Read and translate the 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, quartzsand 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.

3. Complete the sentences using the correct variant:

1. A fuse serves

a) as a load.

b) as a protection.

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.

4. Translate into Russian. Mind both... and, in case, up to:

1. Both solid and gaseous insulators are highly in use.

2. In case a fuse gets faulty it should be replaced by a new one.

3. Capacitors of very high capacity - up to 1000 and more mF - are utilized

in modem installations.

5. Answer the questions. Use them in a talk with your groupmate:

1. What does a fuse serve for?

2. For what type of current are fuses used?

3. What should be done in case of a faulty fuse?

4. What principle is fuse protection based on?

Практическое занятие 20. Компоненты электрических цепей

Lesson 20. Components of Electric Circuits

1. Read and learn the words:

incandescence - накал, накаливание

incandescent lamp - лампа накаливания

copper - медь

steel - сталь

to convert - преобразовывать

to deliver - питать, подавать

according to - согласно

etc. = et cetera - и так далее

Read and translate the text.

Components of Electric Circuits

The main components of any circuit are devices that produce and utilize electric energy. They are: 1. power sources, 2. utilizing loads, 3. connecting conductors.

The most common power sources are electric generators and primary cells. Electric generators convert chemical energy into electric energy. Loads include electric heaters, electric motors, incandescent lamps, etc.

Motors convert electric energy into mechanical, incandescent lamps and heaters convert electric energy into light and heat. Utilizing devices or loads convert electric energy into thermal, mechanical or chemical energy.

Electric power is delivered from power sources to loads by electric wires. According to their material, wires can be aluminium, copper, steel, etc.

Besides, electric circuits use different types of switches, protection devices (relays and fuses), and meters (ammeters, voltmeters, wattmeters, etc.).

3. Complete the sentences using the correct variant:

1. The main components of electric circuits are

a) loads and wires.

b) power sources, load and wires.

2. Power sources are used

a) to produce electric energy.

b) to deliver it to the loads.

3. Electric conductors are used

a) to connect the circuit elements.

b) to deliver electric power

4. Protection devices are utilized

a) in some circuits.