The aim of this investigation is to find out how the resistance of a wire changes when a variable is changed.

Wire Type:

The type of wire will affect the number of electrons travelling, this is because the amount of electrons depends on the atom type and the number of electrons in the outer shell of the atom. The more electrons travelling the lower the resistance, as more collisions between the electrons will occur, and the harder it is for them to flow through.

Wire Diameter:

If the wire's diameter increases the resistance will increase. This is due to the increased space in the wire. The atoms can move around more this means that the electrons can diffuse through more easily. Also more collisions will occur.

Temperature of Wire:

If the wire is heated up, the atoms in the wire will vibrate more vigorously. More collisions will occur and therefore it will be harder for the electrons to diffuse through. The increase of collisions will mean that the resistance will increase.

Wire Density:

If the wire has a higher density the resistance will be greater. This is due to the wire having more atoms in a smaller space, thus creating fewer gaps for the electrons to pass through. And creating more collisions between them.

I predict that when I increase the length of wire the resistance will increase, this is because the electrons have a greater distance to travel therefore it will take them longer to reach the other end of the wire. More collisions between the electrons will also occur because of the more time they will spend travelling, this will also slow them down. I also believe that the resistance will be directly proportional to the length of the wire.

The apparatus that I shall need is:

2 crocodile clips - to clip the connecting wires to the constantan wire

100cm constantan wire

1m ruler - to measure the length of the wire

Multimeter - to measure the ohm's

2 connecting wires - to connect the crocodile clips to the multimeter.

Method

* First I shall collect all my apparatus (listed above)

* Then I shall plug the connecting wires into the crocodile clips and the multimeter.

* The first crocodile clip shall be placed at 0cm.

* The second shall be placed at 10cm.

* I will then record the ohms (200 ohms to 1)

* I will then move the second clip to 20cm and record again.

* Record all the way up to 100cm

To keep the experiment accurate, I will attach the wire to the metre rule so that my measuring does not change. I will also attempt to keep all the other variables (apart from the length of the wire) the same. I will also re do the experiment twice to see if the results changed and if they did I shall get an average. If I get any anomalous results I shall not use them to get my average.

Test One

Length /cm

Resistance/ohm of wire leads, and crocodile clips

0

0

0

.2

20

.9

30

2.6

40

3.7

50

4.2

60

5.2

70

5.9

80

6.5

90

7.4

00

8.4

Test Two

Length /cm

Resistance/ohm of wire leads, and crocodile clips

0

0

0

.2

20

.9

30

2.6

40

3.7

50

4.2

60

5.2

70

5.9

80

6.5

90

7.4

00

8.4

Test Three

Length /cm

Resistance/ohm of wire leads, and crocodile clips

0

0

0

.2

20

.9

30

2.6

40

3.7

50

4.2

60

5.2

70

5.9

80

6.5

90

7.4

00

8.4

Average results

Length /cm

Resistance/ohm of wire leads, and crocodile clips

0

0

0

.2

20

.9

30

2.6

40

3.7

50

4.2

60

5.2

70

5.9

80

6.5

90

7.4

00

8.4

I had no anomalous results and my results did not change at all which is a good sign that my readings were accurate.

My results show that my prediction was correct. And that the resistance of the wire is proportional to the length. I have shown that when the length of a wire is increased the resistance increases. I believe that this is because the electrons have a greater distance to travel therefore it will take them longer to reach the other end of the wire. And more collisions must have occurred between the electrons, this would also have increased the resistance.

I believe that overall my results were quite accurate, this can be seen by the line of my graph, as it goes very straight and does not waver. The inaccuracies may be due to my measuring as you can not rely on just your eyes and a metre rule to measure accurately, but it was the best that I could achieve. The metre rule is only accurate to 1mm and the multimeter is only accurate to 0.01 ohm's.

Bibliography:

AQA GCSE Science book

www.Physicsdepo.com

Exercise book (teacher)

` bbc bitesize