Home Electric Circuits

Electric energy required to operate home electric appliances is obtained from the 

national electric grid. Electric energy generated by electric power stations are 

raised to high voltages such as 132 kV or 220 kV using step-up transformers and 

distributed throughout the island. In distribution sub-centres, these high voltages 

are lowered to voltages such as 33 kV or 11 kV and ultimately they are lowered 

down to 230 V or 110 V before supplying to households. Electricity provided to houses is in 

the form of an alternating current with a frequency of 50 Hz for 230 V and 60 Hz for 110 V

A – Distribution wire    B – Supply cable

C – Overload circuit breaker (or Service fuse)  D – Electric meter

E – Isolator (or Main fuse with main switch)  F – Residual current circuit 

breaker or trip switch (RCCB)

G – miniature circuit breakers or fuses (MCB) H – Switch

I – plug socket    J  – Earth wire

K – Light bulb

Efficiency of electric appliances and conserving power

In many instances, the same purpose can be achieved using various different 

appliances. In order to get illumination we can use filament bulbs, fluorescent 

light tubes or CFL lights (compact fluorescent lights). Choosing a more efficient 

appliance helps us to save energy. A few different types of bulbs giving the same 

illumination, their power output and life times are given in Table

According to Table, it is advantageous to use LED bulbs as light sources. 

However, the use of good quality LED bulbs is limited due to their high initial cost.

Similarly, the efficiencies of cookers used to prepare food are different from one to 

another due to varying amounts of heat wastage. Old cookers that use heating coils 

are the lowest in efficiency. Emersion heater is highly efficient for heating water. 

The reason is that, all the heat generated in the heater is transferred to water when 

using it. Heaters which contains hot plates such as rice cooker is more efficient 

because heat loss is less from them. Although microwave ovens cannot be used 

to cook all types of food, they are very efficient since they produce heat inside the 

food items. In addition to these, induction cookers with high efficiencies are now 

available in the market. In these devices, the variable magnetic field emitted by the 

cooker generates heat only at the bottom of the cooking utensil.