雅思写作教案3

Description 描写Description is a mental process, a way of perceiving objects in space and time. As it pertains to composition, description is a way of picturing images verbally in speech or writing and of arranging those images in logical or associational pattern. Generally, description is concerned with people, places, and things. But in academic writing, especially in IELTS, you have to write a simple description of an object, a process or some data. According to this requirement, two writing techniques are mainly concerned in IELTS when writing a description. They are: static description and process description.Static Description (静物描述)Very often we have to describe the appearance or layout of something. We shall refer to this as static description. In IELTS, you may be required to write a description about an aerosol container, a camera or a microwave oven. When describing such things a number of features may be contained: shape, size, color, location of parts and condition. Usually in writing static description the following principles should be observed:(1)Your description should be well organized, eg general to particular, moreimportant to less important, front to back, top to bottom, etc.(2)You should offer the reader a clear picture in his mind of what you are describing(3)The details must be correct(4)You ought to stick to the important parts.A RelayA relay is a switching device for opening and closing one or more electrical circuits on receipt of an electric signal.A simple kind of relay consists of two parts: a switch in high voltage circuit which is operated by a spring loaded armature and a low voltage electro-magnetic circuitThe electro-magnet comprises a soft iron core shaped like a horseshoe. Each arm of the core has a coil would around it. The coils are connected to each other and to a battery through an on\off switch.In writing static description, the following words are quite useful:above below over underneath at the front of at the back to the left to the rightin the middle near close to apart on top of at the foot of at the base of at the bottom ofon the side on the other side within inside circle vertical line hyperbolic curveProcess Description (过程描述)A process is a series of actions ,changes ,functions, steps, stages, procedures, or operations that bring about a particular end or result. Like narration, process suggests ongoing movement and continuous action. The rhetorical structure of a process may be conveyed by a simple pattern:Introduction (thesis) Step 1 Step 2 Conclusion ( summary and so forth) Describing How to Do SomethingIn describing how to do something the main thing is to arrange the information so thatthe process can be done straight through without unnecessary interruptions. The description should be moving forward in a logical, step-by-step sequence. In order to show the ideas are concerned , some useful conjunctions or links are used.How to Make a RecordThere are many different steps in the making of a record. Here is a description of the process that brings records into the shops.The musicians play and sing. The sound they make is picked up by the microphones. The sounds are changed into electricity and sent through wires to the mixer, where they are made louder or quieter.The signals are then sent to the tape recorder, which records them onto 16 tracks on the tape. All the instrument are kept separate.Afterwards, the recordings are mixed again, and a new tape is made, with only two tracks(stereo). Some sounds are placed on the left of the tape, so they can be heard from the left loudspeaker.This stereo tape is taken to the cutting machine. This cuts a groove into a piece of metal. Two pieces of metal are cut—one for side one and one for side two of the record.This metal disc with grooves is then used to make another metal disc—with ridges. From this metal disc(called a father) a steel disc with grooved is made. This is called a mother. It is played by the engineers, and the sound quality is checked.From the mother, two son discs are made, and are put into a pressing machine with some black plastic in the middle.The press is heated, and the plastic melts and flows betweens the ridges of the metal disc. So a plastic record is made, with grooves cut into each of its sides. This is cooled with water and taken out.The record is put into a sleeve and sent to the record shop.V ocabulary guide: useful conjunctions or linksfirstly first of all to begin with the first step is ….At the first stage….Secondly next then subsequently after this the next step is in the next stage in the following stage at the same time simultaneously finally eventually the last step isDescribe How Something WorksIn describing how something works, the procedure is very similar to the other kind of description. The description must be orderly, step by step. The basic principle involved should be traced. The basic principle must be clearly understood, otherwise the details will just confuse the reader.How a Microwave Oven WorksA microwave oven will cook food much more quickly than an ordinary gas or an electric cooker.In a conventional oven, infra-red heat is used to warm the food and the heat travels from the outside inwards. The microwave oven uses radiation waves. These waves cause the molecules making up the food to vibrate. This vibration leads to friction between the molecules and it is this friction that causes the food to heat up and cook.Microwave are electromagnetic radiation that an ultra-high frequency (UHF). The radiation is produced by means of an electric tube called a magnetron.In a typical microwave oven, the waves of energy are beamed along a metal tube called a waveguide to a stirrer. The stirrer acts like a fan. It is driven by a motor and distributes the energy evenly over the food being cooked.Metal containers are not used in microwave ovens, since they deflect the microwave energy which might damage the magnetron. However nonmetallic materials such as paper, plastic and ceramics do not absorb microwave energy and do not, therefore, become hot. Thus they make excellent containers for cooking food in.Describing a Cyclical ProcessThe process of describing how to do something and how something works usually has a clear beginning and an end. There is another kind of process often used in academic writing which is cyclical process. In a cyclical process there is no clear beginning or end, so that the cycle is continuously repeated.This diagram illustrates the nitrogen cycle. Nitrogen is essential for human, animal and plant life, and over 90% of the earth’s supply exits as a gas in the atmosphere. The diagram shows how nitrogen is provided to living organisms and then returned to the atmosphere.The cycle goes like this. The lightning contributes some nitrogen, in the form of nitrates, to the soil. The nitrates in the soil are absorbed by plant roots. When animals eat the plants, the nitrogen they contain is synthesized into protein. When plants or animals die, protein are decomposed by bacteria into amino acids which are in turn broken down into ammonium. The ammonium is broken down into nitrites. The ammonium resulting from decomposition returns to the nitrites-nitrates-protein cycle. The nitrites are converted into nitrates by soil bacteria. Some of the nitrates are degraded into nitrogen gas in the denitrification process. This gaseous nitrogen os returned to the atmosphere. But at the source of most nitrogen is bacteria on plants, which fix the nitrogen into ammonia.。