# Domestic Electric Circuits

What is electricity? Today, electricity has become an essential part of our lives and its hard to imagine life without it. Our households are full of electrical appliances such as an electric bulb, electric bell, electric fan, iron, electric heater, refrigerator, washing machine, etc. Do you know where does this electricity in our house come from? They come from ‘electric circuits’. So, let us study more about electric circuits below.

## What is an electric circuit?

(Source: FunScience)

In our homes, either the overhead electric poles or underground cables support the power supply flowing through the main supply. One of the wires in this supply covered with insulation in the color red is the live wire (or positive), and another wire colored black is the neutral wire (or negative). At the meter-board, these wires pass into an electric meter through the main fuse. The main switch, live wire, and the neutral wire are in connection to the line wires in our homes; these wires then supply electricity to separate electric circuits within the house.

## How does the distribution of electricity happen?

The spinning turbines produce electricity, that flows into the power lines and to our homes. Electricity moves through the wires very fast. In just a second, electricity can travel around the world several times. From the power station where the electricity is produced, it flows to large transmission lines held up by huge towers. The transmission lines carry large amounts of electricity to substations in cities and towns.

Distribution lines carry small amounts of electricity from the substations to houses. When we turn on the TV, electricity flows through wires inside the set, producing pictures, and sound. Three-phase electrical generation and transmission are an efficient and common use of the conductors as each conductor can utilize its current-rating fully in transporting power from generation through transmission and its distribution can occur for final use.

The metallic assemblage of an electric iron, toaster, table fan, fridge, constitutes the earth wire, giving a low-protection directing way for the current. In this way, it guarantees that any leakage of the current from the metallic body of the machine keeps its capability to that of the earth, and the person doesn’t get a serious electric shock. Various appliances constitute live and impartial wires.

### Electric fuse

An electric fuse is used as a safety device for the protection of electric circuits and appliances due to short-circuiting or overloading of the electric circuits. The electric fuse is a piece of wire having a very low melting point and high resistance. When a high current flows through the electric circuits due to short circuit or overloading, the fuse wire heats up and melts. The circuit is broken and the current stops flowing thereby saving the electric circuits and appliance from any damages. The capacities of fuse wire are rated as 1A, 2A, 3A, 5A, 10A, and 15A.  An electric composes pure tin or alloy of copper and tin.

## Safety measures

### Insulation

The materials which have very high resistivity offer a very high resistance to the flow of the electric current and are insulating materials. These materials play an important role in the domestic wiring as they protect us from shock and also prevent the leakage of the current. Insulators can withstand overloading within permissible limits for a short period of time. They should have the following properties:

• High thermal resistance.
• Insulators should be fireproof.
• They should be durable and readily available.
• Insulators must be non-absorbent of moisture.

### Earthing

When an iron box is in use, the metallic body’s current increases to 110V. If we accidentally come in contact with such a metallic body we are sure to get an electric shock. To avoid shock due to current leakage in electrical appliances the metallic body of the appliance should be in connection with the earth/ground. Suppose due to some defect, the insulation of the live wire inside iron burns, then the live wire may touch the metallic body of the iron. For this purpose, a separate wire, ‘ the earth wire’, runs all through the circuits along with live and neutral wires.

Usually, an electric appliance such as a heater, an iron box, etc. come with the installation of all the three wires namely live, neutral and earth wires. Metal bodies of all the appliances are therefore always in connection with the earth wire. The free end of the earth wire is attached to a copper plate buried deep in the ground. This leaves the body of the electrical appliances at the same potential (zero) as the earth and hence when we touch the metal body we do not get a shock. This is done to avoid accidental shock. Earthing is thus a safety device incorporated in an electric circuit to protect the operator.

• The use of an electric fuse prevents the electric circuit and the appliance from a possible damage by stopping the flow of high electric currents. There are faults in electrical circuits due to which heavy current may flow through the circuit that results in the overheating of live wires. Short-circuiting takes place when a naked live wire touches a naked neutral wire. Normally sub-standard wires wear out soon and may cause short-circuiting.
• Overloading of electrical circuit occurs, when the number of appliances operated on the circuit at the same time exceeds the limits the circuit wiring can withstand. We know that in domestic circuits all the appliances are connected in parallel. In parallel circuits, as we add more and more appliances more current is drawn from the supply. If the total current drawn by all the appliances at a particular time exceeds, the bearing capacity of that wire, the wires of the domestic wiring heat up, leading to ‘overloading’. It may happen because of connecting too many devices to the same (one single) socket.

## Precautions while using electric circuits

• For household wiring, always use good quality wires having proper thickness and insulation. An ISI mark must be there on any plugs, sockets, switches and electrical appliances in use.
• All the wire connections should be tight and an insulating tape should all the wire connections. Replacement of defective switches, sockets, plugs, etc. must happen immediately.
•  The placement of all the switches in your household electrical wiring circuit should happen on the live wire of the circuit so that when the switch it off, the appliance disconnects from the live wire and on touching the device you do not get a shock.
• Switch off the mains before you start working on a repair job on an electrical circuit.
• In case of an electrical accident, switch off the main switch of the electrical supply. Try to insulate the person who has received a shock. In any case, do not touch him directly.
• While earthing and installing a fuse for the household electric circuits, one should be precautious. Ensure that the fuses are placed on live wires and are of proper current rating.

## Solved Example For You

Q. The potential of live wire is:

a. o V                c. 220 V

b. 300 V           d. 1000 V

Sol: c. 220 V

From electric poles situated in our street, two insulated wires L and N come to our house. These two wires are called Neutral wire and Livewire the potential of these two wires are zero volts and 220V.

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