Diagram:
Method:
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This experiment shall be repeated numerous amounts of times so that the result average will be more accurate. I will be investigating how increasing the length of wire will affect resistance. The circuit shown in the above diagram must be set up with the voltmeter in series. The current from the power pack must be kept at 5 volts for it to be a fair test. The wire must be joined to the circuit, it must also be placed onto of a heatproof mat, and this is because the current flowing through the wire will make the wire heat up so it could be dangerous. The wire will be used in the same way as a variable resistor. The wire needs to be straightened and taped to the heatproof mat. This will stop the wire changing shape. This would mean that the lengths would not be accurate, and so it would not be a fair test. Place one crocodile clip at one end of the piece of wire, and the other needs to be 10cm away from the first crocodile clip. Turn the power pack on so that the current begins to flow, after the current has been flowing for 5 seconds readings must be taken from the voltmeter and ammeter. Then immediately switch off the power pack and wait for the wire to cool. Move the 2nd crocodile clip another 10cm away from the first. This would mean that it is 20cm away. Then again take readings as before.
This needs to be repeated so that readings are obtained every 10cm till 10cm’s is reached. The results need to be recorded in a table so that they can be compared. The experiment needs to be repeated three times with a new piece of wire, which has the same properties and thickness. Repeating the experiment 3 times will give enough results so that an average can be obtained and charted.
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Repeat the experiment, but this time with the same metal but of a different thickness so the two can be compared. There will not be sufficient time for this variant to be carried out.
Results:
1st set of results
2nd set of Results
3rd Set of Results
Average set of Results
Conclusion and Evaluation:
From the experiments carried out I found out that when a current needs to flow through a longer piece of wire the resistance increases. My charts clearly show that the resistance increases steadily, creating a straight line when graphed. This is because a longer piece of wire has much more metal atoms than a shorter piece of wire, metal atoms get in the way of travelling electrons, this then increases the resistance and the amount of current is reduced. This is due to the electron colliding with the metal atoms.
I found out that the length of wire is directly proportional to the level of resistance. The experiment also enabled me to find out that even without the use of resistance wire, there is still a level of resistance in the circuit. There is still some resistance in the circuit because the copper leads used have some resistance within them. I found that the longer the resistance wire gets the higher the resistance gets.
From this I can confirm my prediction ‘I predict that increasing the length of the wire will increase the resistance’. My results were very accurate especially those from experiment 3. The resistance increased steadily as the length of wire increased. In experiment one and two I obtained a strange result, which does not conform to the lines of best fit when I reached over 80cm (experiment 1) and 90cm (experiment 2) of resistance wire. The resistance instead of increasing decreased. This could have been because the wire had become very hot at those points and therefore Ohms Law was broken hence the strange result. I conclude that increasing the length of the wire really affects its level of resistance and this conclusion is backed up by my results.
If I were to do the experiment again I would also different metals and thickness of wire, this would give me a better more varied experiment. It would also be better for my averages if I were to repeat the experiments more times to be able to find more accurate averages. If the experiment were to be repeated I would not allow the metal wire to heat up as much as it did. Heating obviously affected my results; they would be more accurate if the wire did not get so hot whilst doing the experiment.
