Electrical and Electronics Appliances

1) what electrical appliances are generally used in houses ?

ANS :

The following electrical appliances are generally used in houses ---

i)            Electric bell,

ii)         Electric iron,

iii)       Electric kettle,

iv)       Electric geyser,

v)          Electric emersion heater,

vi)       Electric grinder,

vii)     Electric room heater,

viii)   Room cooler,

ix)       Washing machine,

x)          Emergency light,

xi)       Water cooler,

xii)     Hair dryer,

xiii)   Electric hot plate , oven.

xiv)   Refrigerator,

xv)     Air conditioner,

xvi)   Electric shaver,

xvii) Coffee percolator,

xviii)      Incubator.

2) what is meant by ‘terminal’ of an electrical appliances ?

ANS :

The terminal is a point at which an electrical connection is made where current enters or leaves a piece of electrical equipment . it is an input or output device connected to an appliance which may be the last end of a cable , wire or electrode or a pin of battery for making electrical connection .

3) what is a n electrical bell ?

ANS :

An electrical bell is a device in which a hammer is vibrated to beat against a bell .

4) what do you mean by continuous ringing bell ?

ANS :

Continuous ringing bell is such type of bell which continuous to ring even when the bell push is released .

5) what is buzzer ?

ANS :

An A.C operated electric bell without a hammer or a gong is called buzzer.

6) what is working principle of a buzzer ?

ANS :

In a buzzer a metal armature vibrates directly against a piece of non resonant metal , the vibration of armature gives a buzzing sound instead of harsh annoying sound of electric bell.

7) what is a bell transformer ?

ANS :

It is a step down transformer .

8) what is the purpose of a bell transformer ?

ANS :

When the bell is connected directly across the supply mains the make and break in the bell circuit produce radio interference . so to avoid the radio interference working on the same circuit the bell is operated at the voltage through a bell transformer.

9) how many types of electric bells are available ?

ANS :

The following types of electrical bells are available –

i)            Ordinary bell

ii)         Buzzer

iii)       Two tone bell &

iv)       Musical door bell

10) what is two tone bell ?

ANS :

It is an electrical device consisting of an electromagnetic armature and two plates at both sides of it, two ball hammers are fitted on the armature which strikes on the plate one after another to produce sound of two different tones.

11) what is a musical door bell ?

ANS :

Musical door bell is an electronic device operated by an IC circuit and a speaker which produces musical sound on pressing the push button switch . it can be operated by 6 volt , 12 volt or 240 volt .

12) what is a thermostat and what is its function ?

ANS :

Thermostat is a switch consisting of a bimetallic strip which bends and disconnects automatically when heated beyond a certain temperature . the function of a thermostat is to control the temperature of a heating element .

13) what are the applications of a thermostat ?

ANS :

Thermostats are used in the following cases :--

i)            In furnace to maintain constant temperature ,

ii)         For operating time switches

iii)       For safety operation in over current relay and

iv)       For regulating the flow of fluids in electricity operated apparatus

14) what are the types of water heater ?

ANS :

The two main types of water heater are as follows :--

i)            Non pressure type ---- it is a self contained single point heater and used where the hot water is required at one point like a wash basin .

ii)         Pressure type :---- it is a cistern type heater and getting its cold water supply from the supply main through a cistern . it is used where the hot water is required at more than one point by using one heater element only.

15) what is domestic geyser ?

ANS :

A domestic geyser is a non pressure type immersion rod based water heater supplying hot water continuously to wash basins and bathrooms which is used for fulfilling the requirements of one place only . it is basically a round water tank fitted with a tubular heating element and a thermostat . it has one inlet hole for entry of water and other outlet tap for flowing water . the temperature is controlled by the thermostat . as a safety device a steam pressure release valve must be provided in geyser . it is generally rated at 1000W to 3000W and made in the capacity of 1 to 100 liters.

16) state the common faults of a geyser mentioning the reasons behind it ?

ANS :

The following six types of faults are found in geyser :--

A) Water is not becoming hot due to any one of the following reasons

i)            Supply failure

ii)         Blowing of fuse on account of short circuits or earth faults

iii)       Calcium deposition on tubular heating element

iv)       Opening in heating element due to burning

v)          Defective switch or loose connection 

vi)       Damaged wire

vii)     Leakage faults in heating element

viii)   Improper setting of thermostat

B)                Water does not become hot upto required level due to very low point adjustment of thermostat

C)                Hot water comes very hot and steam is produced due to burning of thermostat terminals

D)                Fuse blows again and again due to any one of the following reasons

i)            Use of low capacity fuse or draw of more current by geyser

ii)         Short circuit or earth fault occurred in heating element

E)Geyser gives electric shock due to any one of the following reasons:--

i)            Leakage fault occurred in the heating element with poor body earth connection

ii)         Heating element is punctured and water comes in contact with the live element and poor body earth connection

F) Geyser has more water leakage due to loose pipe line joints and leakage in water tank

17) what is immersion heater ?

ANS :

Immersion heater is a coil shaped bent cylindrical metal tube in the middle of which a long nichrome wire is inserted and insulated from the tube by means of insulating powder or sand all round . it is generally used for heating water in a bucket , when it is inserted into water upto a level marked and supply is made on the generated heat is transferred to a water by conduction. It is generally made for rating of 1000 W , 1500 W and 2000 W.

18) state the common faults of an immersion heater mentioning the reason behind it ?

ANS :

The following three types of faults are found in immersion heater—

A) Immersion rod is not heating due to any one of the following reasons :--

                   I.        Open circuit in heating element

                II.        Fuse blown

              III.        Open circuit in connecting lead

             IV.        Defective ON / OFF switch

                V.        Non availability of supply in power socket

B)                Fuse blows up by connecting immersion rod due to any one of the following reasons :--

i)            Use of low ampere capacity fuse

ii)         Internal or outer short circuit in the section of immersion heater

C)                Metal bucket or water is giving electric shock in which immersion heater is used due to any one of the following reasons :--

i)            Leakage in immersion rod

ii)         Water going inside comes in contact with the heating element owing to breakage of immersion rod

iii)       Opening in neutral or earth connection

19) what is called an electric cooking range ?

ANS :

An electrical appliance consisting of a hot plate and one or two electric stoves is called  as a cooking range . generally two elements are fitted in the grooves of porcelain plates which are connected in series or parallel as required by special type of rotary switch . the elements may be of 500 W , 750 W , 1000 W , 1500 W & 2000 W .

20 ) what is an electric kettle ?

ANS :

It is usually a utensil shaped kettle having mica insulated nichrome heating element at the base of the kettle or cooking an immersion type heater . the wattage rating of an electric kettle is 350 to 1000 watts . it is normally used to prepare tea or to heat small quantity of water .

21) what are the precautions to be observed at the time of using electric kettle ?

ANS :

The following precautions are to be observed :--

A.        Kettle without water should never be connected with electric supply

B.        Electric Kettle should not be touched ‘ ON ‘ position and it is to be ensured that the body earth connection is properly done

C.        Plus top must be removed first from wall socket before opening kettle for service

D.       Broken plug and connector should never be used and there should not be any type of loose connection

E.        Kettle should be cleaned and kept reverse after every operation of heating tea or milk so that water may come out of inside

F.         At the time of washing it should be kept in mind that water should not come upto lower part of the kettle because if the element will come in contact with water then it will burn

22) what is soldering iron ?

ANS :

It is a heating element contained in a barrel which heats  up the soldering bit to melt solder wire used for making a permanent mechanical joint of wires , it has a wooden handle for proper holding , it is generally made for ratings of 25 W , 65 W , 100 W , 200 W etc.

23) what is an electric iron ?

ANS :

It is a heat producing electrical appliance which is used in day to day life for smoothing of clothes , it consists of sole plate , a heating element ( mica insulated nichrome wire ) , a pressure plate , a cover case , switch or connecting pins , screws or bolts to assemble the parts and a handle , it may be either automatic or non-automatic , for automatic control thermostat switch is used , it is made in the weight grading of 1.2 to 8 kg , it is generally made for the ratings of 450 W , 750 W , 1000 W , 1250 W , 1500 W & 2000 W.

24) What precautions should be observed while replacing the element of an electric iron ?

ANS :

There should not be any air gap left between the pressure plate and the base plate of the iron .

25) which defects are generally occurred in an electric iron ?
ANS :

A.Leakage of current due to insulation failure or naked wire in connection with the body which causes charging of iron body resulting possible shock on touching .

B.                Burning of fuse due to flow of excess current under short circuit in the iron

C.                No heating effect due to loose connection  or break in element or defective thermostat of defective switch

D.               Becoming quick defective due to use of sub standard element