In this week’s class we conducted a series of experiments concerning photovoltaic cells. We actually had two parts in our experimentation; Part 1 was an experiment to determine whether the distance of the source of light from the photovoltaic cell affects the power the cell produces. The second part was an experiment tp determine whether the power output of the cell depended on the kind of light emitted by the source, which we moderated through the use of some filters.

Distance Difference:

Hypothesis:

Our hypothesis for this series of experiments was the the larger the distance of the source from the cell, the less power it would produce due to the fact that it would receive less energy(since light would be emitted in more directions.

Procedure:

We set up the cell in the desired distance from the light source(the distances used in this series were 0,4,8 and 12 inches away from the light source.)The cell was connected to our computer and gave us readings of the power it produced. Then, after the data was put in excel we determined the average of each distance-reading.

Data:

From the above table we produced another table for the average distances against Voltage, which we used to make a graph of the readings we received.

Data Analysis:

As we can see from the above data, our hypothesis was completely verified since increasing the distance from the source decreased the power output. Furthermore, the graph produced shows a negative exponential(since the graph is not linear) relationship between the distance and the voltage output. If i had to guess i would say that the function would be of the form of y=1/x or y=1/x^2. However, more data is needed to determine the exact relationship between the two variables.

Conclusion:

As we saw from the above information our hypothesis was verified and the power output of the cell decreases as its distance from the light source increases. All in all, even though we calculated some average values in our experiments, i do not think that they hurt the accuracy of our results significantly which makes the experiment a success as far as i am concerned. An area that we could have improved would have been the holding of the cell(which we did manually by hand) so as to negate the effects of our unsteady hands. As i said though, the effect of this error is insignificant and does not interfere with our results.

Filter Difference:

Hypothesis:

In this series of experiments our hypothesis was that the different filters applied on the light source would change the power output of the cell. This is due to the fact that each filter absorbs waves of its own frequency, which means the light that escapes the filter will have slightly different energy levels depending on the color of the filter.

Procedure:

In this experiment we placed the cell right in front of the light source(we wanted to keep the distance the same and the zero distance was the easiest to implement). Then we put a filter between the light source and our cell. We did the same process for four different filters(pink, yellow, blue, orange).

Data:

From the above table we produced another table of averages for power output with which we plotted a graph.

Data Analysis:

From the above information we can see that the filter color does change the power output of the cell, which is in concordance with our hypothesis. We can see that each filter color produces a different frequency for the cell to absorb, thus changing its energy output accordingly.

Conclusion:

The above information indicates that our hypothesis was valid, since filter colors change the produced energy of the cell according to the frequency they absorb. As with the previous series of experiments, the average values we produced did not hamper our results, which again shows the validity of the data obtained. All in all, i cannot think of any ways to improve our accuracy other than the use of more filters to determine the exact relationship of the filter colors and the power output.

This week we were given a presentation by an engineer extraodinaire called Tom Vales, who showed us three relatively unknown devices; the Stirling Engine, the Peltier Device and the Mendocino Motor.

Stirling Engine:

A stirling engine is a heat engine operating on the continuous compression and expansion of a gas. The stirling engine is made up of a chamber that has a hot side heated by an external source and a cold side. Inside the chamber we can find the gas of choice(usually air, helium or hydrogen) and the displacer which is connected to a flywheel. Outside the chamber there is a piston andthe aforementioned flywheel that are also connected to each other. The way the stirling engine works is the following; Initially the displacer is at the bottom of the chamber. As heat is applied in the chamber, the kinetic energy of the molecules of the gas increases which means that in a fixed volume the pressure rises. The increase in pressure then moves the piston upwards. As the piston moves up the flywheel turns. The turning of the flywheel pushes the displacer downwards, thus moving the gas from the hot side to the cold side. As the gas reaches the cold side of the chamber the kinetic energy decreases and in extent the pressure in the chamber. This makes the piston move down, which makes the flywheel turn again(on the opposite direction this time). The flywheel again moves the displacer, but this time it moves it upwards, which transfers the gas to the hot part of the chamber and thus starting the circle all over again.The stirling engine is extremely quit and efficient which makes it very promising, especially if you consider the fact that they can be powered by any heat source. Despite this fact though, Stirling engines have not been used widely due to the cost in building one.(the sides of the chamber have to withstand heat and also the larger the chamber the more effective it is). In addition to this, it takes a while for the engine to start running or for it change its motion in any way, thus making the Stirling engine a good option in some occasions but not an alternative to internal combustion engines(for now at least).For the further information you can look at http://auto.howstuffworks.com/stirling-engine.htm and Ms. Kiki’s explanation of it:

Peltier Device:

The peltier device is a device that is based on the Peltier effect, which was discovered (surprisingly) by someone called Peltier. The Peltier effect of thermoelectric effect is the concept that when a current is applied on two dissimilar metals, one of them gets hot and the other gets cold. Also, the reverse version of this concept exists, which states that when a hot metal and another cold metal come into contact they create a current(this is called the Seebeck  effect found by someone called Seebeck). The effect of the peltier cooling is used in fridges where the cool side is put in the fridge to cool things inside it. A more detailed explanation of the effect can be found here: http://www.activecool.com/technotes/thermoelectric.html. Also, it has been noted that the Seebeck effect could be used for production of electrical energy, but that might be a little too impractical currently. One reason is that for the effect to generate a good amount of electricity the temperature gradient needs to be very big, which is usually hard to accomplish or too expensive. Of course the possibility of using earth’s resources could be a solution to this problem, if, for instance, we used the hot volcanoes and icy waters of the ocean. However, such a solution is too expensive and probably impossible(since i just thought about it). All in all, the peltier device is yet another cool device.

Mendocino Motor:

The mendocino motor is a device created in Mendocino california. Its premise is pretty simple. Light makes a rotor spin. Pretty simple huh? The more detailed explanation of the mendocino motor is the following; Light is cast on a rotor that has solar cells attached to it, which we know create an electric current. The rotor is built around a stick(anything can be used, even a pen). Also, the rotor has a magnet on it and is then put on the magnetic field of repulsing magnets to make it float(its magnet is repulsed my the other magnets, which makes it move away from them, that is upwards). Then, light is shed on the rotor, which produces an electric current due to the solar cells. The current produced then creates a magnetic field due to that weird electro-magnetic relationship, which makes the rotor turn to the next solar cell. Then, the process is repeated. Even though is device is sub-zero cool, it has not been able to be produced for various reasons.The primary reason for that is that we have not been able to take advantage of the rotating rotor due to the fact that it is floating, which means we have only been able to get very low power outputs. However, if this motor is utilized rightly it can provide a super electrical producer, since it could produce electrical energy from the solar cells(photovoltaic effect) and from the rotating rotor(mechanical to electrical energy).Further information on the mendocino motor can be found here: http://www.chessplayingrobot.com/id4.html. A video on the process of this device and how it was build can be found here(the video is made up of parts provided by none other than our very own Tom Vales):

Conclusion:

The three devices described above could be the future of humanity if we invest in them. They all have massive potential that we need to take advantage of. Then, we might stand a chance in this cruel world. The end of the world in 2012 might not even happen. Nah i am kidding. It will happen. Still these devices are cool so invest in them world, invest while you still can!

Mass-Acceleration Experiment:
Hypothesis:

In this series of experiments we tried to determine the relationship between the mass of an object and its acceleration. Based on Newton’s second law of motion we know that F=m*a, where F is the force exerted on an object, a is its acceleration and m is its mass.  From this equivalence we know that a=F/m, which means that mass and acceleration are inversely proportional. Thus, our hypothesis is that the more the mass increases the less the acceleration of the object will be.

Procedure:

In this experiments, we tied a mass to a string that was pulled up by a motor. By using the NXT program we kept the power of the motor constant and changed the mass of the object every time. The results for the power, speed, time and acceleration were produced by the NXT program.

Data:

 

In the table above the colored columns signify the important variables in our experiment. In this case, the speed and time of the object are used to determine the acceleration, which is denoted in the red column entitled(surprisingly) acceleration.

Data Analysis:

Our hypothesis in the beginning was that mass and acceleration are inversely proportional and our table seems to verify our hypothesis. As we can see the acceleration of the object decreases as its mass increases. Also, the graph below seems to reinforce our hypothesis.

Conclusion:

Our hypothesis stated that the two variables were inversely proportional to each other, which was verified by our results (look at Table 1 and Graph 1). However, the relationship between the two variables was of the form y=m/x, which is does not produce a linear function between y and x. Even though, that seems to be the result for our graph that is not the case, due to the fact that the change of the acceleration is not constant. In the beginning the change is 39.1-35.24= 3.8, then it becomes 44.3-39.1=5.2 and then 50.02-44.3=5.72. Since, the difference between its acceleration is not constant the gradient of the graph is not constant either, which means the graph cannot be linear. The fact that it appears linear though is an indication of the fact that we needed to carry out more experiments to fully confirm our hypothesis.

 

Acceleration-Power Experiment:

Hypothesis:

In this series of experiments we wanted to determine the relationship between the power exerted on an object and the acceleration of that object. Based on Newton’s Second Law of Motion we know that F=m*a. Also, we know that power is P=F*Δx/Δt where P is power, F is force, Δx is the displacement of an object and Δt is the difference in time. Since the Power is directly proportional to the force, we expect it to be directional proportional to anything the force is proportional to. Therefore, our hypothesis is that Power and acceleration are directly proportional and their relationship is linear.

Procedure:

This series of experiments had an identical setup to the previous one, with just one difference. This time, the mass of the object was kept constant and the power exerted on it was changed with the NXT program.

Data:

In the table above we can see the acceleration in the red column and the Power percentage used by the NXT motor.

Data Analysis:

From the table we can see that as the power of the motor pulling up the object increases, so does the acceleration of the object. The relationship between the two seems to be directly proportional and probably linear. We can also create a graph for the above data to visualize the relationship between the two variables.

Knowing that the relationship of the two variables is linear, we can determine the gradient of the line which is equal to m=Δy/Δx= (89.98-10.3)/(100-50)=1.59. This gradient should give us the value of Δx*m/Δt, since P=a* Δx*m/Δt.

 

Conclusion:
Our hypothesis stated that the power exerted on an object would be directly proportional to the acceleration of the object and thus produce a linear function. As we can see from our results the acceleration of an object is definitely directly proportional to the power applied to it. This was verified by the results of table 2 and Graph 2. Even though, the graph we produced did not produce a perfectly linear line, we can attribute that to some errors that took place in our experiment. The first and foremost error was that we had to manually stop the object’s ascend, which means we manually affected the estimated time (through which the acceleration was calculated). Therefore, our natural human error(please don’t kill us for it) affected the acceleration itself and prevented us from obtaining a linear graph. Also, we know that our results were random due to the fact that the difference in the acceleration does not follow any sort of pattern, rather it seems to change randomly(unlike in the mass-acceleration experiments. Ultimately, we can assume that our hypothesis was verified as our results were quite close to what they should have been in reality.

Power Percentage-Power Output

Hypothesis:

In these calculations we were trying to determine the relationship between the power percentage levels of the motor and the final power output. Since, all other variables remained the same we expected these two variables to be directly proportional and in some way the same quantity(apparently they are both called POWER).

Data:

Data Analysis:

The above table shows the results of the two variables and illustrates their relationship. As we can see, the two variables appear directly proportional and their graph(below) seems to verify this point. Also, since the relationship between the two variables is linear we can find the gradient for function, which is m=Δy/Δx= (0.34-0.12)/(100-50)=0.0044.

Conclusion:

In the beginning we hypothesized that the power levels and the power output would be directly proportional to each other and produce a linear function. Our data seems to have verified our hypothesis, since the results indicate proportionality and the graph produced is a linear one with a positive slope.

Discharge-Mass:

Hypothesis:

In this experiment we were trying to determine the relationship of the battery discharge and the mass, when the power is kept constant. Since, the battery discharge is the energy spent, we expected it to be directly proportional to the mass of the object. The energy equation for kinetic energy is E=1/2*m*v*v, so the energy and the mass are directly proportional, and the more the mass the more energy will be spent by the battery.

Data:

Data Analysis:

The results above produce the following graph.

Conclusion:

Our hypothesis in the beginning was that Energy(discharge) would be directly proportional to mass. However, our results are not in agreement with our hypothesis. In fact, our results do not seems to indicate any sort of relationship between the two, which means that they were either they were seriously inaccurate or physics is entirely wrong. Due to the fact, that the latter case seems too improbable (not impossible though), we can conclude that our results for this experiment were wrong and produced nothing less than nonsense.

What is a pandemic?

A pandemic is an infectious disease that spreads through large human populations and across various regions. The name pandemic is a derivative of the Greek roots pan(all) and demos(people) and it signifies the vast domain it infects. A pandemic is different from other diseases simply from the number of people it infects and the fact that it is infectious. For instance, cancer is widespread and sometimes fatal but, it is not infectious, thus it is not a pandemic.

Then what disease is a pandemic?

The most prevalent pandemic is HIV/AIDS. Since its onset, the HIV virus has spread in the entire world and has killed more than 2 million people this year alone. Also, more recently the H1N1 virus was categorized as a pandemic(information about the H1N1 pandemic can be found in the following link:http://www.flu.gov/individualfamily/about/h1n1/)

How do these pandemics occur?

Even though the sources of pandemics usually vary, the common denominator for all of them is a process called antigenic shift. During this process, already existing viruses get modified in various ways and create new combinations of proteins in the surface of the virus.(for further information:http://www.flucentre.org/knowledge-centre/pandemic-flu/how-do-pandemics-occur) These new permutations manage to infiltrate the immune system and then spread in other hosts (usually through respiratory processes such as sneezing or coughing).

Why should pandemics worry me?

You might get infected and die.

How can we prevent them?

Even though vaccines and cures are continuously produced for pandemics  they are produced after the pandemic has taken place which means that until a cure is found people will keep on getting infected.  Therefore, the best policy to stop pandemics from spreading is the most apparent one; prevention.

This video provides a brief outline of the course of a pandemic and then suggests ways of coping with it.

Environmental Aspect:

As the information above indicates, viruses originate from other animals or sources other than humans. Due to the fact that our involvement with the environment has increased the past years, we have become more susceptible to viruses. Our over-producing societies have turned the entire world into a big farm that we are cultivating and usually farmers get infected by their farms. From birds, to pigs or flowers, our extreme usage of the earth has produced more dangerous and infectious diseases. And if that was not enough, the climate changes that seem to be taking place, have given pandemics further impetus.

The article below elaborates further into this issue and shows the increasingly dangerous nature of pandemics.

http://www.independent.co.uk/news/science/deadly-animal-diseases-poised-to-infect-humans-1856777.html

In conclusion:

Pandemics are as dangerous for humans as they are infectious. They have the potential to kill millions of humans and if they mutate just right, they could even kill billions of us. For the past 20 years or so, we have been aggravating the problem and increasing our chances of being infected. Further research needs to be done in order to help fight pandemics and of course protective measures should be taken to decrease their offset. A healthier planet means a healthier human race, so all we have to do is keep our environment healthy.And never, ever (this is the most important piece of advice in this blog) make out with other species, not only is it unhealthy,but it also looks pretty bad.