Sunday, July 11, 2010
Hot News Of Anushka
THis is the news from Andra Pradesh.
More news will be soon..
Saturday, June 26, 2010
Introduction:
India got her independence in 1947. Our country faced many problems during the British rule. The British exploited the Indian resources for their development and progress. Some of their policies encouraged communalism in our country. It resulted in the division of India into India and Pakistan. Education was not provided properly to the Indian. Even though our government has taken many steps to eradicate the socio-economic problems of India, still we face some problems like communalism, casteism and anti-social practices.
Communalism:
A great hindrance to democracy is communalism. Communalism means placing one’s own community above, even above the nation. This feeling destroys the unity of the country and retards the progress of our country. The partition of India in 1947 was the result of communalism. There are people belonging to different religions in India. In fact the richness of our culture is the result of diverse religious communities. Our cultural heritage is seen in our monuments. The monuments like Sanchi Stupa, Ajanta and Ellora Caves, our famous temples all over India, the famous Taj Mahal and the melodious music of the North and South belong to people of different religions. When we look at any monument we do not think of the community to which the sculpture belong, but the magnificence of the sculpture. From the ancient period we find that we have developed a secular outlook. But today communal unrest sadly disrupts our lives. Education is the best way to eradicate communalism. Education creates a feeling of brotherhood among the people and fosters nationalism. Open University Scheme has been implemented by the Universities to educate the interested mass. Radio, Television and Newspapers play a vital role in the spread of mass education through various programs. The government is trying to spread national integration through television and other mass media.
Casteism:
Casteism is another major problem in our country. In the beginning, castes were formed on the basis of occupation. In course of time, this became hereditary. Slowly casteism became rigid. This has created many problems in our country. This poses a serious threat to national integration. It also proves to be a serious impediment to the progress of our country. The Government of India has taken many steps to improve the condition of Scheduled Castes and Scheduled Tribes. The Constitution of India has abolished untouchability. The Untouchability Offences Act was passed in 1955. This Act makes untouchability a punishable crime. Government has reserved seats in the Lok Sabha and the Legislative Assemblies and grants of stipends are given to them. The Government is using the mass media like television, radio and films, to educate the people against casteism.
Anti-Social Practices:
Some of the anti-social practices are bribery, corruption and smuggling. Bribery is called a white collar crime. Bribery usually occurs in connection with contracts, construction works, grant of licenses, purchase of land, etc. Bribing at all levels is a crime. Both the bribe giver and bribe taker are criminals. The Government of India has passed the Prevention of Corruption Act in 1947. The term corruption implies all illegal and anti-social activities. It also includes illegal gratification, misuse of power, undue influence in elections, etc. Smuggling is another anti-social activity. Gold, diamond, electric goods and drugs are mainly smuggled from foreign countries to India. Snake skins, crocodile skins, Pancha Loha idols, etc,. are smuggled from India to foreign countries. The Central Excise and Customs Departments are in charge of arresting these smugglers in order to prevent smuggling.
Growth of Population:
The rapid growth of population is one of the biggest obstacles to the progress of our country. Scientific advancements in medicine have lowered the death rate. Along with this higher birth rate also added to the increasing population. In 1951, our population was about 361 millions. In 1981, it was about 685 million. In 1991, it was about 843 millions and in 2001, it was about 1027 millions. India is considered to be the second most populous country. For the steady progress of our country the growth of population must be checked. As our resources are limited, over population will lead to poverty and unemployment. It will also lower standard of living.
The government is taking several measures to control over population by effective propaganda through mass media about family planning programmes, and spread of education particularly among women. Most educated people prefer to have a small family so as to have better standard of living.
Environment awareness:
The greatest impact of man on the environment is pollution. The balance of the eco system is delicate. Pollution affects not only air, water and land but also the organisms in the biosphere. When harmful substances contaminate the environment in large quantities, the eco system is unable to absorb them and the flow of energy form one sphere to another is distributed. This results in the breakdown of the balance in ecosystem and degradation of the environment. Air pollution and water pollution affect the environment. Some plants and animals have become extinct due to these environmental change. It has resulted in the depletion of resources. Man cannot live without progress. But he has to understand that progress does not mean the destruction of environment. He has to learn to live in harmony with the environment. He must try to maintain. He must try to maintain the delicate balance of the ecosystem.
AIDS:
Human body has a control mechanism to fight diseases. It is called immune system. The white blood cells fight invaders successfully. But they fail when a virus called Human Immuno Deficiency Virus(HIV) enters into the human body. This virus destroys the immune system itself. If the immune system is weakened, the person may be affected by all kinds of inflations. Common infections like colds and flu may also become untreatable.
After getting the infection, the stage of AIDS may take anywhere from a few months to 10 or 15 years to develop. The person will not be aware of it and feels as healthy as anyone else. Once AIDS set in, the individual will be quite sick and death follows soon. There is no drug or vaccine to cure this disease.
Aliens exists on other planets
Titan’s Chemical Composition Offers Hints Of Life: Nasa Researchers
Scientists at US space agency Nasa have found vital clues to suggest that primitive aliens could be living on Titan, one of the Saturn’s biggest moons.
On the basis of chemical composition found on Titan’s surface, the experts believe that life forms have been breathing in the planet’s atmosphere and also feeding on its surface’s fuel. The research based on the analysis of data sent from Cassini probe has been detailed in two separate studies.
The first paper, in the journal Icarus, shows that hydrogen gas flowing throughout the planet’s atmosphere disappeared at the surface. This suggested that alien forms could breathe.
The second paper, in the Journal of Geophysical Research, concluded that there was lack of chemical on the surface as it had been possibly consumed by the living aliens, the Telegraph reported.
“We suggested hydrogen consumption because it’s the obvious gas for life to consume on Titan, similar to the way we consume oxygen on Earth”, said Chris McKay, an astrobiologist working at Nasa. “ If these signs do turn out to be a sign of life, it would be doubly exciting because it would represent a second form of life independent from water-based life on Earth.”
Professor John Zarnecki, of the Open University, said: “We believe the chemistry is there for life to form. It just needs heat and warmth to kick-start the process. “In four billion years’ time, when the sun swells into a red giant, it could be paradise on Titan.”
-Surenthiran
Titan’s Chemical Composition Offers Hints Of Life: Nasa Researchers
Scientists at US space agency Nasa have found vital clues to suggest that primitive aliens could be living on Titan, one of the Saturn’s biggest moons.
On the basis of chemical composition found on Titan’s surface, the experts believe that life forms have been breathing in the planet’s atmosphere and also feeding on its surface’s fuel. The research based on the analysis of data sent from Cassini probe has been detailed in two separate studies.
The first paper, in the journal Icarus, shows that hydrogen gas flowing throughout the planet’s atmosphere disappeared at the surface. This suggested that alien forms could breathe.
The second paper, in the Journal of Geophysical Research, concluded that there was lack of chemical on the surface as it had been possibly consumed by the living aliens, the Telegraph reported.
“We suggested hydrogen consumption because it’s the obvious gas for life to consume on Titan, similar to the way we consume oxygen on Earth”, said Chris McKay, an astrobiologist working at Nasa. “ If these signs do turn out to be a sign of life, it would be doubly exciting because it would represent a second form of life independent from water-based life on Earth.”
Professor John Zarnecki, of the Open University, said: “We believe the chemistry is there for life to form. It just needs heat and warmth to kick-start the process. “In four billion years’ time, when the sun swells into a red giant, it could be paradise on Titan.”
-Surenthiran
Wednesday, June 16, 2010
Radar and its types
A variety of radars have been developed and they are classified based on
1. The signal transmitted.
2. The target of interest and
3. The frequency of operation.
Some of the commonly used radars are discussed as follows.
The radar transmitter transmits a continuous signal rather than a pulse one. The echo signal can be easily distinguished from the transmitted signal as there will be a shift in the frequency of the echo signal due to the DOPPLER EFFECT. Also, the echo signal’s strength is many times lower than the transmitted signal strength.
Using a CW radar, the relative velocity of a target can be determined. The drawback of a CW radar is that the range of the target cannot be determined.
MOVING TARGET INDICATION (MTI) RADAR
The MTI radar transmits a train of electromagnetic pulses. This radar system is capable of distinguishing a moving target from the non-moving objects. The non-moving objects in atmosphere that intercept the transmitted signal and scatter it are called CLUTTER. Since there will not be any DOPPLER frequency shift from fixed targets, as there is no relative motion, they are easily identified from the moving target. The echo from the moving target has the varying frequencies due to DOPPLER EFFECT.
TRACKING RADAR
A tracking radar system locks on to a particular target, measures its coordinates and provides data from which the future course of the target can be predicted.
The tracking radar is similar to other radars except that the antenna beam of a tracking radar is made to look at the target always. This is achieved by a servomechanism activated by error signals. The error signals is obtained using several techniques, viz. sequential lobing, conical scan and simultaneous lobing.
APPLICATIONS OF RADAR
Radar systems find their applications on the ground, in the air, on the sea and in space. The ground based radars have been used in the detection, location and tracking of aircraft or space targets. The shipboard radars are used to navigate the ships and to locate buoys, shorelines and other ships. They are also used to observe aircraft. The airborne radars are used to detect land vehicles, ships and aircraft. However, the principal application of airborne radar is for mapping of land storm avoidance and navigation. In space, radar is used for remote sensing purposes.
Megger(working principle)
Megger is the most portable insulation tester. It is used to remove very high resistances of the order of meg ohms.
PRINCIPLE:
The instrument works on the principle of ratiometer/ohmmeter. The required deflection torque is produced by both the system voltage and the current. Due to interaction between the magnetic fields produced by the voltage and the current, the deflecting torque is produced. The required coils are so positioned that the deflecting torque is proportional to the ratio, V/I.
CONSTUCTION:
It consists of
i. A small hand drives d.c. generator
ii. A moving element which has 2 coils, a deflecting coil (or current coil) and a controlling coil (or potential coil)
iii. Calibrated scale in mega ohms.
iv. Pointer and
v. Permanent Magnet.
The two coils are rigidly mounted at right angles to each other. They are connected to the small hand driven generator. The coils move in the air gap of a permanent magnet. To protect the coils under short circuit, a limiting resistor is connected in series with the coils.
OPERATION:
Resistance to be measured is connected across the test terminals i.e. connected in series with the deflecting coil and across the generator. When currents are supplied to the coils, then they have torques in opposite directions.
If the resistance to be measured is high, no current will flow through the deflecting coil. The controlling coil will, therefore, set itself perpendicular to the magnetic axis and hence, sets the pointer at infinity.
If the resistance to be measured is small, a high current flow through the deflecting coil and the resulting torque sets the pointer to zero.
For intermediate values of resistances, depending upon the torque production, the pointer is set at a point between zero and infinity.
The hand driven generator is of permanent magnet type and it is designed to generate from 500 to 2500 volts.
Fax(Fascimile)
This is a telecommunication service for the transmission and reception of picture information like photographs, drawing, weather maps, etc. The picture or any document to be transmitted is mounted on a cylinder and it is scanned by a photocell linked to the cylinder. The photocell produces an electrical analog signal as a voltage variation depending upon the intensity of the light and dark spots on the document. The electrical signal thus produced is converted into frequency variations and transmitted through a telephone line. At the receiving end, the frequency variations are converted back into corresponding voltage variations that is given to a plotter for reconstructing the original picture or document. Thus a photocopy of the original picture is obtained at a distance. Similar to a telephone signal, the FAX message also occupies a bandwidth of 4 kHz.
Computers have undergone revolutionary changes with the advent of integrated circuit technology. Before the appearance of these modern technologies, one of the most popular input devices was the CARD READER. The data to be fed into computer are punched on these cards using punching machines. Computer punch card is a special card of size of 7.5” x 3.25” x 0.007”. It has 12 rows and 80 columns. A special device called punching machine, whose key board is similar to the key board of modern computers, was used to punch data and information on the card. Each character punched will produce a unique set of holes, row-wise in the particular column where the character is punched. The advent of modern technologies has made cards and card readers obsolete.
For browsing on the internet, the following tools are available.
1. Who is – refers to identification of persons.
2. Finger – provides information like username, who has last logged in, how long his session had been idle, when he has viewed his last E-mail etc.
3. UU commands – information could be received about machines connected to Internet by UUCP (Unix to Unix copy).
UU Hosts – information is received about a particular site, who is responsible for it and what sort of UUCP connections it has with other sites.
UU Where – displays the path between the machine, the user is currently using and the site machine.
4. Gopher – Gopher is a software protocol designed to search, retrieve and display documents from remote sites on internet.
5. WAIS – Wide Area Information Service. It is a software protocol having the capability of searching more than one data line. The user has the provision of choosing the data for his requirement. Then he submits the query and gets the response for the query.
6. World Wide Web (WWW) – It is the most important aspect of Internet and has accelerated the growth of Internet. It is an easy to use, point and click graphical interface. It is highly interactive having graphics, text, sound and animation, etc. It is used as a market place, art gallery, library, community centre, school, publishing house, etc. There are search tools like web index and search engines to enable the information searches and discover them more effectively.
Sunday, June 13, 2010
Singam newly updated stills
Friday, June 11, 2010
Health is Wealth
Only a healthy man can be happy. If the body is healthy, the mind will also be healthy. A healthy mind is a happy mind. Id we are cheerful, we can do our work with enthusiasm. We will then be successful in all that we do. Thus good health is the strong foundation on which success and prosperity can be built up. Proverbs like ‘Health is wealth’ and ‘A sound mind in a sound body’ show the importance of health in human life.
Many people think that wealth or money is the most important thing. They try to earn money by sacrificing everything else. They sacrifice their peace of mind and even their health for the sake of money. They overwork and ruin their health. They do not know that an unhealthy man cannot be happy. They suffer much on account of their ill health. But they attribute their sufferings to bad luck. They may sometimes feel that if they earn more money, their sufferings will vanish.
If we have health, we can work hard and earn wealth. But if we lose our health, we cannot get it back by using money. It is true that we can buy medicines and get good treatment if we have money. But a man does not become healthy merely by getting cured of his disease. It is his ill health that makes him susceptible to various diseases. A healthy man can resist the attack of diseases.
If we realize the importance of health; we must take care to preserve our health. The most important thing is proper exercise. We should give proper exercise to every part of the body. We should devote at least half an hour every day to physical exercise. We can do this either in the morning or in the evening. It should become part of our daily routine. We should take breathing exercises also. We must eat balanced diet-food that contains carbohydrates, proteins, fat, vitamins and minerals in the right proportion. We should also sleep properly. A healthy man needs six to eight hours of sleep every day. We should keep our body in the right posture. The main part of the body-from buttocks to head-should always be kept in a straight line. We can remain healthy through proper exercise, proper breathing, proper food, proper posture and proper sleep.
(This essay is suitable for 6th, 7th, 8th and 9th std students)
-Surenthiran
ENERGY CONSERVATION IS THE FOUNDATION OF ENERGY INDEPENDENCE
PLEASE SWITCH OFF
Often over-charging the phone, i.e., leaving if plugged in even after the battery is full, leads to a wastage of electricity that nobody seems to take care of. People also sometimes forget to switch off the charger after unplugging the phone.
With 584 million mobile connections in India, one can only imagine the extent of power wastage, all due to a small act of carelessness.
While most phones have a visual reminder for when the battery is full, cell phone manufacturers could perhaps incorporate audio reminders as well.
LAPTOPS AND NETBOOKS
Students often leave the laptop switched on, even when they take a break which means that electricity is being consumed anyway.
While switching it off each time may not be feasible, one must practice putting it in sleep mode or in hibernation when not in use. A laptop in sleep mode/hibernation consumes 35 watts per hour used by an active screen.
The same applies to desktops and PCs. An attractive alternative here is virtualization, i.e., the process of running two or more logical computer systems on one set of hardware. Instead of installing a particular application on several computers, one could install it on to one of them and it can be accessed by all other PCs at the time. Thus a lot of power which otherwise would have been wasted is saved. Websites such as www.vmware.com and www.instantfundas.com provide details.
TELEVISION
As compared to the global average of 216 televisions for every 1000 people, India ranks 148 at 59 per 1000 people. Yet, considering our huge population, it translates into a stock of 72 million television sets in India, not a small figure by any stretch of imagination.
The television is the most common source of entertainment and news in use today, but not many think of using it in an energy efficient way.
The way one checks the price and picture quantity of television sets before purchase, one must also make a habit of checking for the energy efficiency. While most electric gadgets now come with a energy star rating, it only indicates the power consumed by a television in standby mode which actually accounts for a small amount of the total power consumed by it.
Some novel television models touted to be launched in 2010 are said to save up to 40 percent of the power consumed by television sets of today and by 2012, there will be sets that save up to 65 percent.
Till then, one can look at reducing the brightness and contrast of the television set which helps reduce power consumption. Interestingly, LCD models are more efficient than their plasma counterparts. An LCD of the same size as a plasma saves power by almost 60 percent.
AIR CONDITIONER
The air conditioner is no longer considered a luxury. At home, in malls, offices and even at college, the youth now find it difficult not to have air-conditioning, without realizing the impact of these cooling devices on the environment.
Most people are unaware of the ideal temperature for cooling that will also consume electricity in the most efficient way -24 degrees Celsius. They also do not clean and change the air filters regularly, thus not realizing the additional time taken for an air conditioner to work more effectively. Electronic devices used near the thermostat heat up the machine slower than its full capacity.
The simple act of switching off an air conditioner when the intended space is sufficiently cool can help save up to 10 percent power, as can installing an air conditioner in the right way, i.e., not exposing it to direct sunlight which wastes five percent more power.
AWARENESS ACCORDS
The most important thing for students to do is to work towards self awareness. An understanding of how much our basic facilities cost will help in knowing what steps to take towards reducing wastage.
Students must try and survey the power consumption of each house in their locality and generate subsequent bills. This will help not only to build awareness of how much power we consume and how expensive it is, but also help develop a shared vision amongst groups of students. Once they are aware of the realities, they can take it upon themselves to spread the message of conservation amongst their parents, siblings, friends, relatives and people in general. This would be the first step towards a ‘switching-off’ culture.
Students can make a difference through simple steps of which building self awareness is the first step.
One tends to think about power consumption and conservation only when they run up huge electricity bills and feel the pinch of paying large sums each. Here too, it is usually the parents who pay and students don’t even bother to know the pattern of electricity consumption within their own homes; an attitude that needs complete overhaul.
There is a famous proverb, ‘As you sow, so shall you reap’. If the youth’s indifference is in the solace that it is only the villages that will have to bear the brunt of unavailability of power, they will soon come to realize the extent of their misconception. The crisis is larger than it seems now and larger than it seems now and if not controlled in the not-so-distant future, it could affect urban areas in the same way.
CONCLUSION
It is better that we, as youth, take steps to conserve power today instead of repenting tomorrow. V S Naipaul once described India as an area of darkness. It might seem funny but the truth is that by switching off our lights regularly, we may actually bring light to a large part of the country. It is not about idealism. It is about securing our own future from falling into an area of darkness in a pragmatic way.
(This article is suitable for the students of 10th, 11th, 12th std and engineering.)
-Surenthiran
Cinema and its uses
(This article is suitable for 6th, 7th and 8th std students)
-Surenthiran
India on Mar 18, 1974 conducted its first nuclear explosion in Pokharan, Rajasthan. After a gap of 24 years India again conducted two atomic explosions on 11th and 13th May, 1998. on May 11th, through explosion, India experimented an atomic-fission device, a low-yield device and a thermo-nuclear device and emerged as the first country conducting these three experiments in one explosion. The second explosion of 13th May, ’98 was mainly intended to collect details for conducting an explosion in the computer simulation method. Both explosions were successful and India emerged as a strong member among the atomic nations.
The atomic explosions conducted by India invited pro and anti reactions from India and abroad. Some people are of opinion that a developing country like India is wasting crores of rupees in the preparations of bombs and atomic weapons. But this argument cannot be accepted. The authorities have clearly indicated that India will use its atomic power only for peaceful purposes and defence.
When our neighbours are not friendly, and when they are accumulation weapons for defence purposes India can not sit idle. We must also be prepared to guard ourselves when danger is threatening us. The explosions made recently can be taken as a warning to those neighbours who are not friendly and co-operative.
India’s aim through the atomic experiments is the formation of a comprehensive atomic system. The three devices such as the fission device, the low yield device and the thermo nuclear device were experimented together and its success is a great leap in the progress of atomic power. India is the only country successfully completing these three devices simultaneously. If the plan of India is to make atom bombs, India should not have conducted these three experiments. To make a bomb similar to that exploded in Hiroshima and Nagasaki, India doesn’t need all the technical know-how which India possesses today. The experiments conducted by India through the explosions clearly show that we are not interested in making crude bombs. We are aiming at a believable atomic weapon system as well as a powerful defence mechanism.
We have developed long range missiles of high quality like Prithvi and Agni. These are better than the bombers for the defence purposes. Now through the success in the experiments conducted by the nuclear explosions, India can equip the latest missiles more safely and successfully. In other words, the result of these atomic explosions will clearly set a strong missile system for the defence purposes. The knowledge gained from these explosions can be used in the other fields of Science and technology too.
In this modern world, where dangers through neighbours cannot be predicted, every nation should guard themselves. For this, use of atomic power and the related technologies cannot be blamed. But it should not be used for attacks or destructive purposes. There are so many peaceful uses of this power. All nations should understand the dangers of atomic power misuse and subsequent disasters. The proposed comprehensive Test Ban Treaty is to aim at this direction. But the provisions adopted in the treaty is beneficial for those countries who have stocked enough atomic weapons already. This is the main objection of India in signing the treaty. An atomic Test Ban Treaty is appreciable for a peaceful life. But that should be prepared as per the satisfaction and approval of all nations concerned.
Any way in a fast developing modern world all countries should take care to see that they are self sufficient in all matters. They should move pace to pace with other countries. The developing countries like India should work hard to attain this goal. In this hectic run, we have to take help form various forces and modern technologies. The help we plan to receive from the atomic experiments must also be considered in that way. This is an important leap to safety and prosperity.
(This essay is suitable for 7th, 8th and 9th std students)
-Surenthiran
Sunday, June 6, 2010
television
News, songs, dance, plays, films, cricket matches, football matches and various other programs are telecasted, and we can see them sitting in our drawing-room if we have a television set before us. We can see the newsreader reading the news. When there is some important news, we are shown the visuals depicting the actual incidents. When the newsreader says that Yeltsin met the American President Bill Clinton, we can see on the T.V. screen the two leaders meeting and conversing with each world events than those who listen to news bulletins broadcast by radio stations.
T.V. programs provide education as well as entertainment. The entertainment value of the television is equal to that of the cinema. We see pictures on the T.V. screen just as we see pictures on the screen in a cinema theatre. But the television is more convenient because we see everything sitting in our homes. We need not take the trouble of going to the theatre. Scientific programs and quiz programs are very instructive and of great educative value. Songs, dances, plays and films provide a lot of entertainments to T.V. viewers.
As the impact of T.V. programs is equal to that of films, the television can be used for social reforms and for promoting national integration. The harmful effects of social evils like dowry, casteism, smoking, drug-taking, etc., can be shown in T.V. programs in order to educate the people. As television(i.e. Doordarshan) is controlled by the government, they can easily do it if they have the will to do it. Programs for promoting national integration are being shown. A Keralite sings a Tamil song, a Tamilian sings a Marathi song, a Maharashtrian sings a gujarati song, a Gujarati sings a Bengali song, a Bengali sings a Kannada song, and so on. Such programs promote national integration.
Films can be recorded in video tapes and then telecast. Doordarshan telecasts a few films every week. In addition to this, we see any film we like on the T.V. screen, if we have a video cassette of the film and a V.C.P. or V.C.R. Some people think that this has adversely affected the income from films.
Television is very useful. But it is not an unmixed blessing. Television exerts a bad influence on many people. It makes people lazy. People sit for hours watching television and neglect their duties. This danger is greater in the case of students. They sit before the T.V. set watching interesting programs and neglect their studies. The habit of sitting before the television for hours together has become a dangerous addiction in many homes. Students should see only those programs that have educative value. They should realize that their duty is to study.
(This essay is suitable for 6th, 7th, 8th and 9th std students)
-Surenthiran
social work and students
Students are specially useful for social service. Educationalists, reformers and others want that students should be associated with social service to greater degree than the common man. Countless people have come out with views, urging upon authorities to make it compulsory for students to do social service too. In China, social service is a education, students can make trips to villages and stay there in order to make the rural people literate. Besides, it is expected of them to give them a sense of civic duty. Cleanliness, disciplined way of life, etc. Students can be of real guidance to those who need light of knowledge.
Students can associate themselves with Roadways and Railways and become very useful passenger guides at important stations and bus points. They can also usefully give hints about do’s and don’ts to pedestrians at busy road crossings in large cities for the safety of people, because many people die form road accidents. In the same way, they can do useful service by guiding patients in hospitals properly.
The importance of social work among students is great. The qualities that they acquire during their education days have a lasting effect, being of use to them throughout their life-time. In a democratic country, it is the service of people which endears an individual to the community. Ideals of humbleness, devotion to duty, giving priority to the interest of people, being prepared for sacrifice for the sake of fellow human being in difficulty, etc. are matters which are extremely essential for success, whether in public service or in private business. Even rich industrialists need these qualities in order to get along well with their workers. For these and certain other allied reasons, it is necessary that students should have a period of training through social service.
When the country is faced with enemy threat students can do a really useful work. The country is now going through a rapid scheme of development with plenty of river-valley projects, industrial enterprises and other development works in progress at present. The roadways are being considerably expanded, the railways are being extended and further developed; co
Social service can change the nature of students positively. If it is made compulsory, it will be producing a sense of responsibility and humility among the usually stiff-necked educated persons. They will develop a feeling that they are to be of use to fellow human beings. This will be good for both themselves and for the country. The present indifference to manual work or to mixing up with illiterate villagers will gradually disappear. Such students when they happen to hold important civil posts later in life, will continue to have the feeling that they are there to serve the masses, rather than to rule over them. It is, therefore, advisable that social service should be made a part of the ordinary curriculum of a student. The enthusiasm for demanding social service from students, should not go too far. The idea is to include a sense of responsibility among the students. This, however, should be fulfilled without any harm to the student or to his studies.
(This essay is suitable for 7th, 8th and 9th std students)
-Surenthiran
We read newspapers every morning. We are accustomed to the reading the newspaper, and we cannot live without it. A newspaper gives us news. It satisfies our curiosity by telling us what happened in the world around us during the last twenty-four hours.
We are eager to know what happened in our town, in our country, and in foreign countries. An newspaper keeps us informed of all the important happenings in the world. When we read the newspaper we know what happened at the test match going on in Calcutta, what happened at the political discussions in Delhi and so on. It is therefore necessary that we should read newspapers every day.
We rely on newspapers for our knowledge of what is happening in the world. It is therefore the duty of newspapers to tell us the whole truth, and nothing but the truth. A newspaper should not distort news by suppressing certain facts. It is the duty of every newspapers to find out the facts and to report them faithfully.
Newspapers play a very important role in democracy. Newspapers give not only news but also views. Newspapers form public opinion by the views they express. Newspapers strengthen democracy by making the citizens responsible and well-informed. Newspapers are the watch-dogs of democracy. They should play this role effectively. Newspapers should be fearless. If democracy is to survive, newspapers must not only be fearless but also make the people fearless.
(This essay is suitable for 6th, 7th and 8th std students)
-Surenthiran
Tuesday, June 1, 2010
An essay about the power of Knowledge
Desire for power is inherit in man. Thee love of power comes from the consciousness of man’s mental and moral superiority over other created things. It is instinctive, therefore, that man as superior being must control and dominate others. Again the awareness that all men are created unequal gives birth to the desire to rule and dominate others. The history of the world, so far as man is concerned, is a history of the struggle for power. Thus from the primitive wars of tribes and clans to the ruinous wars of today, there is only one idea behind these wars and that is the thirst for power.
Broadly speaking, power is of two kinds-physical and mental. Physical power is of the lower order as compared to the power of the mind. Primitive men mainly understood one kind of power and that was of the body. In the past the strength of the arms decided things and might alone was right. However, with the growth of civilization and the development of human mind, the mental power has its origin in knowledge.
When man first appeared on the earth he was no better than animals. He was also the beast of prey and was a helpless being, a victim of the wild beast and the hostile forces of nature. But God endowed him with an intelligent mind and ultimately came to his rescue. He discovered fire and learnt its uses and this knowledge of use of fire gave him power. Similarly, knowledge has achieved wonders in the world and given man mastery over many things.
All the great discoveries and inventions on which modern life is based are but the manifestations of the power of knowledge. The conquest of the forces of nature like water and electricity and harnessing of these forces for man’s use, have been made possible by the knowledge of physics. It is the knowledge of mechanics which has lessened distance, broken down the barriers between men and enabled men to realize the affinity of men all over the world. The epoch-making discovery of atomic energy has revolutionized the entire concept of future life of man on the earth. Today completely unheard strides made by man in the field of science are the results of the knowledge and perpetual search of wisdom combined with the hunger of power to rule and dominate.
In fact the development of art, science, culture and civilization, ultimately depends knowledge. Nature has yielded her mysteries to this power. It has made physical power and mental strength to one and the same. But knowledge has not only given man mental strength, it has taught how to utilize his physical strength in a better, surer and more and more disciplined and economic way.
Great ideas make great men and there is no trait more constant in human nature than his habit of pursuing a truth beyond its province. Hence balance is the cardinal virtue of good sense. Great as is the power of knowledge, the tendency to misuse is greater. Knowledge is inclined to fill us with pride and thus stake its real blessings. The need is to translate knowledge into wisdom, for knowledge is proud and wisdom is humble. It is only when we have realized this that we understand the significance of knowledge that is power, and get the desire to acquire that knowledge which enable us to find truth. We must pursue knowledge to its utmost for, ‘Half knowledge is a dangerous thing; Drink deep or taste not the perennial spring’.
This essay is useful for 7th, 8th and 9th std students)
-Surenthiran
• Don’t you receive signal properly?
• Do you have difficulties in charging mobiles during travel
• Do you want to connect mobile phones to TeleVision
• Do you need a charger suitable for all models
Don’t you receive signal properly?
Are you forced to run outside when a call comes due to signal problems? Signal Booster has come to resolve this problem. This is New Jen-X Plus Signal Booster. It is enough to stick a Signal Booster Sticker at the back of your mobile. When you receive a call, it will boost up the signal. Almost it is available for all the modal including Nokia.
Cost: Rs. 129
Available At: Ritchie Street, Chennai
Do you have difficulties in charging mobiles during travel?
Your mobile battery may lose the charge during travel and you may suffer to charge again. A very very useful mobile accessory has come to the market now. It is nothing other than Travel Charger AC-4. The leading mobile company Nokia launched this equipment.
This is suitable for all the Nokia modals.
Cost: Rs. 300
Available At: Univercel and Poorvika shoppes
Do you want to connect mobile phones to TeleVision?
Do you wish to see all the videos, pictures in your TeleVision? An Accessory is available now…
Nokia’s TV-OUT Cable CA-75U. With this, you can connect your mobiles to your television and view the items in the mobiles easily. Not only for Nokia modals, this cable is now available for all the modals.
Cost: Rs. 275
Available At: Univercel, WaveTel
Do you want a charger suitable for all modals?
Usually, Charges are available for a particular modal or three or three particular modals. A charger suitable for one modal will not be suitable for another modal. Here is a charger suitable for all modals. This is TSM UNIVERSAL CHARGER. It consists of Six types of pins and a car charger. Any type of Mobiles can be charged with this charger.
Cost: Rs. 500
Available At: Almost all the mobile shoppes
(For images, please visit www.mobileulagam.com )
-Surenthiran
WHAT IS MEANT BY FOOD ADULTERATION?
The contamination of food materials with low quality, cheap, toxic substances is called food adulteration.
What are the ways by which adulteration is affected?
Adulteration is done in the following ways:
a) Addition of inferior substances and poisonous substances
b) Insect infestation
c) Extraction of superior ingredients from the food
d) Addition of coloring matter not permitted by regulations.
What is an Adulterant?
The substance which degrades(or lowers) the quality of a food material is called an adulterant. The adulterants are much cheaper than the concerned foodstuffs. So, selling adulterated food materials can bring a lot of easy money for the dishonest trader, but at the cost of many lives.
Test to detect adulteration in food
Since food adulteration is a serious matter and concerns us all, so we should know how to detect adulteration in the commonly used food items like butter, ghee, edible oil, dals(pulses) and milk. This is discussed below.
1. To detect the presence of vanaspati in ghee or butter
Take 5ml of ghee or butter in a test tube and add 5 ml of conc. HCL and a small amount of sugar. Shake the test tube well. Appearance of a deep red colour in the lower layer shows the presence of vanaspati in ghee.
2. To detect the presence of starch in milk and butter
A small amount of iodine is added to the adulterated sample. The appearance of the colour shows the presence of starch in the sample.
3. To detect the presence of chicory powder in coffee powder
Take equal volumes of conc. HCl and coffee decotion in a test tube and heat for few minutes. Then, add small quantity of seliwonoff reagent. The red colour formed shows the concentration of chicory powder mixed.
4. To detect the presence of argemone oil in edible oil
Take 5 ml of edible oil in a test tube and add some conc. HNO3 to it. Shake the test tube carefully and observe the colour of the lower layer(the acid layer). Appearance of a reddish-brown in the acid layer shows the presence of argemone oil in the edible oil.
5. To detect the presence of metanil yellow in dal
Take about 5 grams of dal in a test tube and then add about 5 ml of water. Shake the test tube well. Then add a few drops of conc. HCl to the test tube. Appearance of a pink colour in the solution shows the presence of metanil yellow in dal.
6. To test the presence of water in milk
VISCOSITY TEST:
When pure milk is adulterated by mixing water, then its viscosity decreasing that is, it becomes very thin and flows easily on a surface. This fact can be used in testing the presence of water in milk, as follows:
Take a drop of the milk sample on a glass plate and hold the glass plate vertically.
a) If the drop if milk either keeps sticking to the glass plate or flows down slowly, leaving behind a white trail, then the milk sample is pure.
b) If the milk drop run down quickly on the glass plate, leaving no white trail, then the milk has been diluted with water.
-Surenthiran
Monday, May 31, 2010
An essay about Sports And Games
Sports and games are essential for many reasons. They are not only help us to maintain good health but foster friendship and good behaviour. Many people think that the aim of sports and games is to win gold medals in Olympic games. That is not at all important. What is important is that every boy and every girl in our country should be interested in sports and games. Being interested in games does not mean merely watching other people play games. They should participate in sports and games. Sports and games must be given as much importance as academic studies in our schools and colleges. Marks must be awarded for proficiency in sports and games just as marks are awarded for proficiency in mathematics and physics.
When all our school students and college students take part in sports and games, they will be healthy and active. They will participate in their academic studies and scientific experiments with great enthusiasm.
But physical health is not the only advantage of sports and games. Participation in sports and games fosters friendliness and broadmindedness among the participants. Sportsmen forget caste differences and religious differences and become friendly with one another. They look upon the world as one family. Thus sports and games have a lot of educative value.
Sportsmen have often to live together while undergoing training and participating in competitions. They understand one another and learn to make the adjustments necessary for corporate life. They learn to respect one another’s individuality. In other words, they learn the virtue of tolerance.
When they go to other countries to participate in international competitions, they are not merely competitors but messengers of good will. Whether they win medals or not, they will certainly earn a lot of good will. This does not mean that they will not win medals. When all our youngsters take part in sports and games every day, there will be many talented sportsmen and sportswomen. Their talent will improve day by day. It is quite certain that some of them will be able to win medals in international competitions. But the number of medals they win is not important. One year the number may be more, another year it may be less. What is important is that they will spread good will and love throughout the world.
(This essay is suitable for 7th and 8th std students)
-Surenthiran
Nature is our mother. She offers us all facilities to lead a comfortable and peaceful life. She brings us rain. She feed the human beings who are her children. The plants, trees, bushes and the grains we grow all belong to nature. Yet man is not grateful to nature. He pollutes the surroundings and brings destruction on himself.
Environmental pollution may be of three kinds. They are air pollution, water pollution and noise pollution. Air pollution is caused by factories which emit smokes and fumes. They mix with the pure air and pollute it. Air pollution is also caused by fumes from the exhaust pipes of vehicles. It is also caused by all kinds of refuse such as dust bin refuse, lavatory refuse and washing up refuse. When we breathe the polluted air, our lungs are affected by diseases.
Water pollution is contaminating water sources. Factory wastes and gutter water are allowed to flow into rivers. These are also collected in ponds. They pollute the surroundings. Contaminated water causes many diseases. Cholera is the first among them. Stagnant water breeds mosquitoes. It results in malaria.
Noise pollution is caused by vehicles and their horn. Some factories also disturb the peaceful atmosphere around. Loud speakers are the worst pollutants in this regard. They spoil the entire atmosphere.
Man cut and fells trees without any limit. This causes imbalance on the surface of the earth. The result is lack of rain and soil erosion. We must protect trees. Let us keep our surroundings clean and lead a healthy and happy life.
-Surenthiran
Martin Scorcus, a famous director in Hollywood has to shoot on a new big budget film. He has chosen Aishwarya Rai, a famous Indian actress, as heroine. He is directing a Artistic film now.
Few days ago, when attending Canes movie ceremony, Matin met Aishwarya Rai and told his story.
Since she liked the story and her character, She gave him the call shoot.
Martin is a director who impresses people by his different thoughts. By hearing this news, all the other actresses having a envious look on Aishu.
After finishing this movie, She is on another project with Devadas. Presently, she has done Ravanan in both Hindi and Tamil. And she is presently doing Enthiran which is going to be a fabulous hit in this year. So, Aishwarya Rai is very busy in her call shoots now.
-Surenthiran
Sunday, May 30, 2010
VIJAY SOON IN POLITICS
The following is the speech given by S.A. Chandra Sekar, director.
Music release ceremony
Director Chandrasekar’s forthcoming movie ‘Veluthu Kattu’. The starting ceremony function of this movie has happened in Trichy few days ago.
The following is the speech given by him:
Vijay soon in Politics
“Vijay’s fans club is active every where in Tamil Nadu. I have to be blessed to have Vijay as my son.
Vijay has put the base to enter into the politics. His movies are most welcomed and celebrated by the public. His familiarity is increasing day be day. His involvement in the politics is unavoidable. He is waiting for the right time.
Naan Sigappu Manidhan
I have planned to remake my own movie ‘Naan Sigappu Manidhan’, with Vijay as hero. I have planned only to produce that film and give over the chance for the youths.
Likewise, I have a thought of remaking my old movies”.
Mr. Chandrasekar finished his speech in this way.
-Surenthiran
VIJAY’S SURA, A GREAT FLOP
· Double hay-trick flops for Vijay
· Rs. 10 crores loss due to Sura
· Theatre owners request Vijay to repay the amount
Since actor Vijay has given consequently 6 flop movies, the theatre owners has faced a great money loss. Rs. 10 crores is the loss amount for the theatre owners only for Sura. Hence, Vijay has been asked to repay 30% of the amount paid.
Theatre owners pathetic situation this year
The following is the speech given by Mr. Panneer Selvam, the secretary, Tamil Nadu Cine Theatres Association.
“Theatre owners situation this year has become very bad. Almost all the coming films are getting flopped. Hence, collection is getting lowered day by day.
The following are the films which gave a better collection this year:
1. Paiyaa
2. Tamil Padam
3. Angaaditheru
All the other films were a great flop commercially.
Vijay has betrayed not only his fans but also theatre owners. Vijay’s Aadhi, Azhagiya Tamil Magan, Villu, Kuruvi, Vettaikaran are the first five movies. Sura is the 6th flop movie.
Sura
Since this movie released with a great expectation that this is the 50th movie of Vijay, the theatre owners invested a large amount of money to buy this movie. But it become a big flop.
Has to repay the amount
Rajinikanth, Kamal Hasan, Mani Ratnam, Vijaya T. Rajendar used to repay 35% of the money invested by the theatre owners. The same way, Vijay has to repay 35% of the invested money.
Regarding this, we tried to talk to Vijay. But we couldn’t able to visit him. We remembered the same situation when the movie Aathi beacome a great flop.
Decision to be taken in the meeting
A meeting will be conducted in the 3rd week of June. There, a decision will be taken how to deal with the forthcoming movies of Vijay.
The main reason for the failure of Vijay is that he acts in the same manner(dirty dress, rowdy slang, similar make-up). He chooses the same theme of stories everytime. Here after, Vijay’s films will be bought under the basis of percentage.”
In this way, Mr. Panneer Selvam finished his speech.
-Surenthiran
LYRICS OF ADADA MAZHADA FROM PAIYAA
Here is the lyrics of the song Adada Mazhada from the movie Paiyaa….
Thanthaaney thanthaaney thanthananeyThanthaaney thanthananey thanthanaaneynaaaThanthaaney thanthaaney thanthananeyThanthaaney thanthananey thanthanaaneynaaa oooooooohhhh…
Adada mazhaida adda mazhaida,Azhaga siricha puyal mazhaida..Adada mazhaida adda mazhaida,Azhaga siricha puyal mazhaida..
Maari maari mazhai aidika,Manasukulley kodey pidika,Kaazhgal naalachu, kaigal yettachu,Yennachu yethachu, yedhedho aayachu..
Mayil thogha poley iva mazhaiyil aadum bothuRayil thaalam poley yen manasu vaazhum paaruYennachu yethachu, yedhedho aayachu…
Adada mazhaida adda mazhaida,Azhaga siricha puyal mazhaida..
[MUSIC]
Paatu paatu paadatha paatu,Mazhaithan paaduthu keykaatha paatu,Unney yenney serthu vecha mazhai-koru sallam podu,Yenney konjum kaanalaiye unnakkuley theydi paaru,
Maanthiram poley iruku, puthu thanthiram poley iruku,Pambaram poley enaku, thaley mathiyil suthudhu kiruku,Devathai engey en devathai engey, athu santhoshama aaduthu ingey..
[MUSIC]
Unnai-pozha veyrarum illey,Yenney-vitta veyraru solla,Chinna chinna kannu rendey koduth-enna anupuvechan,Intha kannu pothalaiye yethuk-ivala paduchuvechan,
Vattampuchi ponnu nenju pada-padakum ninnu,Poo ivolo onnu, yenna kondu putta konnu..Povathu yengey naan povathu yengey, manam thalladuthey bothaiyil ingey..
[FEMALE]
Adada mazhaida adda mazhaida,Azhaga siricha anal mazhaida..Adada mazhaida adda mazhaida,Azhaga siricha anal mazhaida..
Pinni pinni mazhai adikka,Minnal vanthu kodey pidikka,Vaanom rendachu, bhoomi thundachu,Yen moochi kaathaaley, mazhai koodey soodachu..
Iddiye neeti yaaro intha mazhaiye kaddika veynam,Mazhaiya pooti yaaro yen manasa addaika veynam,Kondaada kondaada, koothadi kondaada..
11 DIGITS NUMBERS FOR MOBILE PHONES
Soon, the number of people using mobile phones in India is on to override 1 crore. So, the Communication department has planned to introduce 11 digits numbers to overcome the shortage of the numbers.
Presently, 10 digits numbers are given for the mobile phones in India. This is suitable only for 100 crore connections. But, it is calculated that viewing the speed of increase in the number of pupils using cell phones, 100 crore pupils will be having cell phones in their hands by 2014.
Hence, TROY has given the idea to all the mobile service companies to change from 10 digits numbers to 11 digits numbers.
But, due to the reason that it will take much cost for 11 digits numbers, the mobile service companies did not come to a perfect decision.
But, it is the fact that 11 digits numbers are very much needed. The companies soon will take a positive decision and bring the system of 11 digit numbers.
-Surenthiran
Friday, May 28, 2010
FIRST TAMILAN ON
Hence, Santhosh Kumar became the first tamilan to reach the top of the Everest peak.
Being reached the top, he shouted “Tamil Vaalga” with joy.
The crew members shared their happiness proudly with their family members through telephone.
The people of Tamil Nadu must be really of Santhosh Kumar crew members.
Mrs. Indira Vetrivel, the famous socialist, spread out this information.
(for images, visit www.thehindu.com)
-Surenthiran
Hot News of Asin
PAYMENT LOW FOR ASIN
Asin who have come from Malayalam to Tamil film industry lowered her payment for the Tamil movie “Kaavalkaran”.
Hindi movie
The actress Asin started as a successful heroine through the tamil movie “Ghajini”. She performed the same role in the hindi movie “Ghajini”. This movie became a powerful commercial hit both in tamil and hindi. Hence, her market raised to the heaven.
Rs.3 Crore
As a result of the success of Ghajinis, Asin raised her payment to Rs.3 Crore.
She performed as a heroine in the movie “
Payment gone down
Later, She did not get any hindi movie chances. When she was residing at her guest house in Mumbai, She was asked the call shoot for the movie “Kaavalkaran” in which Vijay performs Police role.
Asin accepted this tamil movie chance and lowered her payment from 3 crore to 1 ½ crore.
Presently, the big movie “Kaavalkaran” is in shooting process with Asin as heroine.
-Surenthiran
Basics of Electricity
Matter has mass and takes up space. Atoms are basic building blocks of matter and can’t be chemically subdivided by ordinary means. ‘Atom’ is derived from the Greek word ‘atom’, which means indivisible.
STRUCTRURE OF ATOM:
Atoms are composed of three types of particles: protons, neutrons and electrons. These particles have different properties. An atom has a positive centre called the nucleus. The central nucleus consists of protons, neutrons and the electrons revolve round the nucleus. Electrons are very tiny, very light particles having negative electrical charge. Protons are much larger than electrons and have positive electronic charge. Neutrons are large and heavy like the protons but no electrical charge. In any atom, the number of positive charges present in the nucleus is equal to the number of negatively charges electrons revolving round it. Thus, the atom is electrically neutral on the whole.
CHARGE:
When positive or negative charge builds up in fixed positions on objects, certain phenomena can be observed. The charge can be built by rubbing objects together, such as silk and glass or ebonite and fur. The friction between the objects causes electrons to be transferred from one to the other-from a glass rod to a silk cloth or from fur to an ebonite rod-with the result that the object that has lost the electrons has a positive and the object that has gained them has an equal negative charge. An electrically neutral object can be charged by bringing it in contact with a charged object, if the charged object is positive, the neutral object gains a positive charge when some of its electrons are transferred on to the positive object. (When the glass rod is rubbed with silk, the glass rod becomes positively charged.)
If the charged object of negative, the neutral object gains a negative charge when some electrons are attracted on to it from the negative object. (When an ebonite rod is rubbed with fur, the ebonite rod becomes negatively charged.)
CHARGING OF BODIES:
Charging by friction
When a glass rod is rubbed with silk or an ebonite rod is rubbed with fur, the glass rod becomes positively charged and the ebonite rod becomes negatively charged due to friction. Friction between the objects causes the transfer of electrons. The glass rod loses some of its electrons to the silk cloth and becomes positively charged due to excess of positively charged particles. Similarly, when the ebonite rod is rubbed with fur, the rod gets extra electrons from the fur and becomes negatively charged. Charging a body by friction if possible when two bodies of opposite nature (i.e.) one having a tendency to give away free electrons and the other having a tendency to accept the same are made to rub against each other.
In this process, both the bodies, which were not charged, acquire opposite charges.
Charging by conduction
When charges are transferred to an uncharged body from a charged by making physical contact between them, it is called charging by conduction. The undercharged conductor B is mounted on an insulating stand. A positively charged conductor A is brought in contact with the conductor B. Since the conductor A is positively charged, it has a less number of free electrons and hence when B touches A, a few electrons move from B to A. Thus B gets positive charge due to loss of free electrons.
Charges by conduction are possible when one of the bodies is already charged. Here, both the bodies acquire the same type of charge as they share the excess or deficit of electrons.
Charging by induction
When charges are transferred to an uncharged body from a charged body without physical contact between them, it is called charging by induction.
For charge of given sign, it is necessary to start with an inducing charge of the opposite kind. To charge the uncharged body AB positively, a negatively charged rod has been brought near to the end A of the uncharged body AB. Some of the free electrons in the conductor are repelled towards B by the excess of electrons on the negative rod, thereby creating a negative induced charge at B and a positive induced charge at A. The conductor is now earthed by touching it with the finger, as a result some of the free electrons are repelled to earth. The finger is then removed and the charged rod is taken away. The positive charges redistribute themselves uniformly throughout AB. Thus, AB is positively charged.
Conductors and Insulators
Though all materials are made of atoms and all atoms are made of electrons and nuclei, the electrical properties of substances vary widely. According to their electrical properties substances are grouped into conductors and insulators.
Conductors contain free electrons, which can move throughout the material. Metals are good conductors. Silver, copper and aluminum are some of the best conductors of electricity and acidified water and electrolytes are no-metallic conductors.
Insulators or dielectrics have tightly bound electrons, which are not free to move through the material. Hence, electricity cannot move through them. E.g. ebonite, mica, glass, rubber, etc.
GOLD LEAF ELECTROSCOPE
The electroscope is a device used for detecting the presence of charge and testing the given electric charge. It was invented by Nollet in the 18th century.
The gold leaf electroscope consists of a glass bell jar resting on a wooden base. The mouth of the bell jar is closed with an ebonite stopper or a rubber cork having a central hole, through which passed a brass rod. At the lower end of the brass rod are two narrow strips of very thin leaves of gold and the upper end is fitted to a metal disc with a spherical knob. A small cup of calcium chloride may be placed inside the jar to keep the air inside dry. There are two strips of tin foil on the inner wall of the bell jar and facing the gold leaves. The jar protects the leaves from air currnts. When any charged body is dept in contact with the metal disc, the leaves acquire the charges of the same nature, so the leaves repel each other. The divergence of the two leaves indicates the presence of the charge. The increase of the leaves is the only sure test of the electrification of a body. (Brief picture of Gold Leaf Electroscope is available at wwww.encarta.com)
(i) To detect the presence of charge on a body
If a rod of some suitable material is charged by friction and then brought near the disc of the electroscope, the leaves diverge. A charge has been induced on the leaves and consequently the leaves diverge. On removing the charged rod, the leaves collapse, showing that the induced charge on the electroscope is only temporary.
Very small charges may be detected by this method.
(ii) To charge the electroscope by induction
(a) A negatively charged ebonite rod is held near the disc of the electroscope. A positive charge is induced in the disc and a negative charge is induced in the leaves. This happens because the negatively charged ebonite rod repels the electrons from the disc to the leaves. The leaves diverge.
(b) When the disc is connected to the earth by touching it with your finger, electrons from the leaf flow to the earth and the leaves collapse.
(c) Keeping the ebonite rod near the disc, if you remove your finger, the leaves remain in the collapsed position because they do not have any charge in them.
(d) If you remove the ebonite rod, the leaves diverge again. The positive charge flows to the leaves also. Thus, the electroscope is positively charged by induction.
To charge the electroscope negatively, a positively charged glass rod is used.
(iii) Detecting the type of charge present in a body using electroscope
Having charged the electroscope positively as described above, bring a charged rod near the disc of the electroscope. If the divergence of the gold leaves increases, then the rod is negatively charged. If the divergence decreases, then the rod is positively charged.
CHARGE DENSITY
Whenever a conductor is charged, the charges reside on the outer surface of the conductor. The charges are not distributed uniformly over the surface. The distribution depends on the shape of the surface and it is found to be inversely proportional to the radius of curvature. The amount of charge per unit area of the surface of the conductor is known as charge density.
In case of a spherical conductor, since the radius is uniform, the charge distributes uniformly and so the charge density will be equal everywhere. But in the case of a pear shaped conductors, the charge density is greater at the pointed end than at the places. Thus a pointed end acquires a large amount of charge.
As a pointed end acquires a large amount of charge, it sets up a field in its neighborhood. Air molecules entering into the field take the same charge from the pointed end become ionized. Since the pointed end as well as the air molecules are of the same charge, the air molecules which is called the electronic wind. Ultimately, the pointed end loses its charge and it is discharged easily. A point also collects charges easily from its surroundings. This phenomenon is called ‘action of points’.
LIGHTNING ARRESTERS
Benjamin Franklin(1706-1790), an American scientist, proved that lightening and electricity are identical and subsequently invented the lightning arrester also called lightning conductor. It protects tall buildings from being damaged by lightning. The light conductor is based on the principle of action of points.
It consists of a thick copper strip to an outside wall, reaching above the highest part of the building and ending in several sharp spikes. The lower part is buried in the earth.
When a negatively charged thundercloud passes overhead, it acts inductively on the conductor, charging the sharp points and te earthed plate negatively. The negatively charge on the plate is, of course, immediately dissipated into the surrounding earth. At the same time, action of points occurs at the spikes. Negatively ions are attracted to the spikes and become discharged by giving up their electrons. These electrons pass down the conductor and escape to the earth.
The upward stream of positive ions spread out and form what is called a space charge, which reduces the powerful electric forces existing between the cloud and the building. Under these conditions lightening will nor normally strike a building but if it should do so, the discharge passes harmlessly to the earth through the thick copper conductor.
(The pictures and explanatory images of the corresponding topics are available at www.encarta.com. But the explanation which is given here is more understandable than Encarta.)
***This article is more useful for the students of 6th std(sixth std), 7th std(seventh std) and 8th std(eight std).
An article by,
Surenthiran