Investigating how the length of wire effects the resistance

Plan: We will measure out some pieces of wire to 20cm, 40cm, 60cm, 80cm and 100cm. We'll then attach a crocodile clip to each end and connect it up to the circuit. In the circuit there is an ammeter connected in series to the wire and a voltmeter connected in parallel. The power supply is a power pack producing approximately 15 volts. Also connected up to the circuit will be a rheostat to keep the current at the same level.

Circuit Diagram:

We will then, using the results from the volt an amp meters, work out the resistance using the following formula:

Resistance = volts

Current

Each length will be tested twice and an average will be worked out to make the results more accurate.

I will make sure that the experiment is a fair test by controlling variables which may effect the results such as heat. I will keep the current at the same level by using the rheostat.

Results:

length of

wire

amps ohms

volts 1

volts 2

volts av.

resistance

20cm

0.5

0.88

0.94

.88

40cm

0.5

.7

.71

.71

3.42

60cm

0.5

2.35

2.42

2.39

4.78

80cm

0.5

3.1

3.13

3.12

6.24

00cm

0.5

4.08

4

4.04

8.08

Conclusion: The way I got my results was fair, I controlled temperature, voltage, length of wire, and then worked out the resistance of the circuit. My results were all fairly accurate, I didn't get many anomalous results because by taking more than one result then calculating the average increases the reliability. By using a rheostat I got more accurate results. By checking my results with formulas from text books it proves my results are accurate enough to support a firm conclusion that resistance is proportional to the length of the wire. To improve the experiment I would use different thickness´ of wire and different materials of wire. But overall my experiment succeeded the way it was expected to.