Skip to main content
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...
Post a Comment

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.The 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 ignite prior to high compression on passing of firing spark,the energy produced by burning of fuel is not utilized in moving the piston.By the use of catalyst, the straight chain hydrocarbon molecules may be reformed to other molecules which give better performance as motor fuels.This is particularly important in the manufacture of aviation gasoline,In the presence of compounds called antiknock compounds, the knocking can be decreased.Value of the fuel is expressed in terms of its octane number.The octane number of gasoline may also be increased by adding tetrathyl lead Pb (C2H5)4 as knock inhibitor which moderates the explosions in the cylinders of the engine.But fuels containing Pb(C2H5),pollute the atmosphere with lead.

CRACKING :-

The fractional distillation of petroleum yields only about 20% petrol.Additional quantities of petrol are obtained by cracking of higher boiling fractions.Cracking involves splitting the larger molecules of the less volatile fractions into smaller molecules of greater volatility by subjecting them to high temperatures and pressure in the presence of catalyst.Besides increasing the yield of petrol from petroleum, cracking also yields large amounts of useful by products such as ethene, propane, butene and benzene.These are used for making drugs,plastics,detergents,synthetic fibers,synthetic rubber,fertilizers weed killers and important chemicals like ethanol,phenol and acctone.     

Labels:

Comments

Post a Comment

Popular posts from this blog

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...
Post a Comment
Read more
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...
Post a Comment
Read more
Periodic Classification of Elements :   "The arrangement of elements in their blocks,periodic and groups is called classification of elements. Dobereiner's Classification :   In 1829, W. Dobereiner, a German Chemist,made use of Idea of relationship between atomic masses and properties of elements for the classification of elements.He arranged similar elements in to groups of three elements call "triads". Law of Triads : "The atomic mass of the middle element was found to be approximately the average of the other two elements of triads". This is know as "Law of Triads" Li = 7 Na + 23+39/2 =23 K = 39 This classification could not be extended to all elements for their classification. New Land's Classification : In 1864.New Land  an English chemist attempted the classification of elements in order of their increasing atomic masses.He observed the properties of elements & found that properties of elements. Law of Octave : "The properties...
Post a Comment
Read more