"resistance of different thicknesses of wire"

Other predictions

2. As the cross-section of the wire decreases the voltage will raise because the battery needs more power to push the electrons through the thinner wire. This is cause by the narrow wire have less free particles to carry the electrons through.

3. I predict that if I increase the temperature the resistance will increase and current will reduce because it makes it harder for electrons to flow, but if I decease the temperature the resistance will get lower and the current will increase because the cooler the wire the easier it is for electrons to move through the wire.

4. I think that if you increase the length of wire the resistance will increase because there are more particles for the electrons to move through, and the current will decrease because the longer the wire more energy is used to heat the wire and move the electrons.

5. I predict that that if you increase the power by adding more batteries or cells the easier it will be for the electrons to move through the circuit and the wire because of the higher voltage and push to move the electron round the circuit.

Fair Test

I will keep the test fair by:

. Using the same battery, copper wires, ammeter and voltmeter because some of these can vary in resistance and the power they produce.

2. Using the same make of nickel chrome wire.

3. Make sure that the wires are connected in the circuit exactly 30cm.

4. Make sure results are recorded accurately from the voltmeter and ammeter.

5. Redo the tests to confirm and compare the results.

Preliminary Test

I think that the wire with the widest cross section will have the lowest resistance because there is more room for the electrons to move easier through the wire. This will be done by using a functioning circuit with the necessary components to measure the current and voltage to work out the resistance, and placing the required width and length (30cm) of wire in the circuit to complete it and record the results. The most important part of the test is to make sure the wire is the same length each time and stays at the same temperature because these variables can have an affect on the resistance of the wire.

Observation

Apparatus

For Circuit: battery, copper wires, ammeter, voltmeter and crocodile clips

Others: Nickel chrome wire, meter rule, wire trimmers and calculator

Method

Be careful when handling wire because they can get very hot

Set up the apparatus as below:

Make sure it's all connected properly, especially the ammeter and the voltmeter because you can easily put the wires in the wrong positive and negative ports. If this happens a -0.00 will appear on the ammeter, to change this you must change the wires round.

Get a set of wires that have different cross-sectional areas (in our case we had 0.27cm to 0.71cm wire width) and place it in the circuit connecting it in carefully between the two crocodile clips exactly the length that you want to test (in our test 30cm). If they are not exactly the width you want apart it will be an unfair test because they shorter the distance the easier it will be for the electrons to get to the other end because less energy is used to heat the wire and move the electrons. Once in its place record the current and the voltage from the ammeter and voltmeter to 2 decimal places and place in a chart, and from this you can work out the resistance by using R=V rule.

I

Once the results are recorded take the wire out and repeat the test again with the different piece of wire of the same length and record the results again as many times as possible in the time available but we will only have time to do each test twice. Once the first wire is tested get a different thickness of wire and test it in the same way as the first one by placing it in between the crocodile clips exactly the decided distance apart and record the results and repeat at least twice.

You should do the test for as many different cross-sections of wire as possible to give you a better idea of how the thickness of the wire affects the current running through it, and we used the test to test all the different cross-sections that we had available.

Results- also see graphs

Wire Width (cm) Voltage (V) Current (I) Resistance( ) Average Resistance ( )

0.27 1.06 0.19 5.57

0.27 1.02 0.18 5.66 5.62

0.32 1.01 0.23 4.39

0.32 0.97 0.21 4.61 4.5

0.38 0.68 0.24 2.83

0.38 0.85 0.28 3.04 2.94

0.45 0.92 0.45 2.04

0.45 0.84 0.40 2.10 2.07

0.56 0.60 0.44 1.36

0.56 0.75 0.55 1.36 1.36

0.71 0.68 0.64 1.06

0.71 0.80 0.88 0.91 0.99

Analysis

From my results I have found out that my predictions were correct. The greater the cross-sectional are of the wire the smaller the resistance because there is more room for the electrons to move through.

Also as the wire width increased the voltage tended to go down and the current went up but some of these vary due to some inaccuracies. The average resistance shows that the test was relatively fair apart from the 0.32 wire width because the resistance as too high for it's thickness to be correct, but the main problem with the experiment was the varying voltage and current differences for a couple of wires. Some were very close together for example 0.27 test but some were way apart for example the 0.38 wire width tests. This could have been caused by the crocodile clips carrying the current to the wire were not 30cm apart or the temperature was different. Even the ones that are close together have some inaccuracies because the wire is exactly the same and should be 30cm apart so the results should be identical for each but the results show that but there are some differences in the voltage and current that should not really be there. This proves that one of my other predictions is correct that the longer the wire, the higher resistance so there is a lower current and higher voltage.

The graphs that I drew also show that the wider the wire the lower the resistance, this supports my original prediction because there is a quite a smooth curve and are very accurate results apart from the 0.32 wire width again which was far to high a resistance to be correct.

Evaluation

The test that we did was accurate enough to get a reasonable set of results and to make a decent conclusion because the results varied a little bit but not too much.

Wire Width Position

0.71 1st

0.56 2nd

0.45 3rd

0.38 4th

0.32 5th

0.27 6th

As I predicted in order of largest wire first because the larger since there is more room for them to move through the wire the easier for the electrons to move through it.

The main variable that affected our results was probably the length in between the crocodile clips that affected the length the current had to travel along the wire. This variable stood out a couple of times during the test especially the 0.32 test because the resistance results where too high for its wire width because it did not fit into the curve on the graph and 0.38 test the gap of the final resistance results were too large to give a very accurate average result, although there are some small inaccuracy's they are not strong enough not to give a good conclusion of how the width of a wire affects its resistance.

Despite some of the results varying a bit, but the procedure we used was appropriate for what we wanted to do though. If I had to change something though I would change the way we did the measuring of the wire and placing it in the circuit, so we made sure they were 30 cm apart because that is what gave us the iffy results because the length of the wire changes the resistance of the wire.

For further work relevant to this experiment we could find out how other variables such as the length and temperature of the wire affect the resistance of the wire. This would help us understand better how resistance varies under different conditions