42
Part II
Arrange the parts of the text (a-f) in the correct order
1.
2.
3.
4.
5.
6.
a)
The heat produced per second depends both upon the resistance of
the conductor and upon the amount of current carried through it. The thinner the
wire is, the greater the developed heat is. On the contrary, the larger the wire is,
the more negligible the heat produced is. Heat is greatly desirable at times but at
other times it represents a waste of useful energy. It is this waste that is generally
called "heat loss" for it serves no useful purposes and decreases efficiency.
b)
The electric current can manifest itself in some other way. It is the
motion of the electric charges that produces the magnetic forces. A conductor of
any kind carrying an electric current, a magnetic field is set up about that
conductor. This effect exists always whenever an electric current flows, although
in many cases it is so weak that one neglects it in dealing with the circuit. An
electric charge at rest does not manifest any magnetic effect. The use of such a
machine as the electric motor has become possible owing to the electromagnetic
effect.
c)
The last effect to be considered is the chemical one. The chemical
effect is known to occur when an electric current flows through a liquid. Thanks
to it a metal can be transferred from one part of the liquid to another. It may
also effect chemical changes in the part of the circuit comprising the liquid and
the two electrodes which are found in this liquid. Any of the mentioned effects
may be used for detecting and measuring current.
d)
The heat developed in the electric circuit is of great practical
importance for heating, lighting and other purposes. Owing to it people are
provided with a large number of appliances, such as: electric lamps that light
our homes, streets and factories, electrical heaters that are widely used to meet
industrial requirements, and a hundred and one other necessary and
irreplaceable things which have been serving mankind for so many years.
e)
The production of heat is perhaps the most familiar among the
principal effects of an electric current. The heating effect of the current is found
to occur in the electric circuit itself. It is detected owing to an increase in the
temperature of the circuit. This effect represents a continual transformation of
electric energy into heat. For instance, the current which flows through the
filament of an incandescent lamp heats that filament to a high temperature.
f)
The current flow is detected and measured by any of the effects that
it produces. There are three important effects accompanying the motion of
electric charges: the heating, the magnetic, and chemical effects, the latter is
manifested under special conditions.
