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Técnicas de Leitura
As técnicas de leitura, como o próprio nome diz, vão nos ajudar a ler um texto. Existem técnicas variadas, mas veremos as mais utilizadas. Ao ler um texto em Inglês, lembre-se de usar as técnicas aprendidas, elas vão ajudá-lo. O uso da gramática vai ajudar também. As principais técnicas são: a identificação de cognatos, de palavras repetidas e de pistas tipográficas. Ao lermos um texto vamos,ainda, apurar a idéia geral do texto (general comprehension) e utilizar duas outras técnicas bastante úteis: skimming e scanning.
a) Cognatos Os cognatos são palavras muito parecidas com as palavras do Português. São as chamadas palavras transparentes. Existem também os falsos cognatos, que são palavras que achamos que é tal coisa, mas não é; os falsos cognatos são em menor número, estes nós veremos adiante. Como cognatos podemos citar: school (escola), telephone (telefone), car (carro), question (questão, pergunta), activity (atividade), training (treinamento)... Você mesmo poderá criar sua própria lista de cognatos!
b) (^) Palavras repetidas As palavras repetidas em um texto possuem um valor muito importante. Um autor não repete as palavras em vão. Se elas são repetidas, é porque são importantes dentro de texto. Muitas vezes para não repetir o mesmo termo, o autor utiliza sinônimos das mesmas palavras para não tornar o texto cansativo.
c) (^) Pistas tipográficas As pistas tipográficas são elementos visuais que nos auxiliam na compreensão do texto. Atenção com datas, números, tabelas, gráficas, figuras... São informações também contidas no texto. Os recursos de escrita também são pistas tipográficas. Por exemplo:
- ... (três pontos) indicam a continuação de uma idéia que não está ali exposta;
- negrito dá destaque a algum termo ou palavra;
- itálico também destaca um termo, menos importante que o negrito;
- ‘’ ‘’ (aspas) salientam a importância de alguma palavra;
- ( ) (parênteses) introduzem uma idéia complementar ao texto.
d) General Comprehension A idéia geral de um texto é obtida com o emprego das técnicas anteriores. Selecionando-se criteriosamente algumas palavras, termos e expressões no texto, poderemos chegar à idéia geral do texto. Por exemplo, vamos ler o trecho abaixo e tentar obter a “general comprehension” deste parágrafo:
“ Distance education takes place when a teacher and students are separated by physical distance , and technology (i.e., voice , video and data ), often in concert with face - to - face communication , is used to bridge the instructional gap.”
From: Engineering Outreach College of Engineering – University of Idaho
A partir das palavras cognatas do texto (em negrito) podemos ter um a idéia geral do que se trata; vamos enumerar as palavras conhecidas (pelo menos as que são semelhantes ao Português):
- distance education = educação a distancia
- (^) students = estudantes, alunos
- separeted = separado
- physical distance = distância física
- technology = tecnologia
- voice, video, data = voz, vídeo e dados (atenção: “data” não é data)
- face-to-face communication = comunicação face-a-face
- used = usado (a)
- instructional = instrucional
Então você poderia dizer que o texto trata sobre educação a distância; que esta ocorre quando os alunos estão separados fisicamente do professor; a tecnologia (voz, vídeo, dados) podem ser usados de forma instrucional. Você poderia ter esta conclusão sobre o texto mesmo sem ter muito conhecimento de Inglês. É claro que à medida que você for aprendendo, a sua percepção sobre o texto também aumentará. Há muitas informações que não são tão óbvias assim.
e) Skimming “skim” em inglês é deslizar à superfície, desnatar (daí skimmed milk = leite desnatado), passar os olhos por. A técnica de “skimming” nos leva a ler um texto superficialmente. Utilizar esta técnica significa que precisamos ler cada sentença, mas sim passarmos os olhos por sobre o texto, lendo algumas frases aqui e ali, procurando reconhecer certas palavras e expressões que sirvam como ‘dicas’ na obtenção de informações sobre o texto. Às vezes não é necessário ler o texto em detalhes. Para usar esta técnica, precisamos nos valer dos nossos conhecimentos de Inglês também.
Observe este trecho: “Using this integrated approach, the educator’s task is to carefully select among the technological options. The goal is to build a mix of instructional media, meeting the needs of the learner in a manner that is instructionally effective and economically prudent .” From: Engineering Outreach College of Engineering – University of Idaho
Selecionando algumas expressões teremos:
- integrated approach = abordagem (approach = abordagem, enfoque) integrada
- educator’s task = tarefa (task = tarefa) do educador – ‘s significa posse = do
- tecnological options = opções tecnológicas (tecnological é adjetivo)
- goal = objetivo
- a mix instrucional media = uma mistura de mídia instrucional.
Now comes the so-called third generation – or 3G – which generally refers to networks capable of connecting to the Internet at speeds 40 tines the rate of today’s cell phones, promising Interneting connections will be fast enough to download streaming audio and files, swap digital photos, and hold teleconferences. It will also use the existing spectrum space more efficiently and increase the speeds with which basic data can be transmitted over wireless devices.
TEXTO 3 Lamps can be connected in series or in parallel. If you connect lamps in parallel the lamps stay the same brightness however many lamps you add. This is because the voltage across every lamp is the same. In your house the lamps are connected in parallel. This means that even if you have all the lights on, the lights do not dim.
Digital Oscilloscope
For the maximum safety of the person who may use the oscilloscopes, they have been designed and manufactured for full safety features and they are shipped after stringent inspections. And yet, it is unavoidable handle it carefully, in order to avoid damage to the instruments and hazards to the persons. Above, there are notes and warnings which the persons using the instrument must take heed of and observe:
NOTE – Calls for special attention for correct and efficient use of the instrument.
WARNINGS – Calls for attention for a matter which might lead to a damage of the oscilloscope itself or other instruments.
The following symbols may be posted on the oscilloscope as well as indicated in this manual. “DANGER! HIGH VOLTAGE” – This symbol means that the item cannot be charged up to a hazardous high voltage and must not be touched with bare hands.
“REFER TO THE CORRESPONDING SECTION” – This symbol means that relative explanations contained in other parts of the handbook should be consulted.
CAUTION – Means a matter which can lead to electric shock hazards to the person who is operating the instrument or to damage of the instrument itself or other instruments.
USE A 3-PIN PLUG - For the input of AC input cable, be sure to use a 3-pin type (one of the pins is used for safety grounding). AC LINE VOLTAGE – Be sure to operate the oscilloscope on an AC line voltage within is correct range. AC POWER CABLE – When replacing the AC plug of the AC power cable, be sure to replace it with a plug of the correct type and ratings, and to connector the GND, NEUTRAL and LIVE wires which are color colored as shown in figure below:
Fig 1
AC POWER FUSE – Be sure to use a power fuse of the correct ratings. COVERS – This oscilloscope has hazardous high voltages internally. Do not remove the covers of the oscilloscope lest you should expose yourself to such high voltages. The covers should be removed only by qualified experts.
FEATURES
( 1 ) Easy to operate – You can easily use major functions of the oscilloscope which employs a direct knob control system. ( 2 ) Compact and light – COR 5500U series is very compact and light for its sophisticated functions and reliable performance. This has become feasible through dexterous use of flush-mount components. ( 3 ) CRT readout – It displays various items of information on the CRT screen, providing you with powerful means for rapid but accurate measurements. ( 4 ) Comment display – You can display comments by using this feature. ( 5 ) Alternate magnified sweeps – This feature allows you to magnify readily any portion of the waveform you want to observe more closely. This time base can be magnified by 5,10 or 50 times. The Alternate Magnified Sweep mode, which runs a mains sweep and magnified sweep alternately, is also available. ( 6 ) Sampling rate up to 20 MS/s – Each channel has a 5 bit A/D converter, allowing you to store the single-shot data from both channels simultaneously. In single Trigger Mode, you can capture frequency components up to 5.7 MHz (when Curve Interpolation is used).
( 3 ) Checking the power cable - Be sure that the power cable is supplied as an accessory of the oscilloscope. The power cable has a 3-color wire and a 3-pin receptacle; one of the three pins being for safety grounding.
( 4 ) Environments
Avoid using oscilloscope in environments as mentioned below: a) High temperature – Do not expose the
oscilloscope to direct sunlight or other source
of heat. The ambient temperature range for the
guaranteed performance is 10 to 40ºC or 50
to 104ºF.
b) High humidity – Do not use the oscilloscope in high humidity. The humidity range for guaranteed
performance is up to 75% RH.
c) Electronic magnetic field - Do not use the
oscilloscope in strong electric or magnetic field,
lest the displayed images should be distorted,
or otherwise adversely affected.
d) Unstable position - Do not use the oscilloscope
on a swaying bench or other unstable positon.
e) Flammable atmosphere - Do not use the
oscilloscope in flammable or explosive atmosphere,
to prevent fire and explosion hazards.
f) Blocked ventilations holes – Do not block
the rear, side and button panels. Provide an
ample space behind the rear panel, where the air-cooling fan is installed on.
( 5 ) Preserving the CRT
CRT intensity - In order prevent permanent damage
to the CRT phosphor, do not make the CRT trace
Excessively bright or leave the beam spot stationary
for an unreasonably long time
( 6 ) Checking the Oscilloscope operation
Check the operation of the oscilloscope as explained in this section. The oscilloscope will automatically diagnose itself as you turn the power switch on. ( 6 ).)a Confirm if the power switch is off;
( 6 ).)b Connect the power cable to the AC inlet of the oscilloscope;
( 6 ).)c Connect the power plug to an AC outlet.
( 6 ).)d Turn the power switch on;
( 6 ).)e The green indicator LED on the power switch will light up;
( 6 ).)f The readouts and traces will appear on the CRT screen;
( 6 ).)g After a minute, turn the power switch off once;
( 6 ).)h Wait for several seconds and turn the power on again;
( 6 ).)i Your will see the screen for about 2 seconds if the diagnostic results are passed. If a diagnostic result is failed turn the power switch on and off a few times, this fact means that the oscilloscope has a trouble: the ROM or RAM of the oscilloscope might be failed.
( 7 ) Preparation for measurement
This section covers a simple preparative procedure to do first before using the oscilloscope in order to measure waveforms or signals more efficiently and accurately. For the preparative procedure, proceed as follows:
CAUTION – Be sure to read “ Precautions” and the following: )1 Checking the AC line voltage and frequency;
)2 Checking the type and ratings of the fuse;
)3 Checking the oscilloscope operation.
(9) PUSH BUTTON SWITCH: if inserted serially to a circuit, you can have ON-OFF operation.
(10) POWER SWITCH: turns ON and OFF AC 100V or 220 V input.
(11) (^) DC OVERLOAD ALARM: gives a warning sign in case of overloading troubles.
(12) 60 Hz OUTPUT: outputs AC 4.5 V(RMS) with 60Hz. This signal can be applied to clock
signal or time base.
(13) BUZZER INPUT: operates on 2-5V. The input current is less than 1 mA (as small as CMOS
output).
()15 DC OUTPUT: provides + 5V/ - 5V DC power, with is used for digital circuits.
()16 CURRENT METER: measures load current of 5V out put. It is connected serially with output.
()17 COMMON MODE SWITCH (CM SELECTOR): selects input polarity to LED indicator. If put to
“ANODE”, LED will be ON with input “0”. Contrarily, if put to “CATHODE”, LED will be ON with input
“1”.
- Logic Lab Unit operating procedures
- (^) WARNINGS
- Make sure that AC input voltage is 110V or 220 V and select corresponding voltage input
selector at rear panel;
- Keep this unit away from heat and dusty place;
- When you connect the circuit on bread board, use jump wire whose diameter is less than 6
mm;
- Make sure that pin 1 (index notch) identification of all IC is correctly directed as you
designed;
- Check if Vcc/Vdd of every IC is connected to proper power supply.
• PROCEDURES
•..1 Turn the power switch OFF;
•..2 Connect +5V DC and GND with bus strip on bread board. Be aware that pin 14 or 16 of IC is Vcc/ Vdd
and pin 7 or 8 is GND usually;
•..3 Place all the ICs and other parts so that connections between them may be done easily. While doing
this, take into consideration about LED indicators and logic switch too;
•..4 Connect them using jump wire. It is recommended to use wires with different colors according to their
usage for future checking. Example:
+5V……..red Output…………white Others……green
Input …… yellow GND…………..black
•..5 Check the circuit connections again. If everyone is correct, turn the power switch ON. Keep and eye
on current meter. If excess current is indicated, turn the power switch OFF immediately and find out if
there is any shorted circuit between +5V and GND;
•..6 After everything is proved right, do your experiment using those switches and indicators properly.
MINILAB TECHNICAL TERMS
BUZZER INPUT - entrada de sonorizador, buzina BREAD BOARD- placa de alimentação BUS STRIP- barramento, barra ônibus CLOCK SIGNAL - sinal de relógio COMMON MODE SWITCH- comutador de modo comum CONTROL PANEL - painel de controle CURRENT METER- amperímetro ou medidor de corrente FRONT/ REAR BOARD- placa frontal/ posterior FRONT/ REAL PANEL- painel frontal/ posterior HEXADECIMAL DISPLAY- mostrador em hexadecimal HIGH LEVEL- nível alto/ elevado (“1”) INDEX NOTCH- entalhe marcador JUMP WIRE- fio “jumper”, ponte, ligação direta LED INDICATOR- indicador luminoso LOGICAL LEVEL- nível lógico LOW LEVEL- nível baixo (“0”) NUMBER DISPLAY- mostrador de números PANEL CONTROLS- controles do painel POWER SUPPLY- suprimento de energia elétrica, fonte de alimentação POWER SWITCH - chave, interruptor, alavanca ou tecla para alimentação PROTO BOARD - placa para montagem de protótipos PUSH BUTTOM SWITCH - tecla de pressão comutadora SHORTED CIRCUIT- curto circuitado, “em curto” SWITCH OFF - desligado, desarmado SWITCH ON - ligado, armado TIME BASE - base de tempo
Appearence and parts names
- Indicator zero corrector
- Range selector switch knob
- Measuring terminal +
- Measuring terminal – COM (common)
- OUTPUT (series condenser) terminal
- 0 Ω adjusting knob
- Panel
- Indicator pointer
- Rear case bolt
- Rear case
- Connector for hFE test
- Connection pin to tester
- Transistor base clip
- Transistor collector clip
SPECIFICATION
DC VOLTAGE
Ranges:
- (^) – 0.5 – 2.5 – 10 – 50- 250 – 1000V
Accuracy at FSD :4% Sensitivity :20 K Ω / V
AC VOLTAGE:
Ranges: 10-50-250-1000V Accurancy at FSD :5% Sensitivity :9 K Ω / V Decibelmeter : - 10 to + 50dB 0 db = 1mw/ 600
DC CURRENCY
Ranges: 50 μ A (at 0. 1VDC position), 2.5 – 25mA, 025A 10 A Accuracy at FSD: ± 3% Volt Drop : 250 mV
Weith 280g Operation
Ω TEST
(1) Plug the test lead into COM and + sockets; (2) Place the range selector to a prescribed range position; (3) Short the test leads and turn 0Ω ADJ to set the pointer to zero position; (4) Make sure that there is no voltage across the circuit to be tested; (5) Connect the test leads to the tested resistor and read the scale in accordance with the reference table.
DCV TEST
(1) Plug the red test lead into the + socket and the black one into the –COM; (2) Set the range selector to a selected DCV range position; (3) Connect the red test read to the positive polarity of the circuit tested and the black one to the negative; (4) Read the DCV A scale referring the reference table.
ACV TEST
(1) Plug into the red tet leads into the + socket and the black into the – COM socket; (2) Set the range selector to a chosen ACV range position; (3) Connect the test leads to the circuit being tested regardeless of the polarities; (4) Read ACV scale with the reference table.
DCA TEST
- Place the red test lead into the + socket and the black into the –COM;
- Set the range selector at the selected DCA range position;
- Connect the red test lead to the positive polarity of the circuit tested and the balck into the negative;
- Read the DCV A scale converted with the reference table.
ACV TEST ON OUTPUT TERMINAL
- Plug the red tet lead into the OUTPUT socket and the black one into the – COM;
- Set the range selector at the selected range position;
- Connect the test leads to the circuit to be tested and read the scale in the same manner as ACV test. Such a measurement is made to block the DC voltage which presents in the same circuit and must be4 cut out so that AC Voltage can be read alone.
TRANSISTOR TEST
- Iceo (leakage current) test. 1.)1 Plug the test leads into + and –COM sockets; 1.)2 Set the range selector to X10(15mA) for small size transistor, or to X 1(150mA) for small size transistor; 1.)3 Adjust 0Ω ADJ to set the pointer to zero position of the Ω scale; 1.)4 Connect the transistor with the tester: - For NPN transistor, the “N” COLLECTOR ( C ) of the transistor and the “P” terminal with the EMITTER (e) of the transistor; - For PNP transistor, reverse the NPN transistor connection.
- Read the Iceo range, if the pointer is within the LEAK zone or the pointer moves up the full scale, the transistor tested is not good, otherwise it is a good transistor.
hFE (DC amplification) test
(1) Set the range selector at selected range position – X 1K for 0 -150 for 15 mA, X1 for 0 – 150 mA test; (2) Adjust 0Ω ADJ to adjust the pointer to zero position; (3) Connect the diode to the tester:
- For IF (forward current) test:
Have you ever taken an torch to pieces to find out how does it work? Look at Fig. 1 below, which shows the arrangement of parts inside a torch.
Why did the designer of the torch choose this particular combination of materials? The metal parts must conduct electric current if the torch is to function, but they must also be able to stand up to physical forces. The spring holding the cells in place should stay springy, while the parts of the switch must make good electrical contact and be undamaged by repeated use.
Which materials used in making a torch are conductors and which are insulators? ( ) plastic ( ) copper ( ) tungsten (lamp filament) ( ) glass (outside of lamp)
Drawing a circuit diagram A different way of describing the torch is by using a circuit diagram in which the parts of the torch are represented by symbols.
In Fig. 2 there are two electric cells (“batteries”), a switch and a lamp (the torch bulb). The lines in the diagram represent the metal conductors which connect the system together. A circuit is a closed conducting path. In the torch, closing the switch completes the circuit and allows current to flow. Torches sometimes fail when the metal parts of the switch do not make proper contact, or when the lamp filament is “blown”. In either case, the circuit is incomplete. The diagrams show different arrangements of cells, switches and lamps.
Fig. 3
Current An electric current is a flow of charged particles. Current is sometimes carried by positively charged particles, but inside a copper wire, current is carried by small negarively charged particles, called electrons. Metals, such as copper, contain free electrons, which drift in rang]don directions as shown in Fig. 4. Fig. 4
Voltage Each cell provide a push, called its potencial difference or voltage. This is represented by the symbol V, and is measured in volts, V. Sometimes, you will want to measure voltages in thousands of a volt, or milivolts, mV. Typically, each cell provides 1.5 V. If cells are joined together one after the other, they are said to be connected in series. Two 1.5 V cells connected in series provide 3V, while three cells provide 4.5 V. Fig. 5
Resistance If a thick copper wire is connected from the positive terminal of a battery directly to the negative terminal, you get a very large current for a very short time. In a torch, this
does not happen. Part of the torch circuit limits, or resists, the flow of current. Most of the circuit consists of thick metal conductors which allow current to flow easily. These parts, including the spring, switch plates and lamp connections, have a low resistance. The flow of current through the filament causes it to heat up and glow white hot. Lamp filaments are usually made of the metal tungsten because of its very high melting point. In hair, the filament would quickly oxidize. This is prevented by removing all the air inside the glass of the lamp and replacing it with a non-reactive gas.
Ohm’s equations
The relationship between current, voltage, and resistance was discovered by Georg Ohm, who published his results in 1827. Ohm made his won wires and was able to show that the size of an electric current depend upon their length and thickness. The current was reduced by increasing the length of the wire or by making it thinner. Current was increased if a shorter thicker wire was used. In addition, larger currents were observed when the voltage across the wire was increased. From experiments like these, Ohm found that, at constant temperature, the ratio of voltage to current was constant for any particular wire, that is: Where, R = resistance, V = voltage and I = current.
Ohm’s Law states that, at constant temperature, the electric current flowing in a conducting material is directly proportional to the applied voltage, and inversely proportional to the resistance. Rearranging the formula gives two additional equations: and
These simple equations are fundamental to electronics and, once you have learned to use them effectively, you will find that they are the key to a wide range of circuit problems. You are going to need these equations, so learn them now.
Did you know…? Light bulbs
The lamp filament was first invented in 1860 by a British physicist, Sir Joseph Swan. When
electric current passes through a thin filament of conducting material, the filament heats up and, if
the current is large enough, the filament becomes first red hot and then white hot, or
incandescent. In air, this effect is short-lived because the filament burns up and breaks. Swan
had the idea of enclosing the filament in a glass container, preventing oxidation by removing the
air inside the container using a vacuum pump.
These early experiments suggested that a useful light source was possible, but Swan did
not have as sufficiently powerful vacuum pump. Years later, Swan tried again using a better
vacuum pump. In 1878, he has successful in demonstrating a true incandescent light bulb.
Electricity can be dangerous if you short a battery or the supply in your house a very high current flows. Sometimes the wires which carry the current heat up and melt. This may cause a fire or an explosion. Fuses protect against fire caused by electrical faults. When the current gets too high, fuses burn out and break the circuit. This stops the wires from burning. After a fuse burns out, a qualified person must find the fault before the fuse is replaced.
Electric Circuits Electricity is a very useful type of energy. The beauty of electricity is that it can be generated in one place and used in another place. For example, the lamps in your house could be lit by electricity generated by solar panels on the top of a hill. Electric current can flow along move around circuits (loops) like the chain moves on a bicycle. This is why batteries have two terminals. Current flows out of the positive terminal and into the negative terminal. If there is a break in the circuit then current cannot flow.
Inductor An inductor stores energy in an electromagnetic field created by changes in current through it. Its ability to oppose a change in current flow is called inductance, L, and is measured in henrys. An inductor can have any value form μH to H.
Electric motors Electrical energy can be converted into mechanical energy using an electric motor. Electric motors are used in many products. One of the most important uses of the elecrric motor is in electric cars.
Flashlights You can make a flashlight by connecting a lamp across a battery. This would not be a good flashlight because the lamp would always be on. To turn on and off you need to add a switch. Simple switches have two terminals together. This allows current to flow around the circuit.
Dimming lights Switches are useful if you want to turn a circuit on or off. But sometimes you also want to vary how much current flow around a circuit. For example, some lamps have a knob to control their brightness. Putting a resistor in a circuit reduces the current. The higher of the resistor the more the current is reduced. So a resistor can be used to dim lights.
Capacitor A capacitor stores electrical energy in the form of electrostatic field. Capacitors are widely used to filter or remove AC signals form a variety of circuits. In a DC circuit, they can be used to block the flow of direct current while allowing AC signals to pass. A capacitor’s capacity to sore energy is called is capacitance, C, which is measured in farads. It can have any value form pF to mF.
Linear Resistors Resistors are the most numerous components en electronics. Because of their frequent use, they determine the rehabilitee of the whole system in many ways. The ideal
resistor has a purely real conductance. When a voltage is applied, the electrical energy is converted into thermal energy. Since many of the resistor´s electrical characteristics are dependent on the temperature, the behavior of the resistance-temperature curve is significant for determining the range of possible applications. We speak of linear resistors or ohmic resistors, when their voltage/ current behavior is linear and obeys Ohm´s Law R= V/l (where R= resistance, V= voltage, l= current). As a rule the resistance is temperature dependent: RT = TT0. (1 + ά. ∆T). ∆T is the temperature variation and ά is the temperature coefficient.
INTRODUCTION
General
The region under consideration is Northeast Brazil between 1º and 18º south
latitude and between 35º and 47º west longitude. This covers an area of almost 1.
million km 2 (see fig. 1). This region exhibits a pronounced time and space variability in
the rainfall distribution, with a drastic dry inland region where the annual normal rainfall
is below 500 millimeters (~ 20 inches). Serious social and economic problems result
from the regional population requirements of over 20 million people and their
dependence upon agriculture. It is noteworthy that the region is located in a latitudinal
band where a regular distribution of rainfall should be expected. This region was first
