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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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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 gram atoms of hydrogen.Reactions producing less than this energy will not take place spontaneously.For the reactions of atomic hydrogen, there is no such condition.Most of the reactions take place at ordinary temperature and some even below room temperature.Some reactions of atomic hydrogen are given below.

      P + 3H ---------------> PH3

O2 + 2H ------------> H2O2

S + 2H -------------> H2S 

Cl2 + 2H --------------> 2HCl

CuO + 2H ---------------> Cu + H2O

AgCl +H ----------------> Ag + HCl

USES:- 

Atomic hydrogen is used to produce atomic hydrogen torch to attain a temperature of 4000 - 5000 C which is employed in welding aluminium alloys, high chromium and nickel steels.It is based on the fact that when a jet of hydrogen is passed through an electric arc set up between the tungsten rods,atomic hydrogen is produced which at once recombines to give a flame having a temperature between 4000 - 5000 C.The heat is not produced by burning of hydrogen but from recombination of hydrogen atoms.

H + H -------------> H2 + 104K.cal.mol-1 

It is worth to note that hydrogen set free at the time of its preparation from its compounds is also in atomic form and is commonly known as nascent hydrogen.If a substance capable of reacting with these atoms is present, the reaction will take place before any H2 molecules are formed but if a such a substance is not present then hydrogen atoms unite together and form H2 molecules.That is why nascent hydrogen is more reactive than ordinary molecular hydrogen.



Hope after reading this article you will understand

What is Atomic Hydrogen ?
Why atomic hydrogen is more reactive than ordinary molecular hydrogen ?
What is atomic hydrogen gas ?
Uses of Atomic Hydrogen 
What is Atomic hydrogen formula and preparation of atomic hydrogen ?

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