Questões de Vestibular

    As we all know, electricity is a fundamental need. On a daily basis, we consume electricity even without us knowing it. Just a simple task such as listening to your music player consumes electricity. Today, most of our electric generators and power plants are fed with fossil fuels such as petroleum and coal. However, due to the exponential increase of power demand, fossil fuel supplies are slowly being depleted. Not only that, but also burning fossil fuels has given off greenhouse gases and other unwanted byproducts. Because of this, the search for alternative energy sources is now a necessity. One of the most promising alternative energy sources today is Wind Powered Generators. So, what is a wind-powered generator? Basically it is the use of wind as a mechanical force needed to power an electric generator. Utilizing wind as an energy source is not exactly a new idea. The ancient Persians were the first to use wind to pump water, cut wood, and grind food and others by building windmills. Even today you can find windmills still being used on some farms. It was the use of wind as an electric source that came into existence much later. The first practical wind powered generators were built in 1970, but yet we rarely see them in widespread use today, why? Let’s look at the advantages and disadvantages of the wind powered generator.

    The main advantage of wind powered generators is that they have, ideally, zero gas emissions – unlike fossil-fueled power generators. Because of the alarming effects of greenhouse gases and global warming, we want our power generators to be as clean and as environmentally friendly as possible. Since there is no burning process in a wind powered generator that produces toxic gases, it is very safe to build one in residential areas. Also, with proper engineering and enough wind, these generators can provide a high rate of wattage that can go as high as the Megawatt range. Another advantage is that it can be implemented using several small turbines connected together. This is a good thing when there is not enough space for huge structures.

     The major disadvantage of wind powered generators is that wind power varies greatly from one place to another and from day to day and season to season. Sometimes wind may be strong enough to supply energy, but that strength cannot be maintained due to changes in weather patterns. Needing strong, constant wind to most effectively power wind generators is one reason they are often built in coastal areas. Another disadvantage is that the structure of most practical wind powered generators is huge and bulky. Commonly, its size is proportional to the wind power it can collect.

    Research in wind power has now intensified because of its innate advantages over other power generators. With this increase in interest in wind energy and alternative energy sources as a whole, our future will become brighter and more and more remote areas will eventually enjoy the benefits of clean electric energy. In an electricity-dependent world, power supplies must provide the required electricity for communities and businesses. Wind powered generators might just be the solution for power shortages.

Disponível em: http://mysolarcellhome.org/articles/pros-and-cons-of-wind-powered-generators. 

Text 2

    When I got to the airport, I learnt that the plane from Cairo, on which my brother was travelling, had been delayed at Paris with engine trouble and was expected to be about an hour late. As a rule I can pass the time quite happily; watching the planes land and take off, but that evening I had a headache; which I thought that the noise of the engines might make worse. I decided, therefore to walk around to make the time pass quickly.

    First of all I went back to the place where I had left my car to make sure that all the doors were locked. The walk in the fresh air did me good, for I felt slightly better as I entered the main airport building again. I made my way to the restaurant, where I ordered a cup of black coffee. As I stood drinking this at the counter, I studied the faces of the people around me. Some passengers were obviously anxious about the time, and kept looking at their watches; others checked to see that they had tickets, passports and money. Where there was a group of people, it was easy to tell which one was about to leave. He was the object of everyone’s attention and looked either very happy or very sad at the thought of departure.

    There was one woman who burst into tears as she said goodbye to the relatives or friends who had come to see her off. When I had finished my coffee, I went along to the bookstall, where I bought a couple of magazines, both of them about travel, which would help to make the time pass pleasantly. Then I went into one of the waiting-rooms and made myself comfortable in a big armchair. I had hardly had time to open one of my magazines, when someone came up and put his hand on my shoulder. It was an old friend; who was just about to leave on a business trip to South America. Since we had not seen each other for a long time, we found plenty to talk about until the arrival of my brother’s plane from Paris was announced.