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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.