13. Answer the following

(i) Of what lead pencils are made of?

Graphite

(ii) Why is one’s breath visible in cold but not in hot weather?

Because the water vapours present in breath condenses while breathing incold weather and therefore are visible.

(iii) What is the chemical composition of diamond?

pure carbon

(iv) Name the vaccine that protects against tuberculosis.

BCG
bacillus Calmette-Guérin

(v) Name the disease of the liver that causes a patient to turn yellow

Jaundice

rgds

paper 1998
Reaction Time

The interval of time between application of a stimulus and detection of a response.

Your hand accidentally touches the hot plate of an oven and is withdrawn immediately. A young child runs out in front of your car and you hammer on the brakes. A lottery ball falls into its position upside down and you have to shout out the correct number as fast as you can to a colleague who is checking off the numbers for your syndicate. All three examples of reaction time are the time it takes to make a movement in response to a sensory stimulus. However, even if we try to respond as fast as possible in each situation, the reaction time is quite different.

In this context, time is measured in milliseconds (ms) — thousandths of a second. It may take only 100 ms to withdraw our hand from the stove, 200 ms to stamp on the brakes, and 500 ms to read out the number on the ball. The difference occurs because of the different amount of time it takes for the central nervous system (CNS) to process the sensory signals and to choose the appropriate course of action.

rgds

paper1998

Q.3. Discuss in detail the fission and fusion processes. Which one of thee processes in the source of solar energy?

Nuclear Fission

An atom's nucleus can be split apart. When this is done, a tremendous amount of energy is released. The energy is both heat and light energy. Einstein said that a very small amount of matter contains a very LARGE amount of energy. This energy, when let out slowly, can be harnessed to generate electricity. When it is let out all at once, it can make a tremendous explosion in an atomic bomb.
A nuclear power plant (like Diablo Canyon Nuclear Plant shown on the right) uses uranium as a "fuel." Uranium is an element that is dug out of the ground many places around the world. It is processed into tiny pellets that are loaded into very long rods that are put into the power plant's reactor.
The word fission means to split apart. Inside the reactor of an atomic power plant, uranium atoms are split apart in a controlled chain reaction.
In a chain reaction, particles released by the splitting of the atom go off and strike other uranium atoms splitting those. Those particles given off split still other atoms in a chain reaction. In nuclear power plants, control rods are used to keep the splitting regulated so it doesn't go too fast.
If the reaction is not controlled, you could have an atomic bomb. But in atomic bombs, almost pure pieces of the element Uranium-235 or Plutonium, of a precise mass and shape, must be brought together and held together, with great force. These conditions are not present in a nuclear reactor.
The reaction also creates radioactive material. This material could hurt people if released, so it is kept in a solid form. The very strong concrete dome in the picture is designed to keep this material inside if an accident happens.
This chain reaction gives off heat energy. This heat energy is used to boil water in the core of the reactor. So, instead of burning a fuel, nuclear power plants use the chain reaction of atoms splitting to change the energy of atoms into heat energy.
This water from around the nuclear core is sent to another section of the power plant. Here, in the heat exchanger, it heats another set of pipes filled with water to make steam. The steam in this second set of pipes turns a turbine to generate electricity. Below is a cross section of the inside of a typical nuclear power plant.

Power plant drawing courtesy Nuclear Institute


Nuclear Fusion

Another form of nuclear energy is called fusion. Fusion means joining smaller nuclei (the plural of nucleus) to make a larger nucleus. The sun uses nuclear fusion of hydrogen atoms into helium atoms. This gives off heat and light and other radiation.
In the picture to the right, two types of hydrogen atoms, deuterium and tritium, combine to make a helium atom and an extra particle called a neutron.
Also given off in this fusion reaction is energy! Thanks to the University of California, Berkeley for the picture.
Scientists have been working on controlling nuclear fusion for a long time, trying to make a fusion reactor to produce electricity. But they have been having trouble learning how to control the reaction in a contained space.
What's better about nuclear fusion is that it creates less radioactive material than fission, and its supply of fuel can last longer than the sun.

Regards

4. Give a detailed description of global warming and its possible effects on life. What measures have been taken by various nations to tackle this problem?

Global Warming or Climate Change, measurable increases in the average temperature of Earth’s atmosphere, oceans, and landmasses. Scientists believe Earth is currently facing a period of rapid warming brought on by rising levels of heat-trapping gases, known as greenhouse gases, in the atmosphere.

Greenhouse gases retain the radiant energy (heat) provided to Earth by the Sun in a process known as the greenhouse effect. Greenhouse gases occur naturally, and without them the planet would be too cold to sustain life as we know it.Since the beginning of the Industrial Revolution in the mid-1700s, however, human activities have added more and more of these gases into the atmosphere. For example, levels of carbon dioxide, a powerful greenhouse gas, have risen by 35 percent since 1750, largely from the burning of fossil fuels such as coal, oil, and natural gas. With more greenhouse gases in the mix, the atmosphere acts like a thickening blanket and traps more heat.

Effects:
Weather
global warming will affect weather, glacial ice, sea levels, agriculture, wildlife, and human health. Many changes linked to rising temperatures are already being observed.
Scientists project that the polar regions of the Northern Hemisphere will heat up more than other areas of the planet, and glaciers and sea ice will shrink as a result. Regions that now experience light winter snows may receive no snow at all. In temperate mountains, snowlines will be higher and snowpacks will melt earlier. Growing seasons will be longer in some areas. Winter and nighttime temperatures will tend to rise more than summer and daytime temperatures.
storms are expected to be more frequent and more intense in a warmer world. water will also evaporate more rapidly from soil, causing it to dry out faster between rains. some regions might actually become drier than before. overall, higher latitudes are projected to receive more rainfall, and subtropical areas are projected to receive less
Ice Sheets and Glaciers
Warming temperatures are already causing significant changes to mountain glaciers around the world, ice sheets in Greenland and the Antarctic, and polar sea ice in the Arctic. From Europe to Africa to Asia to North America, mountain glaciers have receded over the 20th century, and melting is becoming more rapid. The large-scale melting of ice may accelerate the pace of global warming in what is known as a feedback process. Because ice reflects sunlight back out to space, it has a cooling effect. Water and land, which are darker than ice, absorb and retain more heat
Many species, including polar bears, seals, and walrus, depend on sea ice for their survival.
The rapid loss of Alaskan glaciers represents almost half of the total loss of ice in glaciers worldwide, and makes a significant contribution to observed sea level rise
Sea level

As the atmosphere warms, the surface layer of the ocean warms as well, expanding in volume and thus raising sea level. The melting of glaciers and ice sheets, especially around Greenland, further swells the sea. Sea level rose 10 to 25 cm (4 to 10 in) during the 20th century

Agriculture
In some .parts there would be boost in agriculture initialy and some parts it would be ruined.
Crops and woodlands may also be afflicted by more insects and plant diseases. Agricultural areas will need to adapt to changing conditions, such as by shifting the types of crops grown or investing in drought-tolerant or heat-tolerant varieties.

Animals and plants

Plants and animals will find it difficult to escape from or adjust to the effects of global warming. Scientists have already observed shifts in the lifecycles of many plants and animals, such as flowers blooming earlier and birds hatching earlier in the spring. Many species have begun shifting where they live or their annual migration patterns due to warmer temperatures.
extinction of some plant and animal species.
Effects on human
In a warmer world, scientists predict that more people will get sick or die from heat stress, due not only to hotter days but more importantly to warmer nights (giving the sufferers less relief). More frequent and intense heat waves will further contribute to this trend. At the same time, there will be some decreases in the number of cold-related deaths. Diseases such as malaria, now found in the tropics and transmitted by mosquitoes and other animal hosts, are projected to widen their range as these animal hosts move into regions formerly too cold for them. Other tropical diseases may spread similarly, including dengue fever, yellow fever, and encephalitis. Scientists also project rising incidence of allergies and respiratory diseases as warmer air grows more charged with pollutants, mold spores, and pollens.
migration and displacement of people.
---food crises.
---there would be surge in deseases,people would die earlier,more cancer of skin.
---coral reafs are in danger,these reafs are the algeas that are the major food for many marine animals,they also absorb co2 and convert it in to o2 .

continued.....

EFFORTS TO CONTROL GLOBAL WARMING

Responding to the challenge of controlling global warming will require fundamental changes in energy production, transportation, industry, government policies, and development strategies around the world. These changes take time. The challenge today is managing the impacts that cannot be avoided while taking steps to prevent more severe impacts in the future.

Reducing emissions of greenhouse gases, also called greenhouse gas mitigation, is a necessary strategy for controlling global warming. There are two major approaches to slowing the buildup of greenhouse gases. One is to reduce the consumption of fossil fuels, thereby reducing greenhouse gas emissions. The other is to keep carbon dioxide out of the atmosphere by storing the gas or its carbon component somewhere else, a strategy known as carbon sequestration or carbon capture.
Carbon Capture
One way to keep carbon dioxide emissions from reaching the atmosphere is to preserve and plant more trees. Trees, especially young and fast-growing ones, soak up a great deal of carbon dioxide from the atmosphere and store carbon atoms in new wood
Energy Sources
Significant reductions in carbon dioxide emissions can only be achieved by switching away from fossil-fuel energy sources. Nuclear power plants release no carbon dioxide at all, but nuclear energy is controversial for reasons of safety, security, and the high costs of nuclear waste disposal. Solar power, wind power, and hydrogen fuel cells also emit no greenhouse gases. These energy sources can be practical, low-pollution alternatives to fossil fuels.Other alternatives include fuels made from plants, such as biodiesel (made from used and new vegetable oil) and ethanol (a plant-based gasoline additive). Use of these fuels can help reduce total carbon dioxide emissions from automobiles. The hybrid electric vehicle (HEV), which uses both an electric motor and a gasoline or diesel engine, emits less carbon dioxide than conventional automobiles
International AgreementsInternational cooperation is required for the successful reduction of greenhouse gases. The first international conference addressing the issue was held in 1992 in Rio de Janeiro, Brazil. At the United Nations Conference on Environment and Development, informally known as the Earth Summit, 150 countries pledged to confront the problem of greenhouse gases by signing the United Nations Framework Convention on Climate Change (UNFCCC). To date, more than 180 nations have ratified the UNFCCC, which commits nations to stabilizing greenhouse gas concentrations in the atmosphere at a level that would avoid dangerous human interference with the climate
In 1997 in Japan, 160 nations drafted an agreement known as the Kyōto Protocol, an amendment to the UNFCCC. This treaty set mandatory targets for the reduction of greenhouse gas emissions. Industrialized nations that ratify the treaty are required to cut their emissions by an average of 5 percent below 1990 levels. This reduction is to be achieved no later than 2012, and commitments to start achieving the targets are to begin in 2008. Developing nations are not required to commit to mandatory reductions in emissions. Under the Kyōto rules, industrialized nations are expected to take the first steps because they are responsible for most emissions to date and have more resources to devote to emissions-reduction efforts

In 2007 the European Union (EU) took the initiative in coming up with a new international plan to address global warming. At a “green summit” held in March, the 27 nations of the EU
In the accord EU leaders agreed to reduce emissions by 20 percent from 1990 levels by 2020

rgds

5. Give chemical name of one Nitrogenous and one Phosphorus containing fertilizer. What is the role of Nitrogen, Phosphorous and Potash in the growth and development of various parts of a plant.

Fertilizers : are chemical compounds applied to promote plant and fruit growth. Fertilizers are usually applied either through the soil (for uptake by plant roots) or, by foliar feeding (for uptake through leaves.

1.Ammonium Nitrate.....................Nitrogenous fertilizer
2.Calcium Super Phossphate..........Phosphorous fertilizer

Nitrogen role in plants:

<FONT face=Arial><FONT face=Arial>Role of Phosphorus in Plant Growth

The presence of phosphorus in the soil encourages plant growth because phosphorus is an essential nutrient. Particularly, phosphorus is a major building block of DNA molecules. It is responsible for the storage of energy in the form of adenosine diphosphate (ADP) and adenosine triphosphate (ATP). The energy stored in these phosphate compounds allows for the transportation of nutrients across the cell wall and the synthesis of nucleic acid and proteins. The addition of phosphorus fertilizers ensure that crops will reach their full potential by using the additional phosphorus to encourage root growth and stalk strength while promoting resistance to root rot diseases.

6. Write short notes on the following (paper 1998)

(i) Conductor



(ii) Resistor


An electronic component that resists the flow of current in an electronic circuit. Resistors are often made out of chunks of carbon or thin films of carbon or other resistive materials. They can also be made of wires wound around a cylinder. The common resistor is a two-wire package with a fixed resistance measured in ohms; however, different types of resistors are adjustable by the circuit designer or the user (see variable resistor).

(iii) Semi-conductor
Semiconductor, solid or liquid material, able to conduct electricity at room temperature more readily than an insulator, but less easily than a metal.

for detail:
Electrical conductivity, which is the ability to conduct electrical current under the application of a voltage, has one of the widest ranges of values of any physical property of matter. Such metals as copper, silver, and aluminum are excellent conductors, but such insulators as diamond and glass are very poor conductors (see Conductor, electrical; Insulation; Metals). At low temperatures, pure semiconductors behave like insulators. Under higher temperatures or light or with the addition of impurities, however, the conductivity of semiconductors can be increased dramatically, reaching levels that may approach those of metals.

(iv) Thermistor

Thermistor, a resistor whose resistance varies with temperature.

Thermistors are widely used as inrush current limiters, temperature sensors, self-resetting overcurrent protectors, and self-regulating heating elements.
Thermistors differ from resistance temperature detectors (RTD) in that the material used in a thermistor is generally a ceramic or polymer, while RTDs use pure metals. The temperature response is also different; RTDs are useful over larger temperature ranges, while thermistors typically achieve a higher precision within a limited temperature range.

(v) Transistor

In electronics, a transistor is a semiconductor device commonly used to amplify or switch electronic signals.
Transistors act as the key element in amplification, detection, and switching of electrical voltages and currents. They are the active electronic component in all electronic systems which convert battery power to signal power. Almost every type of transistor is produced in some form of semiconductor, often single-crystal materials, with silicon being the most prevalent. There are several different types of transistors, classified by how the internal mobile charges (electrons and holes) function. The main categories are bipolar junction transistors (BJTs) and field-effect transistors (FETs).

rgds

Paper 1999
4. How the solar and lunar eclipses are caused?


Two kinds of eclipses involve the Earth: eclipses of the Moon, or lunar eclipses, and those of the Sun, or solar eclipses. A lunar eclipse occurs when the Earth is between the Sun and the Moon and its shadow darkens the Moon. A solar eclipse occurs when the Moon is between the Sun and the Earth and its shadow moves across the face of the Earth. Eclipses are rare, however; most of the time, the shadows do not overlap.
A partial solar eclipse can be seen when part of the Earth is within the penumbra, or the outer portion of the Moon’s shadow. The inner portion, the umbra, is formed by tangents to the Sun and Moon, and the outer portion, the penumbra, is formed by tangents that intersect between the Sun and the Moon. These geometric regions occur because light travels in straight lines and casts shadows even at great distances.
A partial lunar eclipse occurs when only a part of the Moon enters the umbra of the Earth’s shadow, leaving a portion of the Moon in total darkness. The extent of a partial lunar eclipse can range from near totality, when most of the Moon is obscured, to a slight or minor eclipse, when only a small portion of the Earth’s shadow is seen on the passing Moon.
During a total solar eclipse, the Moon completely blocks out the Sun for as long as seven to eight minutes. This type of eclipse is visible from the area on the Earth within the umbra, the inner part of the Moon's shadow. The diameter of the umbra is never greater than 268.7 km (167 mi) where it touches the surface of the Earth. As a result, the area in which a total solar eclipse is visible from the Earth is never wider than that, and it is usually considerably narrower.
A total lunar eclipse occurs when the Moon passes completely into the umbra of the Earth’s shadow. If the Moon moves directly through the center, it is obscured for about two hours. If it does not pass through the center, the period of totality is shorter; it may last for only an instant if the Moon travels through the very edge of the umbra.

total lunar eclipse

The type of radiation hat is unaffected by magnetic field is called __________ . Gamma Rays

dear bro columns shold be on a space.. thanx