Basic Technology JS2: Utilization of Electricity - xpino SCHOLARS

A work tool for teachers and students, but especially for Secondary School Students. Comprehensive lesson notes, with exercises. Past questions in specific subjects for revision and research.

Thursday, January 8, 2015

Basic Technology JS2: Utilization of Electricity




Utilization of Electricity
We have discussed how electricity is generated and transmitted from the power station to substations and later to various homes, factories, etc. however, in order to enjoy the many advantages of electricity in premises, certain precautions, accessories and methods of wiring need to be adopted to avoid hazards or dangers associated with the use of electricity.


Classes of electric consumers
There are two main classes of electrical consumers. These are:
1.      Domestic Consumers: these are private houses like bungalows, storey buildings and apartments which are not used for commercial purposes. They utilize less electric power.
2.      Industrial Consumers: these are schools, shopping complexes, factories, offices and industries. They utilize higher amount of electricity because of their activities.


Common household appliances Utilizing Electric Power
The following are some examples of electrical appliances found in homes, and their applications:
1.      Electric pressing iron:  used for smoothing out clothes.
2.      Electric kettle: used for boiling water for tea, pap, eba, etc.
3.      Coffee Percolator: used for preparing coffee drinks, right from ground coffee seeds.
4.      Blender or Grinder: used for liquidizing fruit, tomato, onion, pepper, etc.
5.      Cooker: used for heating, boiling and baking purposes, with an oven.
6.      Radio/TV/Video/Cable-Decoder: used for receiving low frequency radio transmissions.


Power Ratings of Appliances.
Every electrical appliance has a power rating which tells you how much electricity it needs to work.
It is necessary to determine the power consumption of each appliance to be used in a place, in order to determine the total current demand. This is necessary in the selection of appropriate (suitably rated) final sub-circuit, fuses, size and length of cables, types and size of accessories, such as 5A (5 amps), 13A, 15A socket outlets, or 5A, 10A, 15A, 30A or 60A switches, etc.
If these accessories are not properly rated and used there is a huge risk of overloading the circuit. These may result in frequent burning out of the sub circuit fuse or cable, and this may cause fire outbreak.
Appliances like refrigerators and electric cookers should be plugged to 15A sockets. It would be dangerous to plug such appliances to a 13A or 5A socket.  That is one vivid reason why adequate care and wisdom must be utilized when fixing or using electrical appliances.




Building construction: site preparation

It is the job of a qualified architect to design a modern building. Before such building plan can be designed, the site must have been surveyed and approved by the Town Planning Authority. After the design has been made, the owner of the project must obtain permission of the Town Planning Authority to construct the building as designed on the site. After getting the permission, the building owner gets the services of qualified builders to build it.



Site preparation
Buildings are in various shapes and designs, but preparing a building site for construction depends on three main factors, namely:
1.      The location of the building site, e.g. inside a town, village or in the bush.
2.      The type of building, e.g. bungalow, storey building etc.
3.      The type of site, e.g. rocky, sandy, swampy or waterlogged, sloppy, plane, or a virgin site in a forest or bush.
Before the building engineer can use the architects’ designed building plan to construct a building, he must first prepare the site. 

Activities involved in site preparation
1.      Examination of the site to identify its features (the nature of the ground, the dimension of the site, obstructions/obstacles like trees of bushes, main entrance to the site, availability of water and electricity, where to set up temporary office and store, etc.)
2.      Moving site preparation equipment and tools to site.
3.      Site clearing and removal of vegetable soil, where necessary.
4.      Leveling of the site, where necessary.
5.      Setting out the building line, that is, the line which shows the distance between the centre of the road and the building.
6.      Setting up a temporary office.

Site preparation tools and equipment
The tools and equipment for site preparation are many, but some are listed below.


CLASS ACTIVITY:  write the uses of the site preparation tools and equipment listed below:
S/No
Tool/Equipment
Uses
1
Shovel

2
Spade

3
Auger

4
Hoe

5
Rake

6
Spade

7
Axe

8
Cutlass

9
Bulldozer

10
Excavator

11
Grader

12
Power chain saw

13
Dumper



Exercises:
1.      Who designs a modern building?
2.      What is the duty of the Town Planning Authority?
3.      What three factors must be considered when preparing a building site for construction?
4.      What five activities are done during site preparation?
5.      What are the names and uses of ten tools and equipment for site preparation
Research:
1.      What is 3-4-5 method?
2.      Define excavation.
3.      What is a builder’s square?


Building construction: setting out
To set out a building on a site there must be a building drawing and the ability to read drawings accurately. Building construction must be done carefully, because correcting a mistake can be very expensive and it may destroy the purpose of the building project.
‘Setting out’ is the first stage of construction in a site. It involves arrangements on the ground. 

To set out a building;
·         you must first establish the four corners with pegs,
·         out nails on top of each pegs,
·         then establish a point by measuring out a setback from fence to your building line,
·         nail pegs at 3m interval round under the rope marking four building line,
·         then nail the rods on top round the entire area,
·         Finally establish the depth.

The two common methods of setting out
1.      Using the 3-4-5 method
2.      Using the builders square

The 3-4-5 method
This is just like the Pythagoras theorem. A2 + B2  = C


The builder’s square
This is similar to the 3-4-5 method, in that they are based on the same principle of using a right-angled triangle.


Excavation for foundation
The choice of foundation for a building depends on the type of building and the characteristics of the soil type. The most widely used type of foundation is strip foundation which is used for simple buildings at sites with cohesive dry ground. 

Exercises:
1.      Why should a building construction be done carefully?
2.      Mention 5 activities to be done before setting out a building.
3.      Name and describe two types of setting out procedures.
4.      What is the most widely used foundation?


 
Maintenance of domestic good
Maintenance is the routine care or attention given to appliances or products, used either at home, school, office or in the workshop.

Types of maintenance
1.      Preventive maintenance
2.      Corrective maintenance
3.      Predictive maintenance

Preventive maintenance:  is the care or attention given to appliances or products to prevent malfunctioning or damage.

Corrective maintenance: is the care or attention given to appliances or products to correct simple faults, so as to prevent further damage or total breakdown.

Predictive maintenance: is the care or attention given to appliances or products when we feel something may go wrong with them anytime soon.

Maintenance of domestic appliances and equipment
Domestic appliances are very useful instruments or devices used in homes. Examples are: electric kettles, water heater, electric pressing iron, electric cooker, gas lamp and air conditioner.


Methods of preventive maintenance
1.      Washing
2.      Cleaning
3.      Polishing
4.      Greasing
5.      Oiling 

Methods of corrective maintenance
1.      Replacement and mending of damaged or flat parts, in case of battery.
2.      Take the faulty appliances to a qualified electronic engineer.

Exercises:
1.      What is maintenance?
2.      What are the three types of maintenance?
3.      Describe the various types of maintenance.
4.      How can appliances like pressing iron and electric cooker be maintained?

 
Maintenance of Electric/electronics goods
While appliances make our lives much easier, they also pose significant risks if not maintained properly. Appliance maintenance is an absolute necessity if you plan on getting the longest life possible from you purchases. Proper appliance care is also able, in certain cases, to keep performance up to par and ensure that your units are running as efficiently as possible.

Kitchen Appliance Care
Kitchen appliance maintenance is probably going to make the most difference in your home overall, as the machines here are generally used quite often. Though a broken kitchen appliance should usually be handled by a service professional, keeping them clean and using them properly is something that homeowners should pay attention to if they are to function well over their lifetimes. 

Laundry Room Appliance Maintenance
Washing machines and dryers are making an appearance in more and more homes. Just like kitchen appliances, maintenance, and proper care will be a factor in the efficiency and performance of your laundry machines. If the hoses in your washing machine are old, consider replacing them with the tougher metal hoses available at hardware stores. If your washing machine rattles when it runs, it may need leveling. For most items, lowering the water temperature to warm wash and cold rinse will get your clothes clean and reduce your energy bills. Clean the lint traps before you use your dryer; this will prevent a fire hazard, save you energy, and make your clothes dry faster. Regardless of what kind of exhaust tubing you have, clean the outside vent once a year and make sure it opens when the dryer is on and closes properly when the dryer is off. And remember, don't let lint and debris accumulate under a dryer or it can become a fire hazard!

Electricity and Appliance Maintenance
Sometimes, caring for an appliance doesn't involve the unit at all, but instead deals with that appliance's power source. Larger appliances shouldn't be powered by an extension cord if at all avoidable. If it is a necessity, make sure that extension cord connections are secure and that the extension cord is the appropriate size for your needs. If an appliance stops working, test the outlet with a lamp or radio. With gas appliances, it is important to remember that older models often contain a flame that's constantly burning. Never store paints, solvents, and other chemicals anywhere near an appliance with a pilot light.

Electric Cooker/Griller
  • Remove griller tray before cleaning.
  • Wash in hot, soapy water, using a fine, soapy steel-wool pad on heavily soiled areas.
  • Rinse and dry well.
  • Wipe out griller compartment with warm, soapy cloth.
  • Clean racks as for oven shelves.


Refrigerator Maintenance
Most refrigerators have more than one light. Replacement is easiest when at least one bulb is still working. Be sure to take the burn-out bulb with you to the hardware store to make sure you buy the same type. 

Whenever frost gets to be 1/4-inch thick, it's time to defrost. Never use ice picks or similar tools to loosen ice. 

Some refrigerator shelves contain cooling fluids. These racks take longer to defrost. Don't force the process, as the racks are easily damaged. Every year or two, vacuum underneath and behind the unit. After unplugging the unit, use a crevice tool or a feather duster to help you clean the coil and all the metal parts. You may have to remove a panel to get access. This will make your unit run more efficiently and last longer. Keep the door seals and the surfaces they close against clean. This will reduce energy consumption and extend the life of the seal.


Exercises:
1.      What could happen if we do not properly maintain our electrical appliances?
2.      What is the best way of caring for our kitchen appliances?
3.      What are three ways of caring for our laundry equipment?
4.      How can our electrical cooker/grill be maintained?
5.      What is the easiest thing to replace in a refrigerator?
6.      How can we perform maintenance tasks on our refrigerators?



Maintenance of mechanical goods
Equipment and machines have already been around in the industry for a long time. All those machines and equipment that are being used and operated these days were already innovated and developed in order to cater the changing needs and ways that certain products are being produced. 

Everybody knows how important equipment and machines are. But then, have you ever wondered how all those were made or how they were made to operate another machine? Equipment and machines are important, but only a few have realized that behind a well-functioning machine are the doings of mechanics maintenance.

Mechanics maintenance is an important aspect in maintaining any equipment and machines, since all the products that will be produced solely depends on the maintaining actions that were made for it. 

Then again, the machine’s quality performance also depends on the person that is assigned to address that task. In order to secure the maintenance of the machine, qualified mechanics maintenance must be appointed and employed. The mechanic must possess the right qualification in order for that person to perform his tasks and responsibilities.

Mechanics maintenance involves performing his three major tasks which includes regularly doing the scheduled maintenance, setting up the system and do perform emergency repairs. 

Scheduled maintenance for production machines is only done during non-peak hours. This responsibility entails coordinating with the line manager or the production scheduler regarding the maintenance of the machine.
Part of being mechanics maintenance is to take notice whenever the scheduled maintenance must be accelerated and also to inform that to the line manager.
Once the machine is already available it must be immediately cleaned, and all moving parts must be removed, cleaned, lubricated, and reinstalled. All damaged parts must be replaced and afterwards, the non-moving parts must be inspected.
Down time events within a production environment is a usual occurrence especially if it is not addressed soon, it will automatically cost the company loss of money.
In order to prevent that, the mechanics maintenance must always plan a strategy and act that out so as to minimize the occurrence of down time and also to make the machine run and operate in time when it is already needed.

Once a product will be added, the mechanics maintenance will be required to meet the product manager so as to discuss the modifications that will be needed in order to make that new product. 

Basically, during this time, the mechanic is the one who is responsible in doing all necessary changes and the test runs. Once the manager has approved the quality of the machine that is the time when the latest set-up will be added to schedule of production.



SOLDERING AND BRAZING
SOLDERING
Soldering is the joining of metal surfaces or edges with solder. A solder is a type of alloy, often of tin and lead, that is used to join small pieces of metal together.



  
Types of soldering
There are two types of soldering, namely, soft soldering and hard soldering.

Soft soldering
Soft soldering is done when the solder melts below the red hot temperature of the soldering iron

Tools and materials needed for soft soldering:
1.      Soft solder:
2.      Flux
3.      Heat source

Hard soldering
Hard soldering is done when the solder melts below the red hot temperature of the soldering iron.

Soldering copper (bit): this is sometimes called the soldering iron. It is a square piece of copper pointed at one end and fastened to a steel bar with a wooden handle on the other end. 



Types of soldering bits
There are two common patterns of soldering bits:
1.      Straight soldering bit: this is used for general work, and for getting into restricted places.

2.      Hatchet soldering bit: this is used for making long joints because of its blade-like edge. It is also used for soldering in grooves.
      
Why is bit made from copper?
1.      Copper is an excellent conductor of heat.
2.      Solder and copper have a great ‘understanding’ when the solder is in its molten state.

Solder
Solder is the material used in its molten state for the joining of metals. The best soft solder is an alloy or metal made of lead and tin. Solder must have a lower melting point that the metals to be joined, so that they can met at about 230Âșc.
Solder bits are available in long bars and also in wire form on spools.

Flux for soldering
Flux is the substance applied on metals to be joined so that the surface of the metal can be cleaned. Flux cleanses the metal and helps the solder to flow. Flux makes metal surfaces chemically clean and stops corrosion, permitting the solder to stick lightly to produce good joints.

Heat sources
There are mainly two sources of heating a soldering bit:
1.      Heating the soldering bit electrically. This is done by plugging the bit cable into an electricity socket and allowing it to heat up for some time.
2.      The use of blow lamp. Blow lamps use kerosene as fuel. Stoves can also be used to heat soldering bits quickly and economically.
 
Soldering operations
The first thing to do is to clean the soldering bit and the parts to be soldered.
Cleaning up the soldering bit is called tinning the bit.


Process of tinning the bit:
1.      Clean the point thoroughly with a file.
2.      Heat the copper or bit till the flame turns light green.
3.      Dip the heated point into the flux.
4.      Rub a stick of solder over the bit, giving it a thin coating all round.


Holding the work (metals to be joined)
Place the metals to be soldered properly, hold them firmly ready for soldering, and fasten them so that they cannot move while being soldered.


The art of good soldering
Hold the soldering bit in the right hand and the solder in the left hand. Tack the seams or parts together, that is, connect the parts in several places with the hot copper and a few drops of solder, so that the parts will not shift.
Remember, for neat work, use only a little solder. Too much solder on a joint is hard to remove. The thinner the film of a solder, the stronger the joint.
Sweat soldering is used for large surfaces where the bit may not be conveniently soldered.

BRAZING
Brazing is a type of hard soldering which uses filler rods to join the metals together.
Brazing is done at a higher temperature than that of soft soldering. It is used on joints that will need to withstand heat, such as the hinges of an oven.
Brazing rods are used instead of solder. Brazing produces stronger joints than soft soldering.

Exercises:
1.      What is soldering?
2.      What is a solder?
3.      What is the major difference between soft soldering and hard soldering?
4.      What are three materials needed for soft soldering?
5.      What are the two types of soldering bits?
6.      What are the forms of solders we can readily get?
7.      What is flux?
8.      What are the two sources of heating a soldering bit?
9.      What is the first thing to do before soldering?
10. How can you explain the term ‘tinning the bit’?
11. What is the procedure for tinning the bit?

Research:
1.      What is the art of good soldering?
2.      What is sweat soldering?
3.      What is brazing?



 

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