In this investigation I will aim to determine what affect a greater length of a wire in a circuit has on the resistance of the current.

Method:

• Gather up all needed apparatus, and set up the experiment as shown below.

• Measure length of first wire to be 10cm.
• Take 5 readings of voltage and current.
• Then repeat experiment, with increasing the length of wire by approximately 10 cm each time. Repeat until you get up to 100cm

Fair test: To keep this a fair test there are many variables I will not change, which are:

• The thickness of the wire
• The temperature
• The material and conductivity.

This is so I can be sure that I am only looking at the length of the wire and nothing else will be interfering or changing my results, as I would like them to be as accurate as possible.

Also:

• Make sure the length of wire is measured precisely
• Make sure that the wire is straight when we conduct the experiment. If it is not, short circuits may occur and bends and kinks in the wire may affect the resistance
• The reading that we take of the voltage should be done fairly promptly after the circuit is connected. This is because as soon as a current is put through the wire it will get hotter and we want to test it when heat is affecting it the least, i.e. at the beginning.

 

Safety: To keep this experiment safe the wires must not touch each other as it heats up (explanation in hypothesis) and the two connecting wires (crocodile clips) must also not touch as this can deliver an electric shock.

Problems: Whilst doing this experiment I discovered a major problem, every time I  connected the circuit up the wire would burn out. This was because the current was to high and the wire was not strong enough to hold it.

Preliminary Experiment: I had done an resistor experiment before which helped me find out what to do in this situation and how I could help solve this and I decided  to add in a ray box like I had done previously so that the current will be reduced.

The circuit I then setup looked like this

The results for this experiment were as follows.

For a 1 OHM resistor:                                        For a 2 OHM resistor:

        

For a 5 OHM resistor:                                        For a 100 OHM resistor:

Now I will draw the graphs for these 4 result tables.

The average of each result is worked out by dividing the highest voltage by the highest current.

After my preliminary work I found that my original circuit was working well for this experiment. I have no need to change my circuit before collecting my real results.

The results were as follows:

To work out the average I had two options either to use a calculator and add the resistances for each length and divide by 5 as there are five results. But to be more precise I thought  it would be better to do a graph for each length. Therefore next  are 10 graphs of different length wires.

Table Of Averages:

Now I have drawn up a graph to show these averages more clearer and so that I can conclude from them.

Proving My Hypothesis: After drawing up my graph I decided to see if my hypothesis was correct, to do this I have to look back at my graph and double a few lengths and see if there resistances double.

           

        X 1.91

       X 1.92
        

       X 2.06

          X 1.97

         X 1.97

Conclusion: From this I can conclude that approximately as the length of the wire was doubled the resistance was also doubled. This proves that my hypothesis was correct. The longer the wire was the larger the resistance was. Which means resistance of the wire is directly proportional to its length. This means that if the length was 40cm and resistance is 4ohms, then if the length is doubled to 80cm, the stance also doubles to 8ohms. My results support my prediction, they turned out the way I had expected them to. The graph shows a relatively straight line with all points very close to the line of best fit. They are roughly scattered but the line of best fit goes through the origin which also proves my hypothesis that as the length was doubled the resistance also doubled.

Evaluation: Overall I think that this experiment was a great success and that it worked well. The results I managed to collect were straight forward and I could see a pattern. My results were fairly accurate as I had altered the each length 5 times and worked out an average resistance for each length. To make it more accurate, I would try and make my measuring more precise, this can be done by using a wire which is more wide so that I can measure with more ease. I also know that whilst doing the experiment temperature of the wire increased , this was one of the factors that affected  the resistance and this would have affected my results as I have previously mentioned before. Therefore if I was to do the experiment again, I would make sure that the temperature does not vary. To do this I can keep the wire in a tub of water which will make the it remain at a constant temperature. Also keeping in mind that I would need to use an enamelled wire.

The graph is a straight line through the origin, which means R is directly proportional to L. This means that if the length is 40cm, and resistance is 4ohms, then if length is doubled to 80cm, resistance also doubles to 8ohms.

This is because of the scientific idea, stated in the planning that if you double length, you double the number of atoms in it, so doubling the

Mariam says:

number of electron 'jumps', which causes resistance: The results support my predictions well, the results turned out the way I had expected, and they match the predicted line well. I had predicted a straight line through the origin, which means R is directly proportional to L.

So, this effectively means that if the wire was trebled or quadrupled then the resistance would also treble or quadruples.