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# Investigating the Resistance of Wire

Extracts from this document...

Introduction

Investigating the resistance of wire Aim: To find out what affects the resistance of a piece of wire Planning I am going to find out what affects the resistance of a piece of wire, and there are a few variables: * The Temperature: If the wire is heated up the atoms in the wire will start to vibrate because of their increase in energy. This causes more collisions between the electrons and the atoms as the atoms are moving into the path of the electrons. This increase in collisions means that there will be an increase in resistance. * Material: The type of material will affect the amount of free electrons, which are able to flow through the wire. The number of electrons depends on the amount of electrons in the outer energy shell of the atoms, so if there are more or larger atoms then there must be more electrons available. If the material has a high number of atoms there will be high number of electrons causing a lower resistance because of the increase in the number of electrons. Also if the atoms in the material are closely packed then the electrons will have more frequent collisions and the resistance will increase. * Wire length: If the length of the wire is increased then the resistance will also increase as the electrons will have a longer distance to travel and so more collisions will occur. ...read more.

Middle

I will also be using different voltages as repeats to get a fair result. Here is the detailed method of the experiment: 1. Set up the equipment as shown above, the wire is connected by a crocodile clip. It is set up as a variable resistor. The clip can be slid along the wire to change the length of the wire in the circuit. 2. Put the power pack on 2V and measure the Amps and Voltages when the wire is placed on 40cm from the start of the metre stick. 3. Increase the length in 10cm intervals by sliding the clips until you have readings up to 90cm. 4. Switch the power pack up to 4V, 6V and 8V as repeats. Fair test There are a few different types of variables to the experiment, to make it fair, I decided to only change one variable and keep all the other variables the same. I am only going to change the length of the wire and nothing else. There are some other precautions that I will take: * Use the same wire instead of cutting separate pieces into required lengths, because the cuttings might not be accurate and affect the results. Instead, I would use one 1 metre wire, and use a crocodile to slide on the wire to change the lengths of the wire that is connected to the circuit. ...read more.

Conclusion

Evaluation I think the test was very successful, it proved the ohms law, and showed that the resistance is proportional to the length of the wire. So when the length doubled, the resistance doubled. The results were quite accurate to support my prediction. To test the accuracy further, I could work out the gradient of each graph, which would show the resistance per cm. The gradient could be worked out like this: The highest value in the graph - the lowest value in the graph Length of the wire (50cm) Table of gradients Voltages Gradient (resistance per cm) 2V 0.1822 ?/cm 4V 0.1723 ?/cm 6V 0.1753 ?/cm 8V 0.1764 ?/cm The 'book of constants' shows that the resistance for the metal Constantine is 16.7 ?/m, which is 0.16 ?/cm. My results were very close to 16.7 ?/m. The reason that the resistance were slightly higher in my results was because the were resistance in the rest of the circuit, e.g. the crocodile clips and wires, the ammeter and the voltmeters. There were not many anomalous results, however, the resistance per cm were over the figure in the 'book of constants', and the extra resistance were caused by the rest of the circuit. To make the experiment more reliable, less resistant crocodile clips ammeters and voltmeters must be used to measure the resistance more accurately. Overall, my results were accurate, and are reliable enough to support my predictions. ?? ?? ?? ?? Shan Jiang 1 ...read more.

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