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Which arrangement is used for domestic circuits ?
When designing an electric circuit, we should consider whether a series circuit or a parallel circuit is better for the intended use. For example, if we want to connect (or join) a large number of electric bulbs (say, hundreds or thousands of electric bulbs) for decorating buildings and trees as during festivals such as Diwali or marriage functions, then the series circuit is better because all the bulbs connected in series can be controlled with just one switch (see Figure).
A series circuit is also safer because the current in it is smaller. But there is a problem in this series lighting circuit. This is because if one bulb gets fused (or blows off), then the circuit breaks and all the bulbs are turned off. An electrician has to spend a lot of time in locating the fused bulb from among hundreds of bulbs, so as to replace it and restore the lighting.
The parallel electric circuit is better for connecting bulbs (and other electrical appliances) in a house because then we can have separate switches for each bulb (or electrical appliance) and hence operate it separately (see Figure). In addition to having ease of operation, parallel domestic circuits (or household circuits) have many other advantages over the series circuits. We will first give the disadvantages of the series electric circuits for domestic purposes and then the advantages of the parallel electric circuits.
Disadvantages of Series Circuits for Domestic Wiring
The arrangement of lights and various other electrical appliances in series circuit is not used in domestic wiring because of the following disadvantages :
1. In series circuit, if one electrical appliance stops working due to some defect, then all other appliances also stop working (because the whole circuit is broken). For example, if a number of bulbs are connected in series and just one bulb gets fused (or blows off), then all other bulbs will also stop glowing.
2. In series circuit, all the electrical appliances have only one switch due to which they cannot be turned on or off separately. For example, all the bulbs connected in series have only one switch due to which all the bulbs can be switched on or switched off together and not separately.
3. In series circuit, the appliances do not get the same voltage (220 V) as that of the power supply line because the voltage is shared by all the appliances. The appliances get less voltage and hence do not work properly. For example, all the bulbs connected in series do not get the same voltage of 220 volts of the power supply line. They get less voltage and hence glow less brightly.
4. In the series connection of electrical appliances, the overall resistance of the circuit increases too much due to which the current from the power supply is low. Moreover, the same current flows throughout a series circuit due to which all the appliances of different power ratings cannot draw sufficient current for their proper working.
Advantages of Parallel Circuits in Domestic Wiring
The arrangement of lights and various other electrical appliances in parallel circuits is used in domestic wiring because of the following advantages :
1. In parallel circuits, if one electrical appliance stops working due to some defect, then all other appliances keep working normally. For example, if a number of bulbs are connected in parallel circuits and one bulb gets fused (or blows out), then all the remaining bulbs will keep glowing.
2. In parallel circuits, each electrical appliance has its own switch due to which it can be turned on or turned off independently, without affecting other appliances. For example, all the bulbs joined in parallel circuits in a house have separate switches due to which we can switch on or switch off any bulb as required, without affecting other bulbs in the house.
3. In parallel circuits, each electrical appliance gets the same voltage (220 V) as that of the power supply line. Due to this, all the appliances will work properly. For example, all the bulbs connected in parallel circuits get the same voltage of 220 volts of the power supply line and hence glow very brightly.
4. In the parallel connection of electrical appliances, the overall resistance of the household circuit is reduced due to which the current from the power supply is high. Every appliance can, therefore, draw the required amount of current.
For example, in parallel circuits, even the high power rating appliances like electric irons, water heaters and air-conditioners, etc., can draw the high current needed for their proper functioning.