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# How The Resistance Of A Wire Varies With Length.

Extracts from this document...

Introduction

Physics Coursework - Grace Perry

How The Resistance Of A Wire Varies With Length.

Introduction:

This experiment is to see how and if the length of a piece of wire effects resistance within a circuit. I already know that as the tempurature changes then so does the resistance and that if the wire is straight it decreases the amount of resistance opposed to when it is not straight and the resistance is increased. Electricity is a flow of charges in a circuit, a resistor is something that opposes the flow of an electrical current within the circuit. It is the electrons colliding with the atoms in the wire that causes the resistance. As the length of the wire increases the more atoms there will be, therfore more electrons, therefore more resistance. This then causes the charged particles to be pushed around the circuit more.

Resistance is meausured in Ohms from current and potential difference:

R=V/I

R= Resistance in Ohms

I= Current in Amps

V= Potential difference in Volts

Prediction:

I predict that as the lenght of the wire is increased then the resistance will also increase. I think this because within the wire it is  made up of positive fixed ions with the negativly charged electrons, when the wire is connected into a circuit the charged electrons flow along the wire and become the current. When the negative electrons pass the positive fixed ions they then collide and then start to vibrate.

Middle

Solutions:

I found soloutions to the majoraty of my problems.I replaced the ammeter and voltmeter to see if that made a difference but it didn't so I checked to see that I had out the correct leads into the correct places so opposites were together (positive to negative) and the same charges wern't (not positive to positive). I did have this problem at the ammeter and once I changed I was gettin positive readings. The voltmeter however was still showing negative readings even after it was connected properly. I then found out that "The Voltmeter must be placed in parallel around the component under test" - page 86, AQA Modular Science Early Modules, Edited by Richard Parsons. I replaced several of the wires to make sure that they were not loose, and tried as best as possible to straighten the wire. I did this using the side of a ruler running it along it. I also tested the cellotape to see if my readings changed while having it on there which they did slightly so I only taped it down on the side of the wire that wasn't connected in the circuit to make it  a fair test. I decided to make the maximum measurment of 800mm so the measurments of the wire can be made more accurate.

Improved Experiment:

I carried the experiment again taking into consideration how my soloutions could make it a fairer test and much more accurate.

Conclusion

I don't think that my graph of results was directly proportional, this could of been due to the flucuations that occured during some of our readings from the inaccuracy of the voltmeter and ammeter or just some of the leads or the wire not being secure enough. Although none of our results relly stande out as being "wrong" or not in line with the pattern of the rest of the results.

If I could redesign or of improved this experiment I would pay more attention to the fact that temperature is another factor which affects resistance within the circuit. I would try to counteract that by maybe leaving the wire to cool down between each reading, but making sure it for the same amount of time each time so to keep it a fair test. I would also use more accurate equipment such as a power pack to keep the voltage the same throughout to make the readings more reliable. I would also use a piece of wire that has the same cross-section throughout as that also affects the rate of resistance. I would then use a more accurate device to measure the wire and a more stable way to keep it all in place, as sometimes the crocodile clips kept comming out of place or someone might of accidently of knocked them without realising. I would also use a more accurate ammeter and voltmeter as some of my results flactuated from time to time so I would use ones which go further than to just two decimal places.

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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