An Investigation of the Chemical Behaviour of a Light bulb Filament

As I can not find out the temperature of the filament very easily because there is a glass dome restricting my access.

The Key Variables:-

* The Resistance - I can control this variable, this is a major source for my results.

* The Current - again I can control this by increasing and decreasing the resistance.

* The Potential Difference - I'm not able to control this variable; the increasing and decreasing of the current and therefore the resistance as well mainly controls it.

* The Temperature - this again is a variable that I have no control over. I can't even find it out manually. There is a formula that I will use to find out the temperature. It is R = R (1 + 0.04 x )

A Fair Test:-

To ensure that I carry out a fair test I must:-

* Use the same equipment if I need to redo parts of the experiment later on. If I fail to do this, my results may change and become abnormal to the rest of my results.

* Make sure that the batteries are fully recharged. I f this task is failed to be completed it may reduce the amount of results that I am able to acquire because of the reduction of the amount of amps.

* I must repeat my results for 2 or maybe 3 times so I can find an average, therefore making my results more accurate.

My Predictions:-

My predictions are that when the potential difference increases the current also increases. This means the resistance increases and therefore the temperature increases as well.

Here is a table of all my results:-

I have found that when the current increases the potential difference increases, the resistance therefore has to increase and the temperature increases as well.

My current against potential difference graph shows that the resistance increases regularly, this shows that my readings were a reliable base to do this experiment.

To find out the temperature of the filament in the light bulb, I used a formula.

It is R = R ( 1 + x )

= 0.04

I will show how I obtain one result:-

3.54 = 1 x (1 + 0.04 x )

Now I will divide each side of the sum by 1.

3.54 = 1 + 0.04 x

I will now minus 1 from each side of the sum.

2.54 = 0.04 x

Now I will dive each side by 0.04

2.54 =

0.04

So

= 313.7 C

My temperature against resistance graph is a straight line. There is a strong positive correlation. This means as the resistance increases so does the temperature.

My results support my original hypothesis this shows that I carried out my experiment correctly and there were no major problems.

My Evaluation:-

The experiment that I carried out was obviously is not completely accurate as it is only a school experiment and the school do not have the equipment or the funds to carry out a 100% accurate experiment.

This version of the experiment produced a valid set of results which supported my original hypothesis. There were the odd few results which were irregular or out of the ordinary. There were not enough of these to warrant the experiment having to be redone.

Changes that I would make are to find a more accurate way of recording the temperature. I think this is a problem because to find out the temperature you are basing it solely on your results from the current, potential difference and resistance. So if any of these results are wrong your temperature could be very irregular, this could also be said about the resistance.

I think that the evidence that I have found supports a firm conclusion, I think this because my results support the text book results and there are no major irregularities.

Derek Pollard 5M Page 1