MATERIALS USED FOR ELECTRICAL WORKS

Generally the materials used for electrical works divided into three types. There are called Conductors, Insulators and Semiconductors. The materials which conduct the current from one place to other place are called conductors, the materials do not conduct current i.e. it resists the current are called Insulator and the materials which have half of the properties of these two are called semiconductors, i.e. It conducted only a very low value of current. For this purpose conductors and insulators are widely used in Electrical department where as semiconductors are used in Electronics department.

In this chapter, we have to study about the types and properties of conductors and insulators.

2.1. CONDUCTOR

What is called conductor? The wire which carries (Conducts) current from the supply point to the load is called conductors. The material is operated by using the current is called load. Eg. Fan, Radio, Iron box, Mixie, Grinder, Bulb etc. Generally all types of metals are used for conducting purpose, some metals permit easily to allow the current flow through it. This type of metal is called "Good Conductors".

2.1.1 Properties of conductor

•          To conduct the current easily.

•          Would have low resistance.

•          Would have high tensile stress.

•          More flexibility.

•          It will not affected by the corrosion due to air (or) not affected by rain, heat.

•          When a current is flowing through the conductor, it will get heated. Therefore it is not affected by heat.

•          Easy to soldering.

•          Cost is low and is easily available to buy it.

2.1.2 Types of Conductor

Conductors are classified into three types depending upon the conducting property with low resistance there are solid conductors, liquid conductors and gas conductors.

Solid Conductors

Silver, Copper, Brass, Aluminium, Tungsten, Nichrome, Zine Iron are called good conductors. There are converted into thin wire and thin rod or strap for the purpose of conduction.

We have to study about the metal is used for conduction and where there is used.

2.1.3 Liquid Conductors

The conductors in the form of liquids are called as Liquid Conductors. Mercury, Sulphuric Acid, Nitrate are some of the liquid conductors used in batteries. Mercury is used in high power vapour lamps and automatic circuit breakers.

2.1.4 Gas Conductors

Organ, Helium, Neon, Nitrogen are some of the gas conductors. They are used in gas discharge lamps at high temperature.

2.2. INSULATORS

Insulator is non-conducting material, i.e., it resists electricity. It has high resistance value, normally in Mega Ohms.

Properties

•          It has high resistance and specific resistance.

•          High di-electric strength.

•          Good Mechanical strength.

•          Withstands high temperature.

•          May not get change in shape due to temperature.

•          May not absorb water and can be made to any shape.

•        Can not get fire easily. Classification of Insulators

Generally Insulators are classified into three types: l.Hard Insulators

Ex.: Back lite, Porcelain, Wooden Plank, Glass, Mica, Ebonite

2. Soft Insulators

Ex.: Rubber, Poly-Vinyl Chloride, Varnish coated papers, Micanite, Pressphan paper

3. Liquid Insulators

Ex.: Mineral oil, Shellac, Varnish

2.2.1. Tools and their uses

For the betterment of our electrical works a number of minor and major tools are used. In this chapter we are going to learn such tools.

1. CUTTING PLIER:

In electrical tools cutting plier is the most important tool. It is used to cut the cables and to tighten them. The handles of the plier is, wrapped by rubber even to be used in current supply. It is also used to fix or remove screws.

2. LONG NOSE PLIER

It is used to fix and remove screws in narrow gaps. It is widely used while repairing radios and

speakers.                                                                                                 

3. KNIFE

It is used to remove the insulation in electric cables. The handle of a knife is made up of wood or plastic. Its length is in four or five inches to keep easily in shirt pockets.

 4. SCREWDRIVER

It is used to fix and tighten the screws. The point of a screw^driver should be flat to be fixed in the gap in the head of a screw. It is available in different sizes from 4.5 inches to 12 inches. It is named according to its length. Its handle is made up of wood or plastic. Wooden handles are better to be used for long period than plastic handled Screw Driver

5. CONNECTING SCREW DRIVER

It is also a type of Screw Driver. Its handle is made of plastic. It is available in small sizes. It is used to fix and tighten screws in joints, and poles. It is of 4.5 or 5 inches

6. TESTER

It is the essential tool of a electrician. It is also like connecting screw Driver in size. Its handle is also made up of slots. In its handle a visible pipe like part is fixed in it a neon bulb is fixed with a screw metal and there is a clip in its head. All these parts are connected using a cable. It is used to check current supply in electric circuits. If there is a current supply in the circuit the neon bulb glows.

7. POCKER

It has a sharp end. It is used to make holes to fix screws in electric boards.

8. JUMPER

It is used to make holes on walls. It is available in 8 SWG or 6 SWG sizes. Its handle is made up of iron. By hammering its handle, required holes are made by the sharp points.

7. TUBE JUMPER

It is used to make holes on walls. But it is used to make holes between the walls to connect electric cables. One side of this jumper is like a saw. The hammer is used to make holes and rotate the jumper clockwise to make holes easily and quickly.

8. WOOD SAW

It is used to cut wooden boxes, sticks and round blocks for the required size.

9. HACKSAW

It is used to cut PVC or metal pipes and metal frames. The frame of hack saw is made up of Iron and the handle is made up of wood. A clip is fixed in its other end to adjust the length.

10. BALL PANE HAMMER

Handle

As its head is round shaped like a ball it is called so. Its head is made up of iron and handle is made up of wood. It is used to fix needles and bend iron rods. It is available in different weights.

11. CLAWHAMMER

In this type of hammer of end is flat, the other bent and there is a claw in the end. It is used to remove nails and hammering the nails.

12. MALLET

       It is fully made up of wood. It is mostly used for woodet works.

13. HAND DRILLING MACHINE

It is used to make holes in wooden materials. In one end of this machine a chuck is available to fix required drilling bit. Fixing it i wood by keeping the handle tightly, holes are made by rotating the cli

14. FILES

It is used to correct the size and smooth the upper part c metals. It is named according to the size and the rough surface for smoothing other surface.

TRYSQUARE

It is used for measuring angles of 90 (Right angle) Measurements in mile metre are marked in its scale. It is used to measure 90 right angle accurately.

WIRE GAUGE PLATE

It is of round shape. It is used to measure the width of wires. Its unit is gauge. The wire is put into the hole in the centre of the Gauge to measure its width. Wires are available in gauge of 8 SWG, 12 SWG, 18 SWG.

2.3 TYPE OF SWITCH

S.P.T Switch: This is a mechanical divice used for opening or closing an electrical circuit. Single pole switch is used for closing (or) opening one phase only most of the switches are turmbler type but, now a days flush type switches are used.

2.3.1 Intermediate switch: To control a light from more than two different places, the intermediate switch is used for example a long hall, corriders and passage ways with many doors etc.

2.3.2. Knife switch: Knife switch is made of Copper and is generally used in laboratories for switch boards. It has a long piece ofl copper strip hinged in one end and which can go into a copper socket at the other end. It has got an insulated handle and two terminals. Below the main some times there is additional small strip held by means of springs. The small strips makes contact to permits any number of control points.

2.3.3 Main Switch: Main switch is the one which controls the electrical supply for whole house (or) factory. These are also called as Iron clad switches. There are different types, Two pole and Three pole in the Two pole switch, their will be two fuse units, the neutrol one will have a link and the phase 1. will have the rated fuse wire. There is also an earth terminal. The Iron clad switch has a metalic cover which can be screwed out for changing the blown out fuse only. After putting of the switch. From the main switch leads are taken to the distribution box.

2.4 Fuse unit:

Function: A fuse in meant for protecting the circuit from damage if a short circuit developes some were in the wiring (or) in the connected appliances. Like a switch it instantly breaks the circuit and the flow of current in the circuit is interrupted at once. It does so automatically by melting off it self. A fuse in made of a metallic wire (tin, lead and Zinc alloy) having a low melting point and so life at any instant any excessive current passed through the circuit, its heat melts of the fuse. When the fuse blows it is a clear indication that something has gone wrong some were in the system. Every electrical circuit must there­fore have a fuse of the correct rating as a protective device. Fuses are usally rated for 5 Amps, 10 Amps and 15 Amps

Types of fuses: Kitkate porceilin fuse unit, HRC fuse, Cartridge fuse.

2.4.1 Cartridge fuse: This type of fuse in mostly used in T.V, Radio, Record plier, Voltage stabiliser, etc. They are in the shape of a capsule in which the fuse wire is stretched in a gas tube with metalic caps at each end. The blown of fuse wire can be seen stright away. This type of fuse is easy to replace by simply pressing it into its seat.

2.4.2. Kit Kat type fuse: These are the ones mostly used in domestic installations. This fuse consists of a proclaim base having two fixed contacts, for connecting the incoming and outgoing cables. The bottom part of the fuse is called the base and the top is called the fuse carrier. The line and a load wires are connected in the base terminals and the carrier is provided with a fuse. The base fixed but the carrier is removable.

2.5 Wall socket: It has ready to give supply to the soldering iron, Table Fan, Radio, T.V and other electrical appliances. It has two pin, 3 pin and 5 pin socket for connecting plus, it is usually rated for 5 Amps and 15 Amps.

2.6 Ceiling rose: Ceiling fan (or) Tube lamps are get supply from this ceiling rose. It has two or Three brozz plates with connecting terminal screws.

Types of Ceiling rose: Two plate ceiling rose, Three plate ceiling rose.