Wednesday, March 4, 2009

The Jovian Planets


The planets outside the orbit of Mars are called as Jovian planets because their structure is similar to that of Jupiter. These are all gaseous bodies. They have ring systems around them and have large number of moons.
Jupiter is a very bright object in the sky. It can be easily seen with the naked eye. It is the largest and the most massive planet in the solar system. It has a very deep atmosphere, mainly of hydrogen and helium. Because of its large mass and size, Jupiter exerts a strong gravitational pull on other objects which pass by it. The next three planets Saturn, Uranus and Neptune are similar to Jupiter. Saturn has the most beautiful and visible rings. The last planet Pluto is so small that it cannot be observed from the earth and no space mission has been sent into it yet.

Electro Encephalogram(EEG)

Electro Encephalogram shortly called EEG is used to record the electrical activity of the brain. This electric al activity is measured in the form of electric potentials. This process is called as Electro Encephalography. By placing two electrodes on the scalp of the patient, and leading via suitable amplifier to a CRT or to a ink-writing device, a record of four different types of waves can be obtained. These waves are named as alpha, beta, delta and theta. They vary in their frequency. These waves give the characteristic activity of the brain, and that is useful for study of brain problems like tumors, cerebral palsy, etc.

Thursday, February 12, 2009

Superconductors

In 1911, the Dutch physicist H.K.Onnes, studied the variation of resistance of metals with temperature. He tried to cool some metals to a few Kelvins and measured their resistance. He discovered that mercury’s electrical resistance was reduced to zero at 4.2K (-269 degree Celsius). It was found that many other metals show similar behavior at certain low temperatures. This temperature is called as critical temperature. Such metals which exhibit this property is called as superconductors. In superconductors current can be transmitted without loss of energy.
Since superconductors require cooling to extremely low temperatures which were found very difficult to achieve, everyday use of superconductors was found impractical. Therefore, efforts made to search compounds that have higher critical temperatures. If superconductors are discovered which has zero resistance at room temperature, it will indeed greatly revolutionize many of the electrical devices we use today.

Sunday, February 8, 2009

Benefits of Going Green


Trees can add value to your home, help cool your home and neighborhood break the cold winds to lower your heating costs, and provide food for wildlife.







TENTATIVE VALUE OF LONG LIFE TREE

• Generates oxygen worth Rs.8.6 lakhs
• Greatest Air pollution control worth Rs.10.5 lakhs
• Recycles fertility and soil erosion control Rs.8.4 lakhs
• Creates shelter for birds and other animals worth Rs.5.3 lakhs
• Provides flowers, fruits, medicines and other goods worth Rs.4.3 lakhs
Grand Total Rs.32.0 lakhs

So, felling of one tree means a net loss of about Rs.32 Lakhs.Stop using your axe.Start growing trees.

PLANT AND SAVE TREES

Dialysis


Though Kidney failure is not common, but sometimes kidney infection, injury to kidneys or restricted blood flow to kidneys result in kidney damage and malfunctioning. In order to clean the blood of metabolic wastes and to maintain normal levels of water and mineral ions in body fluids, a matching kidney from another person can be transplanted. But this process is very complex and the success percentage is very low. Instead an artificial kidney can be used. This artificial kidney is called as Dialysis.

Principle of Dialysis: Blood is made to flow into the dialyzing machine made of long cellulose tubes coiled in a tank having a dialyzing solution. Waste substances diffuse out of the blood into the tank. The purified blood is pumped back into the patient.

Friday, February 6, 2009

Dr.S.Chandrasekhar

Dr.S.Chandrasekhar, a great Indian Astrophysicist, was born on 19th October, 1910. He got his B.A. (Hons.) degree in physics from the presidency college, Madras. Dr.Chandrasekhar published his first scientific paper, “Compton scattering and the new statistics”, in the proceedings of the royal society at the age of 18. He obtained his Ph.D. degree in 1933 from Cambridge university. After several years of extensive hard work, Chandrasekhar proved that stars smaller than 1.44 times the solar mass end up as ‘White Dwarfs’. The limit 1.44 solar mass is known as ‘Chandrasekhar Limit’.

In 1937, Chandrasekhar joined the university of Chicago, U.S.A. and became professor in 1944. In the same year, he was elected a Fellow of the Royal Society of London. He was awarded the National Science Medal of the United States in 1966, the Padma vibushan from the Govt. of India in 1968, and Nobel prize form physics in 1983. A recent satellite launched by the U.S.A. to study X-ray radiations in space has been named ‘Chandra’ the name by which Chandrasekhar is popularly known. Chandrasekhar died on August 21,1995 at the age of 84.



Heredity and Variation


Heredity means continuity of features from one generation to another. Eggs laid by a sparrow hatch into sparrows, but never into any other bird. A dog reproduces to give birth to pups only. This is the essence of heredity. Hereditary information is present in the fertilized egg of zygote. The zygote develops into an organism of a particular type only. Asexual reproduction individuals belonging to a give line of descent. While in sexual reproduction, both similarity and variation are clearly observed even among the off springs. Thus Heredity is the resemblances among individuals related by descent or the transmission of traits from parents to the off springs.
The concept of Heredity is not new. Selective breeding of horses and cattle used to be done during the ancient civilization of Babylon and Assyria. Ancient Chinese writings mention about creating better varieties of paddy. Charkara(100 BC) , the ancient Indian medical practitioner is evident from the fact that he knew the factors that determine the sex of a child. But the scientific principles, which govern patterns of inheritance, were unknown till the experiments and findings of Gregor Johann Mendel. Thats why he is called as the father of genetics. Mendel factors, the carriers of hereditary information, are what we know today as “genes”, a term coined by Johanssen in 1909.

Wednesday, February 4, 2009

Hydro Electricity


HYDRO ELECTRICITY

Most machines that make electricity need some form of mechanical energy to get things started. Mechanical energy spins the generator to make the electricity. In the case of hydroelectricity, the mechanical energy comes from large volumes of falling water. For more than 100 years, the simplest way to produce the volumes of

falling water needed to make electricity has been to build a dam. A dam stops the natural fl ow of a river, building up a deep reservoir behind it. However, large dams and reservoirs are not always appropriate, especially in the more ecologically sensitive areas of the planet. For making small amounts of electricity without building a dam, the small-scale hydroelectric generator is often the best solution,

especially where fast-fl owing streams on steep slopes are close by. A small-scale

hydro system usually consists of an enclosed water wheel or turbine, which is made to spin by jets of high velocity water. The water is taken from the stream

and moved down slope to the turbine through a long pipe called a penstock. Water fl owing through the penstock picks up speed, and is directed at the blades of the turbine by nozzles. The turbine spins continuously, as long as there is water to drive it. The turbine is connected to an electrical generator, and the electricity is then available for running appliances or charging batteries. The spent water is

returned to the stream. This kind of system is called a “micro-hydro” system, “run-of-stream hydro” or “low-impact hydro.” Canada and many other countries

depend on large-scale hydro developments for electricity. Micro-hydro systems can provide clean, environmentally friendly electricity in rural communities.

Hydropower is one of the three principal sources of energy used to generate electricity, the other two being fossil fuels and nuclear fuels. Hydroelectricity has certain advantages over these other sources: it is continually renewable thanks to the recurring nature of the water cycle, and causes no pollution. Also, it is one of the cheapest sources of electrical energy.

The Itaipu Dam between Brazil and Paraguay, which is 190 meters high and generates more than 12,600 MW, is the largest hydro power dam in the world. (The 185-metre Three Gorges Dam, now being constructed in China on the upper Yangtze River, would take its place by 2009, producing 18,200 MW of power). The Grand Coulee Dam, located near Spokane, Washington, is the largest hydropower dam in the United States, producing 6,480 MW. The Rogun Dam, in Russia, the tallest in the world, is 335 meters high. The Oroville dam, located in California, the tallest in the United States, is 235 meters high. Idukki dam in India is Asia's first and largest arch dam.

Advantages

More Economic than other fuels

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 also tend to have longer economic lives than fuel-fired generation, with some plants now in service which were built 50 to 100 years ago. Operating labor cost is also usually low, as plants are automated and have few personnel on site during normal operation.

No Greenhouse gas emissions

Since hydroelectric dams do not burn fossil fuels, they do not directly produce Carbondioxide(a greenhouse gas). 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.

Disadvantages

Environmental damage

Hydroelectric projects can be disruptive to surrounding aquatic ecosystems both upstream and downstream of the plant site. Generation of hydroelectric power changes the downstream river environment. Water exiting a turbine usually contains very little suspended sediment, which can lead to scouring of river beds and loss of riverbanks. Since turbine gates are often opened intermittently, rapid or even daily fluctuations in river flow are observed. Dissolved oxygen content of the water may change from pre-construction conditions. Depending on the location, water exiting from turbines is typically much warmer than the pre-dam water, which can change aquatic faunal populations, including endangered species and prevent natural freezing processes from occurring. Some hydroelectric projects also use canals to divert a river at a shallower gradient to increase the head of the scheme. In some cases, the entire river may be diverted leaving a dry riverbed..

A further concern is the impact of major schemes on birds. Since damming and redirecting the waters of the for agricultural and energy use, many native and migratory birds have become increasingly endangered

Monday, February 2, 2009

SOLAR CELLS


SOLAR CELLS:


Visible light can be converted directly to electricity by a space-age technology called a photovoltaic cell, also called a solar cell. Most photovoltaic cells are made from a crystalline substance called silicon, one of the Earth’s most common materials. Solar cells are typically made by slicing a large crystal of silicon into thin wafers and putting two separate wafers with different electrical properties together, along with wires to enable electrons to travel between layers. When sunlight strikes the solar cell, electrons naturally travel from one layer to the other through the wire because of the different properties of the two silicon wafers. A single cell can produce only very tiny amounts of electricity-barely enough to light up a small light bulb or power a calculator. Nonetheless, single photovoltaic cells are used in many small electronic appliances such as watches and calculators.


ELECTRICITY STORAGE


Solar panels make electricity in all kinds of conditions, from cloudy skies to full sunlight, in all seasons of the year. But they don’t work at all during the nighttime! To make electricity available after sundown, the energy must be stored during the day for later use. The usual storage device is a rechargeable battery. The batteries used with solar arrays must be able to discharge and recharge again many times. They contain special parts and chemicals not found in disposable batteries. They are also usually larger and more expensive than their disposable cousins. Besides solar panels and rechargeable batteries, modern photovoltaic systems are usually equipped with some kind of electronic charge controller. The main job of the charge controller is to feed electricity from the solar panel to the battery in the most efficient manner and to prevent the solar panel from overcharging the battery. The charge controller also protects the solar panels from electrical damage.


SOLAR ELECTRICITY IN EVERYDAY USE:



Photovoltaic panels, like computers and other technologies, are getting cheaper and easier to buy. In fact, many people consider them a great alternative to gas-powered generators or connections to the regular electricity supply. Some countries such as Japan have encouraged businesses and communities to install solar panels on the roofs of new buildings to reduce the need for electricity from other sources. Many homes and businesses have both a connection to the commercial electrical supply system (often called the “electricity grid”). The solar panels can provide all or most of the building’s electrical supply during the day, and the grid supplies whatever other electricity may be needed during the night.