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1. Electricity: It is a form of energy, which can be transformed to other forms of energy like heat, light, sound etc. The most distinctive feature about it is the ease with which it can be transmitted over long distances. 2. Voltage: It is the electric pressure or degree of electrification, which is responsible for the flow of current. The practical unit of electric potential is volt, which can be measured with the help of a voltmeter. 3. Electric Current: It is the flow of electricity. The difference of potential is a prerequisite for the current to flow. Practical unit of current is Ampere and is measured with the help of Ampere meter (usually called Ammeter). An ordinary lamp of 60 watts draws approximately 1 ampere. 4. Electric Power: It is the rate of doing work and is the multiplication of current (A) and the voltage (V). Electric power is also determined by the voltage and the amount of current flowing. Power = Voltage X Amperage The power derived from a current of one ampere following under a voltage of one volt is said to be equal to one watt. The electricity consuming apparatus is rated in terms of either (Kilowatts) (1000 watts) or in terms of horsepower whereas heaters, coolers, bulbs, fans extra are rates in watts or kilowatts. Electric motors are rated in horsepower. One horse power (H.P) = 746 watts. 5. Electrical Energy: It is the capacity of doing work. The practical unit of electrical energy is kilowatt-hour (kwh) or "unit" as it is called in common language. One unit of energy is said to be consumed when electric appliance with rating of 1000 watts is operated for an hour. Electrical energy is measured by means of an energy meter, which is generally installed at the premises of every consumer. 6. Conductors: Just as a path is required for the water to flow from one place to another, conductor are needed for the flow of electric current. 7. Resistance: It is the inherent property of a substance, which resists or opposes the flow of electricity. Obviously good conductors have low resistance whereas bad conductors have very high resistance. The practical unit of measuring resistance is called 'Ohm'. The resistance of a conductor in which a current of one ampere flows when potential difference of one volt is applied at its ends, is said to be one 'ohm'. 8. Line Losses: Where an electric current flows through a circuit (a closed path), heat is developed, as the current is working to overcome the resistance of the conductor. The generation of heat during the process of flow of current consumers some of the electric power. Line losses are an integral phenomenon of flow of current through any circuit. 9. Transformer Losses: Just as transmission of electric power is accompanied by a certain amount of loss of power, the transformation, whether stepping up or down, also involves some loss of power, which is called transformation losses. 10. Maximum Demand of an installation: It is defined as the greatest of all the demand, which have occurred during a given period say during half an hour, an hour, a month, or a year. The maximum demand is measured with the help of a maximum demand indicator. 11. Demand Factor: It is defined as the ratio of actual maximum demand made by a load to the total connected load. Demand factor = Maximum Demand Connected load 12. Diversity Factor: It is the ratio of the sums of the maximum demands of various consumers to their simultaneous max. demands. It is usually grater than unity. 13. Load factor: It is defined as the ratio of the power requirements during a particular period to the maximum demand. In other words it denotes the extent of utilization of electric power. 14. Power Factor: Most of the load demand on a electric power supply system is composed of A.C. induction motors and such apparatus which by virtue of its inherent characteristics draws more current than its warranted by the actual load requirements. This excess current is usually used in charging and discharging the magnetic system of the electrical apparatus. The drawl of excess current is necessitated because of the current becoming sluggish with reference to the voltage or in other words current lagging the voltage-as it is called in electrical terminology. The extent of 'Lag' depends upon the design features of a particular apparatus. In certain cases a reverse phenomenon i.e. current leading the voltage can also happen as in case of a synchronous motor, but usually the current lags the voltage with the result that the product of current and voltage as explained under its 4 above does not give the true power but is the apparent power. This power is usually greater than the true power. The ratio of the true power to apparent power or of the useful current to the total current known as Power factor. |
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