INDEX
1 The Computer Science
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2 Projects Method. Technical Drawing
9
3 Electricity
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4 Machines and Mechanisms
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3
A Brush-up on Computer Skills One of the first things you will need to do in the Technologies class is to use the computer to write and present your projects.
Word
Writer
• The computer is made up of hardware and software. Hardware refers to the durable, physical parts of computers: the monitor, CPU, keyboard, speakers, printer and so on. Software refers to the programs and applications that allow us to do things with computers. The operating system, the text and image processing programs, the game applications and so on are all software. Peripherals are the devices through which the computer receives and communicates data. The main input peripherals are the keyboard and the mouse and also things like scanners. Output peripherals include the screen, speakers and modem. Operating system (OS) refers to the instructions supplied to a computer about how to administer its computing capacity and run the applications installed on it. At present, Windows is the most widespread operating system in use, although Linux, which is open source or ‘free’ software, is becoming more and more popular.
• Word is a text-processing program designed for Windows. You can use it to write documents and give them the format you like. Its Linux equivalent is a program called Writer, which can also be run on Windows.
Excel
Calc
• Excel is a spreadsheet program which can include text, but is basically used to insert numerical or logical data. It allows us to relate different groups of cells and carry out operations involving them. Its Linux equivalent is a program called Calc, which can also be run on Windows.
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1. THE COMPUTER SCIENCE Exercises on Computer Science Exercise 1.1 Say whether the following statements about computer peripherals are true (T) or false (F). a) The mouse is an input peripheral that allows us to move the pointer, or cursor, freely on the screen.
b) The screen, also known as the monitor, is also an input peripheral that allows us to be in continual communication with the computer.
c) The keyboard has four groups of keys: numeric, alphanumerical, editing and function keys.
d) The scanner can be considered an input peripheral since it is used to digitalize images or texts from paper.
e) The mouse and the scanner are essential elements for the functioning of a computer.
Exercise 1.2 Say what each of the different icons stands for in Word or Writer (answer according to the program on your computer):
Word
Writer
Word
Writer
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Exercise 1.3 Write down the correct name for the cells that are marked in red on the following spreadsheet. A
B
C
D
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
7
E
Normal
Page 1
Page 2
F
G
Times New Roman
H
12
I
N K
J
Cell
S
Page 3
Exercise 1.4 What do you need to type in the formula bar so that cell C1 will show the product of cells A1 and B1?
=
Exercise 1.5 What do you need to type in the formula bar so that cell C1 will show the division of cell A1 by B1?
=
Exercise 1.6 What do you need to type in the formula bar so that cell C1 will show the result of subtracting cell A1 from B1?
=
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1. THE COMPUTER SCIENCE Exercise 1.7 What do you need to type in the formula bar so that cell D4 will show the product of cells A2 and B1?
=
Exercise 1.8 What do you need to type in the formula bar so that cell B7 will show the sum of cells A1, A2, B1, B2 and C3?
=
Exercise 1.9 What do you need to type in the formula bar so that cell C1 will show 50% of the figure in cell A1?
=
Exercise 1.10 In the table below, what do you need to type in the formula bar so that cell C4 will show the sum of all the figures?
=
C4 B4
1 2 3 4
A
12 6
B
C
4 6
16
7
Exercise 1.11 In the table below, what do you need to type in the formula bar so that cell B4 will show the product of the figures in all the cells?
=
B4 B4
A
1 2 3 4
2 6
B
C 4
Exercise 1.12 In the table below, what do you need to type in the formula bar so that cell B4 will show the division of cell A1 by B1?
=
B4 B4
A
1 2 3 4
6
B
2
C
Exercise 1.13 In the table below, what do you need to type in the formula bar so that cell A2 will show 25% of the figure in cell A1?
=
A2 B4
1 2 3 4
8
A
125
B
C
2. PROJECTS METHOD. TECHNICAL DRAWING A Brush-up on the Projects Method. Technical Drawing The projects method is a way of solving technical problems according to a logical process which involves the following steps, in this order: 1.st 2.nd 3.rd 4.th 5.th
Identifying the difficulty to be solved and looking for solutions. Planning your work and building a model or mock-up. Checking whether it works as planned and correcting errors. Writing a technical report including specifications and a description of how the work was carried out. Evaluating the whole process.
• In technical drawing, most of the elements we use are ‘standardised’, that is, they comply with certain previously fixed specifications. We use DIN A-4 paper, HB pencils, and so on. • In order to make our drawings fit within the limits of the drawing paper, we use scales. These can be reduction scales (e.g. 1:100) or enlargement scales (e.g. 2:1). • A line drawing is a simple drawing that depicts our ideas on paper as solutions to a project. • A sketch is a more elaborate drawing which may contain specific details, including measurements. • Views are the different sides of the object that we wish to draw. The most important ones are: front view, top view and side view (left and right). • Drawing in perspective allows us to depict objects in such a way as to create the sensation that they are threedimensional. Two different types of perspective are used: cavalier projection and isometric projection. • You are going to use a computer program for drawing. It is called CorelDraw, a very powerful and easy-to-use tool. The drawings take up very little space in the computer memory and the program allows us to carry out all sorts of modifications and offers a wide range of colours, textures, and other aspects to choose.
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Exercises on the Projects Method. Drawing Exercise 2.1 Whenever you sit down to study, you have the same problem. You do not have enough desk space for all your pencils, pens, rulers, etc. Following the ‘projects method’, make a short outline of the different steps you should follow in order to build a holder for all these objects.
Exercise 2.2 After you finish painting, you never know what to do with your brushes. If you lay them on your desk, you leave paint all over it. Design a system to prevent this, and build the object out of wood.
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2. PROJECTS METHOD. TECHNICAL DRAWING Exercise 2.3 Draw sketches of a pencil sharpener, a pencil case and a car. Fit each sketch in one of the following frames.
Exercise 2.4 Draw the three views (front, top and side) of a flat battery.
FRONT VIEW
LEFT SIDE VIEW
TOP VIEW
Exercise 2.5 Draw the front and top views of a file having the perspective shown here.
FRONT VIEW
TOP VIEW
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A Brush-up on Electricity • Electricity is the most widely used form of energy. It is produced by the circulation of tiny particles called electrons. • Static electricity is the kind of energy that can be produced by rubbing certain materials together. • Conductors are materials that allow electricity to flow freely through them. Insulators are materials that conduct electricity very poorly. • An electrical circuit consists of: – – – –
An element which supplies electrons (for instance, a battery). Electricity-conducting wires. Electricity-consuming loads (for instance, a motor or a bulb). Elements that regulate the flow of electrons (for instance, switches).
• The following universal symbols are used to draw diagrams of electrical circuits:
• Electrical circuit diagrams use these different symbols in order to represent real circuits in a more simplified manner. • There are three types of circuits: series, parallel, and series-parallel combined circuits. – Series circuits: the elements are connected one after the other along a single strand of wire. – Parallel circuits: the elements are each connected to the battery independently by means of separate strands of wire running across each circuit. – Series-parallel combined circuits: elements are connected both in series and in parallel. • The main magnitudes of electrical current are: – Resistance (R): measured in ohms (Ω) or kilohms (k or kΩ). – Intensity (I): measured in amperes (A). – Tension or voltage (V): measured in volts (V). • These three values are interrelated, as stated by Ohm’s Law, which mathematically equates the three as follows:
V=IxR
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3. ELECTRICITY • In order to identify the value of resistors, colour-coded bands are used: Colour band 1 = The 1st figure in resistance value. Colour band 2 = The 2nd figure in resistance value. Colour band 3 = The number of zeros in the resistance value. Colour band 4 = The tolerance. • When the elements are placed one after another along a single strand of wire, we call this a series circuit.
• When the elements are placed next to each other and connected across the circuit by independent strands of wire, we call this a parallel circuit.
• Switches have two parts: the pole is where electrical current reaches it; and the contact is where the current exits the switch. Switches are defined by the number of poles and contacts they have. SPST: Single Pole, Single Throw. SPDT: Single Pole, Double Throw. DPDT: Double Pole, Double Throw.
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Exercises on Electricity Exercise 3.1 As you know, one of the properties that have enabled electricity to become so widespread is its easy transformation into other types of energy. Fill in the following table with appliances that transform electricity into other types of energy.
Exercise 3.2 Some materials are good conductors of electricity and others are not. Fill in the following table with the names of good conducting materials on the left and poor conducting materials on the right.
Exercise 3.3 Fill in the following table with appliances that operate on alternating current and direct current.
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3. ELECTRICITY Exercise 3.4 Match the elements on a circuit on the left with the corresponding symbols on the right.
Exercise 3.5 Which of the electrical circuits below will work? Why or why not?
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Exercise 3.18 Draw an electrical diagram with a DPDT switch which will govern the direction of rotation for a motor installed on the circuit. Draw both positions of the switch.
Exercise 3.19 Look at the diagram below of an electrical circuit. There are three SPST switches, two which are normally open (n.o.) and one which is normally closed (n.c.), and one SPDT switch. Which elements on the circuit will operate when the switches are in the following positions?
Exercise 3.20 The following illustration shows the locations for light bulbs on a small-scale model of a home. Draw the switches needed to operate each light bulb and the wiring needed to connect the bulbs and switches. In each one of the yellow boxes, draw the SPST switches.
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4. MACHINES
AND
MECHANISMS
A Brush-up on Machines and Mechanisms • Simple machines make the work you do easier by increasing your power. • A lever is a simple machine that consists of a bar or bars which can be used to lift loads using different forces. • There are three types of levers: Class one levers (such as see-saws), class two levers (such as nutcrackers) and class three levers (such as a pair of tweezers).
• For all levers, the following is true:
• The force that we apply to the lever is called the effort force; and the force generated by the machine is called the resistance force, or load force. • At times, combinations of levers of different classes may be necessary to achieve a desired end. • Mechanisms are the moving elements which are fitted between a machine’s power input (motor) and its power output. The most important are those that transform a rotational movement of one kind into a rotational movement of another kind. • Chain drive mechanisms are made up of two toothed wheels connected by a chain. Bicycles and motorcycles use chain drives. • Belt drive mechanisms are made up of two grooved pulleys connected by a belt. • Gear drive mechanisms are made up of two toothed wheels that mesh together without the need for other means of connection.
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• The speed with which mechanisms spin is called angular velocity. This is measured as the angular number of turns a mechanism makes in one minute, or revolutions per minute (rpm).
• We call the relationship between the speed of the driver and driven gears the transmission ratio:
• The transmission ratio for the three types of mechanisms described above can be calculated in the following ways: – For chain and belt drive mechanisms:
– For belt drive mechanisms::
• In order to calculate the output speed of any mechanisms, you can use the following formulas:
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4. MACHINES
AND
MECHANISMS
Exercises on Machines and Mechanisms Exercise 4.1 Are these things simple machines? Write T (true) or F (false) in the box next to each item.
Exercise 4.2 Look at the following drawing. Do you think the boy will be able to lift his father? If so, how could he do it?
Exercise 4.3 Look at the following drawing and calculate how heavy a load you could lift if you applied 10 kg of effort force.
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