HOW AND WHY

How does a Microphone work?

admin — Wed, 17 Nov 2010 21:06:22 +0000

How does a Microphone work?

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Microphone and its working

A microphone is a device which converts sound waves into electrical signals. These signals can then be broadcast through the air or sent over to distant points, where they can again be converted back into sound. Microphone can be divided into two groups depanding upon how they respond to sound waves. These are the pressure type and the velocity type. The pressure type Microphones contain a thin metal plate called a diaphragm. This is streched like a drumhead inside a rigid frame. When the sound waves strike the diaphragm, it starts vibrations at the same rate as the sound waves. These vibrations produce corresponding electric signals by changing the electric current that flows through the circuit. In the condenser microphone the vibrating diaphragm changes the capacitance of a condenser.

As the diaphragm vibrates in response to the sound the coil slids up and down the centrepiece of an M shaped permanent magnet. The coil thus cuts through the magnetic lines of force which induce a fluctuating voltage represents the variations in sound pressure. Crystal microphones make use of piezoelectric effect. Whenever certain crystal such as quartz are bent or twisted they generate an electric voltage. A carbon microphone works like a telephone transmitter. In this carbon granules varies the current to create a signal. Ribbon microphones have a metal ribbon instead of coils. The first practical microphone however was envented in 1878 by David Edward Hughes of United states. Other inventors of the microphone are Emaile Berliner Philip mReis Franus Blake and Henry Hunnings.

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What is LPG?

admin — Wed, 17 Nov 2010 19:26:19 +0000

What is LPG?

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Liquified Petroleum Gas

The term LPG Liquified Petroleum Gas. LPG is commonly used for domestic cooking purpose. It is supplied in gas cylinders that need to be replaced when their fuel contents are consumed. The supply in gas cylinders contains a mixture of liquified butane and iso-butane under pressure. LPG is used as a cooking fuel. This is also used in water heater, space heater, and furnaces.

Moreover LPG is highly combustible and forms an explosive mixture with air, therefore any leakage to make gas leakage easily detectable some strong smelling substance is added to LPG. Before igniting the match stick we should be sure that there is no such smell near the gas cylinder or in the Kichen.

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Can Light Travel through Wires?

admin — Wed, 10 Nov 2010 20:49:30 +0000

Can light travel through wires?

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How does light travels through wires

We all know that electricity travels from one place to another through metallic wires. Light can also travel through wires but these wires are not made of metals. They are made of glass or plastic. Light carrying wires are extremely thin and are called optical fibres. The narrow fibres have a thin core of glass of high refractive index surrounded by a thin cladding of another glass of lower refractive index. The core carries light and the covering helps bemd the light back to the core.

Fibres so prepared have to be aligned properly in the form of a bundle. They should not cross each other, otherwise the image transported by it will be scrambled. They are kept in straight lines. Once the aligned bundle is made it can be bent or turned in any desired direction. Fibre optic devices can transmit television programmes and telephone conversations. Many developed countries have installed telephone exchanges using fibre optic cables. The use of optical fibres in video text videophones and computer networks is increasing day by day.

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What is Light?

admin — Wed, 10 Nov 2010 19:52:58 +0000

What is Light?

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Lights and its properties

For thousands of years many scientists groped in dark to understand the true nature of light. The ancient Greeks belived that light consisted of rays of matter given out by whatever object was being looked at. Plato and his followers belived that it was a mixture of different matters coming from the sun. But in the 11th century it was Alhazen the Arabic scientist who was the first to propund the theory that light could be given out by all luminous object. In the 17th century the British scientist Sir Isaac Newton put forward the corpuscular theory of light. According to this theory light travels in the form of corpuscles in stright lines through an imaginary medium called ether. In order to explain the transverse nature of light James Clark Maxwell developed the electromagnetic wave theory.

According to this theory light travels in the form of electromagnetic waves both electric and magnetic fields are perpendicular to the direction of propagation, ie. they are transverse electromagnetic waves. To explain the photoelectric effect max Planck put fourth the quantum theory of light in 1900. He suggested that light is given off in the form of photons. All electromagnetic radiations are given out in the photons. The quanta behave both like particles and waves of energy. When the quanta of sufficient energy fall on certain substances they give off electrons from their atoms. This is called photoelectric effect which means production of electricity by light. Today almost all the physical phenomena of optics are explained on the basis of quantum theory of light as explained above ie. light is made up of waves and particles both.

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What is Liquid Crystal Display?

admin — Wed, 10 Nov 2010 19:49:06 +0000

What is Liquid Crystal Display?

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Liquid Crystal Display

Liquid crystals are of two types: thermotropic liqid crystals prepared by heating the substance and lyotropic liquid crystal made by mising two or more compounds. Some of the imporatant liquid crystals that belong to the first category are p-azoxyanisole cholesteryl nonanoate and p-n octyloxybenzoic acid. In the second category sodium stearate and alpha-lecithin are the two imporatnat liquid crystals. Liquid crystals are used in used in colour TV and electronic display tubes sensitive tapes and electronic device for digital clocks watches and calculators. Liquid crystal displays work on two principles viz dynamic scattering and field effects.

In displays the liquid crystals are sandwiched between two transparent electrodes. The thickness of a liquid crystal film varies from 6 to 25 microns. The cell is sealed to eliminate oxygen and moisture. In dynamic scattering if no electric field is applied the cell is transparent. On applying electric field to the crystal the cell becomes opaque. Digital displays are made by photoetching a seven-segment pattern on tin or indium-coated glass plate. The field effect displays are mostly used in watches and calculators. The output of quartz crystal is given to seven segments of liquid crystalin a watch. Polarizers are also used for liquid crystal cells. Electric field changes the molecular alignment by which liquid crystal becomes opaque on account of a mirror behind the second polarizer.

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How do we see Clearly with Spectacles?

admin — Wed, 10 Nov 2010 19:44:13 +0000

How do we see Clearly with Spectacles?

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What are Spectacles and Lenses

All men women and children, who have weak eye-sight, use spectacles. Scientist have developed spectacles that help in seeing both the near distant object clearly. The history of spectacles was started some 700 years ago. In 1266, Roger Bacon of England used a pieceof glass to magnify the words written in a book. Spactacles are shown on the eyes of one Cardinal Ugon’s portrait made in 1352. In 1784 Benjamin Franklin brought wonders in the feildof spectacles by making bifocal lenses. How does it work the light ray enter your eyes through cornea(black portion of the eye). There is a convex lens inside the eye, and behind this lens there is a screen which is called retina.The light rays coming from any object make in inverted image of object on the retina with the help of this lens. This is carried to the brain by the optic nerve. It becomes erected there. This is how we see an object.

Sometimes, the eyes develop some defacts due to which the image of the object is formed before or behind the retina. and is blurred. Persons having such eyes defacts need the assistance of spactacles.
The defacts of the eyes are mainly of three types:-
1. Myopia:- Persons suffering from this defect can see the nearby object clearly, but the distant object appear blurred. (Solution- Spectacles with concave lens)
2. Hypermetropia:- Persons suffering from this defact cannot see nearby objects clearly but can see distant object clearly. (Solution- Spectacles with convex lens)
3. Astigmatism:- Due to this defact in the eyes, one cannot see with clearity the horizontal and vertical lines simultaneously. (Solution- Spactacles with cylindrical lenses)

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How to Measure Hardness of Material?

admin — Wed, 10 Nov 2010 19:21:57 +0000

How do we measure the Hardness of Materials ?

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Meaurement of Hardness of Material

Hardness is a characteristic property of the solid objects. It is measured by the resistance which the body offers to anything which tends to scratch it. The hardness of the various materials is measured either on the mohs scale or the knoop scale. Mohs scale is numbered from 1 to 10 that is it gives ten grades of hardness. In this scale diamond is the harest material and talc is the softest. Diamond has a hardness of 10 mohs and talc has a hardness of 1 mohs. The mineralogists carry a box containing pieces of the above minerals for testing samples in the field.

For example: If they find a mineral that can be scratched by feldspar but not by apetite, its hardness lies between 5 and 6 on the hardness scale. To measure hardness in the knoop scale an elongated diamond-shaped indenting device is employed to measure the indentation it makes in a given test material. By this method the hardness of extremely brittle materials including glass and even diamond can be measured without damaging either the indenter or the test piece. The size of the indentation is taken as a measure of the materials hardness.

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What is Heavy Water?

admin — Wed, 10 Nov 2010 19:17:17 +0000

What is Heavy Water?

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Heavy Water and its uses

Heavy water was discovered by harold Clayton Urey an American chemist in 1931. He was awarded the Nobel Prize in 1934 for this discovery. Naturally occurring hydrogen contains 99.985% of protium, about .015% deuterium and about 1 part in 1017 tritium. Tritium is radioactive in nature. When deuterium combines with oxygen it gives heavy water or deuterium oxide. Heavy water is prepared by electrolysis of water. If water is electrolysed the gas produced at cathode is mostly hydrogen and thus the residual water is enriched in deuterium oxide. Continued electrolysis of hundreds of liter of water yeild pure heavy water.

Ordinary water as obtained from most natural sources, contain about one part of heavy water for every 6760 parts of H2O. Ordinary water has a molecular weight of about 18 while heavy water has a molecular weight of 20. Density freezing point and boiling point of heavy water are higher than that of ordinary water. Heavy water is used as a moderator for slowing down the fast neutrons in nuclear reactors. In laboratories, it is used as an isotopic tracer in the studies of chemical and biological process. It is also used in the preparation of deuterium and its other compounds. It is also used as the coolant in nuclear reactors.

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What are Hard Drinks?

admin — Wed, 10 Nov 2010 19:05:25 +0000

How are Hard Drinks made?

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Making of Hard Drinks

Wine is probably the first type of hard drink to have come into existence. Archaeological evidence suggests that wine making began in the middle-east over 10,000 years ago, and gradually spread westward to the mediterranean countries and finally into Europe. The ancient Egyptian wall painting reveal that the art of wine making was known to them long before the westerners took to it. wine was common in everyday life of the early Greeks and Romans. It also played an important role in their religious ceremonies. The god of wine was called Bacchus by the Romans and Dionysus by the Greeks.

Wine can be made from a wide range of fruits and vegetables, but the real wine is made from grapes. Another type of hard drink beer is known to have been made by the Egyptians and Babylonians at least 6000 years ago and there is evidence that barley from which it is made was cultivated in Britain and northern Europe some 5000years ago. Europeans drink from barley. Beer is usually made from barley hops yeast and sugar by the process of fermentation. Pure brandy is made by the distillation of wine made from grape juice. The wine is heated and the alcohol that evaporates out of it is condensed and collected. Different types of whisky are made from grain such as barley rye and corn. Rum is made from molasses, a syrup obtained from cane sugar. Gin is made from grain or molasses flavoured with juniper berries. Major wine producing areas of the world include France, Germany, Spain, Portugal, Italy and California in the USA.

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What is Greenhouse Effect?

admin — Wed, 10 Nov 2010 18:56:09 +0000

What is Greenhouse Effect?

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Greenhouse Effect

Our earth reflects a lot of energy back into the atmosphere. But presence of heavy carbondioxide in the atmosphere prevents some of this heat escaping just as a glass or plastic sheet stops escaping heat from the so called “Greenhouse” used to protect groing plants.

The main Greenhouse gas is carbondioxide(Co2). The source of this gas is from fossil fuel combustion like coal, petroleum and natural gas. Methane(CH4), Chlorofluorocarbons(CFCs) and Nitrousoxide(N2O) are among the other Green house gases. The sources of such gases range from Bio-mass buring fumes emitted from refrieration and air conditioning plants industrial fumes and enteric fermentation of cattle, insects and different crops.

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HOW AND WHY

How does a Microphone work?

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