- •Section 1
- •Section 2 understanding electricity
- •Section 3
- •Solar energy
- •Part II electricity and magnetism. Lesson 1
- •The nature of electricity.
- •Lesson 2
- •Starter: Electricity and magnetism are closely linked. In what way?
- •Lesson 3 study section
- •Lesson 4 Fuses
- •Gathering Information
- •Step 4. Warnings
- •Step 5. Conditions and Instructions
- •Lesson 5 the electric motor
- •Word study
- •Lesson 6. Step 1. List the different ways in which electricity can be generated
- •Portable generator.
- •Study these pairs of actions, what is the link between each pair?
- •Word study: Verbs with -ise /-ize Study these statements:
- •Lesson 7.
- •1.Principles of Electricity
- •2. How Electrical Energy is Produced.
- •Electrochemistry, Batteries and Other Sources of e.M.F. Pure liquids are good insulators but liquids containing salts conduct electricity.
- •4. Resistors and Electrical Circuits
- •5. Electromagnetism
- •6. Electrical Generators and Power Distribution.
- •7. The Transformer
- •Lesson 8. Technical books and reports
- •Lesson 9. Safety at work
- •1. Who is this document for?
- •2. Who wrote this document?
- •What are the differences in meaning, if any between these statements?
- •Lesson 10 careers in engineering
- •Jobs in engineering
- •Part III основи перекладу науково–технічної літератури
- •1 Лексичні питання перекладу
- •2. Граматичні особливості науково-технічної літератури
- •В англійській мові підметом пасивноі конструкції може стати непрямий додаток без прийменника, наприклад, речення
- •В англійській мові підметом пасивнї конструкції може стати непрямий додаток з прийменником, наприклад, речення
- •Складна обставина
- •Техніка перекладу
- •To be to do to have shall
- •4 Реферат та анотація як вторинні наукові тексти.
- •Мова реферату
- •Слід відзначити, що дуже часто зустрічаються в текстах рефератів дієпри-
- •5 Навчання анотуванню
- •Структура анотації
6. Electrical Generators and Power Distribution.
Motors action is caused by the force acting on a current-carrying conductor in a magnetic field. The direction of the force can be predicted by Fleming’s left hand rule.
A d.c. motor consists of a rotating part (the armature) and a fixed part (the frame). Electrical connection to the armature is made via carbon brushes and the commutator. When the armature rotates a back e.m.f. is induced in the armature conductors (this is by generator action) which opposes the applied voltage.
The four main types of dc motor are the separately excited, the shunt wound, the series wound and compound wound -machines.
7. The Transformer
The transformer depends for its operation on the principle of mutual induction. The primary winding of the transformer is connected to the power source (which must be a AC) and the load is connected to the secondary winding.
The transformer may have either a single winding (when it is known as an autotransformer) or more than one winding (two winding transformers are the most common single phase transformers). The iron circuit of the transformer is laminated to reduce the eddy-current power-loss. Important rules relating to transformer design are:
1. Each winding supports the same number of volts per turn.
2. Ampere-turn balance is maintained between the windings. The efficiency of a transformer is the ratio of the power it delivers to the load to the power absorbed by the primary winding.
8. Measuring Devices. Ammeters and Voltmeters.
Ammeters measure the current flowing in a circuit and normally have scales, which are graduated or calibrated in amperes, milliamperes or microamperes.
Voltmeters are used to measure the potential difference between two points in a circuit. The calibration of voltmeters is usually in volts, millivolts and microvolts.
The main difference between the two instruments of the same type or design is in the resistance of the operating coil identical moving units may be used for either meter. An ammeter is connected in the positive or negative lead in series with a circuit and, therefore, must have a low resistance coil otherwise the readings would be incorrect as the coil would absorb an appreciable amount of power.
A voltmeter is connected in parallel across the points of a circuit where the difference of potential is to be measured. The resistance of the operating coil must, in this instance, be as high as possible, to limit the amount of current consumed by it, or else a drop in potential due to the meter would occur and the pointer indication would not represent the true potential difference across the circuit.
Wattmeters. - The measurement of the power in a D.C. circuit at any instant can be achieved by means of an ammeter and voltmeter as the power in watts is the product of the current and the voltage. With A.C. circuits however, the instantaneous values are always changing. To measure A.C. power correctly, therefore, it is necessary to use the third instrument to measure the phase difference. The normal practice, however, is to combine these three instruments in one which will give a direct reading of power in watts.
9. Care of the Electrical equipment.
As a rule electrical equipment operates reliably. Still it does not mean that it deserves no attention. It is necessary to give the equipment frequent inspections, keep it well cleaned, lubricated and repaired. Undue heating, vibration, sparking should be immediately removed.
Heating may be due to overload or to a short circuit between turns, lack of oil in bearings, vibration may be due to improper foundation, unbalance in the moving parts of the machine.
Conductors may get heated because of overload or by reason of damage of the insulation of the conductor.
An electrical machine of any kind requires certain conditions under which it may operate reliably: temperature and freedom of access of surrounding air, need for protection against dirt, dust, type and duration of load, etc. Rotating machines should be placed on solid foundations. Conductors should be protected against mechanical damage. All measures or safety precaution must be undertaken.