Science Investigation (Physics) -- Heating Effect of a Electrical Current

Planning:

I will investigate the relationship between the current pass through water and rise the temperature of the water. I will control variables including: the mass of water in the beaker, the voltage, whether the beaker is insulated or not, the time duration used to obtain the results. I will change the values of the resistor. The initial value of the resistor is 3 Ω, I will start off from 3 Ω and the final value I will take is 10 Ω. I will do increments of 1 Ω, therefore I will be able to obtain 7 results and it will be sufficient for me to prove my prediction. Instead of using practical apparatus, I used a computer simulation to investigate the relationship between electrical current and the raise in temperature. The only tool we need for this experiment is that computer simulation.

Fair Test:

Variables that will affect the current, which affects the temperature: voltage, resistance, mass of water, time

I will keep voltage, mass of water and time the same so then I will only be varying one factor that affects current/temperature.

Values I will keep constant: Voltage – 6V, Mass of Water – 30g, Time – 15 minutes.

Variables I will change: Resistance – from 3 ohms to 10 ohms – range of results.

Why voltage should be kept constant: This is because as voltage increases, current also increases. The equation for voltage is V = iR, so if R is kept constant, V increases will cause i (current) increase.

Pretest:

The 3 resistance didn’t produce a temperature that is 100˚C and above so it wouldn’t limit my results.

Obtaining:

The trend of my graph is quite easy to see, firstly the temperature rises dramatically to 74.2˚C and as I increased the resistance, the increments of temperature steadily decreases compared to the initial temperature (0˚C) – trial 1 increased 74.2˚C, trial 2 increased 65.2˚C, trial 3 increased 60.2, trial 4 increased 57, etc.

However, looking at the graph, it seems that the first 4 points creates a line that is steeper in gradient compared to the one the later 4 points can produce (a relatively flat one). This might also be caused by uncertainty.  

The graph does support my original prediction.  

Evaluation:

Overall, I think that this investigation went quite well. My range of 8 resistance was adequate to plot a graph which supports my prediction. However, I would like to take more readings between 5Ω - 8Ω because it started to not follow the line of best fit.

As I stated in my analysis, there were uncertainty in my obtaining. Since I used a computer simulation to do this investigation, there are very few errors I am able to identify and no improvements.

I could investigate on other factors:

• Relationship between temperature and mass of water
• Relationship between temperature and voltage

Temperature and mass of water: I might do this next time because I would then be able to gain more understanding on the affects of water molecules and heat.

Temperature and voltage: So then I would be able to use the formula I used to prove my prediction in this investigation and reinforce my prediction by investigating a factor that is a nominator in that formula.