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...
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...