What is food poisoning?

Answer 1- Food poisoning is caused either by ingestion of food contaminated with chemical ormetallic poisons, My science Schoolbacteria orbacterial toxins or by eating poisonous foods such as certain species of mushrooms.Molds and bacteria are responsible for microbial food poisoning. Molds grow on food (especially if they are moist). During their growing period they produce toxic substances called mycotoxins whose effect on man and animals cause mycotoxicosis. Mycatoxins remain the the food long after the mold producing them has died and can therefore be present in foods that are not visibly moldy. Some mycotoxins are stable and survive the usual conditions of cooking and processing.



 Food grains, especially bajra, rye and jowar get infected with a parasitic ergot fungus Claviceps purpurea. Ergotism, a toxicosis results from eating grains contaminated with this fungus. Alimentary toxic aleukia (ATA) is another mycotoxicosis caused due to eating moldy grains



 


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Why are satellites always launched from the east coast?

Earth rotates from west to east causing the Sun, the Moon, stars andother planets rise frommy science school satellite



east and set in the west. On the surface of the eartheach point is moving eastward with



respect to an astronaut in space.



Thus if a rocket is launched at a small angle eastward vertically the speed of earth gets added to



the rocket's speed. This reduces the amount of fuelrequired. If the rocket is inclined along any



other direction, the speed of the earth gets subtracted from the speed of rocket and will



necessitate burning of more fuel.



In addition, in case of any failure during launch the rocket will fall back to the earth.



Hence if it is launched from the east coast, the rocket will fall into the sea only. If it is launched from the west coast, in case of failure, the rocket will fall on the land endangering human habitats. Thus choosing eastward inclination is scientific but choice of eastern coast concerns safety.


How does a cell phone work?

In normal telephone exchange systems, a pair of wires extends each telephone instrument to the telephone exchange.



Normally, copper conductors are used to give loop to indicate the exchange that the 


my science school


telephone handset had been lifted for making a call or for receiving a call. In advanced countries, Optical Fibre is also used for extending the loop.




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How are minute quantities (like milligrams, micrograms, or nanograms) weighed?

Down to milligrams one can use well-designed physical balances-indeed one can even o below one milligram if proper isolation from vibrations and other disturbances is ensured. But for going lower one needs to use other methods. We have to remember that our objective is to measure the mass, which is the quantity of material and not the amount of gravitational force. Mass is a measure of inertia.

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The moon goes around the earth once in 27.3 days, while a lunar month is 29.5 days. Why the difference?

It is true that the moon makes one rotation around the earth in 27.3 days. A lunar month is the number of days between two new moon days. After one new moon day the moon does arrive at the same position with respect to the fixed stars after 27.3 days.
moon

But it is not aligned with the earth and the sun because during this period the earth has moved some distance around the sun, indeed by about 270. So the moon has to move some more to come to a position between the sun and the earth.
A simple calculation shows that this additional traverse would take about 2.2 days. Therefore the next new moon comes after 29.5 days and not 27.3-the lunar month is longer than the period of rotation of the moon by about Two days!

What is the difference between radial and ordinary tyres?

Answer 1.
Ordinary tyres or cross-ply tyres are the oldest type of tyre and has a case made of two or more layers of fabric. A tyre’s strength and load carrying ability were at one time indicated by its number of plies. Modern materials and man made fibers such as polyester and glass fiber embedded in the rubber are much stronger than the cotton fibers originally used.
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Why are a circle divided into 360 degrees?

The Babylonians 3000 years ago used the hexadecimal system of numbering, which was based upon a multiplication of 6, instead of the decimal system which we now used. They divided the circle for example into 60x6 parts- the 360 degrees. Each degree in turn was divided into 60 parts was again divided into 60.
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What are Euro norms?

The Euro norms are meant for regulating vehicular emission in Europe. The norms are expressed in terms of the weight of pollutants such as carbon monoxide (CO), hydrocarbon (HC), oxides of nitrogen (NOx) and particulate matter emitted per kilometer of vehicular run with load. These ceilings have been fixed for various categories of vehicles. For instance, there are emission levels for petrol – driven and diesel – driven vehicles based on the capacity of the engines. The pollution measurements under engine idling conditions without application of lord on the vehicles does not reflect the exact quantum of various pollution emitted by the engines in reality.
In any internal combustion engines, as the speed or acceleration is increased, the time allowed for combustion of the fuel is varied than the idling condition. This variation is different in a carburetor engine and in a fuel injection petrol or diesel engine. In a carburetor engine, the CO will be maximum at idling speed. In a diesel engine, the smoke will be maximum upon sudden acceleration. The Euro norms adopt certain specified driving cycles related with time Vs speed. During these cycles of operation of the engine, the mass of each exhaust gas component is evaluated. The mass is computed from the measured concentrations of each pollutant in the known exhaust gas volume. Exhaust gas is generated when the vehicle is operated on a chassis dynamometer according to certain standard driving cycles which simulate driving conditions in urban traffic.

How do CFCs damage the ozone layer?

Most of us don’t think about how our everyday activities might influence the global environment. An example is our use of chlorofluorocarbons or CFCs. These compounds which are useful as propellants in aerosol sprays, refrigerants, and coolants, cleaning agents, insult ants and plastic foam are the main Easters of ozone present in the ozonosphere. Ozonosphere is the general stratum of the upper atmosphere in which there is an appreciable ozone concentration and in which ozone plays an important part in the radiative balance of the atmosphere.
It lies roughly between 10 and 50 kilometers, with maximum ozone concentration at about 20 to 25 kilometers. Ozone, O3, a blue gas is unstable allotropic form of oxygen. It is scarce, even in the stratosphere (12 – 50 km from earth’s surface) where it is most concentrated. But each molecule counts. Highly unstable, an ozone molecule readily splits up when hit by ultraviolet radiation. The energy of the life-damaging UV rays is thus converted into harmless heat and never reaches the earth. The breakup leaves a free oxygen atom (O) and an oxygen molecule (O2), the stuff we breathe. The O and O2, in an ongoing cycle, recombine to form new ozone molecules.
The chlorofluorocarbons (trade named freons) released by us are stable and can live up to 100 years.
They are non-toxic and harmless to life. But when they drift slowly upward to reach the stratosphere by convection, they are struck by the high energy short wavelength radiations such as ultraviolet rays and this initiates a ozone clearing process. When a CFC molecule is exposed to strong UV radiation in the stratosphere, it is broken apart.
This release a chlorine atom, which attacks an ozone molecule, pulls away one of the three oxygen atoms and forms a chlorine monoxide molecule thus destroying the ozone molecule. The destructive process continues further.
The oxygen atoms from the new chlorine monoxide molecule are pulled away by free oxygen atoms freeing the chlorine atom to restart the cycle: thus progressively more ozone molecules are decomposed. It has been estimated that one chlorine atom can eat up to 1,00,000 molecules of ozone. A severe depletion in the ozone layer will result in an increase in the case of skin cancer, eye cataract and suppression of the immune system in humans and other species. Food crops sensitive to UV rays could also be affected.
In 1984 a hole in the ozone layer was discovered over Antarctica and more recently a similar hole was discovered which extends over the Arctic, Scandinavia and North America.

Why holes in the ozone layer from only above the poles and not in other areas?

Ozone hole, a drastic depletion of ozone in the atmosphere layer over the Antartic, was noticed by scientists in the early Eighties. The depletion was found to be periodic and far greater than expected from other calculations of the chloro-fluro-carbon effect. So the question arose:
Was this a natural climate variation or was it a chemical decomposition brought about by mankind? In spite of the pioneering research by many researchers, among them Paul Crutzen, Mario Molina and F. Sherwood Rowland who shared the 1995 Nobel prize for chemistry, as well as Susan Solomon and James Anderson of the U.S. the mystery has not been fully understood.
It has been proved beyond doubt that ozone depletion is caused chiefly by ozone reacting chemically with chlorine and bromine from industrially manufactured gases. But, the rapid depletion of ozone over Antarctica could not be explained by transport processes or by gas phase chemical reactions.
According to an information note from The Nobel Foundation of the Royal Swedish Academy, an alternative mechanism must exist which could accelerate the decomposition of ozone. In fact, scientists have identified this mechanism as chemical reactions on the surface of cloud particles in the stratosphere.
Thus, the Antarctic ozone depletion appears to be connected with the extremely low temperatures, which lead to condensation of water and nitric acid to form ‘polar stratospheric’ (PSCs). The ozone-decomposing chemical reactions are greatly reinforced by the presence of these cloud particles. This understanding itself has lead to an exciting new branch of atmospheric chemistry called ‘heterogeneous’ chemical reactions on particle surfaces.

What are cosmic rays?

ANSWER 1 Cosmic rays are electromagnetic waves of extremely short wavelength. As the word suggests their origin is from outer space or the cosmos. These rays consist of positively charged particles coming from various galaxies outside the solar system and comprise mainly of protons, alpha particles and positive ions of some heavy elements. The sun is a poor source of cosmic rays. The distant galaxies are the store houses of charged particles. The high electric and magnetic fields present in these galaxies act as natural accelerators of these particles. The high velocities and the charged nature of these particles attribute the wave nature of these particles. Work on the cosmic rays was first stated by Millikan and Anderson during the early part of this century on balloon flights. The intensity of these rays has been found to vary with altitude, latitude and depth under the sea. The primary cosmic rays interact with the molecules of the atmosphere giving rise to secondary particles like electrons positrons (positively charges particles) and mesons. In fact the anti proton was discovered during cosmic ray studies. Luckily, the thick atmosphere around us is a natural blanket protecting us from these rays. The work of Vikram Sarabhai and Homi Babha on cosmic rays has given us an immense knowledge on the particles that are fundamental constituents of matter and also an insight into the forces that bind them. Continue reading "What are cosmic rays?"

What is solar wind?

ANSWER 1 Solar wind is a combination of electrically charged stream of atomic particles – electrons, protons, with small proportions of heavier nuclei and the entrained solar magnetic field emitted from the sun’s atmosphere. E. N. Parker in 1958 showed that due to the very high temperatures of the corona the pressure exerted results in an outflow of material into the interplanetary space in all directions in a phenomenon he called “solar wind”. Solar wind is an extremely radially outward at a speed of 500 kilometres per second which is variable in response to the varying solar activity. The particles normally takes about 4 to 5 days to reach earth. The radial flow of the solar wind and the rotation of the sun, wind the solar magnetic field into a spiral which makes an angle of 45 degrees at the earth’s orbit. The study of the solar wind becomes important as it contributes to the phenomenon such as aurorae and magnetic storms. Continue reading "What is solar wind?"

Where does dust come from and why does it reappear so soon after we dust?

Terrestrial dust is mostly tiny fragments abraded from things; some of it may be even smaller things aggregating together to form motes of dust. The larger things that turn to dust can be almost anything in the world, from shoes to ships to sealing wax, not to mention cabbages (fragments of dried vegetable matter) and kings (especially if cremated).
dust

Wind-driven dust composed of fragments of stone and clay is so powerful that over the millennia it has cut fantastically shaped canyons and pillars in the badlands of the American west. Drought created the dust Bowl with its penetrating clouds of dry ploughed soil; the fires of ancient plains Indians probably added to the dust in teepees; soot from unburned automobile fuel plagues city apartments.

Dust knows no borders, and dust from volcanic ash lingers in the upper atmosphere to produce brilliant sunsets thousands of miles away from the eruption.

As for why dusting seems worse than futile, one reason is that a dust cloth may simply stir up dust temporarily while the friction simultaneously creates a static electric charge. Charged particles of dust are attracted to surfaces with the opposite charge. An antistatic spray may help by providing a very thin layer of insulation between the opposite charges.