Text. Fuses

Fuses are widely used nowadays as protection devices. They are utilized in various circuits, electrical equipment and installations. Fuses serve to protect them against overcurrents and short-circuits.

There are different types of fuses in use nowadays. Of them, quartz-sand fuses serve for voltages up to 500 volts; fuses of this kind are produced with current ratings of 15 to 60 amp and of 100 to 350 amp.

Fuses are commonly used in low-voltage industrial installations rated up-to 1,000 V.

Fuse protection is based on a very simple principle; in case of a short-circuit or overcurrent, when the max­imum value of current has been exceeded, the fusible link of a fuse is heated to its melting point. This opens the circuit and disconnects the circuit from the power source. In case of a fault, one should replace the faulty fusible element by a new one.

Fuses are used both in direct current (d.c.) and alternating current (a.c.) circuits.

Exercises

VI. Choose the correct variant:

1. A fuse serves a) as a load, b) as a protection device.

2. Fuses are used a) for d.c. only, b) for both a.c. and d.c.

3. In case of a fault a) the whole fuse should be replaced, b) the faulty link should be replaced.

4. Fuse protection is based on, a) a simple principle, b) a complex principle

VII. Translate the article in writing. Use a dictionary: Types of Fuses in Use Nowadays

Fuses are used to protect circuits against overcurrents. In case of an overcurrent, the fuse link made of copper, zink or lead melts and opens the circuit. Zink, lead and their alloys are known to melt at a rather low tempera­ture (200° to 240°C). These metals having a low conductivity, fuse links made from them must have a large cross-sectional area. Copper fuse links have a good con­ductivity, but they melt at a rather high temperature. As to silver fuse links, they are rather expensive and are known to be used at voltages over 1,000 V and low currents. Most commonly, use is made of copper fuse links silvered for protection against oxidation.

There are several types of fuses in use nowadays. Of them, a plug-type fuse has a porcelain container. Fuses of this type are used for voltages up to 380 V and currents up to 60 amp.

As to a sand fuse, it is used for voltages up to 500 V at currents from 100 to 600 amp.

VIII. It is interesting to know...

that the efficiency of a heat-power plant is less than half that of a water-power plant.

КОНСПЕТ

Прилагательные

Прилагательным называется часть речи, обозначающая признак предмета и не изменяющаяся по родам, числам и падежам

По своей структуре прилагательные бывают:

простые	состоят только из одного корня	red - красный, large -большой, old – старый
производные	имеют корень + суффиксы и / или префиксы	dangerous - опасный, unable - неспособный, remarkable - замечательный
сложные	состоят из двух или более основ	ice-cold - холодный как лед, light-blue - светло-голубой