I also think that as more power is put into the circuit and more power goes to the heating element, the more thermal energy will be transferred into the water. As the heating element is emitting more thermal energy into the water, it will heat up faster.
Once I have calculated the power using P=IV, I can then work out the amount of energy transferred from the heating element to the water. I can do this by using the formula;
E=PxT,
Where E = Energy transferred, P= power and T= time taken.
I know that as the voltage increases, the power will increase. Talk about Ohm’s law, resistance and the fact that I ∝ V. Here is an example using substitute numbers.
P=IV
Power =3x2
Power=6 Watts
But if I increase the voltage and therefore the current;
P=IV
Power=4x5
Power=20 Watts
Because the amount of power that I generated from this formula will increase, the energy transferred when using the larger amount of power will also increase; I need to sort out this bit, it doesn’t make sense!!!!
E=PxT
Energy transferred=6x4
Energy transferred=24 Joules
With an increased value for power;
E=PxT
Energy transferred=15x4
Energy transferred=60 Joules
Because there is more energy being transferred into the water, it should heat up faster.
Plan
In my experiment, I plan to investigate the power in a circuit and whether it is proportional to the time taken to heat the water. The factor from the list on page 1 that I will change is the power. As I explained in my prediction, I shall do this by altering the voltage. The current will also change, but only because it is proportional to the voltage. All the other factors that could affect my experiment, I will keep the same. I will use an Ammeter to measure the current and a voltmeter to measure the voltage in the circuit. By measuring these, I can use the values in any relevant formulas.
I will measure the temperature of the water at the start and at the end of the experiment. I will also weigh the water and the beaker it is in on a top-pan balance both before and after heating it up. This means that I will be able to tell if any water has been lost through condensation or steam. To help reduce the loss of water by steam, I shall fit the beaker with a lid made out of polystyrene. I hope that this will stop the majority of steam escaping and cause it to condense on the lid of the beaker and drop back into the water. To reduce the loss of heat throughout the glass walls of the beaker, I will use the smallest beaker possible. This will also reduce the surface area of the water, providing a smaller area from which to loose heat. To reduce heat lost by conduction and convection, I will wrap the beaker in an insulation material, keeping it the same for each result. I will probably use bubble wrap as my insulation. To prevent any possible heat loss by radiation, I will also wrap the beaker in tin foil. Because the foil has a shiny surface, it will reflect the heat waves back into the water. So this will not only stop the water loosing heat, it will cause it to be re-heated by its lost heat. YUK! All these precautions will not directly help the water heat up faster, but they will stop it loosing heat it has already gained.
I will always use the same container, a small glass beaker and the same insulation as explained above. I will also make sure that using a measuring cylinder to measure out the water uses the same amount of water each time. Instead of measuring how much time it takes the water to heat to a certain temperature, I will measure how long it take s the water temperature to rise 20°C. this will also illiminate (how do you spell this word? The spell checker doesn’t like it!) any irregularities in the start temperature of the water. In my preliminary wok, I found that it took a long time to heat 100ml of water to 60°C. Because of this, I need to use as little water as possible because it will heat faster, and aim to get the water to only rise 20°C. Both of these factors will ensure that I don’t have to wait a long time to heat the water when using a very low voltage.
I aim to get … readings at each of the … voltages, ranging from …V to …V. fill in blue sections, talk to Amy about what to fill them in with.
I am going to heat the water using an electrical heating element. The heating element looks like this:
In a circuit, the heating element’s symbol is: draw symbol. The circuit I plan to set up, containing the heating element, to heat the water looks like this:
Draw circuit diagram
