What is resistance?

Fair Test

To make this experiment fair I will have to make sure that:

• The length of wire is correct
• The material of the wire is the same throughout
• The starting temperature of the wire is the same
• The width of the wire is the same throughout

Equipment

• Variable resistor
• Wire
• Voltmeter
• Ammeter
• Power supply
• Ruler

Method

1. Set up apparatus as shown in diagram.

2. Adjust the variable resistor.

3. The positive crocodile clip is put on 0 and the negative is moved up and down the wire stopping at 10cm first and then 20cm, 30cm, 40cm and 50cm.  Start reading at 2 for supply voltage.

4. Record ammeter and voltmeter to work out resistance.

5. Change supply voltage to 3.

6. Record the reading from the voltmeter and ammeter.

7. Change voltage to 4, 5, 6, 8, 10, and 12.

8. Repeat 3 times and work out average.

9. Change wire length to 20cm and measure, start at 2V.

10. Record ammeter and voltmeter readings in table.

11. Change supply voltage to 3.

12. Record ammeter and voltmeter readings.

13. Change voltage to 4, 5, 6, 8, 10, 12

14. Repeat three times and work out the average

15. Do the same experiment for 30cm, 40cm and 50 cm.

OBTAINING RESULTS

Results

10 cm

20 cm

30 cm

40 cm

50 cm

ANALYSING EVIDENCE

As I predicted, the increase in length of wire resulted in an increase in resistance.

The wire shows a straight line therefore the wire is directly proportional to the resistance.

To find the resistance from the graphs I found the gradient.  The resistance clearly increased as the length of the wire did.  This supports my original prediction.

        

        EVALUATION

Overall I think my results are quite accurate as you can tell by the graphs.  

The experiment was repeated three times so the results would be more accurate.  To ensure that my results were more accurate again I could have carried out the experiment several more times, but this would have been very time consuming.

In my experiment there doesn’t appear to be any results that are inaccurate.  To improve on my experiment I could repeat the experiment again to enable more accurate results.

My results support my prediction.  You can see by my graph that the resistance is directly proportional to the length of the wire.

We could have checked the equipment before we started the experiment to ensure that it was not faulty.

The digital ammeter gave results to two decimal places; this made the results quite accurate, as there was little chance of recording the results wrong.  To make the results even more accurate and reliable we could have used an ammeter that gave results to 3 decimal places or more.