TYPES OF WIRES

Тема: Надання першої невідкладної допомоги

FIRST AID

Тема: Техніка безпеки під час роботи

ELECTRICAL SAFETY

1. Read the text and translate it. 

Electricity Is Dangerous 

         When ever you work with power tools or on electrical circuits, there is a risk of electrical hazards, especially electrical shock. Anyone can be exposed to these hazards at home or at work. Workers are exposed to more hazards because job sites can be cluttered with tools and materials, fast – paced, and open to the weather. Risk is also higher at work because many jobs involve electric power tools. 

          Electrical trade workers must pay special attention to electrical hazards because they work on electrical circuits. Coming in contact with an electrical voltage can cause current to flow through the body, resulting in electrical shock and burns. Serious injury or even death may occur. As a source of energy, electricity is used without much thought about the hazards it can cause. Because electricity is a familiar part of our lives, it often is not treated with enough caution. As a result, an average of one worker is electrocuted on the job every day every year! 

         There are four main types of electrical injuries: electrocution (death due to electrical shock), electrical shock, burns, and falls.

MY FUTURE PROFESSION

1. Read the letter and complete the following exercises.

Hello, John

How are you getting on?  I really hope you are fine. Do you remember asking me about my future profession? Today I have some free time and will answer all your questions.

You know I am interested  in electrical experiments, don’t you? So, I am a student of Vocational School №75 and I study at the department of electrical engeneering.

Centuries ago there were only a few jobs: people were farmers, bakers, butchers or carpenters. Today there are thousands of different kinds of jobs, and new ones are constantly appearing. No wonder that it is not an easy thing to make the right choice. I also want to say that the profession should be chosen according to the character and abilities of the person.  As for me my favourite subjects are mathematics and physics. So I made my chose long ago. I want to be an electrician. To my mind it is very useful work. Electricity has become highly important in our modern world. It has made our work easier and our life comfortable. We cannot imagine modern civilization without the electric current, without electric lamps, vacuum cleaners, refrigerators washing machines and other electrically operated devices that are widely used today.

I think that the profession  of electrician can give many opportunities because everything in our life is connected with electricity. Electricians are preparing on specialty “Power engineering, electrical engineering and electromechanics”  with the qualification  “technician-electrician”. Duration of training usually is 5 years on the basic 9 grades and 2 years –  based on full secondary education.

Well, I hope I have answered all your questions. By the way, what are the peculiarities of your future profession? Write me soon.

Best wishes,  Roman

    

ЗАВАНТАЖИТИ

1. Read the and put “True” if the sentence is correspond to the text and “False” if the sentence is not correspond to the text.

Wiring methods 

     Materials for wiring interior electrical systems in buildings vary depending on: 

• Intended use and amount of power demand on the circuit 
• Type of occupancy and size of the building 
• National and local regulations 
• Environment in which the wiring must operate.

   Wiring system in a single family home or duplex, for example, are simple, with relatively low power requirements, infrequent changes to the building structure and layout, usually with dry, moderate temperature, and non- corrosive environment conditions.

     Wires and cables are rated by the circuit voltage, temperature rating, and environmental conditions (moisture, sunlight, oil, chemicals) in which they can be used. A wire or cable has a voltage (to neutral) rating, and a maximum conductor surface temperature rating. The amount of current that a cable or wire can safely carry depends on the installation conditions. 

type of occupancy – тип володіння 

duplex – спарений 

non- corrosive – неагресивні умови 

relatively – відносно 

power requirements - енергоспоживання 

layout – схема, план 

1. All materials for wiring interior electrical systems don’t depend from any causes. 
2. All materials for wiring interior electrical systems depend on power demand of the circuit. 
3. Wiring system in a single family home is not the same that in duplex home. 
4. Wires and cables are rated only by the environmental conditions and chemicals in which they can be used. 

2. Translate the word-combinations into Ukrainian. 

1. interior electrical systems; 2. size of the building; 3. amount of power demand on the circuit; 4. local regulations; 5. a single family home; 6. relatively low power requirements; 7. the building structure; 8. maximum conductor surface temperature rating; 9. installation conditions; 10. the amount of current.

1. Read the text and translate it into Ukrainian.

PPE – personal protective equipment

           There are many types of PPE : rubber gloves, insulating shoes and boots, face shields safety glasses, hazard hats. PPE helps to keep you safe. It is the last line of defense between you and the hazard.

• Wear safety glasses with side shields or goggles to avoid eyes injury.
• Wear proper clothing that is neither floppy nor too tight. Loose clothing will catch on corners and rough surfaces. Clothing that binds is uncomfortable and distracting.
• Wear your hair in such a way that it does not interfere with your work or safety.
• Wear proper foot protection – wear shoes or boots that have been approved for electrical work.
• Wear a hard hat to protect your head from bumps and falling objects. Hard hats must be worn with the bill forward to protect you properly.
• Search out and use any and all equipment that will protect you from shocks and injuries.

1. Read the SAFETY TIPS WHEN WORKING WITH POWER TOOLS than refer them to the proper situation.

SAFETY TIPS WHEN WORKING WITH POWER TOOLS 

A. Power tools are essential for people in the trade who want to accomplish their job in a competent manner as well as for those who won’t to do it yourself’. Using the right tools can prove to be huge benefit in many ways like for example the right tools can save you time and money plus it can also make your job easier to accomplish. 

B. A power tool can be very dangerous object if it used wrongly. Hence it is vital that the tool is handled in the correct way in order to avoid accidents and injuries. Some common reasons for disaster to strike are carelessness, overconfidence and not reading the instructions.

BASIC SAFETY RULES FOR HAND TOOLS

v  ALWAYS WARE EYE PROTECTION.

v  Ware the RIGHT SAFETY EQUIPMENT for the job.

v  Use tools that are the RIGHT SIZE & RIGHT TYPE for your job.

v  Follow the correct procedure for using EVERY tool.

v  Keep your cutting tools SHARP and in good condition.

v  DON’T work with OIL or GREASY hands.

v  Handle SHARP – EDGED and POINTED TOOLS with care.

v  NEVER carry your tools in your pocket

v  DON’T use tools which are LOOSE or CRACKED.

v  DON’T use screwdrivers as chisels or pry bars.

v  AFTER USING A TOOL – clean it and return it to its proper storage place.

v  If anything breaks or malfunctions – report it to your instructor AT ONCE.

v  Use the RIGHT TYPE of tool for the job

28 ТРАВНЯ  ВІДБУЛОСЯ ЗНО З АНГЛІЙСЬКОЇ МОВИ. завдання та інші матеріали можна завантажити тут

Job duties of electricians 

1. Read the text and translate it. 

1. Install ground leads and connect power cables to equipment, such as motors. 
2. Perform business management duties such as maintaining records and files, preparing reports and ordering supplies and equipment. 
3. Repair or replace wiring, equipment, and fixtures, using hand tools and power tools. 
4. Work from ladders, scaffolds and roofs to install, maintain or repair electrical wiring, equipment, and fixtures 
5. Place conduit (pipers or tubing) inside designated partitions /рα:ti∫n/, walls, or other concealed areas, and pull insulated wires or cables through the conduit to complete circuits between boxes. 

Special features of the electrician’s work 

        Maintenance electricians spend much of their time in preventive maintenance. They periodically inspect equipment, and locate and correct problems before breakdowns occur. Electricians may also advise management on whether continued operation of equipment could be hazardous. When needed, they install new electrical equipment. When breakdown occur, they must make the necessary repairs as quickly as possible in order to minimize inconvenience. Electricians may replace items such as circuit breakers, fuses, switches, electrical and electronic components, or wire. When working with complex electronic device, they may work with engineers, engineering technicians, or industrial machinery installation, repair, and maintenance workers. 

       Electricians use hand tools such as screwdriver, pliers, knives, and hacksaws. They also use power tools and testing equipment such as oscilloscopes, ammeter, and test lamps. 

Nature of the work of the electrician 

1. Study the vocabulary

Vocabulary 

electricity - електрика

air condition - кондиціонер
install – установлювати, монтувати 

connect – з’єднувати
test - перевіряти 

electronic control - електрична система управління
maintain - обслуговувати 

blueprint – план
circuit - ел. ланцюг, контур, схема 

outlet – розетка

Voltage

Voltage , otherwise known as electrical potential difference or electric tension (denoted ∆ V and measured in units of electric potential volts, or joules per coulomb), is the electric potential difference between two points – or the difference in electric potential energy of a unit test charge transported between two points. Voltage is equal to the work which would have to be done, per unit charge, against a static electric field to move the charge between two points. A voltage may represent either a source of energy, (electromotive force), or it may represent lost, used, or stored energy (potential drop). A voltmeter can be used to measure the voltage (or potential difference) between two points in a system, usually a common reference potential such as the ground of the system is used as one of the points. Voltage can be caused by static electric fields, by electric current through a magnetic field, or a combination of all three.

VOLTAGE AND AMPERAGE

The strength of EMF or electrical potential is measured in units called volts. The more volts that are present, the greater the electrical potential will be. The voltage level of a dry cell battery will vary depending on how many surplus electrons there are at the negative terminal. A typical small dry cell battery has an EMF of 1.5 volts.

The greater the voltage in an electrical circuit, the greater the flow of electrons will be. Direct current is maintained by a constant or uninterrupted voltage.

Voltage is usually indicated with the abbreviation V. However, you may sometimes see  voltage abbreviated with the letter E, which stands for electromotive force. The  amount of electric      current flowing through a circuit is called amperage. The amount of current is measured in units called amperes or amps. One ampere of current is equal to the charge of 6,240,000,000,000,000,000  electrons flowing past a given point  in a circuit in one second. You can see that it takes many millions of electrons flowing in a   circuit to perform useful work!

In the electrical system, resistance to the flowing electrons (the amperage) can be decreased by using thicker conducting wires. Therefore, high-current circuits will use larger (thicker) conductors, while low-current circuits will use smaller (thinner) conductors.

Amperage is generally indicated with the letter A. However, you may also see amperage abbreviated with the letter I, which stands for intensity.

ELECTROMOTIVE FORCE (EMF)

Current needs a “push” to get its flow started. In a battery, this push is produced by the difference in charge at the two opposing terminals. The electrons’ urge to flow from the negative terminal to the positive terminal will get a current started. Whenever a positive charge and a negative charge are positioned close to each other, electromotive force exists. Electromotive force, often abbreviated EMF, is a force that tends to move electricity.

The term potential is also used to describe EMF. That is, in a battery, the potential or ability to generate current is present. All you have to do is connect wires to the battery to give  the electrons a path to flow on.

          When free electrons are dislodged from atoms, electrical energy is released. Chemical reaction, friction heat and electromagnetic induction will cause electrons to move from one atom to another. Whenever energy in any form  is released, a force called electromotive (e. m. f.) is developed.

         If the force exerts its effort always in one direction, it is called direct; and if the force changes its direction of exertion periodically, it is called alternating. The chemical reaction in a dry cell, heat and friction are sources of a unidirectional force. Electromagnetic induction produces an alternating force. The direction of force depends on the direction in which the field is cut. Whenever an e. m. f. is developed, there is also a field of energy called an electrostatic field, which can be detected by an electroscope and measured by an electrometer.

ELECTROMOTIVE FORCE AND RESISTANCE

      The electromotive force is the very force that moves the electrons from one point in an electric circuit towards another. In case this e. m. f. is direct, the current is direct. On the other hand, were the electromotive force alternating, the current would be alternating, too. The e. m. f. is measurable and it is the volt that is the unit used for measuring it. A current is unable to flow in a circuit consisting of metallic wires alone. A source of an e. m. f. should be provided as well. The source under consideration may be a cell or a battery, a generator, a thermocouple or a photocell, etc.

      In addition to the electromotive force and the potential difference reference should be made to another important factor that greatly influences electrical flow, namely, resistance. All substances offer a certain amount of opposition, that is to say resistance, to the passage of current. This resistance may be high or low depending on the type of circuit and the material employed. Glass and rubber offer a very high resistance and, hence, they are considered as good

insulators. All substances do allow the passage of some current provided the

potential difference is high enough.

      Certain factors can greatly influence the resistance of an electric circuit. They are the size of the wire, its length, and type. In short, the thinner or longer the wire, the greater is the resistance offered.

More links:

Electromotive force

What is Electromotive Force?

Ohm's Law

Ohm’s law states that the current I flowing in the circuit is proportional to the applied potential difference V. The constant of proportionality is defined as the resistance R. If V and I are measured in volts and amperes, respectively, R is measured in ohms. Microscopically resistance is associated with the impedance to flow of charge carries offered by the material. For example, in metallic conductor the charge carries are electrons moving in a polycrystalline material in which their journey is impeded by collisions with imperfections in the local crystal lattice, such as impurity atoms, vacancies, and dislocations. In these collisions the carries lose energy to the crystal lattice, and thus Joule heat is liberated in the conductor, which rises in temperature.

One of Ohm's major contributions was the establishment of a definite relationship between voltage, resistance and current in a closed circuit. A circuit consists of a voltage source and a complete path for current. Ohm stated this relationship as follows: Current is directly proportional to voltage and inversely proportional to resistance.

      As a formula, it appeals like this:

                                           Voltage (in volts)

     Current (in amperes)

                                          Resistance (in ohms)

 This formula is commonly known as Ohm's Law.

     About 1817 Ohm discovered that a simple correlation exists between resistance, current and voltage. That is: the current that flows in the circuit is directly proportional to the voltage and inversely proportional to the resistance. A current is measured in amperes, a voltage, or potential difference is measured in volts. A resistance is measured in ohms.

RESISTANCE

  

Resistance is the opposition that a circuit or substance creates against the flow of electri-cal current. Referring to our water system example again, you can compare resistance to the diameter of the pipe. The narrower the pipe, the less water  that can flow through the pipe.

The only way  to get more water to flow through a narrow pipe would be to increase the water pressure. In the same way, a very thin wire offers more resistance to the flow of electricity than does a thick wire. The only way to increase the flow of electricity in a thin wire would be to apply more voltage to it.

Every electrical circuit contains at least some resistance. This is because no substance is a perfect conductor. For example, silver metal is an excellent conductor, but it’s not perfect — it will always put up some resistance to the flow of electricity through it.

The magnitude of electrical resistance in a circuit is measured in ohms. One ohm is equal to the resistance of a circuit in which one volt of EMF is applied to produce one ampere of  current. The abbreviation for the ohm is the Greek symbol omega.

CONDUCTORS, RESISTORS, AND INSULATORS

One of the first scientists to observe  the flow of electrical current  through various materials was Georg Ohm. In the early 1800s, Ohm performed experiments with electric current. He found that when current was applied to different materials, some materials carried the current readily and others didn’t. He found that different materials put up different degrees of resistance to the flow of electricity.

For example, he noticed that silver and copper readily permitted the passage of almost all of the applied electricity; therefore, he called these metals conductors. Some materials carried almost no electricity, even when a very high voltage was applied. Ohm called these materials insulators. Examples of insulators are glass, mica, porcelain, paper, plastic, and rubber. Other materials passed some (but not all) of the current, so these were called resistors. Carbon is an example of a resistor.

Using your knowledge about the structure of atoms, you can now explain the results of Ohm’s experiments. You learned that some atoms are constructed with free electrons in  their outermost orbits. A material in which electrons can be moved easily from one atom  to another by an outside force is a good conductor of electricity.

In comparison, other materials are made of atoms in which the electrons are very tightly  bound to their orbits.  In these atoms, it’s very difficult to remove electrons from their orbits, so the material is a poor conductor of electricity. If the electrons in an atom can’t  be moved from their orbits at all, the material is an insulator. If at least some of the electrons can be moved, the material is a resistor.

FIXED RESISTORS

We’ve already discussed how some materials resist  electrical flow. Now, we’ll examine how resistive materials can be used to make resistors. Resistors are devices that resist or oppose the flow of electrons through a circuit. Resistors are commonly used to protect circuits and control the flow of electricity through them. However, a resistor doesn’t completely prevent the flow of  electricity. This principle has many practical applications in industry.

The most common type of resistor is the carbon resistor, also called a fixed resistor.  A carbon resistor has a body made of resistive carbon surrounded by a composite sealing material. A stiff wire lead protrudes out of each end of the resistor. A series of colored bands mark the resistor. The color bands identify the resistor’s value as measured in ohms.

Most carbon resistors tend to have a very high resistance to electrical current. While carbon resistor may have a value as small as one-tenth of an ohm, values in the hundreds,  thousands, or even millions of ohms are more common. Carbon resistors are used in electronic circuits to control the flow of current, or to lower the voltage delivered to an electronic device (such as an integrated circuit).

Another type of resistor is the wirewound resistor. A wirewound resistor consists of a porcelain or ceramic tube that’s wrapped with a length of wire. Nichrome, a  type of wire that’s a poor conductor, is often used.

Wirewound resistors generally have lower resistance values than carbon resistors. Typical wirewound resistors have resistance values of tens, hundreds, or thousands of  ohms. The resistance value is largely determined by the length and thickness of the wire  used in the resistor, and how well the wire conducts electricity. These resistors are often used in the high-power circuits found in heaters and DC motor controls.