Resistance is the opposition to current flow. Variables I need to control are:
- Temperature of wire
- Thickness of constantan wire
I will control them by using the same wire for all experiments and I will turn off the power supply when I have taken each set of results to ensure the heat of the wire does not affect my results in any way, making it a fair test.
Plan
Here is the apparatus I will use:
- 1m-constantan wire
- Ammeter
- Voltmeter
- Crocodile clips
- Meter rule
- Connecting leads
- Power supply (0-3v)
Circuit diagram
Wire length will be variable here and will be able to reach 0-100cm. There will be a range of 0-100cm fully utilized while conducting this experiment.
The experiment will be conducted three times.
Preliminary results
I am going to carry out an investigation to see the relationship of a wire and its resistance. I am going to do this by changing the length of the constantan wire and measuring the resistance using ohm’s law. I will change the length of the constantan wire each time. I will change the length by clamping the wire with a crocodile clip at the length I have chosen. I will keep the voltage running through the wire from the power supply the same in each experiment and use the same wire in each experiment to ensure that the thickness of the wire is the same. I will measure the voltage and the current. I will be measuring them by using analog meters, voltmeter and an ammeter. I will make my results accurate by not changing my method in ant way. To make my results reliable I will repeat them three times. To make my experiment a fair test I will control all variables (e.g. thickness, temperature of wire etc).
Table of results
Calculations
I will now calculate the resistance for each length using ohms law: Resistance = V/I (assuming that the wire obeys ohm’s law)
Value of resistance = V/ I = R: -
Final table of results
My table shows that the longer the wire the higher the resistance is. I will now transfer my results into a graph.
Analysis
I have found out that the resistance increased as the length increased.
Evaluation
The measurements I have compiled are reliable because I have carried out three sets of results and they are all approximately the same, which indicates that the results are reliable.
There was an anomalous result identified that was not on my line of best fit. This could have been due to the wires heat because the wire may not have cooled down fully because the interval between experiments was not long enough. Also it could have been caused by inaccurate measurements. May have been a parallax error when using meter.
