Tidal Energy
Tidal power, also called tidal energy, is a form of hydropower that converts the energy of tides into electricity or other useful forms of power. The first large-scale tidal power plant started operation in 1966. Although not yet widely used, tidal power has potential for future electricity generation. Tides are more predictable than wind energy and solar power. Among sources of renewable energy, tidal power has traditionally suffered from relatively high cost and limited availability of sites with sufficiently high tidal ranges or flow velocities, thus constricting its total availability. Tidal power is extracted from the Earth's oceanic tides; tidal forces are periodic variations in gravitational attraction exerted; by celestial bodies. These forces create corresponding motions or currents in the world's oceans. The magnitude and character of this motion reflects the changing positions of the Moon and Sun relative to the Earth, the effects of Earth's rotation, and local geography of the sea floor and coastlines. A tidal generator converts the energy of tidal flows into electricity. Greater tidal variation and higher tidal current velocities can dramatically increase the potential of a site for tidal electricity generation. 
Solar Power Plant
Solar power is the conversion of sunlight into electricity, either directly using photovoltaic’s (PV), or indirectly using concentrated solar power (CSP) or to split water and create hydrogen fuel using techniques of artificial photosynthesis. Concentrated solar power systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. Concentrating Solar Power (CSP) systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. The concentrated heat is then used as a heat source for a conventional power plant. A wide range of concentrating technologies exists. The most developed are the parabolic trough, the concentrating linear fresnel reflector, the Stirling dish and the solar power tower. Various techniques are used to track the Sun and focus light. In all of these systems a working fluid is heated by the concentrated sunlight, and is then used for power generation or energy storage. Solar energy can be stored at high temperatures using molten salts. Salts are an effective storage medium because they are low-cost, have a high specific heat capacity and can deliver heat at temperatures compatible with conventional power systems. Solar energy is not available at night, making energy storage an important issue in order to provide the continuous availability of energy.
Biogas Plant
Biogas typically refers to a gas produced by the biological breakdown of organic matter in the absence of oxygen. Biogas originates from biogenic material and is a type of biofuel. Biogas is produced by the anaerobic digestion or fermentation of biodegradable materials such as biomass, manure, sewage, municipal waste, green waste, plant material and -more problematic- energy crops. Biogas comprises primarily methane and carbon dioxide and may have small amounts of hydrogen sulphide, moisture and siloxanes.
The gases methane, hydrogen and carbon monoxide can be combusted or oxidized with oxygen. This energy release allows biogas to be used as a fuel. Biogas can be used as a fuel in any country for any heating purpose, such as cooking. It can also be used in anaerobic digesters, where it is typically used in a gas engine to convert the energy of the gas into electricity and heat. Biogas can be compressed, much like natural gas, and used to power motor vehicles. Biogas can be produced utilizing anaerobic digesters. These plants can be fed with energy crops such as maize silage or biodegradable wastes including sewage sludge and food waste. During the process, an air-tight tank transforms biomass waste into methane producing renewable energy that can be used for heating, electricity, and many other operations, which can use any variation of an internal combustion engine. The composition of biogas varies, depending upon the origin of the anaerobic digestion process. Landfill gas typically has methane concentrations around 50%. Advanced waste treatment technologies can produce biogas with 55-75%\[C{{H}_{4}}\], which for reactors, with free liquids, can be increased to 80-90% methane. 
Hydroelectric Power Plant
Hydroelectric power plant is the power plant in which electrical energy is produced using the kinetic energy of the water. Hydroelectricity is also the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy. Most hydroelectric power comes from the potential energy of dammed water driving a water turbine and generator. The power extracted from the water depends on the volume and on the difference in height between the source and the water's outflow. This method produces electricity to supply high peak demands, by moving water between reservoirs, at different elevations. At times of low electrical demand, excess generation capacity is used to pump water into the higher reservoir. When there is higher demand, water is released back into the lower reservoir through a turbine. Pumped-storage schemes currently provide the most commercially important means of large-scale grid energy storage and improve the daily capacity factor of the generation system. The major advantage of hydroelectricity is elimination of the cost of fuel. The cost of operating a hydroelectric plant is nearly immune to increases in the cost of fossil fuels such as oil, natural gas or coal, and no imports are needed. Hydroelectric plants have long economic lives, with some plants still in service after 50-100 years. Operating labor cost is also usually low, as plants are automated and have few personnel on site during normal operation.
Where a dam serves multiple purposes, a hydroelectric plant may be added with relatively low construction cost, providing a useful revenue stream to offset the costs of dam operation. It has been calculated that the sale of electricity from the Three Gorges Dam will cover the construction costs after 5 to 8 years of full generation. Since hydroelectric dams do not burn fossil fuels, they do not directly produce carbon dioxide. While some carbon dioxide is produced during manufacture and construction of the project, this is a tiny fraction of the operating emissions of equivalent fossil-fuel electricity generation. However, large reservoirs required for the operation of hydroelectric power stations result in submersion of extensive areas upstream of the dams, destroying biologically rich and productive lowland and riverine valley forests, marshland and grasslands. The loss of land is often exacerbated by the fact that reservoirs cause habitat fragmentation of surrounding areas. Hydroelectric projects can be disruptive to surrounding aquatic ecosystems both upstream and downstream of the plant site. For instance, studies have shown that dams along the Atlantic and Pacific coasts of North America have reduced salmon populations by preventing access to spawning grounds upstream, even though most dams in salmon habitat have fish ladders installed. 
Thermal Power Plant
The power plant in which the electricity is produced by burning of coal is called thermal power plant. A thermal power station is a power plant in which the prime mover is steam _ driven. Water is heated, turns into steam and spins a steam turbine which drives an electrical generator. After it passes through the turbine, the steam is condensed in a condenser and recycled to where it was heated. This is known as a Rankine cycle. The greatest variation in the design of thermal power stations is due to the different fuel sources. The energy efficiency of a conventional thermal power station, considered as salable energy as a percent of the heating value of the fuel consumed, is typically 33% to 48%. This efficiency is limited as all heat engines are governed by the laws of thermodynamics. The rest of the energy must leave the plant in the form of heat. This waste heat goes through a condenser and be disposed of with cooling water or in cooling towers. If the wasted heat is utilized for direct heating, it is called co-generation. An important class of thermal power station are associated with desalination facilities. These are typically found in desert countries with large supplies of natural gas. In these plants, freshwater production and electricity are equally important co-products. The direct cost of electric energy produced by a thermal power station is the result of the cost of fuel, capital cost for the plant, labour operation, maintenance, and such factors as ash handling and disposal. Indirect, social or environmental costs, such as, the economic value of environmental impacts, or environmental and health effects of the complete fuel cycle and plant decommissioning, are not usually assigned to generation costs for thermal stations in utility practice, but may form part of an environmental impact assessment.
The pollution caused by thermal power plant is in large scale due to the burning of fossil fuels. These smokes cause air pollution and water pollution and also cause acid rain. Burning of coal leaves lot of ash behind and causes air pollution. It also produces acidic gases like sulphur dioxide and nitrogen oxides. These gas can cause acid rain which damages plant and crops and reduces fertility of the soil by making it acidic. It also cause problem for aquatic life by making the water of lake and river acidic. It also damages monuments like TajMahal by corroding them slowly. 
Fuel
Fuel are those materials which produce heat energy on burning. For example, the fuel like wood, LPG, coal, petrol, diesel, etc produces heat energy while they burn. All fuels produce heat energy, on burning, in different amounts. It depends on the calorific value of the fuel. The calorific value of the fuel is defined as the amount of heat produced by burning of a unit mass of fuel. For example the calorific value of the fuel is 33000 j/g. Hydrogen has highest calorific value of 150 kj/g and hence it can be the best sources of the fuel. H
Most of the fuel which contains hydrogen and carbon has high calorific value than others. Before a fuel catch fire and starts burning it must be heated to a certain minimum temperature. The minimum temperature to which a fuel must be heated before it catches fire and starts burning is called ignition temperature.
The good fuel has certain characteristics which are as follows:
Fossil Fuel
The fuel, which is obtained by decomposition of remains of the dead plants and animals buried deep inside the earth crust, is called fossil fuel. Coal, petroleum and natural gas are all fossil fuels. The fossil fuels are also the major sources of energy for generating electricity in power plants. The natural gas consists of mainly methane with small quantities of ethane and propane. In fact it contains methane up to 95%. It is found deep under the earth crust, either along with oil or alone. It is formed under the earth by the decomposition of vegetable matter lying under water by anaerobic bacteria in absence of oxygen. The other important fossil fuel is petroleum which is dark colored viscous and foul smelling crude oil. It is found under the earth crust trapped in rocks. The crude oil petroleum is a complex mixture of several solid, liquid and gaseous hydrocarbons mixed with water, salt and earth particles. It also contains small amount of other carbon compounds containing oxygen, nitrogen and sulphur. Since it contains mixture of alkane hydrocarbon with water, salt and earth particles, it cannot be used as a fuel in the same form. Hence it needs to be purified before being used. The process by which the different fractions of petroleum can be separated is known as fractional distillation.
Introduction
We use different sources of energy in different forms. Without energy all our activities will come to stop and we will not be able to survive. For doing work we need energy. For this we need a source of energy which would provide us adequate amount of energy in a convenient form for a long period of time. All the source of energy can be divided into categories, i.e. renewable and non-renewable sources of energy.
Forms of Energy
Renewable Sources of Energy
Those sources of energy which can be replenished in short time in nature and are inexhaustible, are called renewable sources of energy. For example, tree, the wood obtained from trees are renewable sources of energy. If we cut a tree it can be replenished in a period of 5 to 10 years. The other sources like hydro energy, wind energy, geothermal energy, etc are renewable sources of energy. These sources of energy is also called non-conventional sources of energy as it can be used again and again and will never get exhausted. That is why they are also called inexhaustible sources of energy.
Non-Renewable Sources of Energy
Those sources of energy which we cannot be replenish in short time in nature and exhaustible in nature are called non-renewable sources of energy. For example, the fossil fuel, which we are using today as a major sources of energy such as petrol, diesel, natural gas etc are non-renewable sources of energy.
These sources of energy cannot get replenished in short time and can get exhausted after some time. Hence they are also called exhaustible sources of energy. They are also called conventional sources of energy. A good sources of energy is one which are easily available and is cheap. It also must be easy to store and transport and should be safe in use. It should not cause pollution to the environment and should have high calorific value. 
Domestic Circuit
We receives electric supply in our home from the main power supply through cables or poles. It consists of two wires, one with red insulation called live wire and other with black insulation called neutral wire. The potential difference between two wires is 220 volt. These two wires are connected into our homes via meter board through main switch, which consists of safety devices called fuse. From there it is connected to the different switch through the wiring in our house, which are connected in parallel. Often we use two different circuit one with 15 A current used for appliances with higher power rating such as air coolers, geysers etc and other circuit is of 5 A current rating for bulbs, fans, TV etc. There is a third wire with green insulation called earthing and is usually connected to a metal plate deep in the earth, near the house. It acts as a safety device for those appliances having metallic body as it provides low resistance conducting path for the current and prevent any short of leakage of current to the metallic body of the appliance and keeps its potential to that of the earth and prevent any severe electric shock. Thus, electric fuse and earthing are the two safety device used in electric circuit.
The magnetic field pattern given in the figure below is due to which one of the following?
(a) Straight Conductor
(b) Circular Loop
(c) Solenoid
(d) Ring
Answer: (c)
Which types of material is used in the core of electromagnet?
(a) Soft Iron
(b) Steel
(c) Alloy
(d) Non Metals
Answer: (a)
Which one of the following is the correct statement for the magnetic field near the straight conductor?
(a) The field consists of straight lines parallel to the wire
(b) Field consists of radial lines starting from the wire
(c) The field consists of concentric circles with centre on the wire
(d) The field consists of straight lines perpendicular to the wire
(e) None of these
Answer: (c)
Which one of the following is not used in DC generator?
(a) Coil
(b) Brush
(c) Slip Ring
(d) Magnet
(e) None of these
Answer: (c)
Electric Generator
Electric generator is a device which convert mechanical energy into electrical energy. A small generator is called a dynamo which is used in bicycle. It works on the principle of application of electromagnetic induction.-When a straight conductor is moved in a magnetic field, the current is induced in the conductor. It is of two types: alternating current generator and direct current generator. An A.C. generator produces current which reverses its direction continuously after every half cycle. A simple A.C. generator consists of a rectangular coil PQRS which can be rotated rapidly between the poles of the horseshoe magnet as shown in the figure given below.
The coil is made up of large number of turns of insulated copper wire. The two ends P and S of the coil are connected to two circular pieces of copper metal called slip rings \[{{R}_{1}}\]and \[{{R}_{2}}\]. As the slip rings rotate with the coil the two fixed pieces of carbon called carbon brushes X and Y keep contact with them so that the current produced in rotating coil can be carried out through the brushes to the out sources. As the coil rotates between the pole of the magnet in anticlockwise direction, the arm PQ of the coil moves in downward direction cutting the magnetic line of forces near the north pole of the magnet. The arm RS moves in upward direction and cuts the magnetic line of forces near the south pole of the magnet. Due to this the current is induced in the arm PQ and RS of the coil and the current flows in the direction QPSR. After half revolution, the side PQ and RS of the coil interchange their positions. The arm PQ moves in upward direction which earlier moved in the downward direction and vice versa. As a result of this the direction of current in arm PQand RS is reversed giving rise to the net induced current in the direction of RSPQand the current flows through brush X and Y to the outer circuit. In India the A.C. produced is of frequency 50 HZ i.e. the coil is rotted at the rate of 50 revolution per second. In one revolution, the current reverses its direction two times so in 50 revolution of the coil the current reverses its direction 100 times.
The DC generator is the generator in which the current do not changes its direction after every half cycle. The basic difference in construction of AC and DC generator is that, in DC generator slip ring of AC generator is replaced by commutator half ring due to which the current always flows in one direction, through the coil. 
Electromagnetic Induction
This concept was first introduced by Michael Faraday in 1831 when he discovered that magnet can be used to produced electric current. The production of electricity from magnetism is called electromagnetic induction. This can be demonstrated by moving the conducting wire between the poles of the magnet or by moving the magnet, or by keeping the conductor fixed and moving the magnet. A galvanometer is an instrument which can detect the presence of feeble current in the circuit. Take a galvanometer and connect in series with the circuit of the conducting wire and place it between the poles of the magnet. When the wire is stationary, no deflection in the galvanometer can be seen and as we move the wire between the poles of the magnet we see the deflection in the galvanometer.
Fleming's Right Hand Rule
The direction of induced current produced by electromagnetic induction can be found by using Fleming Right Hand Rule. According to this rule, if we hold the thumb finger, the fore finger and the middle finger of our right hand at perpendicular direction to each other in such a way that, the fore finger points in the direction of magnetic field, the thumb finger points in the direction of motion of the conductor, then the middle finger will point in the direction of induced current.
Let us take a thick copper wire suspended freely from a support by the means of a flexible wire and the wire is free to move. The one end of the wire is placed between the poles of a horse shoe magnet and is connected to a current sources. When the current is switched on through the wire, we observe that the wire is deflected out of the horse shoe magnet. When we switch off the current it returns to the original position between the poles of the magnet. The direction of the current in the wire placed in a magnetic field is perpendicular to the direction of the current and perpendicular to the magnetic field. The direction of the force on the conductor placed between the magnetic field is given by Fleming left Hand rule. According to this rule: Hold the fore finger, middle finger and the thumb finger of your left hand at right angle to each other in such a way that the forefinger points in the direction of the magnetic field and the middle finger points in the direction of current, then the thumb will points in the direction of the force acting on the conductor.
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