Investigate how the resistance of the wire changes as the length of the wire changes.

GCSE Science

Physics Coursework

Aim: To investigate how the resistance of the wire changes as the length of the wire changes

Background information: Some information that I must take into account is: That the resistance of a wire is

Directly proportional to its length
Inversely proportional to its cross section area

I can use Ohms law in my experiment to calculate the resistance.

Ohms Law = V =IR

Voltage = Current Resistance

This can be rearranged to give me the resistance to

R = VI

Resistance = Voltage Current

Prediction: I predict that if the length increases then the resistance will also increase in proportion to the length. I
think this because the longer the wire the more atoms and so the more likely the electrons are going to
collide with the atoms. So if the length is doubled the resistance should also double. This is because if
the length is doubled the number of atoms will also double resulting in twice the number of
collisions slowing the electrons down and increasing the resistance. My graph should show that the
length is proportional to the resistance.

Plan: There are some variables that would affect the resistance of the wire, they are

The temperature
The length
The thickness of the wire
The material of the wire

I will be keeping constant the temperature, the thickness, and the material. I will change the length of the wire and measure how the resistance increases or decreases as I change the length of the wire.

Apparatus:

Power supply
Ammeter
Voltmeter
Wire
Meter ruler
Crocodile clips

Method: I am going to test my prediction by doing an experiment and drawing up ...

This is a preview of the whole essay

Plan: There are some variables that would affect the resistance of the wire, they are

The temperature
The length
The thickness of the wire
The material of the wire

Apparatus:

Power supply
Ammeter
Voltmeter
Wire
Meter ruler
Crocodile clips

Method: I am going to test my prediction by doing an experiment and drawing up a graph. I conducted my experiment as follows I attached the voltmeter and ammeter to the power pack and then stuck a meter length of wire to a meter stick. On each length I attached crocodile clips to each end and took results. It may be clearer using the diagram below

I will make sure it is a fair test by repeating each length of wire 3 times so I can get average resistance. I will keep all the other variables the same and only change the length. Lastly I will keep the power pack on 2volts.

Risk assessment: There are a few different factors, which could make this experiment unsafe they are.

I must be careful with the power supply
I must turn the power supply of after each go otherwise the length of wire will heat up. This will firstly ruin the results and secondly I could get a burn
be sensible with crocodile clips meter ruler

Results:

I took these results safely by following the risk assessment.

Analysis:

From the graph on the previous page I can see that the resistance of the wire is proportional to the

Length of the wire. I know this because the Line of Best Fit is a straight line showing that if the length of the wire is increased then the resistance of the wire will also increase.

Conclusion: Conclusion
In my prediction I said that:
if the length increases than the resistance will also increase in proportion to the length.
From my graph I have shown that my prediction was correct, as the Line of Best Fit is a straight line proving that the resistance of the wire is proportional to the length of the wire.
The length of the wire affects the resistance of the wire because the number of atoms in the wire increases or decreases as the length of the wire increases or decreases in proportion.

The resistance of a wire depends on the number of collisions the electrons have with the atoms of the material, so if there is a larger number of atoms there will be a larger number of collisions, which will increase the resistance of the wire. If a length of a wire contains a certain number of atoms when that length is increased the number of atoms will also increase.

Evaluation: Overall I feel this has been a successful investigation and I have learnt a lot. My prediction was supported by the evidence, which I withdrew from the experiment. I had said as the length of the wire increases so will the resistance. I feel the experiment was accurate but could of bees improved by measuring the pieces of wire more accurately. I kept all the variables the same, kept the power pack on 2volts and repeating each test 3 times all these contributed to making it a fair test. It was hard to control the temperature.

If I could do the experiment again then I would do some things differently. I would of looked into and done some preliminary experiments about other variables. I would of used a higher voltage on the power packs and recoded my results clearer. I would use the same equipment. If I had more time I could of looked into more variables such as the area of the wire or different temperatures.