In closing we can say that this experiment was an overall success! We gained a better understanding of manipulating the formula Q=mcâT to find specific heat capacities of metals. We established an understanding that in fact now we can calculate the specific heat capacity of an unknown substance and then, we can make and educated guess on what the make-up of that substance may be. Having an understanding of a few physics laws were required for this lab and proved to be vital in the proper execution of this lab.
Evaluation As the percent error expresses the experiment overall could have been more accurate. Many simple adjustments could be made to result in better quantitative data being recorded. One source of error could be the error of validity of the scale. The triple beam balance is a good tool but if you desire more accurate results the electronic scale with zeroing would be a better alternative. Another source of error was the heat lost from the cup and the air flow coming into the cup.
Heat from the cup would have dispersed into the open air since the top was open. A simple way of solving this problem would just be to put a lid over the top of the cup to prevent major heat loss. Some still would be loss but the ratio would be much smaller. If the ratio increases, this means that there will be a stronger magnetic field in the second coil. This means that there will be a greater current induced in the iron core. This so called ‘eddy current’ will oppose the current in the coil.
This means that if the magnetic field of the coil is positive at a point (north pole), the magnetic field in the iron core will be negative at that point (south pole). Because the current is alternating current the poles will change direction the whole time. This will lead into the shaking of the whole transformer (change of magnetic energy into kinetic energy). This shaking is the energy ‘lost’ by the transformer.
When the difference in coils will get bigger, the magnetic field formed by the coils and the core will get bigger. This means that the attraction between the poles will be bigger as well, resulting in more shaking thus a greater ‘loss’ of kinetic energy. Hence there will be a decrease in efficiency, as the ratio of the coils will increase. Variables: – Independent variables This is the ratio of the number of coils. This will be measured by comparing the number of turns of the first coil with the number of turns of the second coil. The number of turns on the first coil will be constant, whereas the number of turns on the second coil will increase with 300 turns per reading. The first coil has 300 turns.
This means that the ratio will always be – Dependent variables The dependent variable is the power output from the second coil. This will be found by using an Ampere meter and a voltmeter. Using the equation P=VI will give the power output and this can be compared with the power output (power input – power output / power input 100%). – Controlled variables There are several controlled variables. 1. The first coil. This coil will not be changed during the experiment and has 300 turns.
2. The power input The power input will remain constant throughout the whole experiment. This is measured during the whole experiment, each time before getting a reading of the power output. 3. The temperature of the room The temperature will remain constant by using the air conditioning and it will be measured each time before performing the experiment. This has to stay constant, because if not it will increase/decrease the resistance of the coils/iron core. There will be 10 reading taken of dependent variable. This will be repeated 3 times, which will give a total of 30 readings. The number of turns in the second coil will start at 600 turns, increasing up to 3300 turns. The change of size will be 300 turns per new reading.