SOME NATURAL PHENOMENA
Basics of Electricity and Magnetism
A Story of Symmer`s Stockings
In the mid-eighteenth century, the Reverend Robert Symmer followed fashion and wore silk stockings. In November 1758 the weather was cold so he took the precaution of first putting on a pair of dark woollen stockings over which he pulled on his silk stockings.
On returning home he sat on his bed and pulled off his stockings and noticed to his amazement they flew away from each other. So began his experiments into electricity. He found the woollen stockings would be attracted to the silk ones; that woollen stockings pushed each other away and so did the silk ones and on very cold nights the stockings seemed to still have a leg inside them.
At first he thought the colour of the material may be responsible for their electrical properties but abandoned that idea. He decided that the material from which the stockings were made somehow governed their electrical behaviour.
Symmer reasoned that the woollen stockings had one kind of electricity and the silk another. He proposed the hypothesis that the two kinds of electricity exist in all things. It is sometimes possible to draw off a quantity of one kind and so leave a surfeit of the other and that electrical phenomena resulted from this imbalance of what he called the electrical `fluids`.
called a two fluid theory of electricity.
I will not outline all the theories proposed to account for electrical phenomena - but I can recommend reading up on the history to gain an insight both into experimentation, apparatus design and, at times, frantic activity to explain observed phenomena.
Out of all this enthusiasm,
fun, name-calling, claim and counter claim, came the basics listed below and once you have these you are
well on the way to understanding most of what goes on in natural
phenomena, your own electrical experiences and applications of
ELECTRICITY - Like Charges Repel. In other words:- a negatively charged object will try to push away another negatively charged object. Similarly a positively charged object will push away another positively charged object.
Charges Attract. A positively charged object and a
negatively charged object will pull on each other.
Insulators - are materials which oppose the flow of an
electric current. If a
charge is generated on an insulator - for example if you rub a
piece of PVC with a woollen cloth - the electric charge stays put
on the plastic. It is STATIC - stationary - stays put. The study of charges on insulators
is called ELECTROSTATICS. The early experimenters called
insulators ELECTRICS. Examples are dry wood, dry glass, amber,
rubber, most plastics.
Conductors - are materials which permit the flow of an electric current. If you rub a length of metal, say a piece of copper pipe, no charge can be detected. We now know the reason is that as the charge is produced it flows away through the pipe, through your body and into the earth.
Gray et al had immense
problems with this phenomena. It seemed at the time that
electricity could be produced on ELECTRICS, that is, on
INSULATORS but not on what they called NON-ELECTRICS (that is
CONDUCTORS). It was a major discovery to find if a NON-ELECTRIC
is not in contact with the person or the earth then it will
behave like an ELECTRIC (an INSULATOR) and hold a static charge.
DUFAY following on the researches of Stephen Gray demonstrated
this by placing the material he was rubbing on a glass support.
Examples of CONDUCTORS are - most metals, salt water or any water
containing ions, living plants.
SEMICONDUCTORS - these
days our lives have undergone dramatic changes due to materials
which are insulators which can be made to conduct. Since I am
dealing with the basics of e & m I will not be including
semiconductors here - essentially speaking if you get the idea of
insulators, conductors and the basics then semiconductors are as
it were the next stage.
MAGNETISM - LIKE POLES REPEL. The North pole of any magnet will push away the North pole of any other magnet. Likewise the South pole of any magnet will push away the South pole of any other magnet.
POLES ATTRACT. The North pole of a magnet will pull
to it the South pole of any other magnet and vice versa.
Notice the similarity
to the behaviour of electric charges. Also, it seems that
although you can have individual polarities of electric charge,
say all negative; you cannot have an individual magnetic pole -
if there is a South pole then somewhere not too far away is its
attendant North pole.
ELECTRICITY AND MAGNETISM -
electric current flowing through a conductor produces a magnetic
field around the conductor.
magnetic field moving where there is a conductor will produce an
electric current in the conductor.
Some Natural Phenomena
CAVES - The radioactive decay of radium into radon
daughters in the clays and rocks of caves and mines results in
the air being ionised - made electrically conducting. The
presence of an atmospheric Low (Pressure) has the effect of
releasing more gas. The ionised air rises upwards from the cave
or mine entrance. This constitutes a natural lightning conductor
is dangerous to shelter in a cave or
mine entrance during a thunderstorm. A lightning discharge may
well travel down the column of conducting air rising from the
cave or mine.
LENARD discovered that
the spray around waterfalls is charged with electricity. This is
most likely due to the shattering of water droplets - a process
known to generate electricity in thunderclouds and sea spray.
Sea Spray - Each time a bubble bursts in water an
upwardly moving WORTHINGTON jet is produced. This jet of water
breaks up into a number of droplets, the smallest being at the
tip of the jet. In the case of sea water these tiny droplets are
electrically charged and evaporate to form beautiful crystalline
structures. BLANCHARD estimated some 3,000 million tons of salt
per annum are released into the earth`s atmosphere by bursting
Thunderstorms - There are some 1200 thunderstorms per hour in
the earth`s atmosphere. The storm cloud is called a CUMULO-NIMBUS and has several electrical cells in
its structure. The average height of the cloud is 9 miles but
some reach up to 15 miles. A cell recharges inside the cloud
within 30 seconds after a lightning discharge.
Volcanic Lightning - During eruptions a lightning whose structure
seems peculiar to volcanoes is often seen in the ejectamenta
cloud. Some lightning is probably due to impacting dust but many
volcanoes are submarine, on the rims of oceans or have water in
their structure. These are electrically charged by contact of
water with hot lava - first demonstrated by D.C. BLANCHARD at the
eruption of Surtsey - In later investigations C. POUNDER
discovered the mechanism by which electrically charged solute
particles are produced.
Dust Storms - The impacts between grains and the separation
of grains produces electricity in clouds of dust. In sand storms
electric sparks are seen. MILLS demonstrated in a simple
experiments how such dust storms may occur on Mars, the lightning
in them produces radio noise.
Snow storms - Lightning has been observed in snow
Crosse recorded that on
a still night with no storms in his neighbourhood the Leyden
Battery he used to collect atmospheric electricity began to ring
a small bell attached to it. He looked from his windows to see
snow falling and concluded it was electrically charged.
Tornado - Inside the whirlwind funnel lightning has
been observed flashing across the core. First hand eye-witness of
this came from a man who, thinking the tornado has passed over,
opened his storm shelter door to find himself looking straight up
inside the funnel of the tornado. BERNARD VONNEGUT did some
investigative work on this incident - a part of his ongoing many
years study of thunderstorms. It is with great sadness, since he was
a friend of mine, I have to record the news which came during my
writing this that Bernie is dead.
Lightning - Japanese scientists in particular
are investigating violent, often horizontal, lightning witnessed
during earthquakes. One hypothesis is that tons of quartz bearing
rock strata are dislocated in the event and the lightning results
. Another hypothesis is
that aqueous solution contact charging (see above on Volcanic
Lightning) may be the cause.
Origin of Life
- The amino-acids found
in proteins have been synthesised in experiment simulating early
conditions on the planet. The first of these by STANLEY MILLER in
1953AD set up a laboratory flask and spark apparatus to model the
lightning through the earth`s primitive atmosphere.
Radio Signals from
Space - Radio Astronomy was initiated by
KARL JANSKI of Bell Telephone Laboratories when he realised
interference on long telegraph lines came from the Sun and
Jupiter. MILLS as mentioned demonstrated similar noise from dust
storms on Mars. The whole science now investigates electrical
discharge generated radio signals from discharges in galaxies,
stars and planets.
Electric Eels and Fish - Great argument `about it and about` basically along the lines , "Electricity and water don`t mix!" Anyone who had made a fool of himself with his electrostatics demonstrations because his glass machine or Leyden Jars were damp was not keen to even think that the Electric Eel was powered by the sometimes elusive electric charge. Faraday and Cavendish made investigations. Cavendish constructed a model eel from a leather cylinder connected to a charged Leyden battery. Visitors were invited to grasp it and decided for themselves whether electricity was involved.
More recent investigators
have lit an electric lamp. Which suggests another reason why we
should keep our fingers out of tropical aquaria.
Neurology - The brain and nervous system work by the
transmission of electrical signals produced by the interchange of
Sodium and Potassium ions through membranes. The basic law that a
conductor carrying an electric current is surrounded by a
magnetic field leads one to speculate that complex magnetic
fields, ever changing, must exist around each one of us - and
plants of course.
Bacteria - There are several kinds of bacteria which
either synthesise or ingest Magnetite Fe3O4 which enables them to navigate, presumably
along the inclination of the earth`s magnetic field, downwards
into Oxygen free regions in mud. The flagellea of E-Coli are
turned by electric motors employing ion movement. Nano-
technology is beginning to copy this ancient electric motor
Earth - William Gilbert the earth was a magnet following on from his experiments with a sphere of Magnetite. One hypothesis suggests that the magnetism arises in consequence of large electric currents circulating in the molten Mantle. Whence come the currents one wonders.
Flares on the Sun pour
electrically charged ions into the Solar Wind which sweeps the
planet`s upper atmosphere. Ionised layers are formed which
reflect radio waves and in part shield us from ultraviolet. The
ions cause the aurora -Borealis and Australis. Magnetic storms
from the wind distort radio signals and induce large currents in
power transmission lines.
Plants - Lightning produces nitrous and nitric acid (see Henry Cavendish). These dissolve in water drops which then fall as acid rain. The rain is drawn into the ground by gravity and capillary action and dissolves minerals. This solution of water and ionised minerals is an electrolyte. (An ion is an atom -the smallest part of an element - or a molecule - the smallest part of a compound - which has lost or gained one or more of electrically charged particles. Usually this involves only electrons).
The electrolyte is taken up by the plant roots, in particular by the root hairs. It is converted by various processes, for example Photosynthesis, into cellular material.
Hence lightning produces our food.
A TREE IS A POSSIBLE LIGHTNING CONDUCTOR. Electrically speaking the Cambium of a tree filled with an electrolyte is a vertical conductor. Lightning striking a tree causes the electrolyte to flash into steam and there may be a steam explosion which shatters the tree. If the tree bark is smooth and wet the discharge may pass along this into the ground. Rough bark in part prevents an easy path to ground. In either case however side flashes are common. A tree through which a small electrical discharge passes is subject to cellular damage.
If you are standing next
to this vertical conductor when lightning strikes it the
electricity will find another easier passage to ground through
the vertical conductor of bloodstream and organs and you will
suffer cellular damage.
Electrostatic Hazards - Many of the natural manifestations of dust and spray electrification arise in manufacturing processes. Sugar, flour, powdered chocolate and grain silos have all exploded in instances where there has been charging of the dust clouds and subsequent spark discharge. Coal dust explodes due to dust electrification and discharge. The cleaning of tanks on oil supertankers by the use of high pressure water spray led to Waterfall Electricity which produced sparks which ignited resident gases causing death and insurance claims.
Rev. Symmer would not these days be greeted with incredulity and laughter by those who wear man made fibre. In the dark we are often entertained, or scared stiff, by blue corona, brush discharge and crackling sparks. Although the voltage involved is very high the current is extremely low and risk of electrical injury is low. Most injuries occur to limbs when reaction causes a person to hit a limb on the furniture.
In the Court of St. Petersburg there was a game of throwing a fur muff charged up the people taking part and they discharged sparks to the furniture or each other.
Liquid fuel will generate charge so much so that sparks have been seen in petrol passing through a transparent pipe. Tankers and the vehicle receiving fuel need to be well earthed (grounded).
Sellotape flips back to the roll due to electrostatic charging when it is peeled.
Fabric woven in machines in which fibres pass at speed over metal rollers generate high charges which may tangle the threads. Sheet plastic produced over rollers build up high charges which can affect production -and anyone standing nearby. Precautions have to be devised in all these cases to reduce the build up of charge. Sometimes a radioactive source ionises local air to make a conducting path for discharge to take place continuously.
Helicopters may charge to 500,000volts when rotors collide with rain drops or ice particles.
One use of spray
electrification is in electrostatic paint spraying in which the
charged paint droplets form even coats everywhere on the article
to be painted. Another use is in the application of pesticides
which attach all over leaves.
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