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...
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...