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ELECTRICAL MEASURING INSTRUMENTS For the detection or measurement of electric current, potential difference, and resistance certain instruments have been devised viz. The galvanometer for the detection of small currents measurements of small currents of the order of micro amperes or mili amperes the voltmeter or potentiometer for the measurement of potential difference (and voltage) between two points of a circuit are the EMF of a source the ammeter for the measurement of large currents the wheatstone bridge the meter Bridge the post office box and the ohmmeter for the measurement of resistance. THE MOVING COIL GALVANOMETER The moving coil galvanometer is a basic electrical instrument it is used for the detection (and Measurement) of small currents. Its underlying principle is the fact that when a current flows in a rectangular coil placed in a magnetic field it experiences a magnetic torque. If it is free to rotate under a controlling torque, it rotates through an angle proportional t...

THE ATOMIC NUCLEUS INTRODUCTION: The beginning of twentieth century. not only witnessed the successful development of atomic hypothesis the old quantum theory of radiation by plank, and Einsteins special theory of relativity; these years also marked the beginning of nuclear physics as a new field of scientific activity. In 1886 Henri Bacqueral first observed the phenomena of radioactivity.A year after J.J Thomson discovered the electron.Later on Thomson demonstrated that cathode rays were constituted of electrons..In the way of notion of the atom as the ultimate indivisible unit of matter had to be discarded, and it become evident that atoms included electrons among their structure and these electrons could be liberated by electromagnetic excitation as in a gas discharge spontaneously as in radio activity. In 1902 Rutherford and Soddy showed that in radioactive decay an atom transform itself into a different chemical element.This discovery led to the development of models for nuclear s...

NUCLEAR RADIATIONS INTERACTION OF NUCLEAR RADIATIONS WITH MATTER In the previous article we have discussed natural radioactivity in which α and β particles and γ-rays are emitted from the disintegrating nucleus of an atom.In nuclear fission and fusion reactions neutrons and other particles together with certain radiations are emitted from the nucleus.Moreover, interaction of high energy particles (neutral or artificial) with matter produce certain nuclear or atomic reactions with emission of particles like protons,deutrons,neutrons and ionizing radiations like γ-rays from the nucleus and x-rays and ultraviolet rays from the atom.These particles and radiations have been studied carefully for their properties and effects with are as follows: ALPHA (α) PARTICLES It shoots out from the nucleus with a high velocity ( 0.1 × 10 ^ 8 m/s ). Thus it possesses very high energy 7.7 MeV for the most energetic from R ac.Due to its large size more charge and high energy it can make very l...

HEAT AS A FORM OF ENERGY IN TRANSIT Many scientist have tried to explain the nature of heat.Up to the beginning of the nineteenth century, it was considered a weightless fluid called caloric which existed in every material body.Hot bodies were said to contain more caloric than the cold bodies.The caloric theory could explain satisfactory many processes such as heat conduction and mixing of substance in calorimeter. This concept of heat fluid was challenged by Count Rumford.He observed while supervising the boring of cannon that as cannon barrels were being bored.A tremendous amount of heat was given off.According to the caloric theory since the metal chips cut off by the drill have lost caloric i.e the heat given off in the drilling process, the chips should not be the same as the original metal, which had not lost caloric.But Rumford was unable to find any difference between the chips and the original metal in respect to their ability to hold or give off heat.In order to further inves...

METALLURGY OF COPPER Copper occurs both in free as well as in combined states.In combined state,it occurs mainly as the sulphide and oxide ores.The chief ores of copper are copper pyrite or chaleopyrite (CuFeS2), chalocite (Cu2S) and malachite [Cu(OH)2] and azurite [2CuCO3 Cu(OH)2 blue. Extraction Copper is mostly extracted from sulphide ores which contain about 6% Cu.The sulphide ore is first roasted (i.e., heated strongly in a current of air) on the hearth of a large flat furnace whereby the following changes occur. (i) Large amount of sulphur burns to sulphur dioxide (SO2). (ii) Iron present oxidizes to ferrous oxide (FeO) (iii) Copper changes into cuprous sulphide (Cu2S) 2CuFeS2 + 4O2 -----------> Cu2S + 2FeO + 3SO2 The roasted material is then mixed with sand to remove iron as ferrous silicate a slag which floats on the surface of the molten matte of copper.The liquid copper matte containing cuprous sulphide with some unreacted ferrous sulphide (FeS) and silica oxidi...

GROUP TRENDS IN ALKALI AND ALKALINE EARTH METALS In this article,the group trends in properties such as electron negativity,ionization potential,heat of hydration,sizes of atoms and ions and other physical properties are discussed. (i) Electronegativity:- The elements have very small electronegativity values and very generally called electropositive elements.Electronegativity decreases from Li through Cs as one moves down the group.Pauling's electronegativity values IA ans IIA group elements are summarized. (ii) Ionization Potential:- s-Block elements in general have low first ionization enthalpies because the outer s-electron is shielded very effectively from the nucleus by the inner electrons.The first ionization enthalpy of each of the alkali metal is lower than corresponding alkaline earth element in the same period, because the latter has an extra nuclear proton which causes an increase in the electrostatic attractive force between the nucleus and the outermost electrons.Secon...

OPEN CHAIN AND CLOSED CHAIN HYDROCARBONS In aliphatic hydrocarbons, the carbon atoms are attached to another carbon to form chains.These chains may be either open or closed (rings) chains.The open chains on the basis of saturation of valence are classified as saturated and unsaturated hydrocarbons. (i) Saturated Hydrocarbons: The compounds in which all the valencies of carbon carbon atoms are fully satisfied by single bonds,are called saturated hydrocarbons.The examples of saturated hydrocarbons are alkanes. (ii) Unsaturated Hydrocarbons: The compounds in which all the valencies of carbon atoms are not fully utilized,are called unsaturated hydrocarbons.Alkanes and alkynes are the example of unsaturated open chain hydrocarbons. The hydrocarbons which contain closed chain of carbon atoms are called cyclic hydrocarbons and examples are cyclo alkanes and cyclo alkenes. Aromatic compounds are benzene and its homologs.These compounds are further divided into homonuclear and hetero-nuclear ar...

HOW TO PREPARE POTASH ALUM? OBJECT : To prepare potash alum (K2SO4,Al2(SO4)3.24H2O) APPARATUS : China dish,beaker,watch glass,funnel,conical flask,glass rod,filter paper,water trough,wire gauze,tripod stand and bunsen burner. CHEMICALS : Solid Aluminium sulphate [Al2(SO4)3.16H2O](7.7 gms) , K2SO4 (2.0 gms), 50 mls of distilled water,few drops of conc H2SO4 EQUATIONS : K2SO4 +Al2 (SO4)3.16H2O + 8H2O --------------> K2SO4.Al2(SO4)3.24H2O THEORY : The term alum was originally used for potassium aluminium sulphate [K2SO4.Al2(SO4)3.24H2O] commonly known as potash alum.The term alum is now used for all double sulphates having general formula R2SO4.M2(SO4)3.24H2O PROCEDURE : Weigh out 7.7 gm of aluminium sulphate and dissolve it in about 30 mls of boiling distilled water.Add few drops of H2SO4 (conc) to make the solution clear.In another beaker dissolve 2.0 g of K2SO4 in 20 mls of distilled water.Mix the two solutions and concentrate the solution to crystallization by heating it in a china...

HOW TO PREPARE IODOFORM? To prepare Iodoform by the action of iodine on ethyl alcohol in the presence of alkali.\ APPARATUS: Two 100 mls beakers ( one for ethanol and other NaOH solution),glass rod,filter paper,funnel,watch glass . CHEMICALS: Ethanol (ethyl alcohol absolute) 10 mls 10% NaOH solution (20 mls) powdered iodine (2 gms) distilled water. THEORY: The reaction of halogens with alcohol or carbonyl compounds (acetaldehyde CH3 - CHO or methyl ketones CH3 - C R) in the presence of alkali NaOH to form haloform (CHX3) is called haloform reaction.If the halogen is iodine the the formation of iodoform will take place and the reaction is called iodoform reaction. In the first reaction,ethyl alcohol is oxidized to acetalhyde.In the next step acetalhyde reacts with iodine to give tri-iodo acetaldehyde or iodal which on reaction with NaOH gives iodoform. EQUATION: C2H5OH + 4I2 + 6NaOH ------------> CHI3 + HCOONa +5NaI + 5H2O PROCEDURE: Take 2gms of powdered iodine in a beake...

CHLORINE ELECTROLYSIS METHOD: Chlorine is manufactured by the electrolysis of aqueous solutions of sodium chloride.For this purpose two cells are used which are described below: (a) NELSON'S CELL: This cell consists of U-shaped perforated steel vessel which acts as cathode and carbon rod as anode.This U-tube is separated from anode by asbestos layer on the inner wall of the U-Tube as shown in figure The U-tube is filled by aqueous solution of sodium chloride.On passing the electric current,chlorine is obtained at anode reaction: (i) Ionization NaCl ---------> Na + Cl (ii) Reaction at anode 2Cl - 2e ----------> Cl2 (b) CASTNER-KELLNER'S CELL: This cell has a Cathode consisting of layer of mercury at the bottom of cell which flows from right to left.Saturated solution of sodium chloride also flows slowly through the cell in same direction as the mercury.The anode rods are of graphite which dip into the solution of sodium chloride. On electrolysis chlorine is liberated at ...

ATOMIC HYDROGEN Ordinary hydrogen exists as diatomic molecules (H2). Therefore it is also called as molecular hydrogen.The two atoms in a molecule of hydrogen are held together by shared pair of electron known as covalent bond having very high bond energy (104 cal. mol-1.The molecules are very stable and dissociate into atoms only under extreme conditions.The product obtained as a result of dissociation of molecular hydrogen is known as atomic hydrogen. These atoms have very short life and quickly combine together to form molecules again. PREPARATION OF ATOMIC HYDROGEN:- Atomic hydrogen is prepared by thermal decomposition of ordinary hydrogen or by electrical dissociation under reduced pressure. H2 + 104K.cal -------------> 2H H2 ------------------------------>2H PROPERTIES OF ATOMIC HYDROGEN:- Atomic hydrogen is much more reactive than molecular hydrogen.Expected reactions of molecular hydrogen are only those in which more than 104K.cal per mole are evolved per two g...

REFINING OF PETROLEUM Petroleum is refined by distillation.Crude oil is carried by pipes to a fractionating column and heated to above 400 C.A number of products are obtained at different temperatures and condensed. More than 500 compounds have been formed in petroleum distillate boiling below 200 C.Gasoline or petrol is a mixture of hecane (C6H14) and heptane (C7H16) and Heptane (C7H16) Since the demand of gasoline is increasing due to to its increased use a fuel for automobiles, airplanes etc.The cracking is employed to obtain increased quantities of petrol from crude oil. REFORMING OF PETROLEUM :- Knocking is a sharp metallic sound produced in the internal combustion engine.Its a cause is gasoline of low octane number.T he octane number of gasoline is improved by reforming,a process some what similar to cracking,which again brings about the arrangements of straight chain alkanes into branched chain alkanes.If the petrol used is of such quality that its vapour mixed with air can...

NATURAL SOURCES OF ORGANIC COMPOUND The mineral sources of organic compound are coal,natural gas and petroleum.Plants are also among natural sources of important organic compounds. COAL :- The bituminous or soft coal is a very important source of organic compounds.This when subjected to destructive distillation, products of industrial importance are obtained. FRACTIONAL DISTILLATION OF COAL-TAR:- When coal is destructively distilled four principal fractions are obtained, viz: coal gas , coal tar ,coke and ammonical liquors. Of these coal gas which consists mainly of methane and hydrogen is used as a fuel,while coke a form of carbon,is used in the manufacture of iron and steel industry.The composition of coal tar varies depending on the nature of the coal.However, coal is composed of various aromatic hydrocarbons. These components are separated by fractional distillation of coal tar.It has been calculated that 100 Kg of coal tar yield 1-2 Kg of benzene. NATURAL GAS :- Natural...