Key Variables:
The key variables that could alter my results are the equipment and atmospheric conditions. The temperature of the room and bulb will affect my final results, as temperature affects the resistance of a component. The hotter the component, the higher the resistance. Broken links (for example broken wires) will drastically change my results as the circuit will not even work.
Prediction:
My prediction for my experiment is that the higher the current is, the higher the voltage will be.
Ohms law states that:
V (voltage) = I (current) x R (resistance)
This means that the voltage and the current should be in proportion, when one is increased. Because of this, we can estimate what the graph should look like:
The graph shows that the voltage goes up in proportion to how much current there is. But I predict that the resistance of the bulb will not change throughout the experiment.
However as the filament is used for a longer period of time, the filament inside the bulb will get hotter.
How resistance is caused:
It is stated in the particle theory that as molecules and atoms are heated, they will begin to vibrate. Its vibration will cause the resistance to increase by scattering the electrons so that less electrons can get through.
So the hotter the filament gets, the higher the resistance. In theory, this should cause the light bulb to slowly stop increasing in current due to the resistance, as shown in the graph below.
The line will curve and level out as the temperature of the bulb stabilizes. This will have an effect on the voltage and current.
Preliminary Test:
Preliminary Test Analysis:
My preliminary test showed that my method has a flaw. The flaw is that the power pack will not produce more then 13V. So from the experiment results, I will now lower the voltage of my experiment to 1,2,3,4 and 5V to get more results to verify my prediction.
Primary Results:
Primary Results Analysis:
This experiment went very well, one piece of data does not fit in with the others (V=2 I=1). I think this must be an error on my part.
Results Graph 01:
Analysis:
As you can see, the graph which came out of my final results is just what I had predicted. Through my investigation I have proved that Ohms law (V=IxR) and the particle theory work and that they worked in the way that I predicted.
I have managed to prove my theory that the higher the voltage is in a circuit, the higher the current. I have also proved that temperature does affect the amount of resistance a component has. You can see this by looking at the graph above, the trend line is leveling out, this shows that the amount that current is going up is leveling off, this is because the resistance of the bulb shot up as the heat increased and leveled out as the temperature stabilized.
The trend line on my graph is not a good representation of the experimental data. The trend line is a 2nd order polynomial which may not represent reality. With a higher order polynomial (eg. 4th or 5th) we get a trend line which represents the data more accurately.
Results Graph 02:
This graph shows that the resistance is going up in a complex way. This could be because the temperature is not rising in a steady manner. This will affect the amount of resistance as we know that resistance is linked to temperature. This could be one explanation for having a complex shape curve. Another explanation for having points outside the trend line is that there could be experimental error (eg. Not reading the ammeter correctly).
Evaluation:
I think this experiment went very well as I got the results I had expected. I executed the experiment very well as I did a very fair test, I did everything I mentioned in my fair test section.
However, there was an anomaly in my data, I think this is down to human and equipment error as the equipment is not 100% accurate.
All in all this was a successful experiment as I got the results I needed, analyzed them and found out what I wanted to know.
