Explain how solar energy can be used to produce electricity Essay

Explain how solar energy can be used to produce electricity - Essay Example The amount of energy emitted in one second is more than the world has used since time began. All energy comes from within the sun. Like other stars present in the cosmos, the sun is also a star made up mostly of hydrogen and helium gas. The cultivation of energy inside the sun is done through a process called nuclear fusion. However, only a small amount of energy reaches the earth but that is huge enough to supply all our energy needs. The energy radiated by the sun reaches the earth in just eight minutes at a speed of 186,000 miles per second, which is the speed of light. Photovoltaic Electricity as the name suggests is a combination of two words: photo meaning light and volt, a unit for the measurement of electricity. In short, it is often called PV cells or solar cells. The most common devices, which use PV cells include solar-powered toys, calculators, and roadside telephone call boxes – all use solar cells to convert sunlight into electricity. Scientific investigation of photovoltaic effect started in 1839 and the effect was first observed in a solid material (Selenium) in 1877. Solar cells are made up of silicon, the second most common substance on earth. Solar cells can be applied to produce energy to anything that is powered by batteries or electrical power in general. Electricity is generated when sunlight hits on the solar cell plates, which cause the electrons to get activated. However, the generation of electricity takes place mutely and at once. A PV or solar cell consists of two or more layers of semi conducting material, silicon, which is used most commonly in PV cells. When the silicon layer is exposed to the sunlight, a photo-voltage or potential difference between the layers is generated. This voltage is capable of driving a current through an external circuit, as direct current (DC). Since the electrical output from a single

Plato and Aristotle on the Just Man and the Good Citizen Essay - 1

Plato and Aristotle on the Just Man and the Good Citizen - Essay Example In fact, these very virtues make a city or an individual just - â€Å"Then a just man won’t differ at all from a just city in respect to the form b of justice;† (Plato, 110) This discussion starts from the state level and eventually moves down to the level of an individual but Plato makes it absolutely clear that the presence of the above mentioned virtues in an individual citizen leads to a state, which has these same virtues. In The Republic’s Book XIII, there exist many examples showing how an unjust society shapes the souls of its citizen. The vice versa then should also be true. Therefore, it can be derived from this discussion that there exists a kind of â€Å"virtuous circle† between the state and a citizen. They are both cause and effect of each other. To sum this up, it can be said that a state shapes the souls of its inhabitants; meanwhile the nation itself is a product of all the individual souls comprising it. If this structure is disrupted, harmony will suffer, inner conflict will increase and this might lead to the whole set-up coming down. Plato believes that the most important goal of education is knowledge of Good. In the fictional city of Kallipolis, there are three different classes: the producers, guardians and the rulers. All these three classes have some specific qualities that they need to display in order to make Kallipolis the â€Å"just city†. The guardian class needs to be the educated group who will be able to absorb all the laws in the best possible manner - â€Å"†¦Hence the guardians must above all protect their system of elementary education, for this provides the training in civic virtue without which no system of laws, no constitution, can hope to achieve†¦Ã¢â‚¬  (Plato, 94) The rulers of the city need to possess wisdom, using which they ensure that the city will have good judgment and will be really wise. Since an ideal city needs to be governed by