The variable I am choosing to alter is the length of wire because that is what the whole experiment is about.
I will improve what we did in the prelim by controlling all the variables i.e. I will keep the power supply at one amp, I will allow the wire to cool and I will use the same thickness of wire.
Step by Step Plan:
- Set up the equipment as shown in the diagram.
- Set the crocodile clip at a certain length, start at 10 cm.
- Turn on the power supply and set it at one amp, according to the ammeter.
- Turn off the power supply and leave the wire to cool, DO NOT TOUCH THE WIRE.
- Turn on the power supply and take the volt and amp readings. Turn off the power supply.
- Take a total of three readings at this length.
- Repeat steps 2-6 and remember to let the wire cool.
Fair Test:
To make a fair test, I will need to keep the following variables the same:
- Temperature of the wire
- Thickness of the wire
- Voltage from power supply
I will do this by using the same wire, allowing the wire to cool, and always setting the power supply at one amp.
It is important to keep these variables the same because they will affect my results.
Safe Test:
I will make this investigation safe by assembling the equipment properly and not touching the wire.
Prediction:
I predict that the resistance of the wire will increase as the wire length increases. I also think that as the length of wire doubles, the resistance will double. I think this because it is a sensible prediction.
Results:
Conclusion:
From this experiment, I have concluded that as the wire length increases, so does the resistance, this is proved by the results above. My graph also shows that if you double the wire length, you would double the resistance. There is a positive correlation between the resistance and length. I have also noticed that the resistance increases by approximately ½ and ohm each time the length increases by ten centimetres.
Evaluation:
I feel that the experiment was, on the whole, a fair test. I have noticed an anomalous reading. The resistance of 30cm is the same as the resistance for 20cm. I believe that this was because the wires were not connected properly. I think that my results are reliable because they were carefully recorded.