Find out how different lengths of wire can change the resistance.

0.60

.00

5.00

Manganin

28

00

0.09

0.12

0.19

0.50

0.65

.50

6.30

Fair Test:

To make this experiment a fair test we had the same person recording the amount of volts each time, the same person recording the amount of amps each time and the same person changing the length of the wire each time. The same wire will be used each time and the same rheostat will be as well so that the resistance will be worked out for the same wire. The length of the wire will be changed each time so that the resistance for different lengths can be worked out so that we have a range of results. Each length will be tested three times but at different positions in the rheostat. The amount of volts and amps will be recorded after every attempt so that a resistance can be calculated.

Prediction:

I predict that the longer the wire is the more resistance there is going to be. This is because the longer the wire the further the electrons have to travel causing them to lose energy therefore slowing down the current. According to my preliminary results at 50cm the resistance is 3.15 and at 100cm the resistance is 6.30 which means as the length doubles then so does the resistance. At 100cm the resistance will be the highest and at 0cm the resistance will be the lowest.

Apparatus:

* Voltmeter

* Ammeter

* 100cm long wire

* Rheostat

* Meter rule

* Power supply

* Connecting wires

* Crocodile clips

Method:

When first starting this experiment you would have to collect all of the apparatus that is required. Once you have collected all of the apparatus, then you need to set the circuit up as shown above. Then you have to measure the length of the wire and choose the desired length. Once you have started the experiment you have to, measure the amount of volts and then the amount of amps. Then you have to calculate the resistance by using the equation, R=V/I. Once you have worked the resistance out, you then have to change the position in the rheostat. Then you repeat it in two different positions and once you have done that change the length of the wire and repeat the whole experiment to get a range of results.

Length of Wire (cm)

Volts (V)

Amps (A)

Resistance (?)

Average Resistance (?)

Wire Type (SWG)

00

0.20

0.30

0.55

0.10

0.20

0.30

2.00

.50

.80

.77

Constantin (0.66)

90

0.10

0.30

0.50

0.10

0.20

0.30

.00

.50

.70

.40

Constantin (0.66)

80

0.10

0.30

0.40

0.10

0.20

0.30

.00

.50

.30

.30

Constantin (0.66)

70

0.10

0.30

0.40

0.10

0.20

0.30

.00

.50

.30

.30

Constantin (0.66)

60

0.05

0.10

0.40

0.10

0.20

0.30

0.50

0.50

.30

0.80

Constantin (0.66)

50

0.02

0.09

0.14

0.10

0.20

0.30

0.20

0.45

0.47

0.37

Constantin (0.66)

40

0.02

0.05

0.10

0.10

0.20

0.30

0.20

0.25

0.33

0.26

Constantin (0.66)

30

0.01

0.03

0.09

0.10

0.20

0.30

0.10

0.15

0.30

0.18

Constantin (0.66)

20

0.01

0.02

0.04

0.10

0.20

0.30

0.10

0.10

0.13

0.11

Constantin (0.66)

0

0.01

0.02

0.03

0.10

0.20

0.30

0.10

0.10

0.10

0.10

Constantin (0.66)

0

0.01

0.01

0.02

0.10

0.20

0.30

0.10

0.05

0.07

0.07

Constantin (0.66)

Analysis:

The graph shows that as the length of the wire gets shorter, the less resistance there is. This is because of the electrons flowing around the circuit don't have as far to travel along the wire and don't lose a lot of energy, where as at 100cm the electrons have to travel the furthest and lose energy and slows down the circuit. There were no major anomalies within the test but they have been identified on the graph and the majority of the results matched with the best fit line. This might have been because of the ammeter and voltmeter went up in fives and it was hard to get a correct reading. For 70cm the resistance should have been around 1.1? but it was 1.4?. The resistance gradually rose from 0cm to 50cm and then it rapidly rose from 60cm to 100cm. From this graph we can tell that if the resistance was to be 1.0? the distance would have to be around 64cm. Also if the distance was 55cm the resistance should be around 0.45?. My prediction was correct because I said that when the distance decreases so would the resistance.

Evaluation:

The repeats in this experiment showed a consistency and all of the repeats showed that roughly the same resistance was being produced each time. The results showed that the resistance gradually rose from 0cm to 50cm and then it rapidly rose from 60cm to 100cm.The results fell reasonably well into a best fit line and they are clear and easy to understand. There were no major anomalies within the experiment but there were a few minor anomalies and this may have been because of the voltmeter and ammeter went up in fives and it was quite hard to get an accurate reading. I think that our group had a good method because our results showed what we were trying to find out which was to see if the change in length of a wire affects the amount of resistance. To get rid of any anomalies within the experiment we could have used an ammeter that went up in ones or twos as well as the voltmeter, instead of going up in fives. We could have also tested to see if the thickness of a wire affected the amount of resistance in the circuit. I think that the procedure that we had used was adequate to test and that it was reasonably reliable because we had the same person doing the measuring of the wire, the same person measuring the volts and the same person measuring the amps. In my prediction I had said that as the length of the wire decreases the amount of resistance would also decrease because the electrons wouldn't lose there energy because they only have a little way to go where as if they had to travel further they would lose energy and slow down. In future experiments we could increase the range of results as well as having more intermediate results.

Ricky Pitt 1180

Edenham High School 14320

Mrs Dibbs