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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...
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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 gas is also one of the important source of simple organic compounds specially like methane.It is found at sui in Pakistan and known as sui gas.It is also found at other places.

COMPOSITION OF SUI GAS :-

METHANE                                94.60%
ETHANE                                   1.05%
PROPANE                                  0.28%
BUTANE                                    0.17%
NITROGEN                               3.88%
CARBON DIOXIDE                 0.02%

PETROLEUM :-

Petroleum means rock oil in latin.Is is usually found below the surface of the earth. It is a viscous liquid comprising of components with different boiling points.It contains alkanes,alkenes,cyclo-alkanes,aromatic hydrocarbons,besides some inorganic compounds and is called crude oil.When subjected to fractional distillation several groups of products are obtained.This is known as refining of petroleum.


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