My Science School

          The concept of electricity cannot be complete without Faraday’s Law of induction. It describes how changing magnetic fields can cause electric current to flow in a conductor.

          The working principles of electric motors, transformers, generators, are all based on Faraday’s Law of Induction.

          Faraday discovered electromagnetic induction in 1831. He had conducted many experiments before concluding his theory. He experimented with magnetic fields that stayed the same, and realized that they do not induce current. Then he experimented by changing magnetic fields, and saw that they induced current and voltage.

          Faraday’s discovery of electromagnetic induction did not receive much acceptance from scientists when it was introduced. But Scottish scientist James Clerk Maxwell realized its importance, and used the ideas as the basis of his quantitative electromagnetic theory.

       Maxwell’s equations refer to a set of four equations that describe the creation and propagation of electric and magnetic fields. They are named after the Scottish physicist James: Clerk Maxwell, who made significant contributions to unify the theories of electricity, magnetism, and light. The early form of these equations was published between 1861 and 1862, and it proposed that light is an electromagnetic phenomenon.

       The equations formed from these laws could give an explanation to many phenomena around. For instance, how hair stands on end when one removed a nylon sweater, how a compass needle points north all the time, how a power station turbine generates electricity etc. Together, they could also describe the transmission of radio waves, and the propagation of light.

       Hence, Maxwell’s equation, along with the Lorentz force law, is said to form the foundation of classical electromagnetism. Lorentz force law describes the force acting on a moving point charge ‘q’ in the presence of electromagnetic fields. 

        A power station is a place where electricity is produced on a large scale for distribution. It is also called a power plant, or power house.

       The electricity generated here, mostly in several thousand watts, is transmitted to power grids through power lines. It is from these grids that people get electricity for homes, schools, businesses etc.

       A majority of the power stations in the world burn fossil fuels to generate electricity. This includes coal, oil, and natural gas. They are called thermal power stations.

       There are also plants that use nuclear power instead. It is said that over 11 per cent of the world’s power is produced by nuclear power stations.

      

Continue reading "What are power stations? "

      Hydroelectric power plants use the force of falling water to generate electricity. It’s one of the safest sources of energy that is also reliable and cheap.

      Some of the earliest hydroelectric power plants were set up in and around London. In the 1870s, English industrialist William George Armstrong built one such plant at Crag-side, in England. This was perhaps the world’s first hydroelectric power scheme. It used water from the lakes on his estate to power the generator.

        In 1882, a central station was built In Godalming, England, using hydroelectric power. This time, it was to provide street and household lighting to the public. But this project ended up as a failure.

       However, many hydroelectric projects were conceived all over the world by then. It is said that in 2015, hydro power generated 16.6 per cent of the world’s total electricity. Almost 150 countries have hydro power plants today, with China being the largest producer of hydroelectricity. 

        The ‘War of Currents’ was the term used to refer to the dispute between two brilliant inventors - Thomas Alva Edison and Nikola Tesla. It happened towards the end of the 19th century, when there arose a question over which was better-direct, or alternating current.

        Edison was the brains behind the development of DC, which ran continually in a single direction. In the early years of electricity, DC was regarded as the standard. But it had a problem; it couldn’t be easily converted to higher or lower voltages.

       Tesla strongly believed that alternating current was a solution to this. AC, which he co-developed could reverse its direction unlike DC, and could also be converted to different voltages using an electrical transformer. It made possible long distance electricity transmission too.

       However, Edison saw Tesla’s argument as a threat to his work. He thus started off a public campaign, trying to discredit AC. The main reasons for the campaign was that Edison did riot want to lose the royalties he had been earning from his DC patents.

      But in spite of all the efforts Edison made, it was Tesla and his AC that won in the end. Today, electricity is mainly powered by alternating current.

 

A thermal power station is where heat energy is used to generate electricity. It is the most conventional, and common source of electric power.

Let’s see how it works. A thermal power plant burns fossil fuels like coal, oil, and natural gas to produce steam. The steam thus formed, creates a pressure that spins the turbine inside the plant. Electric power is generated by these spinning turbines.

The advantages of a thermal power plant is that it requires less initial cost, and less land compared to other power stations. The fuel used - fossil fuel- is also cheap. Many countries in the world depend mainly on thermal power for electricity. It is said that around 40 per cent of the world’s power is made out of fossil fuels.

However, thermal power plants have been criticized for the pollution they cause, due to the large amount of smoke and carbon dioxide emitted. This is a cause of global warming. Besides, the overall efficiency of a thermal power station is below 30 per cent. 

         As we saw earlier, hydroelectric power plants make use of the force of flowing water to generate electricity. There are many reasons why experts hold that hydroelectricity is more acceptable than the other. One of the most significant advantages is that hydroelectric power plants do not require any fuel for power production. They only need water, a renewable source of energy. Thermal power stations need fossil fuels like coal, natural gas, oil etc., to function.

         Since no fuel is required, the cost of electricity produced by hydroelectric plants is also somewhat constant. In the case of other kinds of plants, it depends on the cost of fuels in the international market.

         Another important factor is pollution. Hydroelectric power plants do not burn fuel; hence do not cause pollution either. The heated water that comes out of them threatens aquatic lives too.

         Hydroelectric plants also have longer lives compared to thermal plants. Besides these, hydroelectric plants are known to facilitate irrigation of farms and preventing floods.

         Hence, around 150 countries in the world use this technology for power generation.

 

       As we know, it is flowing water that creates the energy required to generate electricity. Wonder how it works?

      Well, there is a huge amount of energy created from the falling of water. This energy is harnessed by forcing it through a pipe, which is called a penstock. At the end of the pipe, there is a turbine propeller. So, when water flows through the pipe, it reaches the propeller, and turns the blades of the turbine. This spins an electric generator. Hence, as long as water is flowing, the generator will be spun, and there will be electricity.

      There are mainly three ways in which hydroelectric plants are designed.

       The most common type follows a storage system. To put it clearly, there is a dam used in this system. It slows the flow of a river and stores the water in a reservoir above it. When needed, a portion of the water is released into the river flowing below the dam. The pressure thus created from the fall of water, spins turbine generators lying below. From this is created hydroelectricity.

 

Continue reading "How is electricity produced in hydroelectric power stations? "

       Osmotic power is the energy that comes out of the difference in salinity between sea water and fresh water. This energy can be harnessed to generate electricity.

        Sounds strange, doesn’t it? Let’s see how this happens. When we separate fresh water from sea water by a semi permeable membrane, we can see that the fresh water moves through the membrane into the sea-water. This happens by a process called osmosis. It means the movement of something from a less concentrated solution into a concentrated one.

        There is a pressure created by the process of osmosis. This pressure combined with the permeating flow rate together, turns a hydraulic turbine, and produces electricity.

        Statkraft, the Norwegian energy firm was the world’s first test plant that harnessed osmotic power. Experts note that there are many advantages to this kind of power production over others. However, the biggest challenge this technology faces is the cost. Osmotic power plants are just too expensive to install.

        Yet another renewable energy is biomass, a fuel that is developed from organic materials like certain crops, manure, forest debris etc. In biomass power plants, waste is burned to produce steam that runs a turbine, producing electricity. 

        By now, we should all know that electric power is very precious and has to be saved. There are of course many ways to do that. Let’s look at a few of them.

       The first and foremost step is to make sure that any appliance is turned off when not in use. For lighting, you could use LEDs or CFLs instead of incandescent bulbs. And if it’s daytime, try to make use of the day light instead of other lights. They could very well serve the purpose!

       The next thing to remember is that electrical appliances should never be left on standby. It’s a major waste of power. A TV consumes 10 watt power in standby mode.

         If you are using an air conditioner, make sure the doors and windows are closed, so that the power is not wasted. But any day, ceiling fans are recommended instead of coolers and air conditioners.

         The appliances that account for a big chunk of your electricity bill are refrigerators, air conditioners, washing machines etc. And as they get older, power consumption too goes up. So, old appliances should be replaced by energy-saving models on time, so as to save power.

        These are some of the methods you can try to save power in homes.

 

            An aurora is a display of coloured lights that occur naturally in the night sky. It is mainly seen in high latitude regions like the Arctic and the Antarctic.

            When they happen in the northern latitude, the effect is also called the Northern Lights, or Aurora Borealis. When it occurs in the southern latitude, it is referred to as the Southern Lights, or Aurora Australis.

            Scientists and witnesses say that auroras mostly appear like curtains that extend in the east-west direction. They also happen to be the brightest, and the most distinctive kind.

            Depending on the altitude, they shine in different colours, including blue, violet, red, bright green, ruby red etc.

           Reasons behind the formation of auroras are still debated. According to one of the theories, the effect is caused by charged particles from the sun that interacts with the Earth’s atmosphere.

            Many myths and legends are also built around the presence of auroras. 

          Sprites are a natural phenomenon that is related to electricity. They occur above thunderstorm clouds, giving rise to a variety of visual shapes that glow in the night sky. Scientists believe that sprites happen when neutrally charged clouds discharge some electricity to the ground.

          In short, sprites are rare, large scale electrical discharges, occurring above thunderstorm clouds that appear as attractive visuals. Sprites have a reddish-orange colour in the upper region and bluish tendrils that hang below.

          In most cases, sprites are witnessed by those in flight above storms. But since they appear for a very short time, the spectacle is often missed!

          This phenomenon is known to have been occurring for centuries- it’s just that no one could really record it. In July 1989, scientists at the University of Minnesota accidentally caught a sprite on camera. Years later, on April 30th, 2012 some astronauts captured a red flash of sprite, which was then used by researchers and people across the world, to study and research. 

       The first account of St. Elmo’s fire surfaced a few centuries ago, when sailors spotted a bright glow around their ships during thunderstorms. They believed it was something supernatural, and this belief continued to be so until scientists came up with their findings.

        In fact, St. Elmo’s fire is a phenomenon that is similar to lightning. It is a form of plasma caused by potential difference in atmosphere. Appearing like fire, the spectacle of St. Elmo’s fire is seen mainly on tall and pointed structures like lightning rods chimneys, aircraft wings etc. The glow comes along with a sound, because of which it is often confused with ball lightning.

         Let’s put it clearly with the same example of a ship. There is a difference of voltage in the atmosphere and the sea. This causes the ionization of gases surrounding the ship’s masts, which in turn, results in a glow. This is what the sailors mistook as a miracle during thunderstorms. 

     Ball lightning is an unexplained natural phenomenon that happens very rarely. It appears as a glowing ball during thunderstorms, following a lightning strike. It is said that these fireballs shine too brightly, and can be white, blue, yellow, orange, or red in colour. They vary in size and form; from that of a pea, to the size of a small bus.

      Accounts of ball lightning have been recorded for the past few centuries. According to witnesses, these fireballs move in an unpredictable and fast manner, followed by smoke that forms spirals around them. Believe it or not, they can even enter buildings through doorways or windows, travel down corridors, and even navigate their way to certain points. They make hissing noises and sometimes, loud ones too. And all of a sudden, they disappear.

      The reason behind the formation of ball lightning is unknown, and there are many theories talking about the same. Even though there are many explanations for this phenomenon, none is accepted widely. 

        Electric charge is something that is seen everywhere in the Universe - even inside living things. Some fishes, for instance, have a surprising amount of electricity in them - like the electric eel.

        Eels are freshwater predators found in the shallow, muddy areas of the Amazon and Orinoco rivers in South America. They often live in stagnant waters.

        They possess enormous amounts of electricity that can possibly knock off a large horse, or even kill humans. It is said that the electric discharge from eels can be stronger than 500 volts. They are also known to have around 6000 cells called electro-plaques that can produce electricity. Since eels have very poor eyesight, they emit weak electric signals for navigation to find a mate or prey. But when they spot a prey, strong shocks are given to stun them.

        Other than eels, many fishes including sharks, lampreys, and cat-fishes have the ability to generate electric fields around them.