ELECTRICAL WORKSHOP I LAB MANUAL PREPARED BY NATNAEL M OCTOBER 2018‘habits in workshops are essential ‘To develop and maintain safe working condition in ali workshops ‘© To prevent accidents which may result in personal injury or health hazards, damage of tools, equipment and property. ' Common causes of shop accidents are: a Improper use of tools and equipment, etc. o& Failure to use protective equipment. s& Protective and safety equipment that has beon rendered inoperative, & Failure to follow correct procedures. & faulty equipment and tools © condition of walking and working surfices Unguarded or inadequately guarded machinery. Safety rules that need to be observed in the Electric workshop > Each laboratory student will be made aware of the use and location ofall safety equipment (ie. goggles, gloves, apron, fume hood (cover), safety shoes, etc.) > Safety procedure and Safety signs, warnings stated in all laboratory activities must be strictly observed. > Careless behavior in a laboratory can cause accidents, Horseplay, teasing, loud talking or tossing objects are not allowed in a laboratory ‘Sharp-edge or pointed-tip tools should be handled with care No eating, drinking or applications of cosmetics is allowed in the laboratory Keep your work area hazard free ‘Never turn on power line without the permission of the instructor ‘All tools must be used for the purpose thet they are designed for mrermcacworcsmorrixrmanon—{ | }——arwarner ———— Woy Vw y¢ Of the laboratory period or when an experiment is complete, return all ‘equipment to proper storage and clean the work area, “Know the location of emergency exits and of safety equipment for your area(s), Know the location and general operation of hand fire extinguthers and other emergency ‘equipment in your department, Keep exit paths clear. Report the use of any emergency *quipment to your supervisor immediately, Fluids spilled on floor areas must be cleaned up immediately. Keep tools and cords away from heat, oil and sharp edges that can damage electrical insulation Disconnect tools and extension cords by holding the plug, rot by pulling on the cord, Be sure thatthe control switch on electrical equipment is inthe YofP" position before putting in plug or pulling it out. Do not use electrical equipment in damp or wet areas. Do notuse electrical equipment on or near metal ladders, which conduct electricity, Report immediately any damaged tool or equipment. Do not attempt to make repairs yourself Avoid using extension cords. When an extension cord must be used, choose one with the same ampere rating as the tool Make sure that the insulation is intact and that all connections are tight. Use a Ground Fault circuit interrupter (GFCI) when using portable tools. > Do not overload circuits.Safety precautions in handling of tools ‘% You will become familiar with the instructions of laboratory procedure prior tothe i of any related activity. Read all directions for the experiment at least two times. Ask questions if you don't understand any part of the direction, No changes from the instructions will be allowed without permission from the teacher or instructor. ‘& Handle sharp-edged tools with special care. a) Never carry them unshielded in pockets. b) Never hand such a tool to a friend with the cutting edge frst. ©) Avoid placing your fingers or hands in the path of motion of the cutting tools. © Never leave tools on top of a step-ladder or any other place above your head. ‘& Never abuse tools, Never use them for purposes other than those for which they are designed. If tools or cords run very hot, report the condition to the instructor. The insulation could be deteriorating. Never wrap a cloth around a tool to hot to hold. Sparks can ignite the cloth. Electric shocks and its treatment Electric shocks are received by touching the metal parts of the equipment, machine or other devices when the phase wire (live wire) comes in contact w ith the metal parts of the equipment, machines ste, The outcome of these shocks may be 0 dangerous that it my even cause death depending ‘upon the strength of the current and on the path of the current i takes in sassing to earth. The effect of electric shocks is dependent up on the following Factors a. The strength of current b, The frequency of the cument ¢. The path taken by the current through the body. ‘The strength of current The alternating current af low frequency between I mA are just tolenble but between 8 mA and 15 mA results a painful shock and contract the muscles too. The leakage current between 20 mA. and 50 mA passing through the chest may stop breathing and betweer 100 mA and 200 mA may result the failure of heart. Current above 200 mA may cause burning of skin. It is not only theleakage current which gives shock but also other fuctors like supply voltage and resistance of bodY ‘which help in giving the shock i.e, Leakage current is formulated as, ILeakage= V/R body. Frequency of currents ‘The low frequency of the current may result very simple shocks. The direct current shock is also very dangerous. Path taken by the current through the body Survival is possible, ifthe path of leakage current is not found through chest or heart but it may result severe bums on the parts of the body depending upon the value of current. Treatment (care) of Electric shocks The following points should be taken into consideration at the time of treatment of electric shocks: 4 Switching off the current or Isolation of the supply & Removing the person from the contact of current db Removing the person from fire. % Treating the bums. . »& Giving artificial respiration. & Sending the person to hospital. Switching off the current or isolation of the supply ‘When 2 person comes in contact with live conductor switch off the mains immediately if itis nearby and ifthe switch is at far -off distance, then pull the plug out, if possible or cut the wires ‘with insulated pliers from the switch board or from the wiring circuit. Removing the person from the contact of current “Push the person witha dry stick of wood or pull him from his clothes, if hey are dry to remove an from the contact of the current without touching his body. rrrRemoving the person from fire If the person's clothes are smoking, extinguish the sparks; if catches fire, t urn the clothes. Wrap him in the blanket or coat and roll him on the ground to extinguish the fire. Treating the burns Tf any bums or wound occurs on the body of the operator, use proper oil or ointment on them and cover them with proper dressing. Giving artificial respiration If the person is not breathing immediately start artificial respiration until the medical aid arrives. Sending the person to the hospital Even after apparent recovery, send the casualty to the hospital to ensure that the person is quite well or call at the doctor for check-up.CHAPTER 2 COMMON TYPES OF ELECTRICAL HAND TOOLS 1. ‘Screw Driver: Used to drive screws into/out of wood or some other materials. 4) Standard blade screw driver- for general use +b) Square blade screw driver- a strong screw driver used for tuming stubby or heavy screws; it has the possibility of increasing hand pressure and turning moment by means of plier or wrench ©) Thin blade screw driver- used for installing a screw past an obstacle ora nearby object (c.g. insidesmall holes) 4) Philip's head screw driver- used for working on cross hand screws mostly on electronic gadgets oyauito electric circuits. 2, Electrician's knife/pocket knife- used for removing insulation in electrical wiring. The blades shovld be of high grade, tempered steel 3, Pliers- used for cutting and gripping wires 8) Side-catting plier (sometimes combination plier)- used for cutting and gripping wires; it also pills on snake wire through conduits. b) Diagonal-cutting plicrs- used to cut off wires close to connecting points, e.g. , at the switch and outlet terminals which are located close to the fitting as the side cutting plier may not be able to get close enough. ‘¢) Gas or Slip-joint pliors- the slip joint permits the jaws to be extended to a Greater width than is possible with a cutting plier of the samessize, Itis used for gripping ‘whes and other things, cutting wires and holding conduit while making up locknuts and bushings. ) Flat-nose plicre-used for bending , twisting and forming conductors and Bus bars ) Round-nose pfer-used for looping conductors in order to connect them to the rere ————‘Terminals 1) Long (sharp) nose plicrs-used for pulling wires and other materials through Narrow holew/areas 4 ‘Wire Stripper- used for quick, clean, and easy insulation removal from wires Before splicing or connesting to devices, S Insulation Remover- used for skinning wites of different sizes as well as for Cutting them. © Hammers: ~ used to drive chisels, straighten metals, pick out nails, ete, 7 Test lamp: - for the same purpose as the voltage indicator, 8 Soldering iron: - used for tinning and soldering the conn which can be easily soldered. A 9 Electric oven or furnace: - used for heating and meiting solder or lead to be used in the tions of wires or other materials tinning process, 10 Voltage indicator or neon tester: - for testing the presence of voltage in a certain line. ‘The springs ensure good contact between the components of the tools, the resistors are used ‘or limiting the current flowing through the lamps as well as the voltage applied to them 11 Goggles: - used to protect the eye from the are during welding or from flying chips during ‘grinding and boring holes on brick or concrete surfaces, 12 Glove: - used to protect the hand from mechanical damage, from the burning effect of acids or from the high voltage of electrical installation (e.g. 500V), 13. Brush-used for cleaning files after work and removing chips during some ‘outing Operations.CHAPTER 3 SPLISING AND JOINING 3.1 Definition of splicing: Good joints and splices are of vital importance in a wiring installation and may result in a considerable trouble if not made mechanically and electrically secure. If they are made as to permit the wires to be worked back and forth, or not soldered properly they will due to the formation of a coating of film produced by oxidation, cause poor conductivity at the point where the conductors join and prevent the current from flowing through readily, making the circuits where these splices ‘occur constantly inefficient and troublesome, On the other hand, due to the high resistance at the point of loose fitting contact, these poorly constructed joints will cause abnormal heating and arcing and, if near inflammable material, will result in a fire hazard. 3.2. Advantages of proper splicing -It makes the installation become mechanically and electrically secure ~The disadvantage of poor splicing if the splice is loose, these poorly constructed joints will cause abnormal heating and arcing if near inflammable material will result in a fire hazard 3.3 Types of splice There are four basic types of splices . The pigtail splice The T- tap splicing (branch) ‘The western union splicing Sow > Britannia splice, Joining wires with connector tubes Is used to connect terminal of one wire with another wire it is in the form of Bakelite, porcelain or plastic it also has small screws are used to make the connection the connector must be able to take all strands of conductors to be joined together memeacworsnorrxrwanoa—{ | |} reece1 Pig tail splice \ : ions in outlet, switch boxes, a. Single wire pig tail seas wel 0900 een ‘Application:-It is used for perma! i and other confined space where there I ig tail splice no pull on the wire a oe Be es of single copper and aluminum wire, each 12 em long, diagonal Materials and Tools:-The piec: cutting pliers, pocket knife, wire stripper, flat nose pliers, soldering iron, ruler, soldering paste, insulating tape general purpose pliers, solder, nipper, flux, ...ctc. Procedure: |, Measure about 2.5 em from the ends of the wires to be applied 2. Remove the insulation of the meastire portions as shown above in fig (a) 3. Clean the wire and prepare two of them as in fig (b) 4. Cross the pieces of wire as shown in fig (c) 5. By means of pliers, twist the wires together as shown in fig (d) 6. Cut or Bend of the projecting wires beyond the last twist (e) 7. Solder the joint to strengthen the connection. 8 Insulate the splice by means of tape or insulating eup Safety: Do not touch surface being soldered. b. Bunch splice (pig tail) Application: used for joining more than two wires at ceiling-Fixture outlets, switch boxes, ete where a number of wires from different parts are brought to one box and splicing together,‘Materials and Tools:-Four pieces of single copper and aluminum wire, cach 12.¢m long, diagonal cuiting pliers, pocket knife, wire stripper, lat nose pliers, soldering iron, ruler, soldering: pss: insulating tape general purpose pliets, solder, nipper, flux, ...etc. Procedures: 1. Measure about 2.5 em from the ends of the wires to be spliced ‘Skin the wires and prepare them as shown in fig (a) 3. Cleanthe wire and prepare them in parallel (insulation to insulation 4, By means of pliers, twist the wires together as shown in fig (5) 5. Cut of the projecting wires beyond the last twist, 6. Solder the splice then cover by means of insulating tape. ‘Additional task: Make the bunch splice in accordance with the above procedure using five wires. ¢, Flexible wire to solid wire splice (pig tail) Application: This splice is used for joining the solid wires used in pemanent wiring together with the exible condactors used inwiring fixtures and appliances (wo wires of different cross section)Materials and Tools; - Wires (solid and flexible) nove pliers, soldering iron, ruler, soldering paste, insulating tape general puFpose pliers, solder, nippet, flux, file, brush, insulation remover, ... ete, Procedures: }) Measure and skin the portions of the wires as shown in fig (a) 2) Clean the bare wires thoroughly 3) Gross the wires as shown in fig (b) ammonic, pocket knife, wire stripper, fat 4) By means of pliers, wrap the flexible wire around the solid conductor for a distance of about 2em 5) Bend the solid conductor parallel to the splice 6) Out the extra flexible wire 7) Solder the joint to strengthen the connection. 8) Insulate the splice by means of tape, Note: The bend at the end strengthen the joint and provides an excellent solder le 2. Western union splice Application: Used for extending the length of wires. ie— a : a a oo eS i) <=)’ eer” DB ati Say GS Sheep ee spa ——p=oissfomctP oe Materials and Tools:-Pieces of wires, soldering lead, pocket knife, vire stripper, flat nose pliers, Soldering iron, ruler, soldering paste, insulating tap general purpose plers, solder, nipper, flax, file, brush, insulation remover, ... ete. Procedures:1, Skin the to wire to be joined (see fig a) ‘Clean both wires thoroughly. Cross the two bare wite ends as int fig (b). Make # neck turn as in fig (¢), . Using pliers, make a numberof shoulder or twisty as shown in fig (d), Cut off the excess wire. . Tighten the shoulders by means of pliers: Repeat operations 5, 6 and 7 with the remaining free wire winding the shoulders in the opposite enon een direction. 9, Solder and then insulate the splices by an insulating tape ‘Note; Sometimes the western union splice with greater number of neck tumns, greater number of shoulders and no neck tums may be used, 3. Tap (branch) splicing: A. Single branch splice Application: Used for making a connection anywhere along the length of another wire g = r a eee 8 im aie Se ee ee ae out = “Tools:-Pivces of wires, soldering lead, pocket knife, wire stripper, Mat nose pies, li Hs, soldering iron, ruler, soldering paste, insulating "ape ‘general purpose pliers, solder, nipper, x ‘brush, insulation remover, etc. Procedures:Procedures: 1. Prepare (wo pieces of copper single wire (12 ¢m long for main wire, 14 em long for making tap) as shown in fig (a) & (b) above. ‘Skin the main wire’about 2 om at the center position as in fig (a) & (b). ‘Skin the connecting wire for about 7 cm at either ends of the wire as in fig, (b), Place the branch wire across the main wire (insulation to insulation should be at an angle of 90 dogree) as in fig (¢) 5, Make a neck turn and five to eight shoulders as shown in fig (d) (use pliers to bring the twists close together and tighten them up as shown in fig (d), Solder and then wrap the splice with insulating tape: Double branch splice, Application; used in where two branch wires, lending in opposite directions, connected to-« main wire at one point. i. es eine a wire stripper, flat nose pliers, ‘Soldering iron, ruler, soldering past, insulating tape general purpose pliers, so Ider, nipper, fx, file, brush, insulation remover, ... ete: 1) Prepare three pieces of copper single wire (2 em long for main Wire, 14 cm long for making faps) as shown in fig (a), (b) &(c) above. 2) Skin the main wire about 4 cm at the center position as in fig (a), \p3) Skinthe connecting wires for about 7 em at either ends of the wires as in fig (b) & (c). 4) Place the branch wire across the main wire (insulation to insulation should be at an angle of 90 degree) as in fig (), 5) Make five to eight shoulders on the main conductor as shown in fig (d) above, (Making. shoulders should be in the opposite direction.) 6) Cut off the excess wire. 7) Solder and then wrap the splice with insulating tape. 4. Britannia splice. Application: Used for joining large non-flexible single core wires. It is commonly applied in distribution system. Materials and tools: Two pieces of solid wire each 11 cm. long; a piece of wrapping wire — diameter 1, 1Smm. length about 1m., soldering materials, diagonal cutting pliers, normal pliers, flat nose pliers, soldering iron, file, brush, ...ete. Procedures: ‘1. Clean about 7 cm. of strand line wires thoroughly as fig (2). _ 2, Bend one of the ends of every solid wire for a distance of about 8 mm. and prepare the two wires as shown in fig (a). _ Clean the wrapping wire thoroughly.Wire along the position of contact of the two solid wires and bewi 4. Extend the wrapp ght as shown in fig (b) wrapping towards the 5: Make 3 to LOtumns of the banding wire around wire 2 atthe right band end ofthe splice (see fi 6. Twist ihe two free ends of the joining wire muke 3 to 6 twists 7. Cut the excess wire and press dows the ends (see fig c) 8. Solder the splice ened. Note that: The turns should be tig 8. Cover the splice with insulation tapeCHAPTER 4 ‘TERMINATION Termination: The process of connecting lugs or connectors to the wires as well as the Preparation of the wire ends so as to enable them to be connected to the terminals of electrical equipment is called termination. Single-strand copper (solid) wires in sizes up to 10 sq.mm and Tnulti-core (stranded) wires in sizes up to 2.5 sq mm may be connected to the terminals of various instruments and apparatus without lugs. In this case the ends of multi-strand conductors should be tinned while single strand aluminum wires, before being connected to the terminals, should be Scraped bright and coated with Vaseline to protect them from oxidizing. Heavy gauge copper wires and multi-core aluminum wires should be fitted with special lugs. 4.1. Types of termination 4.1.1 Ring-end termination Procedure: A. Ring-end termination for solid- wire Skin sbout 20-25mm of the wire. Scrap the bare wire by knife and prepare it as in figure Using a tound nose plier bend back the wire to form aring as shown in figure below. ‘Cheek the diameter of the ring by means of the serew. 1. 2. 3 4. Tin the ring-end terminal for to protect the wire from oxidation, 5. 6 Shape out the ring 7. Fasten the ring by the screw and make sure that itis securely connected, Note: 1. The wire should be lopped in the same direction as the tightening of the Screw.2 Rleg ead termination Procedure: B.Blng-end termination for stranded- wire 1 2 oe a 5 6 ‘Fasten the ring by the screw and make sure that it is securely connected. Se generally used for terminating small gauge stranded i ‘Skin about 20-25mm of the wire. Twist the multi-core wire to make it solid wire. Using a round nose plier bend back the wire to form a ring as shown in figure below. Tin the ring-end terminal for to protect the wire from oxidation and to make the ting stronger. ‘Check the diameter of the ring by means of the serew. Shape out the ring.CHAPTER 5S ve aes SOLDERING Mt iy ‘ gt Soldering gun, 9% A soldering gun isa tool for soldering metals using tin-based solder to achievea highly conductive contact. The tool uses a pistol shape, and has & trigger style switch so it can be easily operated with ‘one hand. The body of the tool contains a transformer with a single-turn seeondary element. A soldering tip, made of a loop of copper wire, is secured to the end of the transfermer secondary by serews, When the primary of the,transformer is energized, the secondary produces a fraction of @ volt and several hundred amperes of current, which rapidly heats the copper tip, Since the tip has 4 much smaller cross section than the rest of the tubular copper winding, most of the heat is produced near the point of use. A tap on the primary winding is often used to light @ pilot lamp which also provides illumination of the workpiece. Applications such as soldering high current load wires, often found in inconyerient locations such as automobile bodies, preclude the use ofa soldering station. A constant-heat device has to be set ing safe place when not in use, to prevent damage or fire, The fast switching gun cools quickly enough to be set down just seconds after use. Soldering guns are used where more heat is needed than from pencil-style soldering irons. They can be used far heavy electrical connections, stained glass assembly, and light sheet-metal work Typical soldering guns are rated between 100 and 240 watts power. A gun may include a twostage ingger to give two heat settings. Consumer soldering guns are often packaged with accessory tips intended for cutting and shaping plastic, A disadvantage of soldering gun is that the copper wire loop slowly dissolves in the solder and has to be regularly replaced, The soldering gun generates an electromagnetic spike when the button 'sreleased, which can be a problem for electromagnetically-sensitive devices. Electronics‘Temperature-controtted soldering station ‘Tempereture-controlled soldering station A temperature-controlled soldering station consists of an electrical power supply and a soldering iron, It is most commonly used for soldering electronic components. Soldering iron station A soldering iron stand keeps the iron away from flammable materials, and often also comes with a cellulose sponge and flux pot for cleaning the tip. Some soldering irons for continuous and professional use come as part of.a soldering station. which allows the exact temperature of the tip, to be adjusted, kept constant, and sometimes displayed Cleaning When burnt flux and oxidized material begins to accumulate on the tip, t blocks heat transfer and contaminates the joint, making soldering difficult or impossible. Many soldering stations come vith a cellulose sponge which is dampened, and used to wipe the hot irvn’s tip clean, Wet denim performs the same job but may wear down the tip. A wire brush or wre wheel (mounted on a bench grinder) is sometimes used to carefully remove very severe oxidaion, though this may risk ‘damaging the tips protective iron plating. A smail amount of fresh solderis usually then applied to the clean tip in a process called tinning. The working surface of the ip is usually kept tinned (coated with wet solder) to minimize oxidation, Oxidation blocks heat transfer, corrodes the tip and contaminates the joint. \4CHAPTER 6 ‘WIRING MATERIALS AND ACCESSORIES to assemble properly and intelligently the great number of available ele rica! materials, /ives, fittings, and equipment to form a complete wiring system, we must understand the basic ‘principles regarding them, WIRE AND CABLES “The term wire and cable are used tyore nor less synonymous in house wiring, Strictly speaking single wire, may be bare or covered with insulation is known as @ wire and several wires stranded together is known as a cable, But in practice bare conductors, whether single oF stranded together are termed as wire and conductors covered with insulition are termed\as eables, The necessary requirements of cable are that it should conduct electricity efficiently, cheaply, and safely. This should neither be so small so as to have a large intemal voltage drop nor be too large so a5 10 cost too much. Its insulation should be such as to prevent leakage of current in unwanted direction and to minimize risk of fire and shock Accable consists of three parts: & The conductor or core- the metal wire or strand of wires caring current. 4 The insulation or dielectric-a covering of insulation material to avoid leakage current from the conductor. o& The protective covering: for protection of insulation from mechanical damage. Copper and aluminurm are the materials used as conductors in power and lighting cables. INSULATING MATERIALS. “The insulating material used in electric cable must possess the following properties, + High resistivity * High flexibility + Non-in flammability + High resistivity to moistureVarious types of insulating materials used in cables are: & Rubber +Ppve + Vulcanized Indian Rubber: Colors of conductors: Color identification of bare conductors and cable cores are given by EEP’S regulation + Earthing - white % Live of a.c single-phase circuit - Green ‘+ Neutral of ae single or three phase ac circuit ---black -Green - Yellow + + Phase R of three-phase ac circuit = Phase S of three-phase ac circuit - Phase T of three-phase ac circuit LIGHTING ACCESSORIES AND FITTINGS Switches: + Are used to control lighting circuits, + Most are rated at S/6A, but ratings at 15A are also available + Are available in three types: single pole, two-way and four-way (intermediate) each for control of a practical circuit arrangement Lamp Holders Are designed for quick removal and replacement ofthe lamp and yet they must hold the lamp in firm metalli¢ contact to prevent overheating, Plugs and socket outlet These are used to enable portable apparatus to be connected to the fixed wiring and comprises of two or three contact tubes and terminals. The plug is the movable part connected to the apparatus ontacl in to the contact tubes. by flexible wire, and consists of two or three contact pins to fit in to LePROTECTIVE DEVICES Que Mece Liem to pre yet elecrice appliece Spree ORache Apasetiet oy ptt ale Gages Oy Rone aot Pd FUSES ) ©) Ovetland 4) ofegusirrs 7 cri", ee prere ce wetter 27° Ay Y Consists of a pie of copper or tin-lead alloy wire, which will met when carrying # © predetermined current. This element with contacts, carrier and base is called a fuse ¥ Is placed in series with the circuit to be protected, and automatically bresks the circuit whem over loaded, The time for blowing out of @ fuse depends on the magnitude of excess current, ie, the larger the fault current the more rapidly the fuse blows CLRCUIT BREAKERS / eadevice designed t0 open and close circuit by non~ automatic means and to open the cérevit automatically on @ predetermined qver-cument without injury (0 itself when properly applied within its rating, So a circuit breaker i « combination deviee composed ofa manual switch and an over — current device. Y Acircuit breaker has several advantages over any type of fuse DIE tres op PTA ieee flee nd © Covet ) 5p Rem womerorr carro } rere ot @ mover we of more Ee wot pohofvorr oP oe teen AcwereeCHAPTER 7 ELECTRICAL SYMBOLS AND WIRING DIAGRAMS Laboratory Job.1 Simple circuits 7.1 One lamp controlled by a single pole, single throw switch. N.B as we equipped with low voltage power supply we will be workiug on 220V, 50Hz. Lamp lamp J.B. 220V 30Hz 220V SOHGz S.w. Single line representation diagram Wiring diagram (multi line representation) (Fig.7. 1. Lay out diagram & Wiring diagram) 7.2 Two lamps connected in series controlled by a single pole, single throw switeh Fig,7. 2. Lay-out & Wiring diagram Te7.3 Two lamps connected in parallel controlled by single pole, single throw switch. Fig7. 3. Lay out & Wiring diagram Questions 1) Using two lamps with equal power ratings, compare visually the intensity of light between the two lamps when power is turned on. 2) Repeat questions | for two lamps with different power ratings. 3) What happens if you unscrew one of the lamps and tum on power? 4) What is the advantage of paralle! wiring over series wiring? $) Discus the application of the previous labs DA7.4 Bed room lighting iB 1B JB es = + 7 Sz ue tT t = + SI i | s3 Fig.7.4, Wiring Diagram for Bed Room Lighting Conclusive Questions: 1. Draw single line representation & schematic diagram for 7.4 2. Draw the wiring diagram of living room, the room has tw of the room. 0 lamps controlled from three entrancesby means of ewo, two -switches and By ssive Question: ithe applications of this cireuit, ug res “3 P st s2 ss sa Wiring diagram for corridor lighting| Annunciator Circuit ‘sitcuit is often arranged so that the bell can operated from any one of two or more positions. € circumstances it is necessary install an indicator 10 show which push button has been, ‘The bell gives an audible signal and the indicator lag visuall signal at some central point, that a service is required, or an emergeney has arisen mt a particular push position, ‘This type of circuit is used in hospitals, Individual pushes are available at each bed and the indicator board is situated in the ward supervisor's office, Large fire alarm system also uses bourds to indicate the Zeon or part of the building where the call was initiated. Complete he wiring diagram shown below and construct the installation on the wiring boartl, lor FY AL IAP AL HAY A