An Experiment To Find The Resistivity Of

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An Experiment To Find The Resistivity Of Nichrome Essay, Research Paper A. Planning Plan of the method to be used: – The resistivity of nichrome can be determined using the equation ??=?RA/L Where: R:- Is the resistance of the wire in ?”ohms“ and can be determined using the equation R=V/I where ”V“ is voltage in volts and ”I“ is current in amperes. L:- Is the length of the nichrome wire used in metres. A:- Is the cross-sectional area of the wire in metres square and can be determined using the equation A= ??d2 where ”d“ is the diameter of the wire. If I plot a graph of length on the x-axis against resistance on the y-axis. From the relation R = ? L /A which corresponds to the st. line equation ? y=mx the graph should be a st. line passing through the origin

where ”m“ is the gradient of the st. line graph and corresponds to ?/A. Since the cross-sectional area of the wire can be found by knowing it´s diameter. Therefore the resistivity of nichrome can be calculated. ? Diagram of the circuit used in this experiment List of the apparatus used: – 1- Power pack supply of 4V 2-A variable resistor 3-A full scale deflection ammeter with a measuring range of 0-1 A 4-A digital voltmeter with a measuring range of 0-5 V 5-P, Q represents terminal blocks. 6-Circuit wires 7-PQ=Nichrome wire 8-A meter ruler 9-Michrometer screw-gauge 10-Sellotape Detailed method: – I set up the circuit as shown in the diagram that I have drawn. I started the experiment by taping a meter ruler between the terminal blocks P, Q so that I could measure 100cm of

nichrome wire.I made sure that the wire was carefully tightened at both terminals to try to minimise the kinks or twists in the wire. I then switched on the power pack supply and adjusted the variable resistor until a constant current of 0.2A was flowing through the circuit. I then recorded the corresponding voltage reading that was displayed on the digital voltmeter. I repeated this procedure using different lengths ranging from 30-100cm and adjusting the variable resistor until 0.2A was flowing through the circuit. After recording the corresponding voltage readings for each length and tabulating them I decided to repeat the whole experiment again another 2 times so that I could take the average voltmeter reading for each length. Using a micrometer screw-gauge I measured the

diameter of the wire at 3 different positions along the wire and then calculated its average diameter from the 3 values. I then plotted a graph of the length of the wire against average resistance and used it to calculate the resistivity of nichrome as mentioned in my plan where the average resistance can be calculated using the relation??? R=??V . I Variables in the experiment: - *In this experiment I varied the length of the wire each time using a range of lengths from 30-100cm. *I kept the current flowing through the circuit constant using a variable resistor which I kept varying for each length of wire so that the ammeter would always read 0.2 A. I then recorded the voltage readings from the voltmeter which corresponded to the length of the wire being used. *The temperature

of the wires in the circuit needed to be kept constant to prevent the whole circuit from overheating. I managed to do this by quickly switching off the power pack supply every time I had recorded my set of readings. I then left the power pack to rest for a small interval of time before switching it on again to record the next set of readings. * I also kept the diameter of the wire constant by using the same piece of wire throughout the whole experiment. Justification of the equipment range: – Ammeter: – I used a full scale deflection ammeter of current range from 0-1A because I only wanted to measure small currents passing through the circuit and not large currents however all the digital ammeters that were available had a current range of 0-20A and there weren´t any