Resistance of a Wire is Affected by Length

GCSE Science

How Resistance of a Wire is Affected by Length

Aim: To investigate how resistance changes over different lengths of wire

Equipment

Volt and ammeter
Ohm meter
Constantan wire 0.4

2 Meter ruler
2 crocodile clip
6 electrical connecting leads

Method

Set up apparatus as shown in diagram
Take readings every 10mm along the Constantan wire
Record readings

I think that the longer the wire the higher the resistance the science involved applies to my task because I will be able to make a better prediction for investigating this in the future.

I will control the variables, which will affect my task by keeping the wire the same diameter and the same wire. The Variables I cannot control is temperature by doing this experiment so I will do it at room temperature. I plan to take one reading every 100mm for the ohmmeter and the same for the volt and ammeter. With the volt and ammeter I will change the voltage flowing through the wire.

As I said earlier I thin the longer the wire higher the resistance. I think this because the longer the wire the more electrons will hit atoms there for increasing the resistance. Also there resistance will decrease if you made the wire shorter this is because there electrons would pass through without hitting more atoms. Temperature would affect my readings because the higher the temperature of the wire the faster the atoms would move and the harder the electrons would find it to pass through the wire. I chose Constantan wire from my preliminary work because it has the greatest range of resistance over 1 meter this would let me explain how resistance changes through length of a wire.

I would make it a fair test by keeping all the variables the same and trying not to let the wire have kinks in it when its on the 1 meter ruler. Also I would make the wire tight so it was the exact 1-meter. Also for my readings I would try to do it to the nearest half a millimeter.

Results for ohmmeter

I worked out the resistance by using this equation

VI=R

Resistance = Voltage  Current

The game me the resistances in ohms ()

...

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Results for ohmmeter

I worked out the resistance by using this equation

VI=R

Resistance = Voltage  Current

The game me the resistances in ohms ()

From my results you can see that there is positive correlation. When you increase length resistance increases this shows you it is proportional. My prediction was right as you increase length resistance will increase this is because there more atoms to block the path of the electrons I thin the density of Constantan wire is thicker then copper because the resistance was higher. If the temperature in the wire increased as well the resistance would increases also

Evaluation

My results were very accurate as my repeat reading with 4.5v were very close to my first reading with a ohmmeter there was only a few experimental errors, where points did not fit exactly on the straight line or curve. There was a few anomalous on to sets of my readings these could be due to any number of factors most probably temperature. Experimental errors could be due to flickering of the voltmeter and ammeter or slight kinks I the wire or human errors whilst trying to measure accurately.

Due to some experimental errors, reading voltmeters and ammeters and measuring the wires, my results or not that reliable

If I took the typical value of voltage 5 v and the voltmeter flickering was o.01v the error would be :

If my ammeter reading was 0.01a out of my worst (lowest) reading of 0.4a the error would be

If the length was not accurate due to kinks in the wire, or not measuring accurately, the error of my lowest length 60 cm would be:

If the crocodile clips (2) did not grip the wire I the right place so that the wire was the exact length , the error would be

This means the total estimated error of my results would be 3.56% my results there not very reliable as this error may be due to more kinks or more inaccurate readings. If I was to repeat the experiment again, to reduce the experimental error I would stretch the wire out completely , free of kinks and I would use sellotape.

To extend my investigation I would carry out a experiment on how temperature affects the resistance eof a wire I would heat the wire to different temperatures and take readings.