Basic Technology JS3

Topic:  PERIODIC MAINTENANCE: DEFINITION, TYPES, AND METHODS OF MAINTENANCE

Periodic maintenance is a scheduled care or maintenance of pieces of equipment. We need to maintain hour equipment to prolong their years of usage. When carrying out periodic maintenance, it is advisable to keep maintenance record.

Types of periodic maintenance

1.      Short-term periodic maintenance: this involves scheduled maintenance activities to be carried out on a daily, weekly or bi-weekly basis.

2.      Medium-term periodic maintenance: this involves scheduled maintenance activities to be carried out on monthly, bi-monthly or quarterly intervals.

3.      Long-term periodic maintenance: this involves scheduled maintenance activities that are carried out at long intervals such as twice a year, annually or once in two years.

Methods of maintenance

1.      Cleaning

2.      Dusting

3.      Washing

4.      Oiling

5.      Adjusting selected parts

6.      Replacing faulty parts 

Importance of periodic maintenance

1.      It helps to increase the work-life of our tools and equipment.

2.      It is the only way that the breakdown of equipment can be prevented.

3.      it saves cost in terms of time, money and energy.

4.      It shows that we are good technicians.

Exercises:

1.      What is periodic maintenance?

2.      Why should we carry out regular periodic maintenance on our equipment?

3.      What is short-term periodic maintenance?

4.      What is medium-term periodic maintenance?

5.      What is long-term periodic maintenance?

6.      What are five methods of maintenance?

7.      What are three importance of periodic maintenance?

Research:

List the names of six household furniture.

Topic: Building Construction: Roof, definition, types and uses

A roof is the cover at the top of a building. Roofs protect the internal decorations or fittings from weather. Roofs also protect humans and property inside the building.

Materials for roofing a building

1.      Corrugated sheets of asbestos

2.      Copper sheets

3.      Thatches

4.      Plain tiles

5.      Aluminium sheets

6.      Zinc

7.      Timber, etc

Classification of roofs

Roofs are always classified based on their angle of slope or how they look. Some roof types are:

(a)  Single Roof

1.      Flat roofs:

2.      Lean-to roofs

3.      Double lean-to roofs

4.      Couple roofs.

5.      Close couple roofs

6.      Collar roofs

CLASS EXERCISE: draw the roof types mentioned above then briefly describe each.

(b)  Double or purlin roof: purlins are used to support the common rafters. This type of roofing is done when the roof has large spans.

(c)  Triple or framed roofs: this roof has three sets of members, namely: spars, purlin and trusses.

Exercises:

1.      What is a roof?

2.      What are two functions of a roof?

3.      What are five materials for roofing a building?

4.      What are the classes of roofs?

5.      How can lean-to roof be differentiated from double lean-to roof?

6.      What are the physical differences between a flat roof and a collar roof?

7.      What are the functions of:

(a)  Purlin

(b)  Spars

(c)  Trusses

Research:

Draw five (5) kinds of roof covers.

Topic: Simple Blue Print Reading

An architectural blueprint is a detailed technical drawing showing all the technical details of a building, and often using symbols to depict doors, windows, etc. Architectural blue prints are also commonly known as building plans.

An architect is the professional specialist who designs building plans. A draughtsman is a person skilled at drawing engineering or architectural plans.

A building plan, for the purpose of construction, is prepared in such details that will leave the builder in no doubt about what to do. A building plan, therefore, is normally made in a set comprising the floor plan, elevations, sections, component details (electrical installation plan, water supply), foundation and site plan.

These plans are made to the specifications of the building regulations. A typical plan for a two-bedroom house is shown below.

Culled from:  www.interiordesigninspiration.net

Common symbols on building plans

It is very important to be able to recognize and interpret symbols and dimensions in a building plan. Symbols are representations on a building plan of actual things, appliances or gadgets that are to be provided in buildings during construction.

CLASS ACTIVITY:

Building symbols and meanings

	Symbols	meaning
1		Earth or soil
2		Strip foundation
3		Hardcore
4		Mass concrete slab
5		Stone work
6		Brickwork
7		Block work
8		Timber
9		Bath
10		Water closet
11		Sink
12		Wash hand basin
13		Fluorescent tube
14		Filament bulb
15		Socket outline
16		Switch
17		Electricity meter
18		Window
19		Door

Symbols are presented in the following categories:

1.      Mechanical symbols: kitchen sink, bath, water closet, wash hand basin, switch, drainage,  etc.

2.      Electrical symbols: electrical fittings, accessories, telephone outlet, gear swich, consumer unit etc.

3.      Sewage symbols: these show the fittings for taking off both solid and liquid wastes from the building.

4.      Water pipes symbols: drainage, hot water supply,

         

 Exercises:

1.      What is an architectural blueprint?

2.      What can architectural blueprints be called?

3.      Who is an architect?

4.      Who is a draughtsman?

5.      What are the six sets of drawings that make up a complete building plan?

6.       What are basic elevations in building plans?

7.      What are five parts of a ground floor plan?

8.      What are the symbols for doors, windows, hardcore, concrete and socket outlets?

9.      What are symbols used for in a building plan or blueprint?

10. What are the different categories that building plan symbols are presented?

Research:

1.      What is periodic maintenance?

2.      Why should we carry out regular periodic maintenance on our equipment?

Topic:  PERIODIC MAINTENANCE: DEFINITION, TYPES, AND METHODS OF MAINTENANCE

Periodic maintenance is a scheduled care or maintenance of pieces of equipment. We need to maintain hour equipment to prolong their years of usage. When carrying out periodic maintenance, it is advisable to keep maintenance record.

Types of periodic maintenance

1.      Short-term periodic maintenance: this involves scheduled maintenance activities to be carried out on a daily, weekly or bi-weekly basis.

2.      Medium-term periodic maintenance: this involves scheduled maintenance activities to be carried out on monthly, bi-monthly or quarterly intervals.

3.      Long-term periodic maintenance: this involves scheduled maintenance activities that are carried out at long intervals such as twice a year, annually or once in two years.

Methods of maintenance

1.      Cleaning

2.      Dusting

3.      Washing

4.      Oiling

5.      Adjusting selected parts

6.      Replacing faulty parts

Importance of periodic maintenance

1.      It helps to increase the work-life of our tools and equipment.

2.      It is the only way that the breakdown of equipment can be prevented.

3.      it saves cost in terms of time, money and energy.

4.      It shows that we are good technicians.

Exercises:

1.      What is periodic maintenance?

2.      Why should we carry out regular periodic maintenance on our equipment?

3.      What is short-term periodic maintenance?

4.      What is medium-term periodic maintenance?

5.      What is long-term periodic maintenance?

6.      What are five methods of maintenance?

7.      What are three importance of periodic maintenance?

Research:

List the names of six household furniture.

Topic:  Periodic Maintenance: Appliances e.g., Furniture

Examples of Household furniture are tables, cupboards, shelves, chairs, beds and others.

The maintenance of furniture depends on the type of material used in making it.

Class Project:

(1)   How can table tops with vanish be cared for?

(2)   Describe how painted wood can be maintained.

(3)   Suggest ways of caring for polished wood

(4)   What steps must be taken when cleaning polished wood?

EXERCISES:

1.      What are four examples of household furniture?

2.      How can table tops with vanish be cared for?

3.      Describe how painted wood can be maintained.

4.      Suggest ways of caring for polished wood

5.      What steps must be taken when cleaning polished wood?

Research:

1.      What are 5 common electrical appliances?

2.      How can a radio set be maintained?

Topic:  Periodic Maintenance: Appliances e.g., electrical/electronics

Some common household electrical appliances are television, radio, blender, refrigerators, decoders and microwaves. Television and radio especially, should not be turned so high as to disturb others.

Manuals of each appliance should be studied properly so as to prevent wrong or dangerous usage. The directives must be followed strictly.

Preliminary tasks before maintain an electronic appliance (day to day care).

1.      If the plug is detached, unplug the cord from the wall outlet before removing it from the appliance.

2.      Unplug small electric appliances, such as toasters, blenders, etc. after using them. Fires can start if an electrical component malfunctions.

3.      Do not put plugged-in electrical appliances where they could drop or be pulled into water, as in the kitchen sink, toilet or tub. Drain all water before plugging in the appliance nearby. Electrical appliances are “electrically alive” when plugged in even though the switch is off. If it falls into water, you could be electrocuted if you touch it.

4.      Never plug in an electrical appliance, either “on” or “off”, anywhere near water, and go away and leave it if there are children around who could pull it into the water and be electrocuted.

5.      Never wrap a cord around a hot appliance. Do not wrap a cord too tightly around anything. Coil loosely, and keep it free from kinks and knots which can break wires. Plug only one heating appliance into a circuit at a time unless the circuit is for a heavy-duty appliance. Small Electrical Appliance Cleaning Unplug and cool appliance before cleaning. Wipe with a damp cloth and dry with a soft cloth or paper towel. If grease or food spills on exteriors, use a sudsy cloth, followed by a damp cloth. Do not get any moisture into electrical parts. Do NOT immerse any appliances or parts in water unless specifically labeled “immersible” in the care guide.

6.      Wash the interiors of appliances tor food preparation such as the inside of frying pans, slow cookers, etc., taking care not to get electrical parts wet.

7.      Clean the bottoms of frying pans, etc., after each use to avoid grease build-up. Use fine soap-filled steel wool pads for stubborn grease.

CLASS ACTIVITY: summarize five ways of caring for televisions and radios.

EXERCISES:

1.      What are 5 common electrical appliances?

2.      How can a radio set be maintained?

3.      How can a television set be cared for?

4.      What are four preliminary tasks that must be done before cleaning an electrical appliance?

Topic:  Career Prospect and opportunities in Technology

Fields of Technology

There are numerous studies and work areas that are within the field of technology. Technology is in the area of producing things, and providing service or using things in given ways.

Such areas of human endeavour include: engineering and construction

1.      Medicine

2.      Pharmacy

3.      Agriculture

4.      Business and

5.      Commerce.

Although Economics, history, languages, religion and pure science are not under the field of technology, in a way technology may be used to advance them.

In each field of technology, there are many occupations. There are many aspects of technology that only qualified people with a level of education and training. For example, in the field of engineering and construction, the families of professionals comprise artisans (semi-skilled), craftsmen, master craftsmen, technicians, higher technicians, technologists and professional engineers. However, some occupations in technology may not have the equivalent grade of engineering, artisans or craftsmen, due to the high level of scientific training required in the practice. An example of such occupation is Medicine.

Occupations in the engineering profession

S/No	Occupation	School
1	Artisan/Craftsmen	Vocational institutions, including Technical Colleges
2	Technicians, Higher Technicians and Technologists	Polytechnics and Monotechnics (for single occupation)
3	Professionals	Universities/Professional Institutions

Career Planning

Career planning involves the careful planning and systematic actualization of one’s general course of action or conduct in life as regards his/her chosen future profession or occupation. It is very necessary that, when you are planning your career in technology occupations you should think of your chosen profession and its educational route. For examples, if you choose to be a professional engineer, your educational route may be like this:

Technology Occupation/Training Routes

	Field	Occupation
1	Engineering	a.     Mechanical engineering b.     Electrical engineering c.     Electronic engineering d.     Computer engineering e.     Aeronautic engineering f.        Chemical engineering g.     Building engineering h.     Civil engineering i.         Agricultural engineering j.         Telecommunication engineering
2	Architecture	Architecture
3	Medicine	a.     General practice b.     Dental medicine c.     Veterinary medicine d.     Pharmacy e.     Ophthalmology f.        Gynaecology and obstetrics g.     Surgery
4	Agriculture	a.     Animal production b.     Crop production
5	Business	a.     Management b.     Crop production
6	Information and Communication Technology	Information management system

Technology has a vast array of opportunities for education and training – from the lowest level to the highest level. Skills in these various levels are studied in various schools.  Individual nations and even the World Bank are striving to better the lots of people going into various aspects of technology.

 However, the success in any technology occupational career depends on a number of factors, among which are:

1.      Natural and developed abilities, and

2.      Interest and drive.

Discover and develop your natural abilities, discover your interests and drive, or motivate yourself to learn your chosen occupation in technology and you will be among the most successful.

Exercises:

1.      What are three different occupations in technology?

2.      What various schools are readily available for a person who aspires to work in the field of technology to attend?

3.      What is the educational route of an engineer in Nigeria?

4.      What is career planning?

5.      What are five different occupations available to students aspiring to go into the engineering profession?

6.      What are five different occupations available to students aspiring to go into the medical profession?

7.      What two factors can determine the success in any technology occupational career?

Research:

1.      List the combination of science and technology subjects necessary for the study of engineering, architecture and medicine in the university.

2.       What is timber?

Topic:  Wood Processing

A timber is a wood suitable for engineering work. Wood is one of the raw materials used in engineering. Wood/timber is worked upon before they can be worked upon to make them useful for various purposes.

Production of wood

The body of a tree which has not been felled (cut down) is called standing timber while that of felled trees is called rough timber.

Growth of timber

Trees grow by obtaining their food in the form of sap from the soil by suction through their roots. The sap contains moisture and minerals such as phosphates and nitrates. The sap is transported through the stem to the branches and leaves of the tree. The sap loses moisture through the leaves, absorbs carbon dioxide from the atmosphere by the process of photosynthesis, and becomes heavier. The dense sap later descends and gets deposited under the bark in the form of a thin layer known as cambium. The cambium hardens with time, and adds a new annual ring to that section of the tree stem. Annual rings show the number of years growth has occurred in a tree.

Trees grow in two directions, namely: vertical and horizontal. Vertical growth occurs near the tips of the shoot and root of the plant. Vertical growth starts at germination and continues throughout the life of the plant. It is known as primary growth, while horizontal growth is called secondary growth. Horizontal growth occurs mostly in the cambium. The cambium divides to form two new layers of cells: wood cells in the inside, and bark cells on the outside of the cambium.

Felling of timber

Felling of timber is the act of cutting down a tree. Timber is usually felled for one form of engineering work or the other. However, certain factors need to be considered in order for the timber to serve a useful purpose. These reasons are:

1.      Age of the timber: timber should be felled only if it is mature. Under-matured timber has a large quantity of unused sap, while over-matured timber could develop a number of defects in the heartwood. Defects reduce the quality of the timber.

2.      Season of the year: timbers should be felled during dry season because during this season the wood sap is reduced and is least active. Also, during the dry season the forest ground is firmer, and timber evacuation from the forest is easier.

3.      Method of felling: it is important to determine the direction to which the timber will fall before it is felled. The stem is then cut as near as possible to the ground to avoid waste. Chain saws are usually used in felling trees. Only experienced persons should handle the task of timber felling to avoid an accident.

Conversion of timber:

Conversion is the process of cutting and sawing timber into commercial sizes.  The tree trunk or stem is first cut into transportable sizes called logs. At the sawmill, the log is converted (cut) into commercial (marketable) sizes such as boards and planks. The popular methods of conversion are plain-sawn and quarter-sawn.

Ø  The plain-sawn method is also called the through and through method. The log is sawn plank after plank. It is a very cheap method of conversion of timber. It is used extensively in the building industry.

Ø  The quarter-sawn method is very expensive because of the need to double-handle the log. There is also more wastage. It is however more decorative and less prone to cup or distort.

Seasoning of timber

Seasoning is the controlled process of reducing the moisture content (MC) of a timber so that it is suitable for the environment and the intended use.

Freshly felled timber or green timber has a large amount of moisture in the form of sap which makes it heavy. Such wet wood has low strength and cannot be used for engineering work. The sap in timber is a food for fungi and wood parasites. It’s important to remove/reduce the sap so that the wood will be less attractive to these dangers.

 Seasoned timber, although lighter will be stronger and more reliable. Dry-seasoned timber is easier to work with.

Methods of seasoning timber:

1.      Natural (or air) seasoning: this method is used with the timber planks stacked in the open air one on top of the other with pieces of wood called stackers used to separate them.

2.      Artificial (or Kiln) seasoning: this method relies on a controlled environment to dry out the timber. A kiln is used for seasoning timbers. The kiln is an oven or furnace which is heated up for reducing the excess moisture contents in a timber.

Reasons for seasoning or drying timber

Timber is seasoned or dried for the following reasons:

1.      It makes the wood more stable for engineering work.

2.      It makes wood lighter in weight and, therefore, easier to transport.

3.      It makes wood stronger.

4.      Seasoning makes wood durable, because insects and fungi will seldom attack the wood for sap.

5.      It enables wood to be well polished.

6.      It makes wood take preservatives more easily.

Preservation of wood

Preservation is the process of applying chemicals on wood to prevent insect and fungi attack. Because of the starch and sugar in wood, insect, fungi and termite usually attack it. To drive away or kill these organisms in wood, wood preservatives are applied.

Examples of wood preservatives

1.      Creosote

2.      Coal-tar

3.      Solignum

4.      Chlorinated phenols

5.      Sodium PCP

Methods of applying wood preservatives

1.      Charring: this method involves keeping the wood wet for between 30 and 60 minutes, and then burning it to a depth of 15mm and finally cooling it in water. This way, a layer of coal which is not affected by moisture, fungi or white ant is formed on the wood surface.

2.      Tarring: in this method, a layer of hot tar is applied on the surface of the wood. This treatment is usually given to ends of wooden poles/timbers that will come in contact with concrete and masonry (building work in stone).

3.      Painting: this is probably the commonest of the wood preservation methods. Paint is applied to wood in order to beautify and preserve it.

4.      Creosoting: this is the process of applying creosote oil on timber surface. Creosote oil is obtained by the distillation of tar. The process is done at high pressure and is applied mainly on poles, railway sleepers, etc.

5.      Vacuum pressure process: this is one of the most effective wood preservation methods. The timber to be treated with preservative is stacked in a strong, closed cylinder, and subjected to an air pressure between 5 and 12.2kg/cm².

6.      Fire-proofing: this is done by applying chemicals on the timber. Examples of such chemicals are 21 solutions of borax or sodium arsenate, ammonium chloride, ammonium phosphate, ammonium sulphate, sodium silicate, potassium silicate and zinc chloride.

Defects in timber

Defects are blemishes in timber that reduce the quality or utility value of timber. Defects in timber can be natural or artificial.

Natural defects

Natural defects occur during the growth of the tree. Examples of such defects in wood are knots, shakes, upset grain and cross grain.

Artificial defects

These are caused by careless handling and faulty seasoning and preservation of wood. Improper handling especially during stacking can shrink and warp the planks. Examples of artificial defects are cup, bow, twist, check and insect attack.

Exercises:

1.      What is timber?

2.      What is the difference between a standing timber and a rough timber?

3.      What is the name of the food that makes tree grow?

4.      How is cambium formed?

5.      What is the difference between the primary growth and secondary growth in a timber?

6.      What two layers are formed when the cambium divides?

7.      What are the three factors that should be considered in order for the timber to serve a useful purpose?

8.      What is conversion?

9.      What is seasoning of timber?

10.  What is preservation of timber?

rk hand tools need careful handling during and after use. They should also be kept or stored properly, to remain accurate, and to serve in future.

The following guidelines will help you to care for workshop tools:

1.       Use the right tool for the right operation. Using the wrong tools can damage the tool and the work. It can also cause injury.

2.       After use, clean the tool before it is stored away.

3.       Store tools in an orderly manner.

4.       Store tools away from pathways, so that they do not cause obstruction to free movement.

5.       Avoid keeping tools in a damp place. 

Class exercise:

Draw any ten (10) from the following tools:

a.      surface plate

b.      surface table

c.      Scriber

d.      odd-leg calliper

e.      inside callipers

f.        outside callipers

g.      divider

h.      punch

i.         box square

j.         try square.

k.       steel ruler

l.         T-square

m.    Protractors

n.      Chisel

o.      Hammer

p.      Mallet

q.      Screw driver

r.        Long-nose plier

s.        Flat-nose plier

Exercises:

1.       What are metals?

2.       What are the two classes of metals?

3.       What are the five categories of metal work tools?

4.       What are three examples of each category of metal work tools?

5.       What are four general suggestions on how to maintain metal work tools?

Topic:  Ceramics Processing

Ceramics are objects made of clay that is hardened by heat. Clay is the most common ceramic material. Pottery is the art of using clay to make different objects like pots, flower vases, tea cups, and dishes. Clay is a heavy sticky soil. There are many varieties of clay, but the most useful one is the type used for making ceramics.

Clay is first dug from the soil. It is thoroughly mixed with water in the right proportion, and pounded using //hands, feet, or pestle and mortal. As we continue to mix and pound the clay, air bubbles are removed and it becomes soft like chewing gum. Sand particles are also removed from the clay. This is to prevent the shaped or moulded materials from cracking or exploding during the heating stage.

After the removal of air and sand, the sticky clay is then shaped or moulded into the desired object. The object is soft and wet. It is left in the sun to dry so as to become hard and strong. The final stage is heating (firing) the shaped object.

The two common methods of making objects from clay e.g. Pots

1.      The Pinch method of producing clay pot: a hollow is formed in a portion of the mixed sticky clay made. The hollow is gradually expanded, and the sides are made thinner by using fingers to press inside the hole. The process is continued until the desired shape is formed. Smoothening, which is the next step, is carried out using fingers and water. To make the pot hard it is baked. It is baked in either an open fire or a kiln.

http://en.wikipedia.org/wiki/Pinch_pot 

2.      Potter’s wheel method of making a clay pot:  the potter’s wheel is a special piece of equipment which spins around very fast. The clay is placed inside its shaping disc so that when the wheel is rotated the porter’s hand can shape the wheeled clay.

http://en.wikipedia.org/wiki/Potter%27s_wheel

Clay Bricks

Clay bricks are among the first materials used by man to build houses and fences. Clay bricks are still being used today to build houses because of its cheapness, durability and ability to absorb heat, thereby making the house cool. Mud clay from earth is used to make clay bricks. This mud must not contain ordinary sand. The mud is mixed with water and pounded, using our feet. A rectangular mould with an open top is used to produce the clay bricks to the desired shape, e.g. 6” or 9” bricks. The bricks produced are usually soft. They are left in the sun to dry. After a few days they are baked in fire to make them very strong.

Making Cement

The major materials for making cement are limestone and clay. In Nigeria, there are large deposits of limestone at Nkalagu, Ewekoro, Ukpilla, etc. Cement factories have been located in and around these areas because of large deposits of limestone. Limestone is processed into powder form (calcium oxide) and mixed with clay to produce cement.

Making Mortar

Mortar is a mixture of cement, sand and water. Mortar is used for moulding blocks and laying them. Sharp sand is usually mixed with cement and water to make blocks.  However, a type of sand called plaster sand is mixed with cement and water for making the mortar for plastering walls.

Making Concrete

Concrete is a hard material formed when cement is mixed with sand, gravel or broken stones and water. Correct quantities of sand and gravel are measured and mixed properly with cement and water. The mixture is done using shovels, or a concrete mixer.

Making Glass

Glass is made by thoroughly mixing sand, soda, lime, potash and lead oxide.

The following are the stages involved in glass making:

(a) Mixing the raw materials

(b) Heating (firing) to produce molten glass

(c) Cooling to form rigid glass

(d) Heating again and allowing to cool gradually.

Annealing is the process of reheating and allowing the glass to cool.

Exercises:

1.      What are ceramics?

2.      What is pottery?

3.      What is clay?

4.      What happens when clay is mixed and pounded?

5.      What are the two common methods of making objects with clay?

6.      What is the material for making clay bricks?

7.      What are the major materials used for making cement?

8.      Where can limestone deposits be found in Nigeria?

9.      What is mortar?

10. What materials are needed for making mortar?

11. What is concrete?

12. What materials are needed for making concrete?

13. What type of sand is mixed with cement and water for plastering walls?

14. What are the materials for making glass?

15. What is annealing?

Research:

1.      What is plastic?

2.      What is rubber?

3.      What is latex?

4.      Mention two differences between plastic and rubber?

   

Mechanical Transmission System: Friction, Definition and Causes, Laws of Friction

When one object rubs and grates another, it causes friction.

Friction can be defined as a force that resists the relative motion or tendency to such motion of two bodies in contact.

When a solid material slides over another solid surface, there is always resistance to motion. This resistance is what the scientists refer to as Friction.

There is friction between the wheels of a car and the road. Friction exists between our shoes/legs and the ground. To sit on a chair there must be friction between our buttocks and the chair so that we don’t slip off the chair.

Note:

·         The tougher the surfaces rubbing against each other, the more the friction.

·         The smoother the surfaces rubbing against each other, the less the friction.

Causes of Friction

The causes of the resistive force of friction are molecular adhesion, surface roughness, and the plowing effect.

Adhesion is the molecular force resulting when two materials are brought into close contact with each other. Trying to slide objects against each other requires breaking these adhesive bonds. For years, scientists thought that friction was caused by surface roughness, but recent studies have shown that it is actually a result of adhesive forces between the materials.

When two objects are brought into contact, many atoms or molecules from one object are in such close proximity to those in the other object that molecular or electromagnetic forces attract the molecules of the two materials together. This force is called adhesion. Trying to slide one object across the other requires breaking these adhesive bonds. Adhesion is the essence of friction.

Surface roughness is a factor when the materials are rough enough to cause serious abrasion. This is called the sandpaper effect.

All solid materials have some degree of surface roughness. If you looked at what seems to be a smooth surface under a high-powered microscope, you would see bumps, hills and valleys that could interfere with sliding motion.

When one or more of the materials is relatively soft, much of the resistance to movement is caused by deformations of the objects or by a plowing effect.

Laws of friction

There are five laws of friction. These are:

1.      When an object is moving, the friction is proportional and perpendicular to the normal force (N).

2.      Friction is independent of the area of contact so long as there is an area of contact.

3.      The coefficient of static friction is slightly greater than the coefficient of kinetic friction.

4.      Within rather large limits, kinetic friction is independent of velocity.

5.      Friction depends upon the nature of the surfaces in contact.

Class activity:

1.      How can friction be created?

2.      How can friction be reduced?

3.      What are the advantages of friction?

4.      What are the disadvantages of friction?

Lubricant:

A lubricant is an oily substance that makes surfaces smooth and slippery, thereby reducing heat, wear, friction and vibration caused when two or more surfaces rub together.

Lubrication reduces friction. To lubricate means to apply oil in order to reduce friction, heat, and wear and tear.

Exercises:

1.      What is friction?

2.      What occurs when two objects rub against each other?

3.      What is the frictional difference between tougher surfaces and smoother surfaces?

4.      What are the three main causes of friction?

5.      What is surface roughness?

6.      What are the five laws of friction?

7.      What is a lubricant?

8.      What does it mean to lubricate?

Research:

1.      What is adhesion, in relation to friction?

2.      Explain plowing effect.

Mechanical Transmission System: Drive Mechanism (gears and chain drive)

A drive mechanism is one that takes the power coming from a motor without any reduction. Gears, chains and belts are used to transmit energies.

Gears

A gear is a rotating machine part having cut teeth, which mesh with another toothed part in other to transmit mechanical energy.

              

The gear system requires friction. The friction in the gear system is extremely high hence lubrication is needed at all times to reduce the friction. The pushing action enables one gear to move another gear – thereby transferring energy to that gear.

Belt drives and Chain drives

Belts are made of rubber and materials whose length and nature change with temperature. Examples of belts are motor fan belts, grinding machine belts, sewing machines. etc.

Chains are made of metals. Common examples are bicycle and motorcycle chains.

Friction is greatly needed in belt and chain drives. Belts and chains cannot work when friction is absent. Belts and chains are used in pulley mechanisms.

Belt and chain drives are used to:

1.      Transmit energy from one shaft to another when both shafts are separated by a distance greater than that require for gears.

2.      Change the speed of a pulley.

3.      Change the running direction of a pulley.

4.      Carry materials as conveyors from one point to another.

Types of belts and pulleys

1.      Open belt

2.      Crossed belt

3.      V-belt

4.      Chain belt.

Class activity:

1.      Sketch the four types of belts and pulleys in your Basic Technology notebook.

2.      Mention six materials used for making belts.

Relationship between belts and pulleys

A pulley is the wheel on which a belt runs. The pulley from which power is taken is called the driving pulley or driver. The pulley to which power is carried is called the driven pulley.

Exercises/Research:

1.      What is a drive mechanism?

2.      What is a gear?

3.      How does gear system differ from pulley mechanism?

4.      c

5.      What is the main difference between belts and chains?

6.      What are four uses of belt and chain drives?

7.      What are the names of four types of belt and pulleys?

8.      What is the difference between a driving pulley and a driven pulley?

Mechanical Transmission System: Motion in Engineering Systems (Types and Conversion)

Motion simply means movement. There are four basic types of motion in engineering. These are:

1.      Rotary motion is turning around in a circle, such as a wheel system. This is a kind of motion that takes place in a rotating form (360º or less).

2.      Linear motion is moving in a straight line, such as a paper trimmer. This motion could be horizontal or vertical.

3.      Reciprocating motion is moving backwards and forwards or up and down in a straight line, as in cutting with a saw.

4.      Oscillating motion is swinging from side to side, like a pendulum clock.

Conversion of motion

In producing machine appliances, it is commonly necessary to convert motion from one type to another.

Conversion of rotary motion to linear motion is possible through the use of lever arms, linkages, cams, pins, clutches, threads and springs.

Clutches are included in motor vehicles to facilitate the conversion of rotary motion of the engine to linear motion. Clutches do this through the use of friction force. When a car is to be moved, the clutch is pressed against the friction plate. The face of the clutch has a high coefficient of friction and a low rate of wear. The friction transfers engine power to the driving shaft through the clutch.

When clutch is disengaged the engine power is not transmitted. However, when the clutch is in engaged position, engine power is transmitted.

Exercises:

1.      What is motion?

2.      What are the four types of motion?

3.      What is the difference between reciprocating motion and linear motion?

4.      How can you explain conversion of motion?

5.      What is a clutch?

6.      What happens when a clutch is disengaged?

Research:

1.      What is wind?

2.      What is pneumatic?

3.      Define hydraulic?

Mechanical Transmission System: Air Flow

Air in motion is known as wind. Air moves from areas of higher pressure to areas of lower pressure. However, very high speed winds cause great damage.

Air in motion is can be used to transmit energy. Likewise, gases and liquids under pressure are used to transmit energy over long distances.

Pneumatics is the application of pressurized gas and liquids to produce mechanical motion.

Hydraulics is the application of pressurized liquid to produce mechanical motion.

Effects of air motion around objects

Every object moving in the air, such as airplanes, birds and kites, has two vertical forces and two horizontal forces acting on it.

·         The vertical force acting downward is the weight of the object.

·         The other, which acts upwards, is called the lift. For lift to be produced, the velocity of air below the object must be higher than the velocity of the air above. Lift is developed when air flows round the airborne object shaped like an aerofoil. 

·         The horizontal force which pushes the object forward is called the thrust, and

·         The other which pushes the object backwards is the drag. Drag tends to slow down a moving object. This force is produced by the action of air on the surface of the object.

Note: both lift and drag are effective when air moves round an object.

Streamlined body of objects makes it possible for air pressure on their bottom surface to be greater than the one on top.

Pneumatics

Gases and liquids under pressure are good mediums when transmitting energy over a long distance. Hydraulic systems are also categorized under pneumatic systems.

Examples of hydraulic and pneumatic devices

1.       Pumps: these are used to move gases and liquids by applying pressure greater than those of the gases or liquids. For instance, bicycle pump moves air through the pump into the tyre tubes.

2.       Centrifugal pump: this has a set of moving vanes which receive the fluid (air or water) at a smaller radius. The moving vanes increase the speed of the fluid. At a larger radius, the fluid enters a row of stationary vanes. These reduce the speed of the fluid, so that the fluid pressure rises. The fluid is then discharged at high pressure.

3.       Hydraulic jack: this moves the liquid into a high pressure compartment. The piston is equipped to carry heavy loads such as cars. Machines like forklifts, cranes and even trailers make use of hydraulics to function effectively.

4.       Garden sprinkler: this consists of one or more water jets which can revolve about the centre as it sprinkles water in a lawn or garden.

Exercises:

1.       What is wind?

2.       What do you understand by the term pneumatic?

3.       Define hydraulic?

4.       What are the forces acting on an object moving in the air?

5.       What are the differences between lift and drag forces?

6.       What are three examples of pneumatic and hydraulic devices?

Research:

1.       What is an electric circuit?

2.       What is a circuit diagram?

3.       What is the difference between series and parallel electric circuits?

Simple Electrical Wiring: Schematic Diagram

An electric circuit is an arrangement of conductors for the purpose of carrying current.

However, before electric current can flow in a circuit, two conditions must be met; namely:

1.      There must be a source of electromotive force (emf) to overcome the resistance of the circuit, and so drive the current round it.

2.      There must be a complete path of conducting materials through which the current can flow.

A schematic diagram is a representation of the elements of a system using abstract graphic symbols rather than realistic pictures.

An electric circuit diagram is a schematic diagram in the sense that symbols are used to depict various components of an electric circuit.

Class activity:

Draw the symbols of the following electrical accessories:

cell
Battery
Capacitor
Switch
Ammeter
Voltmeter
Galvanometer
Resistor
DC supply
AC supply
Transformer
Fuse
AC supply
Earth (ground)
Lamp (lighting)

Types of schematic (circuit) diagrams

There are two classes of circuit diagrams, namely:

1.      Series circuit; and

2.      Parallel circuit

In a Series circuit, the same current flows from the positive terminal of the battery through all the bulbs. However, fault in one bulb will affect others because current will not get to the other parts of the circuit. All the accessories share same current, so if the accessories (e.g. bulb) are increased without increasing the current reduces the current flowing through each accessory. (PRACTICAL CLASS for confirmation)

 

In a Parallel circuit, each device is placed in its own separate branch. The presence of branch lines means that there are multiple pathways by which charge can traverse the external circuit. 

Class activity:

In tabular form, state at least two major differences between series and parallel circuits in your notebook.

Practical class:  (Basic Tech for JSS3 pages 190 – 194)

Exercises:

1.      What is an electric circuit?

2.      What is a schematic diagram?

3.      What is an electric circuit diagram?

4.      What are two conditions that must be met before electric current can flow in a circuit?

5.      What are the symbols of some common electrical accessories?

6.      What are the major differences between series and parallel circuits?

Homework:

1.      List 5 tools used in electrical wiring.

2.      List 5 accessories used in the wiring of a house.

3.      List four materials used in house wiring.

Simple Electrical Wiring: Wiring Tools and Materials

Supply of electricity to a house through wiring makes it convenient and efficient for living in. Electrical wiring requires three classes of resources, namely: tools, materials and accessories/fittings.

Electrical wiring tools

1.                  Hammer

2.                  Pliers

3.                  Bending pipes

4.                  Screwdriver

5.                  Testers

6.                  Ohmmeters

7.                  Knives

8.                  Gimlet

9.                  Hacksaw

10.              Fishing tapes

Electrical wiring materials

1.                  Cables

2.                  Nails

3.                  Clips

4.                  Conduits

5.                  Screws

6.                  Paper tapes/ rubber tapes

7.                  Wooden blocks

Electrical wiring accessories

1.                  Switches

2.                  Sockets outlets

3.                  Joints boxes

4.                  Lampholders

5.                  Ceiling roses

6.                  Distribution box

7.                  Lamps

8.                  Cooker control units

Parts of a cable

1.      Insulator

2.      Conductor

3.      Mechanical protection (the cable cover)

Exercises:

1.      What are the three classes of resources required for wiring a house?

2.      What are the names of eight tools required to wire a house?

3.      What are the names of five materials for elecrtical wiring?

4.      What are the three part of a cable?

Research:

1.      What are the functions of a building?

2.      What are 5 materials for making traditional houses?

Building Construction: Foundation, types and uses, name types of foundation, name types of soil

Building has two parts, namely:

1.      Substructure: the part buried in the ground (foundation);

2.      Superstructure: the part above the ground (house, workshop, etc)

FOUNDATION is the part of a building which is in direct contact with the ground. Foundation carries the weight (load) of the building.

Foundations are designed to carry three types of load (pressure), namely:

a.     the weight of the building structure;

b.     the weight of goods (e.g. furniture, tv, freezer, water tank) and human beings in the building; and

c.     wind loads – particularly storms.

Types of foundations

1.      strip foundation

2.      pad foundation

3.      raft foundation

4.      raft foundation

*NOTE: the type of foundation to be used depends on the nature of the soil at the building site and the weight (load) to be carried by the foundation.

CLASS ACTIVITIES:

1.      Briefly describe each of the four types of foundations.

2.      With the aid of neat diagrams describe the four types of foundations.

SOIL

Soil is the uppermost part of the earth crust in which plants grow.

Soil exists in two layers, namely: top soil or vegetable top soil, and subsoil.

Vegetable top soil may vary in depth down to 300 mm.

Below the vegetable top soil is the subsoil.

The top soil cannot withstand heavy load, hence it is always removed before foundation trenches are made.

In building construction, excavation is the digging and removal of the soil to prepare trenches for constructing foundations. Excavation can be done manually or by the use of machines. 

TYPES OF SOILS FOR BUILDING PURPOSES

1.       NON-COHESIVE SOIL

2.       COHESIVE SOIL

3.       ORGANIC SOIL

4.       MADE GROUND

MATERIALS FOR MAKING FOUNDATIONS

1.       REINFORCED CONCRETE

2.       CEMENT

3.       AGGREGATE

4.       WATER

5.       MORTAR

EXCERCISES:

1.       What are the two parts of a building?

2.       What is foundation?

3.       What are the three main types of load foundations carry?

4.       Sketch and name the four types of foundation.

5.       What is soil?

6.       What are the differences between vegetable top soil and subsoil?

7.       Why is top soil removed before foundation trenches are made?

8.       What is excavation?

9.       What are the characteristics of the four types of building soil?

10.   What are the differences in the load bearing capacity of the four types of building soil?

Research:

1.      What are four common materials for constructing building walls?

2.      What is the full meaning of DPC?

Building Construction: Walls and Floors, definition, types and uses

WALLS

Walls of traditional buildings like huts are made from mud, grass and timber, while walls of modern buildings like duplex are made from bricks.

Walls are reinforced to make them stronger.

What do walls  provide to buildings?

1.      Strengthen and stability;

2.      Protection against weather conditions and external danger;

3.      Durability;

4.      Fire protection; and

5.      Sound control as in a theatre, music studio or big assembly place.

Materials for making traditional houses

1.      Mud

2.      Clay

3.      Laterite

4.      Grass

5.      Leaves

6.      Corrugated iron sheets

7.      Sawn timber

The two classes of modern walls:

1.      Load bearing wall: this carries its own weight and the weight of the materials put on it, e.g. roof and floor slab.

2.      Non-load bearing wall: this carries no load, but serves the purpose of partitioning, protection and beautification, e.g. fence and partitioning walls.

CLASS ACTIVITY:

1.      List 7 common types of walls

2.      What is DPC?

3.      List the functions of the DPC.

FLOOR

Floors carry the load in a building. The two main types of floors are concrete and timber floors.

Timber floors are cheap and durable. They make the building cool. But they are not as durable as concrete floors.

Concrete floors are widely used today. They are strong, solid and last longer. Concrete floors may be reinforced with iron rods.

Examples of floor finishes

1.      Tiled floor;

2.      Floor screed;

3.      Rubber sheet;

4.      Terrazzo;

5.      Sheet floor;

6.      Slab floor;

7.      Marble mosaic

8.      Para Jana

EXERCISES:

1.      What are the functions of a building?

2.      What are 5 materials for making traditional houses?

3.      What are the differences between load bearing and non-load bearing walls?

4.      What are the differences between concrete floors and timber floors?

5.      List 5 examples of floor finishes.

Research:

1.      What is the function of doors and windows in a building?

2.      Draw two types of windows you know

Building Construction: Doors and windows, definition, types and uses

Doors are entries or exits into and out of a building or room. Doors are made of wood or metals.  Doors are fixed to the wall with hinges so that they can swing freely. They have handles to help open and close them, and locks that ensures that it cannot be opened without a key.

Types of doors

1.      Flush door

2.      Panel door

3.      French door

4.      Louvre door

5.      Double sliding door

6.      Garage door

7.      Sliding door

8.      Folding door

9.      Revolving door

Windows are openings made of glass, wood or metal, to allow light and air from outside to enter a building.

Types of widows

1.      Casement window

2.      Pivoted Sash window

3.      Sliding sash window

4.      Louvre window

Class activity:

1.      What are three functions of doors and windows?

2.      Sketch three different types of doors.

3.      Sketch three different types of windows.

Exercises:

1.      What is a door?

2.      Why are doors fixed to buildings?

3.      What is a window?

4.      Why are windows fixed to buildings?

5.      Draw two types of doors you know.

6.      Draw two types of windows you know.

Research:

1.      What is a roof?

2.      Draw the symbols of the following:

a.     Hardcore

b.     Strip foundation

c.     Filament bulb

d.     Sink

e.     Wash hand basin

f.        Closet