# Title: and the resistance of the wire. I

Title: Investigating Resistance Lab Report Aim: The aim of this investigation is to discover the relationship between the length of the wire and the resistance of the wire. I will do this by measuring the resistance by changing the length of the wire. The Ohm’s law will investigate the relationship between the electric current, voltage and resistance. The formula is: Hypothesis:I hypothesize that when the length of the Nichrome wire increases, the resistance of the wire increases as well. The formula is R = (rho)x l (length)/ A (area). Since and A are kept constant, the resistance is only affected by the length, creating: R= kL (with k being the constant). This displays that R is directly proportional to L. Furthermore, as the electrons collide more often with the ions in the metal, it makes it more difficult for the current to flow. Furthermore, with the formula:Expected graph:As the length increases, the resistance increases proportionally. Variables: Independent:The independent variable is the length of the Nichrome Wire. I will change the independent variable each time by increasing the length of the wire by 10cm. The range of values for the independent variable is 10 cm to 80cm, with an increment of 10cm. I chose this range because if the range is too small it will be insignificant and if it is too large, it will cause the wire to heat up and there will be no accuracy in the results. These cm values will be converted into meters when recording the results. To measure the dependent variable accurately, I will take more than one reading and have three trials and an average.DependentThe dependent variable is the measure of the resistance of the Nichrome wire. I will measure the dependent variable by measuring the potential difference and the current. The resistance is given by the ratio of the potential difference and the current. I will use an ammeter and voltmeter to take these measurements. To measure the dependent variable accurately, I will take more than one reading and have three trials and an average. Controlled variables: (give units) ControlledI will keep it at this value I will keep it constant by… I must keep it constant because… The Power pack setting (the amount of emf)4 volts Not changing the setting throughout the experimentChanging the volts can affect the measuring of volts and current and it can cause the results to be invalid. The material must be kept the same NIchrome SWG 30 Not switching the wire to other materials (such as copper) throughout the experiment I must keep it constant because changing the material and integrating it into the equation can change the resistance. Diameter of the wire The diameter should be (SWG) 30. Not increasing or decreasing the diameter of the wire throughout the experimentThe diameter can affect the cross sectional area of the wire, which can affect the resistance. The connecting wires and the volt and ammeter settings Should be connected to each other and the power pack Not changing the apparatus of the experiment in any way I must keep it constant because it can affect the values of the voltmeter and ammeter, thereby changing the resistance and causing the results to be invalid. To ensure that my measurements are reliable, I will keep the controlled variables unchanged to avoid inaccurate data. To make certain that my measurements are valid, I will perform 3 trials of the experiment, calculating and using the data average.Materials/ Equipment and Diagrams:Material QuantityCrocodile clips 4Plastic coated wires6Power Pack1 (4-6 volts) 1 meter long ruler 1 Nichrome wire 1 meter long Ammeter 1Voltmeter 1Diagram: Method:Set up equipment as shown in the diagram Draw results table as shown belowPut one crocodile clip (attached to the ammeter) at the 0 cm mark of the ruler, connected to the nichrome wirePut another crocodile clip (attached to the power pack) at the 10 cm mark of the ruler, connected to the nichrome wireSwitch on the powerpack at 4 volts throughout and record the reading on both the ammeter and the voltmeter in the results table Switch off the powerpackMove the crocodile clip attached to the powerpack to the 20 cm mark on the ruler Switch on the powerpack and record the readings of the ammeter and voltmeter in the results table Repeat steps 6 to 8 for the length of the wire until 80cm. This is Trial 1 Repeat steps 1 to 9 for Trial 2 and 3 Calculate the average Voltage and Current for each length Calculate the resistance using the formula: R= V/I Plot the graph of resistance (y axis) against length (x axis) of the wire Safety precautions:Ensure that the nichrome wire cools and do not touch the wire when the reading is being taken Safety goggles Covered shoes incase anything is dropped Tied hair Results Table: Table of the relationship between the length and the resistance of the wireLength of Wire (m)Trial 1 (V)Trial 1 (I) Trial 2 (V) Trial 2 (I)Trial 3(V) Trial 3 (I) Average (V)Average (I) Resistance ()0.12.727 02.81 2.76802.872.79902.83 2.7652.84 0.970.2 3.138 01.723.156 01.73 3.155 01.76 3.151.741.81 0.3 3.322 01.26 3.34901.24 3.312 01.24 3.33 1.25 2.660.4 3.425 00.983.44100.993.39700.973.421 0.983.490.5 3.466 00.803.50900.81 3.47000.813.4820.814.290.63.52500.683.55400.683.53100.683.4630.685.090.73.57400.593.58400.603.57100.603.5760.5975.990.83.59500.5203.6100.5203.6000.543.6020.536.80Graph: Gradient = 8.6 (/m) () = Gradient x Cross sectional wire= 6.702066x 10^-7 ( x m) Conclusion: As shown in the graph: As the length increases, the resistance increases. In addition as shown by the straight best fit line, the relationship is linear. This supports the previously mentioned hypothesis, which is the length of the wire is directly proportional to the resistance of the wire. Ohms law provides evidence as well, stating that electric current is proportional to the voltage. This also displays the scientific reasoning behind the relationship, which states that it will require more energy to travel a longer distance, leading to higher resistance because of the electrons colliding with the ions in the metal wire. It is shown by the increasing value of the voltage as the length increases (voltage means the energy per electrons). For example, when the length of the wire is 0.4, the resistance is 3.49, and when the length of the wire is 0.8, the resistance is 6.80. The relationship based on the graph is that the resistance is equal to 8.6 x the length (R=8.6L). As displayed by the graph, there is a positive correlation and there is no anomalous data in the results. This may be because the controlled variables were kept unchanged throughout the duration of the experiment. Evaluation of method: In this experiment there is a possible source of error due to the heating up of the wire. This is due to the long period of usage of the circuits. The heating up of the wire might affect the resistance (increasing it) as there will be more collisions between the electrons. However, this is minimized by turning the powerpack off when changing the length of the wire and on when taking the measurements. Overall, my method is still valid. Another possible source of error could be due to inconsistent cross sectional area. It was not stated in the method to check the consistency of the diameter of the wire throughout the length of the wire during the experiment. Cross sectional area affects the resistance which can lead to inaccurate results therefore this can be an improvement.  Another improvement to the method could be to place the wire on a water bath to ensure the temperature is unchanged during the experiment. Furthermore for the diameter, I can use a micrometer screw gauge to check it at random points of the wire to make certain that each part of the wire has the same diameter. The experiment’s range of values for the length of the wire is only 10 cm to 80 cm but the hypothesis assumes that the relationship is correct for every value of length. However, as the best fit line shows a perfect linear relationship, it is safe to assume that this will be true for both a higher and lower value, therefore my hypothesis is valid. As an extension to the investigation, it would be better to record measurements for a larger range of the length of the wire to ensure that relationship is valid. Investigation relates to the statement of Inquiry; Statement of Inquiry: Scientists use models to explain the flow of electrical energy and its transformations to other forms as the consequence of movement of electrical energy. The outcome of my investigation proves that the resistance of the wire is directly proportional to the length. Resistance is directly related to the transformation of electrical energy to other forms of energy. On the other hand, the length of the wire is directly related the movement/ collisions of the electrical charges. The longer the length of the wire, the further the electrical charge has to move, therefore this experiment serves as a model for the relationship between the flow of electrical energy and its transformations to other forms as the consequence of movement of electrical energy.