed.
An approximate resistivity can be calculated. The results for the tests on a 10 cm SWG 32 length of nichrome appear to be very accurate. The first experiment recorded 21Ω and the second experiment also recorded 21Ω . To calculate the (m) of the cross section of SWG 32 which = 0.
28 mm, these steps would have to be taken: 1. 0. 28 mm: 0. 00028 m (has to be put into m) 2. 0. 00028 then has to be put into the equation (rπ ) to find the area of its circle in (m).
3. (0. 00014 = 0. 0000000196) π = 0. 0000000615. 7522 It can now be put into the equation.
ρ = (21 x 0. 0000000615. 7522 = 0. 0000012930. 7962) / 0. 1 = 0.
0000129307962 Ω m. The resistivity of Nichrome according to this investigation is 0. 0000129307962 Ω m. This practical calculation will now be repeated for Copper. The results for the tests on a 20 cm SWG 26 length of copper appear to be very accurate.
The first experiment recorded 0. 273Ω and the second experiment also recorded 0. 273Ω . SWG 26 = 0. 45 mm = 0. 00045 m (0.
000225 = 0. 000000050625) π = 0. 000000159043. 1281ρ = (0. 273 x 0.
000000159043. 1281 = 0. 00000004341877397 / 0. 2 = 0. 0000002170938699 Ω m.
The resistivity of copper according to this investigation is 0. 0000002170938699 Ω m. There is naturally a large margin for error, although it appears correct because copper’s resistivity should be a lot lower than nichromes. General Conclusion The success of each experiment has been good. The results from every experiment have gone as predicted in the hypothesis and have obeyed all of the previous information that is displayed in the Introduction.
There has been not one experiment where the results have been problematic. There has not been one result in any experiment that can be defied as wrong and there has been no need to alter the basis of the experiment or question any of the conclusions given from results. That is the level of how effective the results have been in concluding the objectives and predictions of each experiment and the investigation as a whole. The following theories have been proven identifiably by the results.
&mid dot; Resistance increases with temperature. The results of experiment 1 a undoubtedly prove temperature affects resistance and that temperature rise causes a rise in resistance. The evidence to support is found in graph 1-6. Nichrome is a metal conductor and obeys Ohm’s Law. Therefore the line displaying the proportion of the voltmeter to the ammeter should be straight but it is a curve. The resistance is increasing because temperature is changing the constant.
&mid dot; Resistance is proportional to length. The results of experiment 1 undoubtedly prove that resistance increases in proportion to length. The evidence to support this is clearly there in Graph 1-8. As the length of the wire is increased, the resistance also increases. Also, there is a practically straight line indicating that they are in proportion.
They rise at the same percentage. &mid dot; Resistance is inversely proportional to area. The results of experiment 2 undoubtedly prove that resistance is inversely proportional to area. The evidence to support this is found in Graph 1-10.
There are two lines on the graph both indicating copper wire. However, one wire has a diameter of 0. 45 mm where as the other has a diameter of 0. 28 mm. It is clearly seen on the graph that 0.
45 mm wire has a much lower resistance than the 0. 28 mm wire. They are both practically straight lines indicating that they are both proportional to resistance. As the thinner wire has the higher resistance it is said that resistance is inversely proportional to area. &mid dot; Material Affects Resistance. The results of experiment 3 undoubtedly prove that material affects resistance.
The evidence to support this is found in Graph 1-12. There are two lines of best fit on the graph; one indicates a length of copper. The other line indicates a length of nichrome exactly the same length and SWG as the copper. Both materials distinctly have different levels of resistance. As the lengths of both wires are increased in proportion to each other, the difference in resistivity becomes even clearer. Nichrome definitively has a higher resistance than copper General Evaluation of Investigation Whether this investigation has been a success can only be determined by the accuracy of the results.
Without scientifically accurate results, the investigation would be meaningless and disruptive to the person acting upon it. The results shown in this investigation are true and are believed to be correct. In this sentence ‘correct’ is also meaning as accurate as can possibly be attained. There are many ways in which this investigation could have improved its scientific standing.
One way to improve the reliability and accuracy of the results would be to repeat the experiment ‘n’ times so that a true average could be obtained. The experiments were repeated to obtain an average but they were only repeated once. This is more reliable than conducting the experiment once but when it is repeated once and both experiments differ by a significant margin such as that shown in the experiment on Copper SWG 32 it is annoying at least to be working with inaccurate results. If there were a longer period to perform this investigation then the experiments would have been repeated many more times to attain a true average. Even if the experiment were repeated many times, the results would still not be able to be interpreted as scientifically accurate. The performance of the equipment was satisfactory but that is all.
The equipment worked well enough to give an accurate answer but with imperfections. Every line on every graph should have been straight with the exception of experiment 1 a. Any imperfection on any line on the other graphs is a flaw in the experiment and in the investigation. It is a flaw because of this rule – Ohm’s Law ” Provided that the temperature remains constant, the ratio of potential difference (p. d. ) across the ends of a conductor (R) to the current (I) flowing in that conductor will also be constant ” The temperature could have caused theses minor imperfections in the constant but it is doubtful as the voltmeter and ammeter recordings were taken down over a period of up to 30 seconds to ensure that the readings did not change and were true.
They were all taken in the same conditions. It is believed that these minute flaws could have been caused by any of these several points. &mid dot; Ammeter readings only including 2 decimal figures (0. 005 A possible margin for error).
This is only significant because of the extremely low currents being used for temperature control of the wire.
A milli ammeter would have been far more accurate&mid dot; Imperfections in the circuit. Any basic faults in the circuit such as a faulty wire could have caused a change in results especially as it was not possible to use the same equipment for each experiment. If it was possible to use new / tested equipment and to be able to use the same equipment for each experiment then there may be less available controversy. &mid dot; Accuracy on Length. The only available method for measuring was by ruler and hand. It would be impossible to get an accurate length using this technique.
It was measured to the best ability but the margin of error could easily have been up to 1 cm considering the poor method in which the conductor was held in position; ‘crocodile clips’. A more accurate method of measuring the wire is necessary, as well as a more effective method of connecting the conductor. Although this display of controversy is founded, the experiment was very reliable and efficient. There is no way to improve the method of the experiment used as a basis for all of the experiments. It was a perfect method of calculating resistance although there are some negative technicalities, which were explained above. For the purpose of allowing the equation…
R = V / I… to be calculated there is no better substitution although scientific knowledge of how resistance is calculated to extreme military precision is regrettably absent. The experiment was simple, quick and effective. Possible changes in the investigation were noted earlier. The results are true and so is the conclusion.
Apart from the above brief demonstration of negativity, the investigation was a success. After examining the basic out come of each experiment in the summary, there can be other statement for the outcome of this investigation other than that it was a success. This was the target for the investigation ‘The conclusive objective will be that research on the subject matter is proven by experimentation.’ ; It can now be elaborately stated that the research on the subject matter has been proven by experimentation. Every experiment has successfully confirmed the research. The following equations have been verified: R = V / I (Resistance (Ω ) = Voltage (V) / Current (I) ) R “u L (Resistance is proportional to length) R “u 1 A (Resistance is inversely proportional to area) ρ = RA / L.