When you have recorded this result you need to change the knob at the top to 4 volts. After you have taken each recording you move the knob up one each time.
Repeat this experiment 3 times and you should have 3 sets of results, for a fair test and for finding the average. When you have done this experiment change the resistor over to a 10.5 Ω resistor. Then record all of the measurements again the same way you did the 3.9-ohm resistor.
Diagram
The layout of how you set out the experiment should look like this:
Safety
There are not any serious safety precautions to watch out for but common sense is needed to know things like keeping water away from electricity and not playing with any electrical equipment or the mains. Make sure you use the right resistors and voltage so that you don’t burn and melt the resistors.
Fair Test
For a fair test the only variables that I will change are the Voltage, the 12-volt lamp and the resistors, everything else will stay the same for example the amount of wires and the amount of time the experiment is left on to avoid unnecessarily heating up the lamp and melting the wires.
Prediction
I predict that the current will be slightly larger in the circuit with the lamp because the lamp will have less resistance than the resistor as the resistor is designed to resist the current. The current will obviously increase as the voltage increases in both of the circuits. From preliminary work I know that Voltage (V) equals (=) Current (I) times (*) by Resistance(R). This is Ohms law and can be put in a triangle like this.
V
I R (V=I*R)
Results 1
Attempt 1
Attempt 2
Attempt 3
Average
Results 2
Attempt 1
Attempt 2
Attempt 3
Average
Readings
I only took my readings up to 10 volts because when we tried 12 volts the resistors and wires began to melt and burn. We decided to only go up to 10 volts because we didn’t want to waste resources for everyone else.
Fair Test and Variables
In the experiments that we do we are going to keep the resistance the same except when changing from 10.5 ohms to 3.9 ohms in the three experiments. Voltage and Current are both dependant on resistance so if the resistance was different we would have inaccurate results. (V=I*R). I would also keep the resistor the same one for all 3 experiments in its category. The same 3.9-ohm resistor 3 times and the same 10.5-ohm resistor 3 times
Conclusion
Looking at my results I can see a fairly clear pattern. It looks like some of the numbers in the A column of the average results are related to the V column next to it. In the A column there is a decimal e.g. 0.25. In most of the results, it has been multiplied by 10 and either rounded off or another number put on the end.
Evaluation
I think that my experiment went fairly well and my results were fairly accurate. I could have cooled the lamp down in between experiments to make it more of a fair test. I thought my method was good even though it took some preliminary work to help me out. I didn’t have any major anomalous results and I think that if I do this experiment I will calculate the relationship between resistance and temperature by measuring the temperature of the lamp.
