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...
METALLURGY OF COPPER Copper occurs both in free as well as in combined states.In combined state,it occurs mainly as the sulphide and oxide ores.The chief ores of copper are copper pyrite or chaleopyrite (CuFeS2), chalocite (Cu2S) and malachite [Cu(OH)2] and azurite [2CuCO3 Cu(OH)2 blue. Extraction Copper is mostly extracted from sulphide ores which contain about 6% Cu.The sulphide ore is first roasted (i.e., heated strongly in a current of air) on the hearth of a large flat furnace whereby the following changes occur. (i) Large amount of sulphur burns to sulphur dioxide (SO2). (ii) Iron present oxidizes to ferrous oxide (FeO) (iii) Copper changes into cuprous sulphide (Cu2S) 2CuFeS2 + 4O2 -----------> Cu2S + 2FeO + 3SO2 The roasted material is then mixed with sand to remove iron as ferrous silicate a slag which floats on the surface of the molten matte of copper.The liquid copper matte containing cuprous sulphide with some unreacted ferrous sulphide (FeS) and silica oxidi...