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# Factors Affecting the Resistance of a Wire.

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Introduction

Factors Affecting Resistance of a Wire Factors Affecting the Resistance of a Wire Introduction There are four variables that affect the resistance of a wire. These factors are THICKNESS/DIAMETER, LENGTH, MATERIAL and TEMPERATURE. The two factors I am going to discuss are thickness and length because the effect on the resistance is more measurable than the effect of resistance with material and temperature. Also we can model the effect of thickness and length The thickness of a wire affects the resistance because if you double the size of the diameter, you quadruple the resistance. Think of water in a pipe, if you double the diameter of the pipe, you quadruple the cross-section. Look at the table: Radius ? R2 1 3.14 2 12.56 3 18.84 If you take radius' 1 and 2, you will see that 2 is four times as big as 1, showing that the surface area is quadrupled. This means that the resistance is quartered. The length of a wire affects the resistance because if you double the length you double the resistance. Think of a corridor with chairs in it. It would be fairly hard to get through it. Now imagine another corridor added on to the end of it, exactly the same as the first. ...read more.

Middle

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 reading from essaybank.co.uk s from the voltmeter which corresponded to the length of the wire being used. ...read more.

Conclusion

Length of the wire: - At the beginning when I did a preliminary experiment I was using crocodile clips instead of terminal blocks to connect the wire to the circuit. Although the crocodile clips made it easier for me to measure the length of the wire however I found it very difficult to keep the wires in these clips since it kept slipping out so the wire wouldn�t get connected successfully to the circuit. I therefore decided to use terminal blocks because even though these blocks make it more difficult for the wire to be measured accurately using a meter ruler, this can be overcome by using large wire lengths so that the inaccuracy in measuring its length will become very tiny and so can be neglected. I decided to chose 8 different lengths between 30-100cm because when I did a preliminary experiment I found that these lengths gave accurate results and that 8 readings was sufficient enough for me to plot a st. line graph and draw a good line of best fit through the points. Micrometer screw-gauge: - I decided to measure the diameter of the wire at 3 different positions on the wire. I then calculated the average diameter from the 3 measurements taken to enable me to measure the diameter of the wire as accurately as possible. ...read more.

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