Solar cells are in fact large area semiconductor diodes. Due to photovoltaic effect energy of light (energy of photons) converts into electrical current. The term “photovoltaic” comes from the Greek φῶς (phōs) meaning “light”, and from “Volt”, the unit of electro-motive force, the volt, which in turn comes from the last name of the Italian physicist Alessandro Volta, inventor of the battery (electrochemical cell). The term “photo-voltaic” has been in use in English since 1849.

Solar cells produce electricity in three steps;

1. Photons in light hit the solar cells and are absorbed by semiconducting materials, such as silicon.
2. Electrons (negatively charged) are knocked loose from their atoms, causing an electric potential difference. Current starts flowing through the material to cancel the potential and this electricity is captured. Due to the special composition of solar cells, the electrons are only allowed to move in a single direction.
3. An array of solar cells converts solar energy into a usable amount of direct current (DC) electricity.

 

In this lab, we discovered the relationship between a light source and solar cell. In two different experiments, we measured the voltage output of the solar cell. In the first experiment, using a flashlight and solar cell connected to the NXT in order to measure the voltage output, we placed the light source in different distances and measured the voltage output of the solar cell. It was noticeable that the further the light source the lesser the voltage output. In the second experiment, the distance of the light source was kept constant and we changed the light color using colored filters. Therefore, the voltage output varies because of changing the color of the light leads to changing in the energy of the photons according to the following formula:

E= hc/λ

Where E is the energy of the photon, h is Planck constant (6,626·10-34Js), λ is the wavelength, and c is the speed of light.

Experiment (1)

The main point of this experiment is to determine the relationship between the solar cell and the light source in terms of the distance. Basically, if the light source is placed far from the solar cell, the light intensity becomes smaller resulting in smaller voltage output.

Therefore, we can conclude that the voltage output is inversely proportional to the distance of the light source.

Experiment (2):

For this experiment, we had to figure out the relationship between the wavelength of light and its energy of the photons. As stated before by the equation, the energy of the photon (E) is inversely proportional to the wavelength. Therefore, light consisting of high energy photons (such as “blue” light) has a short wavelength. Light consisting of low energy photons (such as “red” light) has a long wavelength.

References

http://www.pvresources.com/introduction/solarcells.aspx

http://en.wikipedia.org/wiki/Solar_cell

http://www.pveducation.org/pvcdrom/properties-of-sunlight/energy-of-photon

our class went on a tour to the Sawyer library. We were introduced to several services at the library such as the circulation and reserve desk and the reference desk, which are very essential for a library to have. The three-floor Sawyer library has numerous study group rooms and the students are provided with computers and printers.The study group rooms can be reserved online 24 hours before the next day . Also, the rooms are limited so if your reservation time is over you need to leave the room immediately or you will be charge late fees for the lateness .

 

Circulation and reserve desk provides students the opportunity to borrow text books for 20 minutes at a time. Reference books can be borrowed and taken out of the library for a period of time. This desk is a huge source for students to get their questions answered regarding their study and search. Our tour guide from the reference desk demonstrated all the possible ways to search using the computers in the library. By entering a title or keyword of a book, report, or journals, we are able to find an enormous amount of information from the list of sources the university supplied. For instance, Library catalog option allows students to view all of Suffolk University library on the screen. Databases by subject is a gate to find any subjects or articles , which the library provides associated with EBSCO Host.

 

we were given robot parts to build according to the instruction in one class, and we had to make it moving backwards and forwards . In the next class, we continued working on the robot we built to perform certain tasks.  Lecture was given on distance, velocity, and acceleration. One of the most important tasks was to connect the robot to the PC and program it in order for it to perform. We measured the circumference of the wheel, which was 0.1760m, to determine how far it can travel in one complete rotation of the turn.  By programing the robot different numbers of power due a constant time, the results of rotation, number of wheel turns, velocity, and distance will change directly proportionally. The following table illustrates the relationship previously described.

 

Time= 1s

Circumference of the wheel= Pi* wheel diameter = 0.1760m

 

With time being constant at 1 second, velocity and distance are always equal according to the famous formula: velocity= distance/time.

Power	Rotation 1	Rotation 2	# Of wheel turns	Distance	Velocity
75	558	567	1.55	0.2728 m	0.2728 m/s
50	348	353	0.967	0.1701 m	0.1701 m/s
25	145	147	0.4026	0.0709 m	0.0709 m/s

 

 

 

All in all, although it was more of entertaining activity, it was very informative and encouraging in way that connects my preference in doing physical work with physics.Also, we got to know how to program the robot using some programing languages .

In class, Tom Vales introduced us to some amazing devices. Some of these devices were invented in the 18th century. The purpose behind some of them was mainly to generate electricity. It is really interesting for me to see how the development of making generators has become from the past up until the present. It is very crucial for every electrical engineering student to have knowledge about these various electrical inventions. 

A Tesla coil is an electrical resonant transformer circuit invented by Nikola Tesla around 1891. It is used to produce high-voltage, low-current, high frequency alternating-current electricity. His invention of the alternating current motor set the stage for the power and lighting systems now used every day around the world.

here is a link that explain how it is works

https://www.youtube.com/results?search_query=tesla+coil+how+it+works