Direct Current And Alternating Current
The current drive from a cell or a battery is Direct Current (d.c) - since it is unidirectional. The positive and negative terminal of d.c sources have fixed polarity, therefore, level of d.c remains constant with time. Despite what might be expected, there is additionally a present which changes its extremity over and over.
Such a current direction after equal intervals of time is called Alternating Current (a.c). This type of current produced by AC generator.
The time interval after which the a.c voltages or current repeat its value is known as its Time Period.
The change in the value of voltages and current corresponds to the frequency of the source. In Pakistan, alternating current oscillates 50 time every second. Thus, its frequency is 50 Hz. Alternating current has advantages that make it more practical for use in transferring electric energy. For this reason, current supplied to our homes by power companies is alternating current rather than direct current.
Supply to a House
The electric power enter to a house through three wires. One is called Earth Wire or Ground Wire (E). This carries no electricity. The earth wire is connected to a large metal plate buried deep in the ground near the house. The other wire is maintained at zero potential by connected it to the earth at the power station itself and is called neutral wire (N). This wire provides the return path for the return path of current. This third wire is at high potential and is called Live Wire (L). The potential difference between the live wire and the natural wire is 220 V.
Our body is a decent conduit of power through which current can without much of a stretch pass. Therefor, if a person holds live wire, current will start following toward ground while passing through his body which may prove fatal for the person. All electric appliances are connected across the neutral and live wires. The same potential difference is therefore applied to all of them and hence these are connected in parallel to the power source.
House Wiring
The bellow fig shows the system of house wiring. The wires coming from the mains are connected to electricity meter installed in the house. The yield control from the electric meter is taken to the fundamental conveyance board and after that to the household electric circuit.
The main box contains the fuses of rating about 30 A. A separate connection is taken from the live wire of each appliance. The terminal of the appliances is connected to the live wire through a separate fuse and a switch. On the off chance that the circuit of one apparatus wears out, it doesn't influence alternate machines.
in housing wiring, all appliances are connected in parallel with each other. This means they all get the full mains voltage and one can turn ON appliances without having to turn ON another.
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