Dam walls are mostly made of a material called concrete. These dams retain a large amount of water. The retained water puts very high pressure on the lowermost layers of water. If the water in these lowermost layers is diverted, it flows at a very high speed, and hence a high energy is produced with the help of a device called turbine. In the turbine, the energy is used to generate electricity. Continue reading “How is electricity generated by using a dam?”
High and low tides come alternately, that is, one after the other. In high tides, the level of water rises and covers a 
part of the coast, and in low tides it flows away again. This energy of the tides is used to run turbines. Special water turbines are used in tidal power plants. Water – rising in case of high tides and receding in case of low tides – can flow through these turbines in both the directions. Electricity is generated in tidal power plants due to the rotary movement of the turbines. These power plants need a tidal hub – the difference in the height of water between high and low tides – of more than 5 m to be able to work economically. Such a power plant is in the French Bretagne, in St. Malo. Here, the tidal hub is at 12-15 m.
Ferries without engines are driven by the flow of water. They are attached to a wire cable, which is spanned across the river by means of two short ropes. When the ferryman shortens one of the two short ropes with the help of a device called ‘winch’, the ferry is tilted at an angle to the current, and the force of the current propels the ferry across the river.
At room temperature, there is always some air dissolved in water. The colder the water, the more air is dissolved. Air becomes less soluble in water as the temperature rises. When the water boils the air is released in the form of bubbles. Two thousand years ago, an attempt was made to use the power of steam with Heron’s ball, but the great breakthrough came only with the steam engines. The steam engine improved by James Watt is the most well-known. A little later the steam engines were used to drive locomotives and paddle steamers – the modern steam turbines followed later.
The Heron’s ball is a bellied vessel, which is partly filled with water and sealed with a cork. A pipe which is open on both the sides goes inside the vessel through a hole in the cork. When the air pressure inside the vessel becomes higher than the atmospheric pressure, the water pushes out through the pipe. The internal air pressure can be increased in different ways: by connecting two vessels, by blowing air in the vessel through another pipe, or by heating the water. The water vapour that is formed needs more space and pushes water out from the pipe; the water actually sprays out. In principle, the Heron’s ball is the first steam engine.
James Watt is often called the inventor of the steam engine, but in reality he improved upon the working steam engine of Thomas Newcomen and got his design patented in 1769. In the steam engine of James Watt, hot steam is passed inside the cylinder not just from the side but alternatively from top and bottom. The expansion force of the steam causes a piston in the cylinder to rise and fall. Watt converted this up and down movement into the rotational movement of a flywheel. From there, the force generated by steam could be transferred to machines – to sewing machines or weaving looms.
[custom_search_and_filter]