SUMMARY
By the late 19th century, despite the fact
that the phenomenon of current flow had not been fully explained, most known electric phenomena
were successfully described by physical formulae.
It was already possible to measure quite accurately the charge
of an insulated object, the intensity of current flowing in a wire connected to a
battery, or to calculate the forces acting on a known charge placed at a known distance
from another charge (Coulomb's law). It was
possible to reckon the magnetic field in the vicinity of a conductor with current and
the force acting on the conductor through which current flows and which is placed
in the magnetic field. They learnt how to reckon current induced in a wire coil
placed in a variable magnetic field. They also knew how to calculate the charge which
could accumulate on an insulated conductor connected to a battery of a potential that was
higher than the potential of the conductor.
Actually this knowledge had been acquired by scientists since mid
19th century. It enabled the development of many branches of
technology. However, at that time a single model of the structure of electricity did not
exist. Only purely empirical methods enabled scientists to gather so much information on
electricity.
Certainly there were attempts at the creation of those models.
A decisive majority of scientists considered the flow of current to consist in a flow
of some substance in the conductor. However, researchers differed on whether there
was one, or two different "liquids". The first of those concepts assumed that there
was a substance, a definite amount of which renders a body neutral, surplus makes it
positive and shortage - negative. The other concept assumed the existence of two
different "liquids" - a positive and a negative one. Both models explained the known
electric phenomena equally well.
Another big unknown was the structure of electricity. Some scientists
shared the view that it was infinitely divisible (the liquid model) whereas others considered
it to be in granular, molecular form.
Cathode rays phenomenon was equally
strange and provoked as much controversy. Scientists managed to examine and determine many
of their properties like: deflection in a magnetic field, phosphorescence of glass of
vacuum tube where the beam falls, the phenomenon of their perpendicular emission in the
relation to the cathode, occurrence of certain photochemical reactions under the influence
of the rays. It was shown that those rays transmitted energy and the direction of their
divergence did not need to follow the direction of the current field in the vacuum tube.
Also diffusion of rays through thin metal foils was observed. During researches of this
phenomenon two theories emerged explaining their properties: one supported corpuscular and
the other undulatory nature of rays. Behaviour of the rays in a magnetic field would be
explained by the assumption that they constituted of molecules of negative charge.
However such charge failed to be discovered. Schuster
only managed to estimate that if rays actually consisted of negative molecules, their charge
to mass ratio could not be less than 5*106 coulombs per kilogram nor more
than 1010 coulombs per kilogram.
Scientists boasted numerous achievements in the field of the research
of matter. Since the early 19th century occurrence of numerous
chemical phenomena had been explained by references to the atomic theory. They managed to
show that the whole variety of substances existing in nature actually consists of a
small number of elements. Considering their properties, those elements can be arranged
into a table - the Mendelejev's periodic
table. Moreover, scientists managed to figure out many laws and relationships
governing the microcosm. They formulated basic laws of thermodynamics and laws describing
the ideal gas. They learnt how to determine the mean distance covered by gas molecules
between collisions. Also behaviour of actual gases was profoundly researched.
By the end of the century new elements were discovered, the existence
of which was predicted by the Mendelejev's periodic
table. All elements of the puzzle started to fall into place. The world was made
of elements, of which an uncountable number of substances consisted of and which were
the smallest components of the matter. It seemed to scientists in 1894 that the final solution
of few remaining secrets of nature was the matter of a few coming years.
However, that was not the case. Scientists only made their
first step on the way to explain mysteries of the microcosm. They discovered much
but even more remained to be discovered.
ANCIENT TIMES |
MIDDLE AGES |
THE 16th AND 17th CENTURIES |
THE 18th CENTURY
THE 19th CENTURY |
THE CATHODE RAYS |
SUMMARY
