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...
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...