Temperature of wire: The temperature of the wire would affect the resistance because as the wire gets hotter the net begins to vibrate because they are given more energy; this therefore makes it harder for the charged electrons to get through the net without colliding with it and causing resistance. Therefore the higher the temperature the higher the resistance. Material of wire: The material of a wire would affect it resistance because different materials have different resistivity because the have different nets.
Some of the nets may have smaller holes that others and this would increase the resistance because there would be a larger chance of the atoms colliding. Similarly some materials may have larger nets, which would mean that there would be a lesser chance of the atoms colliding. The variable that I am going to change is going to be the resistance because I think it will be the easiest to change with the apparatus I have available to me and I think it will give fair results.
Research So far I have taken a lot of information from my G. C. S. E.textbook but some of my work has come from the Internet. I used many different search engines but the two main engines, which I used, were www. ask. com and www. google. com and here is some of the information, which I got by using these engines: Resistance alloy data Material Nominal Resistivity Microhm. cm Maximum Operating Temp i?? C Density g/cm3 Nominal Temp Coeffic. of Resistance.
This information was very useful because the type of wire I am going to use is Nickel Chrome and it has a lot of information on it and it tells me its resistivity. Prediction I predict that as the length increases the resistance will also increase in proportion to it. I think this because the longer the wire the longer the net of atoms and therefore the larger the chance of the electrons colliding with the net and losing some of their charge. Therefore if the length is doubled the resistance should also double, because the length of the wire has doubled therefore the amount of atoms will have doubled so the amount of collisions should double.
When I draw a graph it should hopefully show that the length is directly proportional to the resistance. The diagram below should show this more clearly: Apparatus Meter rule to measure out the length of the wire. 1-meter length of nickel chrome wire to test its resistivity. Ohmmeter to measure the resistance of the wire. Crocodile clips to connect the ohmmeter to the wire. Wires to connect the ohmmeter to the crocodile clips. Masking tape to stick the wire to the ruler. Preliminary Work I did some tests to see what distance I needed to space my readings at and this is what I got:
Length (mm) Resistance (ohms) My preliminary results have shown that altering the length by 10mm is too little because the resistance gain is too uneven, but if I change the length by too much i. e. 500mm the gap is too large. Therefore I am going to take my results every 50mm. I also found that the wires connecting the ohmmeter to the wire had a resistance of 0. 3mm so I will have to To make it a fair test I need to make sure that I keep all of the other variables the same.
I will use the same wire every time and in I will use it again in my repeat experiment, so that the width and material of the wire will remain the same. The temperature of the wire will be very hard to keep constant because each time an electron collides with the net its energy change from electrical to heat therefore every time the atoms collide with the electrons the wire will heat up. Hopefully this will not affect my experiment too much because I am only going up to a meter in length therefore it should not heat up too much. Diagram My apparatus will be set up like so: Method 1.
First I will gather up all the needed apparatus and set it up as above. 2. Then making sure that one of the crocodile clips is on exactly 0mm and that the other is on exactly 100mm I would take a reading. 3. Before I record the reading I would make sure that the ohmmeter had come to a complete stop and was not flashing. 4. I would the repeat this every 50mm until my I got to 1000mm making sure that the first crocodile clip was always on 0mm. 5. Then I would repeat the whole experiment making sure that I used the same wires so that the width and material of the wire were kept constant. 6.
Whilst repeating the experiment I would make sure that I did it in the same place as before because if I repeated it next to a radiator the resistance would go up. Results Length Of Wire (mm) Results 1 (Ohms) Results 2 (Ohms) Average (1dp) (Ohms).
Explanation Of Results My first set of results has an anomalous result, which is circled on the first graph. This could be because I did not wait for the ohmmeter to settle and I took the reading too quickly. My second and average set of results are good with no anomalous results and they show a definite relation between the resistance and the length of the wir they show that as the length goes up so does the resistance. In my prediction said that if the length doubles so should the resistance and my first set of results show that at a length of 250mm the resistance was 5.
2W and at a length of 500mm the resistance was 10. 1W which is very close to my predicted answer. Conclusion I think that my experiment went quite well because all my graphs had straight lines showing a strong relationship between the length and the resistance. But I could have improved this method in a couple of ways. For example I should have used pointers instead of crocodile clips because they are far more accurate, this is because they have a far smaller tip than crocodile clips and they would give a more accurate measurement of the wire. Also pointers would not have compressed the wire like crocodile clips.
Crocodile clips have a spring in the to keep them shut and this could have compressed the wire therefore increasing the resistance. I also should have been more careful about making sure the wire was taught when I took the readings because if it was loose it would have been a longer length that the one I thought I was reading. Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.