JEFIMENKO, Oleg : Electrostatic
PDF copy of the out-of-print classic. Run motors with atmospheric
Popular Science (
April 1971 )
The Amazing Motor That Draws Power from the Air
by C.P. Gilmore & William J.
Would you believe an electric motor made almost entirely of
plastic? That can run on power transmitted through open air? And
sneak free electricity right out of the earth's electrical field?
At the University of West Virgina we saw a laboratory full of such
exotic devices spinning, humming, and buzzing away like a swarm of
bees. They are electrostatic motors, run by charges similar to
those that make your hair stand on end when you comb it on a cold
Today, we use electromagnetic motors almost exclusively. but
electrostatics have a lot of overlooked advantages. They're far
lighter per horsepower than electromagnetics, can run at extremely
high speeds, and are incredibly simple and foolproof in
"And, in principle," maintains Dr Oleg Jefimenko, "they can do
anything electromagnetic motors can do, and some things they can
Jewel-like Plastic Motors.
Jefimenko puts on an impressive demonstration. He showed us motors
that run on the voltage developed when you hold them in your hands
and scuff across a carpet, and other heavier, more powerful ones
that could do real work. Up on the roof of the University's
physics building in a blowing snowstorm, he connected an
electrostatic motor to a specially designed earth-field antenna.
It twirled merrily from electric power drawn out of thin air.
These remarkable machines are almost unknown today. Yet the
world's electric motor was an electrostatic. It was invented in
1748 by Benjamin Franklin.
Franklin's motor took advantage of the fact that like charges
repel, unlike ones attract. He rigged a wagon-wheel-sized,
horizontally mounted device with 30 glass spokes. On the end of
each spike was a brass thimble. Two oppositely charged leyden jars
-- high voltage capacitors -- were so placed that the thimbles on
the rotating spokes barely missed the knobs on the jars ( see
As a thimble passed close to a jar, a spark leaped from knob to
thimble. That deposited a like charge on the thimble, so they
repelled each other. then, as the thimble approached the
oppositely charged jar, it was attracted. As it passed this second
jar, a spark jumped again, depositing a new charge, and the whole
repulsion-attraction cycle began again.
In 1870, the German physicist J.C. Poggendorff built a motor so
simple it's hard to see what makes it work. The entire motor, as
pictured here, is a plastic disk ( Poggendorff used glass ) and
two electrodes. The electrodes set up what physicists call a
corona discharge; their sharp edges ionize air molecules that come
in contact with them. These charged particles floating through the
air charge the surface of the palstic disk nearby. Then the
attraction-repulsion routine that Franklin used takes place.
A few papers on electrostatic motors have trickled out of
the laboratories in recent years. But nobody really showed much
interest until Dr Jefimenko came on the scene.
The Russian-born physicist was attending a class at the University
of Gottingen one day shortly after World War II when the lecturer,
a Prof. R.W. Pohl, displayed two yard-square metal plates mounted
on the end of a pole. He stuck the device outside and flipped it
180 degrees. A galvanometer hooked to the plates jumped sharply.
"I could never forget that demonstration," said Jefimenko. "And I
wondered why, if there is electricity in the air, you couldn't use
it light a bulb or something."
The earth's electrical field has been known for centruries.
Lightning and St Elmo's fire are the most dramatic manifestations
of atmospheric electricity. But the field doesn't exist just in
the vicinity of these events; it's everywhere.
The earth is an electrical conductor. So is the ionosphere, the
layer of ionized gas about 70 kilometers over our heads. The air
between is a rather poor insulator. Some mechanisms not yet
explained constantly pumps large quantitites of charged particles
into the air. The charged particles cause the electrical field
that Jefimenko saw demonstrated. Although it varies widely,
strength of the field averages 120 volts per meter.
You can measure this voltage with an earth-field antenna -- a wire
with a sharp point at the top to start a corona, or with a bit of
radioactive materials that ionizes the air in its immediate
vicinity. near the earth, voltage is proportional to altitude; on
an average day you might measure 1200 volts with a 10-meter
Over that past few years, aided by graduate-student Henry
Fischbach-Nazario, Jefimenko designed advanced corona motors. With
David K. Walker, he experimented with electret motors. An electret
is an insulator with a permanent electrostatic charge. It produces
a permanent electrostatic charge in the surrounding space, just as
a magnet produces a permanent magnetic field. And like a magnet,
it can be used to build a motor.
Jefimenko chose the electrostatic motor for his project because
the earth-field antennas develop extremely high-voltage
low-current power -- and unlike the electromagnetic motor --
that's exactly what it needs.
The Climactic Experiment
On the night of Sept. 29, 1970, Jefimenko and Walker strolled into
an empty parking lot, and hiked a 24-foot pole painted day-glow
orange into the sky. On the pole's end was a bit of radioactive
material in a capsule connected to a wire. The experimenters
hooked an electret motor to the antenna, and, as Jefimenko
describes it, "the energy of the earth's electrical field was
converted into continuous mechanical motion."
Two months later, they successfully operated operated a corona
motor from electricity in the air.
Any Future In It?
Whether the earth's electrical field will ever be an important
source of power is open to question. There are millions -- perhaps
billions -- of kilowatts of electrical energy flowing into the
earth constantly. Jefimenko thinks that earth-field antennas could
be built to extract viable amounts of it.
But whether or not we tap this energy source, the electrostatic
motor could become important on its own.
* In space or aviation, it's extreme light weight could be
crucial. Jefimenko estimates that corona motors could deliver one
horsepower for each 3 pounds of weight.
* They'd be valuable in laboratories where even the weakest
magnetic field could upset an experiment.
* Suspended on air bearings, they'd make good gyroscopes.
In a particularly spectacular experiment, Jefimenko turned on a
Van de Graaff generator -- a device that creates a
very-high-voltage field. About a yard away he placed a
sharp-pointed corona antenna and connected it to an electrostatic
motor. The rotor began to spin. The current was flowing from the
generator through the air to where it was being picked up by the
The stunt had a serious purpose: The earth's field is greatest on
mountaintops. Jefimenko would like to set up a large antenna in
such a spot, then aim an ultraviolet laser beam at a receiving
site miles away at ground level. The laser beam would ionize the
air, creating an invisible conductor through apparently empty
To be sure, many difficulties exist; and no one knows for sure
whether we'll ever get useful amounts of power out of the air. But
with thinking like that, Jefimenko's a hard man to ignore.
Science ( May 1971 )
Electrostatic Motors You Can Build
C.P. Gilmore & William J.
When we crank up the electrostatic motor at the top of this page,
people always want to know what makes it run. It is mysterious --
there's nothing but a plastic disk and two strange electrodes. Yet
there it is, spinning merrily.
In "The Amazing Motor That Draws Power From the Air", last month,
we told about our visit to the laboratory of Dr Oleg Jefimenko at
the University of West Virginia, who has designed and built a
variety of these ingenious machines. now, as promised, we bring
you details on how you can build your own electrostatic motor from
The devices that you see here are corona-discharge motors. The
sharp-pointed or knife-edge electrodes create a corona, which
ionizes or charges the air particles floating by. These charged
particles transfer their charge to the closest part of the plastic
rotor and charge it up, just as you can charge your body by
walking across a wool rug on a dry winter's day.
Once a spot on the rotor assumes a charge, it is repelled from the
chargin electrode by electrostatic forces, and at the same time is
attracted to the other electrode, which has an opposite charge.
When the charged section of the rotor reaches the opposite
electrode, another corona discharge reverses the polarity and
starts the whole thing over again.
The Concept is Simple
And so are the motors. But that doesn't mean thery're easy to
build. These motors run on millionths of a watt; they've got no
power to waste turning stiff bearings or slightly misaligned
rotors. So they must be built with watch-making precision.
They're made of acrylic sheet, rod, and tube stock -- Plexiglas
and Lucite are two of the better-known brands. Acrylic cuts and
works beautifully. Cut edges can be sanded so they have a white,
frosted appearance that, in contrast with clear surfaces, gives
your finished motor a sparkling, jewel-like appearance. If you
like clear edges, you can buff them on a wheel and the whole thing
Drill and tap the acrylic and assemble parts with machine screws.
This allows for fine adjustment and alignment. Later, you can make
the whole thing permanent by putting a little solvent along the
joints. The solvent flows into the joint and fuses it permanently.
Details of framework, support and so on aren't important; change
them if you like. but work with care if you want to avoid
headaches. The Poggendorff motor looked simple; we slapped it
together in a couple of hours, hooked up the power source -- and
nothing happened. We gave it a few helpful spins by hand, but it
wouldn't keep running.
The cure took about 3 hours. First, we noticed that the outer edge
of the disk wobbled from side to side about 1/16 of an inch as the
wheel revolved. So the rotor-electrode distance was constantly
changing. There was a little play in the 1/4" hole we had drilled
for the electrodes -- so they weren't lined up absolutely square
with the disk. Then we noticed that the disk always stopped with
one side down. The imbalance was only a fraction of an ounce --
but it was too much.
We drilled out the old hub and cemented in a new one -- this time,
carefully. We lined up the electrodes -- precisely. Then, once
more spinning the disk by hand, we added bit of masking tape until
it was perfectly balanced. We connected the power -- and slowly...
slowly... the disk began to turn. After about a minute, we clocked
some turns with a watch and found it was spinning at 200 rpm. A
moment later, we lost count. It was a great feeling.
Where Tolerances Are Brutal
We had even more trouble with the octagonal-window machine. When
it wouldn't run and we turned the shaft by hand, we could feel the
rotor dragging. We took it apart, felt all the surfaces on the
rotor and the framework's insides and found a few bits of hardened
cement, which we removed. We filed down all edges on the rotor adn
the windows to make sure there were no beads or chips dragging.
The rotor and corner separators are made from the same sheet of
1/2" plastic, so rotor clearance is achieved by putting shims at
the corners to hold the side plates slightly more than 1/2" apart.
With the 1/16" shims we were using, we could see that the sides
were slightly misaligned so the shaft was not being held at a true
90 degrees. We drilled slightly oversized holes in the corners of
one side piece and carefully adjusted until the rotor was turning
true in the slot. To give the motor more torque, we put a bead of
cement along the outer edge of each aluminum-foil electrode to
stop corona leakage. The motor ran.
Take A Giant Step
Once you've built these machines, why not design your own? Start
with the Jefimenko 1/10 hp model (pictured) as a challenge. Then
plan one from scratch. You can power your motors with a laboratory
high-voltage supply, a Van de Graff generator, or a Wimhurst
machine or any other high-voltage source. We've been running ours
on the home-built Wimhurst machine shown in the photos. (If you
don't want to build one, Wimhurst machiens are available from
scientific supply houses such as Edmund Scientific ).
The discharge globes are traditional for high-voltage machines.
They aren't necessary, but they give a quick check on machine
operation and a satifying arc when you move them within 1/2" of
each other. Incidentally, that funny smell is ozone. But its
concentration is too low to be harmful. The generator is safe,
too. You can hold both electrodes in your hands and all you'll
feel is a tingle. This particular generator, we estimate, puts out
about 30,000 volts.
To make wiring simple, we used standard connectors on the Wimhurst
collectors, and meter leads with regular banana plugs and
alligator clips to hook up the motors.
Last month, we mentioned seeing Dr Jefimenko run his electrostatic
motors on electricity tapped from the earth's field. We haven't
had a chance to try this yet with ours, but it should work. If you
want to try, you'll need a needle-pointed piece of music wire a
few inches long to start a corona, plus several hundred feet of
fine copper wire.
Connect the pointed wire to the fine conductor, get the sharp
point up into the air at least 200-300 feet with a kite or
balloon, and hook the wire to one side of the motor. Hook the
other side of the motor to ground. The earth field antenna should
at times be able to develop up to 20,000 volts from the earth's
electrical field. If nothing happens, check your equipment, or try
another day. The field changes constantly.
Oleg D. Jefimenko
(October 14, 1922, Kharkiv, Ukraine - May 14, 2009, Morgantown,
West Virginia, USA) - physicist and Professor Emeritus at West
Jefimenko received his B.A. at Lewis and Clark College (1952). He
received his M. A. at the University of Oregon (1954). He received
his Ph.D. at the University of Oregon (1956). Jefimenko has worked
for the development of the theory of electromagnetic retardation
and relativity. In 1956, he was awarded the Sigma Xi Prize. In
1971 and 1973, he won awards in the AAPT Apparatus Competition.
Jefimenko has constructed and operated electrostatic generators
run by atmospheric electricity.
Jefimenko has worked on the generalization of Newton's
gravitational theory to time-dependent systems. In his opinion,
there is no objective reason for abandoning Newton's force-field
gravitational theory (in favor of a metric gravitational theory).
He is actively trying to develop and expand Newton's theory,
making it compatible with the principle of causality and making it
applicable to time-dependent gravitational interactions.
Jefimenko's expansion, or generalization, is based on the
existence of the second gravitational force field, the
"cogravitational, or Heaviside's, field". This is might also be
called a gravimagnetic field. It represents a physical approach
profoundly different from the time-space geometry approach of the
Einstein general theory of relativity. Oliver Heaviside first
predicted this field in the article "A Gravitational and
Electromagnetic Analogy" (1893).
* "Electrostatic motors; their history, types, and principles of
operation". Star City [W. Va.], Electret Scientific Co. .
* "Electromagnetic Retardation and Theory of Relativity: New
Chapters in the Classical Theory of Fields", 2nd ed., Electret
Scientific, Star City, 2004.
* "Causality, Electromagnetic Induction, and Gravitation: A
Different Approach to the Theory of Electromagnetic and
Gravitational Fields", 2nd ed., Electret Scientific, Star City,
* "Electricity and Magnetism: An Introduction to the Theory of
Electric and Magnetic Fields", 2nd ed., Electret Scientific, Star
* "Scientific Graphics with Lotus 1-2-3: Curve Plotting, 3D
Graphics, and Pictorial Compositions". Electret Scientific, Star
* "What is the Physical Nature of Electric and Magnetic Forces?"
in Has the Last Word Been Said on Classical Electrodynamics? --
New Horizons, A. E. Chubykalo, Ed., (Rinton Press, Paramus, 2004
* "Does special relativity prohibit superluminal velocities?" in
Instantaneous Action at a Distance in Modern Physics: "Pro" and
"Contra", A. E. Chubykalo, Ed., (Nova Science, New York, 1999).
* "A neglected topic in relativistic electrodynamics:
transformation of electromagnetic integrals". arxiv.org, 2005.
* "Presenting electromagnetic theory in accordance with the
principle of causality", Eur. J. Phys. 25 287-296, 2004.
* "Causality, the Coulomb field, and Newton's law of gravitation"
(Comment), American Journal of Physics, Volume 70, Issue 9, p.
964, September 2002.
* "The Trouton-Noble paradox," J. Phys. A. 32, 3755–3762, 1999.
* "On Maxwell's displacement current," Eur. J. Phys. 19, 469-470,
* "Correct use of Lorentz-Einstein transformation equations for
electromagnetic fields", European Journal of Physics 18, 444-447,
* "Retardation and relativity: Derivation of Lorentz-Einstein
transformations from retarded integrals for electric and magnetic
fields", American Journal of Physics 63 (3), 267-72.
* "Retardation and relativity: The ease of a moving line charge",
American Journal of Physics, 63 (5), 454-9.
* "Direct calculation of the electric and magnetic fields of an
electric point charge movingwith constant velocity," Am.J.Phys.
62, 79-84, 1994.
* "Solutions of Maxwell's equations for electric and magnetic
fields in arbitrary media," Am. J. Phys. 60, 899-902 1992.
* "Electrets," (with D. K. Walker) Phys. Teach. 18, 651-659, 1980.
* "How can An Electroscope be Charged This Way?", TPT 56, 1979.
* "Water Stream 'Loop-the-Loop'", AJP 42, 103-105, 1974.
* "Franklin electric motor," Am. J. Phys. 39, 1139-1141, 1971.
* "Operation of electric motors from atmospheric electric field,"
Am. J. Phys. 39, 776-779, 1971.
* "Demonstration of the electric fields of current-carrying
conductors," Am. J. Phys. 30, 19-21, 1962.
* "Effect of the earth's magnetic field on the motion of an
artificial satellite," Am. J. Phys. 27, 344-348, 1959.
* "'Maxwell's Equations'", Macmillan Encyclopedia of Physics,
Macmillan, New York, 1996.
The next energy breakthrough is Dr. Oleg Jefimenko's electrostatic
motors. Discovered by Ben Franklin in the 18th century,
electrostatic motors are an all-American invention. They are based
on the physics of the fair-weather atmosphere that has an
abundance of positive electric charges up to an altitude of 20 km.
However, the greatest concentration is near the ground and
diminishes with altitude rapidly. Dr. Jefimenko discovered that
when sharp-pointed antennas are designed for a sufficient length
to obtain at least 6000 volts of threshold energy, the
fair-weather current density available is about a picoampere per
square meter. Such antennas produce about a microampere of
current. However, small radioactive source antennas may be used
instead that have no threshold voltage and therefore no height
requirements. Similar to a nuclear battery design of Dr. Brown,
these antennas have larger current potentials depending upon the
radioactive source used (alpha or beta source) and ionize the air
in the vicinity of the antenna. Electrostatic motors are lighter
than electromagnetic motors for the same output power since the
motor occupies the entire volume. For example, it is expected that
a motor one meter on a side will provide a power of one megawatt
and weigh 500 kg or less. Electrostatic motors also require very
little metal in their construction and can use mostly plastic for
example. They can also operate from a variety of sources and range
of voltages. As Dr. Jefimenko points out, "It is clear that
electrostatic motor research still constitutes an essentially
unexplored area of physics and engineering, and that electrostatic
motor research must be considered a potentially highly rewarding
area among the many energy-related research endeavors." The
atmospheric potential of the planet is not less than 200,000
megawatts. He has succeeded in constructing demonstration motors
that run continuously off atmospheric electricity. Jefimenko's
largest output motor was an electret design that had a 0.1 Hp
rating. Certainly the potential for improvement and power
upgrade exists with this free energy machine.
So I go out on my step and what to my wondering eyes doth appear
but the box from Amazon.com containing the Jefimenko books that
Bill Miller shamed me into finally buying. So I take a quick look
inside and decide to give an initial report here. (Too much vector
math in there for a thorough review.)
These books have some amazing advanced thinking in the
understanding of Maxwell and EM. One first thought is the
consideration of causality. This is typically totally ignored in
the EM community. Evidence of that is the fact that EM waves are
widely held to be propagated by the E field creating the H field
and the H field creating the E field as it goes along. Too bad
it's just not true! Jefimenko points out that causality demands
that that an event must be PRECEDED by it's cause! Simultaneous
events CANNOT be "causal" of each other. Hence E and H fields of
waves are created by the WAVE SOURCE not each other! Same things
goes for the E field created by Faraday induction. It simply
cannot be "caused" by the time-varying Magnetic Field. "Magnetic
induction" is therefore a misnomer. Such induction is caused by
the source CURRENT and NOT the magnetic field!
This leads Jefimenko on to note that contrary to the "one E field"
theory that has been believed for so many years, the inductive E
field is clearly NOT the same field as an electrostatic E field.
Jefimenko terms this inductive E field the "Electrokinetic Field"
to show that it is a different field from the electrostatic E
field. Very good. However, old habits die hard and even Jefimenko
persists in writing an expression for a "total E field" following
Maxwell as consisting of a sum of the electrostatic and
electrokinetic parts as if they were both the "same" kind of E
Jefimenko then proceeds to illustrate the electrokinetic fields
with a series of calculations and examples using his formulas as
an approach. He presents it as basically a "new" way of doing this
and in one sense it is compared to the commonly used and
non-causal bogus "flux linkage" methods. However, he fails to note
that the causal Neumann formula is in essence identical to his
formulation and has been a standard formulation for years for the
calculation of the "electrokinetic field" or what is usually
termed "mutual induction". Nevertheless his example calculations
are important basic references to the topic of Faraday induction.
And the consideration of causality clearly shows that the Neumann
approach has the edge over the "flux linkage" ideas with at times
fail to give correct results.
But the subject doesn't end with induction, he pulls gravity into
the mix. Of particular interest is that he shows that once you
introduce causality into Newton's theory of gravitation,
interesting things start to happen! Relativity suddenly begins to
show up and even more interesting "action-reaction" is soon
discovered to actually be a law that does NOT hold in all cases!
The electromagnetic nature of gravity quickly becomes strongly
hinted at and without action-reaction laws, those dreamed of
devices such as anti-gravity ships and the "force-glove" that you
wear to push over a building become theoretical possibilities!
These are truly books full of thought-provoking new ways of
looking at tired old physics!
I'm not going to be going through the large quantity of field
theory math in these books in a hurry, but that's OK because
clearly taking the time to go through in detail WILL be worth the
effort! What can I say? Listen to Bill Miller and get that order
off to Amazon.com now. At roughly $25 each these two books are a
huge bargain to the usual EM text books costing hundreds of
dollars and then being full of bogus ideas and misunderstandings
of the established theories. Just do it! I did and I'm not sorry I
The Bizarre and Intriguing Story of Oleg Jefimenko
and the Solutions to Maxwell's Equations
I recently heard the story of Oleg Jefimenko during a lecture on
Electrodynamics, specifically the general solution to Maxwell’s
Jefimenko’s tiny bit of fame comes from Jefimenko’s Equations,
which are the general solution to Maxwell’s equations expressed
solely in terms of sources, that is charge and current
distributions. The equations are messy and difficult to work with,
and aren’t used much in practice. But they do reveal certain bits
of physics (such as the applicability of the quasistatic
approximation (the link goes to a thermodynamics page, but the
idea is the same) and that fields must be created by sources), and
it’s always nice to have the general solution to a problem
These equations weren’t written down until 1966, about a century
after Maxwell’s Equations were known. Some people will claim (as
the Wikipedia article cited does) that Jefimenko’s Equations were
written down earlier, but those earlier versions are always
slightly different and not quite complete. What’s really funny is
that Jefimenko wrote them down in an attempt to formulate an
alternative to Maxwell’s equations.
When my current Professor, David Griffiths, was in the process of
writing a paper on the subject, he independently derived
Jefimenko’s equations, and tried to figure out if anyone had done
it before. Other than some slightly tricky and annoying math,
they’re not hard to derive, so someone must have done it. He found
that Jefimenko had written them in a book that was published by a
company that had only published one other work, also by Jefimenko
(apparently regular publishers wouldn’t take his books, so he went
to a prestige press). He contacted Jefimenko, and Jefimenko didn’t
believe that he had solved Maxwell’s equations, but that he had
created an electromagnetic theory separate from (and doubtless
better than) Maxwell’s. Of course he had done no such thing, his
formulation is exactly equivalent to Maxwell’s, but he wasn’t
According to Griffiths, Jefimenko currently submits one or two
papers a week to American journals, gets denied, then publishes
them in Europe (where review is apparently not as stringent). I
don’t know what they’re about, the Wikipedia article says he
focuses on overthrowing Einstein’s General Relativity and Maxwell.
I found this story behind some esoteric equations to be pretty
amusing, and thought others might agree. I hope you’ve enjoyed the
convoluted and intriguing story behind Jefimenko’s equations.
[Most of my information comes from a lecture with Griffiths, and
as such could not be found online. Anything that is available
online has been referenced.]
Electret Scientific Co
P.O. Box 4132
WV 26504 USA
Books by Professor Oleg Jefimenko
Gravitation and Cogravitation --
Developing Newton's Theory of Gravitation to its Physical and
(also available from www.Amazon.com)
Paperback - List Price US$ 22.00
Hardback - List Price US$ 32.00
Electrostatic Experiments -- An
Encyclopedia of Early Electrostatic Experiments,
Demonstrations, Devices, and Apparatus,
by G.W. Francis (author), Oleg Jefimenko (editor)
Paperback - List Price US$ 24.00
Hardback - List Price US$ 48.00
Electromagnetic Retardation and
Theory of Relativity -- New Chapters in the Classical Theory of
, 2nd edition,
Paperback - List Price US$ 24.00
Hardback - List Price US$ 44.00
Induction, and Gravitation -- A Different approach to the Theory
of Electromagnetic and Gravitational Fields
Paperback - List Price US$ 22.75
Hardback - List Price US$ 32.50
An Introduction to the Theory of
Electric and Magnetic Fields
, 2nd edition,
Hardback - List Price US$ 72.00
Electrostatic Motors -- Their
History, Types, and Principles of Operation,
Out of Print -- free e-book download available soon
Electrostatic Experiments: An
Encyclopedia of Early Electrostatic Experiments, Demonstrations,
Devices, and Apparatus
by Oleg D. Jefimenko
Scientific American (
October, 1974 )
Electrostatic Motors Are Powered
by Electric Field of the Earth
Although no one can make a perpetual motion
machine, anyone can tap the earth's electric field to run a
homemade motor perpetually. The field exists in the atmosphere
between the earth's surface and the ionosphere as an electric
potential of about 360,000 volts. Estimates of the stored energy
range from a million kilowatts to a billion kilowatts.
Energy in this form cannot be drawn on directly for
driving ordinary electric motors. Such motors develop mechanical
force through the interaction of magnetic fields that are
generated with high electric current at low voltage, as Michael
Faraday demonstrated in 1821. The earth's field provides
relatively low direct current at high voltage, which is ideal
for operating electrostatic motors similar in principle to the
machine invented by Benjamin Franklin in 1748.
Motors of this type are based on the force of
mutual attraction between unlike electric charges and the mutual
repulsion of like charges. The energy of the field can be tapped
with a simple antenna in the form of a vertical wire that
carries one sharp point or more at its upper end. During fair
weather the antenna will pick up potential at the rate of about
100 volts for each meter of height between the points and the
earth's surface up to a few hundred feet. At higher altitudes
the rate decreases. During local thunderstorms the pickup can
amount to thousands of volts per foot. A meteorological
hypothesis is that the field is maintained largely by
thunderstorms, which pump electrons out of the air and inject
them into the earth through bolts of lightning that continuously
strike the surface at an average rate of 200 strokes per second.
Why not tap the field to supplement conventional
energy resources? Several limitations must first be overcome.
For example, a single sharp point can draw electric current from
the surrounding air at a rate of only about a millionth of an
ampere. An antenna consisting of a single point at the top of a
60-foot wire could be expected to deliver about a microampere at
2,000 volts; the rate is equivalent to .002 watt. A
point-studded balloon tethered by a wire at an altitude of 75
meters might be expected to deliver .075 watt. A serious
limitation appears as the altitude of the antenna exceeds about
200 meters. The correspondingly higher voltages become difficult
At an altitude of 200 meters the antenna should
pick up some 20,000 volts. Air conducts reasonably well at that
potential. Although nature provides effective magnetic materials
in substances such as iron, nickel and cobalt, which explains
why the electric-power industry developed around Faraday's
magnetic dynamo, no comparably effective insulating substances
exist for isolating the high voltages that would be required for
electrostatic machines of comparable power. Even so,
electrostatic motors, which are far simpler to build than
electromagnetic ones, may find applications in special
environments such as those from which magnetism must be excluded
or in providing low power to apparatus at remote, unmanned
stations by tapping the earth's field.
Apart from possible applications electrostatic
motors make fascinating playthings. They have been studied
extensively in recent years by Oleg D. Jefimenko and his
graduate students at West Virginia University. The group has
reconstructed models of Franklin's motors and developed advanced
electrostatic machines of other types.
Although Franklin left no drawing of his motor, his
description of it in a letter to Peter Collinson, a Fellow of
the Royal Society, enabled Jefimenko to reconstruct a working
model [see illustration at right]. Essentially the machine
consists of a rimless wheel that turns in the horizontal plane
on low-friction bearings. Each spoke of the "electric wheel," as
Franklin called the machine, consists of a glass rod with a
brass thimble at its tip. An electrostatic charge for driving
the motor was stored in Leyden jars. A Leyden jar is a primitive
form of the modern high-voltage capacitor. Franklin charged his
jars with an electrostatic generator.
The high-voltage terminals of two or more Leyden
jars that carried charges of opposite polarity were positioned
to graze the thimbles on opposite sides of the rotating wheel.
The motor was started by hand. Thereafter a spark would jump
from the high-voltage terminal to each passing thimble and
impart to it a charge of the same polarity as that of the
terminal. The force of repulsion between the like charges
imparted momentum to the wheel.
Conversely, the thimbles were attracted by the
oppositely charged electrode of the Leyden jar Franklin placed
on the opposite side of the wheel. As the thimbles grazed that
jar, a spark would again transfer charge, which was of opposite
polarity. Thus the thimbles were simultaneously pushed and
pulled by the high-voltage terminals exactly as was needed to
accelerate the wheel.
Franklin was not altogether happy with his motor.
The reason was that running it required, in his words, "a
foreign force, to wit, that of the bottles." He made a second
version of the machine without Leyden jars.
In this design the rotor consisted principally of a
17-inch disk of glass mounted to rotate in the horizontal plane
on low-friction bearings. Both surfaces of the disk were coated
with a film of gold, except for a boundary around the edge. The
rotor was thus constructed much like a modern flat-plate
Twelve evenly spaced metal spheres, cemented to the
edge of the disk, were connected alternately to the top and
bottom gold films. Twelve stationary thimbles supported by
insulating columns were spaced around the disk to graze the
rotating metal spheres. When Franklin placed opposite charges on
the top and bottom films and gave the rotor a push, the machine
ran just as well as his first design, and for the same reason.
According to Franklin, this machine would make up to 50 turns a
minute and would run for 30 minutes on a single charge.
Jefimenko gives both motors an initial charge from
a 20,000-volt generator. They consume current at the rate of
about a millionth of an ampere when they are running at full
speed. The rate is equivalent to .02 watt, which is the power
required to lift a 20-gram weight 10 centimeters (or an ounce
2.9 inches) in one second.
Jefimenko wondered if Franklin's motor could be
made more powerful. As Jefimenko explains, the force can be
increased by adding both moving and fixed electrodes. This
stratagem is limited by the available space. If the electrodes
are spaced too close, sparks tend to jump from electrode to
electrode around the rotor, thereby in effect short-circuiting
the machine. Alternatively the rotor could be made cylindrical
to carry electrodes in the form of long strips or plates. This
scheme could perhaps increase the output power by a factor of
Reviewing the history of electrostatic machines,
Jefimenko came across a paper published in 1870 by Johann
Christoff Poggendorff, a German physicist. It described an
electrostatic motor fitted with a rotor that carried no
electrodes. The machine consisted of an uncoated disk of glass
that rotated in the vertical plane on low-friction bearings
between opposing crosses of ebonite. Each insulating arm of the
crosses supported a comblike row of sharp needle points that
grazed the glass.
When opposing combs on opposite sides of the glass
were charged in opposite polarity to potentials in excess of
2,000 volts, air in the vicinity of the points on both sides of
the glass was ionized. A bluish glow surrounded the points,
which emitted a faint hissing sound. The effect, which is
variously known as St. Elmo's fire and corona discharge,
deposited static charges on both sides of the rotor.
Almost the entire surface of the glass acquired a
coating of either positive or negative fixed charges, depending
on the polarity of the combs. The forces of repulsion and
attraction between glass so charged and the combs were
substantially larger than they were in Franklin's charged
thimbles. The forces were also steadier, because in effect the
distances between the combs and the charged areas remained
constant. It should be noted that adjacent combs on the same
side of the glass carried charges of opposite polarity, so that
the resulting forces of attraction and repulsion acted in unison
to impart momentum to the disk, as they did in Franklin's motor.
By continued experimentation Poggendorff learned
that he should slant the teeth of the combs to spray charge on
the glass at an angle. The resulting asymmetrical force made the
motor self-starting and unidirectional. When the teeth were
perpendicular to the glass surface, the forces were symmetrical,
as they were in Franklin's motor. When the machine was started
by hand, it ran equally well in either direction.
Poggendorff was immensely pleased by the rate at
which his machine converted charge into mechanical motion. He
concluded his paper with a faintly odious reference to
Franklin's device. "That such a quantity of electricity must
produce a far greater force than that in the [Franklin] electric
roasting spit," he wrote, "is perfectly obvious and nowadays
would not be denied by Franklin himself. With one grain of
gunpowder one cannot achieve so much as with one hundred
Electrostatic motors are now classified in general
by the method by which charge is either stored in the machine or
transferred to the rotor. Poggendorff's machine belongs to the
corona type, which has attracted the most attention in recent
years. Although its measured efficiency is better than 50
percent, Poggendorff regarded it merely as an apparatus for
investigating electrical phenomena. He wrote that "it would be a
sanguine hope if one wanted to believe that any useful
mechanical effect could be achieved with it."
Poggendorff's negative attitude toward the
usefulness of his design may well have retarded its subsequent
development. A modern version of the machine constructed in
Jefimenko's laboratory has an output of approximately .1
horsepower. It operates at speeds of up to 12,000 revolutions
per minute at an efficiency of substantially more than 50
percent. In one form the modern corona motor consists of a
plastic cylinder that turns on an axial shaft inside a
concentric set of knife-edge electrodes that spray charge on the
surface of the cylinder [see illustration at left]. Forces that
act between the sprayed charges and the knife-edge electrodes
impart momentum to the cylinder.
Machines of this kind can be made of almost any
inexpensive dielectric materials, including plastics, wood and
even cardboard. The only essential metal parts are the
electrodes and their interconnecting leads. Even they can be
contrived of metallic foil backed by any stiff dielectric. The
shaft can be made of plastic that turns in air bearings. By
resorting to such stratagems experimenters can devise motors
that are extremely light in proportion to their power output.
Corona motors require no brushes or commutators. A potential of
at least 2,000 volts, however, is essential for initiating
corona discharge at the knife-edges.
C. L. Stong
A smaller and simpler version of the machine was demonstrated in
1961 by J. D. N. Van Wyck and G. J. Kühn in South Africa. This
motor consisted of a plastic disk about three millimeters thick
and 40 millimeters in diameter supported in the horizontal plane
by a slender shaft that turned in jeweled bearings. Six radially
directed needle points grazed the rim of the disk at equal
intervals. When the machine operated from a source of from 8,000
to 13,000 volts, rotational speeds of up to 12,000 revolutions
per minute were measured.
I made a corona motor with Plexiglas tubing two
inches in diameter and one and a half inches long. It employed
stiffbacked single-edge razor blades as electrodes. The bore of
the tube was lined with a strip of aluminum foil, a stratagem
devised in Jefimenko's laboratory to increase the voltage
gradient in the vicinity of the electrodes and thus to increase
the amount of charge that can be deposited on the surface of the
cylinder. I coated all surfaces of the razor blades except the
cutting edges and all interconnecting wiring with "anticorona
dope," a cementlike liquid that dries to form a dielectric
substance that reduces the loss of energy through corona
discharges in nonproductive portions of the circuit.
The axial shaft that supports the cylinder on pivot
bearings was cut out of a steel knitting needle. The ends of the
shaft were ground and polished to 30degree points. To form the
points I chucked the shaft in an electric hand drill, ground the
metal against an oilstone and polished the resulting pivots
against a wood lap coated with tripoli.
The bearings that supported the pivots were
salvaged from the escapement mechanism of a discarded alarm
clock. A pair of indented setscrews could be substituted for the
clock bearings. The supporting frame was made of quarter-inch
Lucite. The motor can be made self-starting and unidirectional
by slanting the knife-edges. Those who build the machine may
discover, as I did, that the most difficult part of the project,
balancing the rotor, is encountered after assembly. The rotor
must be balanced both statically and dynamically.
Static balance was achieved by experimentally
adding small bits of adhesive tape to the inner surface of the
aluminum foil that lines the cylinder until the rotor remained
stationary at all positions to which it was set by hand. When
the rotor was balanced and power was applied, the motor
immediately came up to speed, but it shook violently. I had
corrected the imbalance caused by a lump of cement at one end of
the rotor by adding a counterweight on the opposite side at the
opposite end of the cylinder. Centrifugal forces at the ends
were 180 degrees out of phase, thus constituting a couple.
The dynamic balancing, which is achieved largely by
cut-and-try methods, took about as much time as the remainder of
the construction. To check for dynamic balance suspend the motor
freely with a string, run it at low speed and judge by the
wiggle where a counterweight must be added. Adhesive tape makes
a convenient counterweight material because it can be both
applied and shifted easily.
I made the motor as light and frictionless as
possible with the objective of operating it with energy from the
earth's field. The field was tapped with an antenna consisting
of 300 feet of No. 28 gauge stranded wire insulated with
plastic. It is the kind of wire normally employed for
interconnecting electronic components and is available from
dealers in radio supplies.
The upper end of the wire was connected to a
20-foot length of metallic tinsel of the kind that serves for
decorating a Christmas tree. The tinsel functioned as multiple
needle points. Strips cut from window screening would doubtless
work equally well.
The upper end of the tinsel was hoisted aloft by a
cluster of three weather balloons. Such balloons, each three
feet in diameter, and the helium to inflate them are available
from the Edmund Scientific Co. (300 Edscorp Building,
Barrington, N.J. 08007). The weight in pounds that a
helium-filled balloon of spherical shape can lift is roughly
equal to a quarter of the cube of its radius in feet. To my
delight the motor began to run slowly when the tinsel reached an
altitude of about 100 feet. At 300 feet the rotor made between
500 and 700 revolutions per minute.
A note of warning is appropriate at this point.
Although a 300-foot vertical antenna can be handled safely in
fair weather, it can pick up a lethal charge during
thunderstorms. Franklin was incredibly lucky to have survived
his celebrated kite experiment. A European investigator who
tried to duplicate Franklin's observations was killed by a bolt
of lightning. The 300-foot antenna wire can hold enough charge
to give a substantial jolt, even during fair weather. Always
ground the lower end of the wire when it is not supplying a
load, such as the motor.
To run the motor connect the antenna to one set of
electrodes and ground the other set. Do not connect the antenna
to an insulated object of substantial size, such as an
automobile. A hazardous charge can accumulate. Never fly the
balloon in a city or in any other location where the antenna can
drift into contact with a high-voltage power line. Never fly it
below clouds or leave it aloft unattended.
A variety of corona motors have been constructed in
Jefimenko's laboratory. He has learned that their performance
can be vastly improved by properly shaping the corona-producing
electrodes [see illustration at right]. The working surface of
the rotors should be made of a fairly thin plastic, such as
Plexiglas or Mylar. Moreover, as I have mentioned, the inner
surface of the cylinder should be backed by conducting foil to
enhance the corona. Effective cylinders can be formed
inexpensively out of plastic sewer pipe. Corona rotors can of
course also be made in the form of disks.
One model consists of a series of disks mounted on
a common shaft. Double-edged electrodes placed radially between
adjacent disks function much like Poggendorff's combs. This
design needs no foil lining or backing because a potential
gradient exists between electrodes on opposite sides of the
disks. It is even possible to build a linear corona motor, a
design that serves to achieve translational motion. A strip of
plastic is placed between sets of knife-edge electrodes slanted
to initiate motion in the desired direction.
Notwithstanding the problem of handling potentials
on the order of a million volts without effective insulation
materials, Jefimenko foresees the possibility of at least
limited application of corona power machines. In The Physics
Teacher (March, 1971) he and David K. Walker wrote: "These
motors could be very useful for direct operation from
high-voltage d.c. transmission lines as, for example, the 800 kV
Pacific Northwest-Southwest Intertie, which is now being
constructed between the Columbia River basin and California. It
is conceivable that such motors could replace the complex
installations now needed for converting the high-voltage d.c. to
low-voltage a.c. All that would be required if corona motors
were used for this purpose would be to operate local low-voltage
a.c. generators from corona motors powered directly from the
high-voltage d.c. line."
As Jefimenko points out, a limiting factor of the
corona motor is its required minimum potential of 2,000 volts.
This limitation is circumvented by a novel electrostatic motor
invented in 1961 by a Russian physicist, A. N. Gubkin. The motor
is based on an electret made in 1922 by Mototaro Eguchi,
professor of physics at the Higher Naval College in Tokyo.
An electret is a sheet or slab of waxy dielectric
material that supports an electric field, much as a permanent
magnet carries a magnetic field. Strongly charged carnauba-wax
electrets are available commercially, along with other
electrostatic devices, from the Electret Scientific Company
(P.O. Box4132, Star City, W.Va. 26505). A recipe for an
effective electret material is 45 percent carnauba wax, 45
percent water-white rosin and 10 percent white beeswax. Some
experimenters substitute Halowax for the rosin.
The ingredients are melted and left to cool to the
solid phase in a direct-current electric field of several
thousand volts. The wax continues to support the field even
though the external source of potential is turned off [see "The
Amateur Scientist, SCIENTIFIC AMERICAN, November, 1960, and
July, 1968]. The electret reacts to neighboring charges exactly
as though it were a charged electrode, that is, it is physically
attracted or repelled depending on the polarity of the
Gubkin harnessed this effect to make a motor. The
rotor consisted of a pair of electrets in the shape of sectors
supported at opposite ends of a shaft. The center of the shaft
was supported transversely by an axle. When the rotor turned,
the electrets were swept between adjacent pairs of charged
metallic plates, which were also in the form of sectors.
The plates were electrified by an external source
of power through the polarity-reversing switch known as a
commutator. The commutator applied to the electrodes a charge of
polarity opposite to the charge of the attracted electret. As
the electret moved between the attracting plates, however, the
commutator switched the plates to matching polarity. The
alternate push and pull imparted momentum to the rotor in exact
analogy to Franklin's motor.
Gubkin's motor was deficient in two major respects.
The distances between the electrodes and the electrets were
needlessly large, so that the forces of attraction and repulsion
were needlessly weak. Moreover, during the electret's transit
between electrodes its surfaces were unshielded. Unshielded
electrets attract neutralizing ions from the air and lose their
charge within hours or days.
Both inherent deficiencies of Gubkin's motor have
been corrected in Jefimenko's laboratory by taking advantage of
what is termed the slot effect. Instead of sandwiching the
electret alternately between pairs of metal plates, Jefimenko
employs opposing pairs of adjacent plates [see illustration at
rightt]. The adjacent plates are separated by a narrow slot.
When adjacent plates carry charges of opposite polarity, the
electret experiences a force at right angles to the slot and in
the plane of the electret. The strength of the force is at a
maximum because the electret is close to the electrodes.
Simultaneously the electrodes function as shields to prevent the
neutralization of the electret by free ions.
Motors based on the slot effect can be designed in a number of
forms. One design consists of an electret in the shape of a
wafer-thin sheet of Mylar supported by a flat disk of balsa wood
100 millimeters in diameter and three millimeters thick. (A
long-lasting charge is imparted to the Mylar by immersing it in
a field of a few thousand volts from an electrostatic generator
after the motor is assembled.) This rotor is sandwiched between
four semicircular sectors that are cross-connected [ see
The electret is mounted on a four-millimeter shaft of plastic
that turns in jeweled bearings. The conducting surfaces of the
commutator consist of dried India ink. The brushes are
one-millimeter strips of kitchen aluminum foil. The motor
operates on a few microwatts of power.
Jefimenko has demonstrated a similar motor that was designed to
turn at a rate of about 60 revolutions per minute and develop a
millionth of a horsepower on a 24-foot antenna having a small
polonium probe at its upper end. (By emitting positive charges
probes of this type tap the earth's field somewhat more
efficiently than needle points do.) The performance of the motor
easily met the design specifications. The charm of these motors
lies in the fact that, although they do not accomplish very
much, they can run forever.
ATMOSPHERIC ELECTRICITY. J. Alan Chalmers. Pergamon Press,
ELECTROSTATIC MOTORS: THEIR HISTORY, TYPES AND PRINCIPLES OF
OPERATION. Oleg D. Jefimenko. Electret Scientific Company,
ELECTROSTATICS AND ITS APPLICATIONS. Edited by A. D. Moore.
John Wiley & Sons, 1973.
de la Fondation Louie de Broglie 32 (1 ) : 117 ( 2007 )
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