Here are some of the findings encountered during my experiments
Electromagnetic absorbing material
Current generation by friction
It is known that an intense magnetic or electric field is capable
of influencing the polarization of light (Faraday and Kerr effect respectively). As I did
not have access to neither of them I thought that a lightning would be able to generate
enough current, and hence a strong magnetic field, which could polarize the emitted light.
The picture was taken during a summer storm using a 35mm camera and a 35-85mm zoom set to about 40mm. The film had a 100ASA sensitivity and the stop setting was 4. A polar filter was placed in front of the lens and several shots were taken with the filter set at different angles. The shutter was kept open until one or more lightnings appeared in the field of view. Out of the total number of pictures only one clearly showed the effect of the polarization of light. This appears as a cancellation of the central portion of the lightning, probably it is the place where the magnetic field is more intense. A second lightning further on the right shows the same effect. Unfortunately I did not have the opportunity to replicate the experiment and this is the only proof available.
ELECTROMAGNETIC ABSORBING MATERIAL
If you try to screen an
oscillator coil with a metal screen you get an alteration of the oscillating frequency and
also a decrease of the amplitude due to the damping factor introduced by the screen. An
experimented solution is to wrap the coil with semiconductive material. The material was
prepared using a sheet of paper covered with graphite from a soft pencil. The type of
pencil and the thickness of the deposited layer gives the degree of conductivity.
Incidentally this screen is also effective against outside fields: i.e. an
electromagnetic field will not be able to detect the presence of a metal object if it is
screened by a semiconductive material. Another source of suitable material is recording
tape: ferric oxide or chromium oxide tapes work well and the same applies to VHS
videotapes. Wrapping the oscillator with such a tape gives only a modest damping and the
advantage is that you can increase the screening effect by wrapping more and more tape.
I tried also the thin conductor foil of a disassembled capacitor but conductivity is too
high: probably an even thinner layer of metal would do the job. These experiments are
several years old and I did not experiment with the new metal tapes used in the
"HiBand" standard.
Maybe the Stealth aircraft is not detected by radar because it is "painted" with a semiconductive material and the microwave is absorbed and transformed into heat rather than reflected. The best solution would be in this case to have a multilayered paint: the layer in contact with the body of the aircraft would have a relatively higher conductivity while a second layer would have a lower conductivity.
A sound may appear to move from one
speaker to the other if the sound level is slowly decreased in one speaker and, in the
same time, slowly increased in the other. With this principle in mind I designed a
modulator that changes the sound level fed to three speakers, in sequence. The process was
repeated for the other channel of a stereo system with a total of 6 speakers. Depending on
the positioning of the speakers, you will be able to get a sound depth and spatiality you
never heard before and it will make the most sophisticated surround system sound dull and flat. The period of rotation of the sound should be
adjustable between 1 and 10 seconds depending upon the size of the listening room and the
type of music being played. This is accomplished with a circuit that generates a
triangular signal driving an incandescent bulb. A second triangular signal is triggered at
the peak of the first one, the peak of the second one will start a third signal and the
third will trigger again the first signal and so on. Each circuit will drive its own bulb
(12V 50mA) and one (two for a stereo system) cadmium sulphide photocell placed right next
to it. The photocell will change its resistance, and hence the level fed to the final
amplifiers. Of course, you need also 6 power amplifiers, each driven by the circuit shown
in the picture. The input comes from the preamplifier. The cadmium sulphide element is
very slow but it is quite adequate for this purpose. The bulb never switches off
completely in order to have a quick response from the cell and, in order to avoid the
"pumping" effect, the high frequency content of the sound is bypassed and it is
not modulated. The bulb is not fully on either, this will lengthen the bulb life and will
provide the right resistance for the cutover frequency of the circuit. With this system
you will be able to recreate a true echo and the most incredible effects can be reproduced
by simply placing one of the speaker in another room or mixing the left and right channel.
After a while you will no longer like the music in the traditional way although I found that the voice
sounds a bit unnatural if it wonders about in the room so the system is not suitable to
play vocalist pieces (except for yodeling). The same bulb can drive one speaker of the
left channel and one speaker of the right channel. The original circuit used a total of 16
transistors and was built many years ago. I would think that a new version might use DSP
(Digital Signal Processing) thus obtaining a higher quality and more versatility with the
capacity to exclude one of the channel or to change the depth, hence the effect, of the
modulation or to drive independently the left and right channel. The system will not be
cheap: not much for the cost of the power amplifiers but for the cost of the speakers and
it is suitable only for large spaces: six speakers crammed together is not a nice view and
will not give the best effect.
All this started
with the idea that negatively charged balloons would float in the air and lift up on their
own against the positively charged air, a sort of electric buoyancy. Actually it did not
work, maybe because of the relatively low voltage available (-30KV) or maybe because the
idea was just not right. Instead I got the unexpected result that the charged balloons
would stick to the ceiling for a remarkably long time, several days in certain
circumstances.
In order to charge a balloon you have to rub it against a cloth, curtain, tapestry, whatever, or bring it in touch with the screen of a switched on TV. Next, give it a gentle push until it reaches the ceiling where it should stop and not fall down. The critical part is to calibrate well the push imparted to the balloon, it has to "land" softly on the ceiling: if the push is too weak it will not manage to reach the surface and if it is too strong it will recoil and come down again. If you have difficulties with one balloon try another color: it appears that the pigment used changes the electrical properties of the balloon and this could be the reason why white balloons seem more difficult to place into "orbit". This effect can be used for didactic purposes or simply for entertainment: surprise is guaranteed.
If you set the
camera shutter at 1/1000 or faster, you will be able to record the moment when the light
bulb goes off between on pulse of light and the other. As it is known, light bulbs
pulse with a frequency twice the mains frequency: 120Hz in the States and 100Hz in Europe.
Our eye is not able to follow this fast pulsing but a properly set camera may show exactly
what happens to the light over one or two pulses. The "picturegrams" on the left
were obtained by setting the camera at 1/1000 and then taking the pictures with the lens
wide open, actually if you remove the lens altogether you get a better result as the
picture must be totally out of focus. The camera shutters take a certain time to travel
across the film area and this time, in my case it was 1/60 of a second corresponding to
16.7 msec, becomes the "timebase" of the pictures. In this specific instance the
laboratory where I printed the negatives cut about 10% of the area so the actual timebase
of the picturegrams is reduced to 15 msec but enough to catch the luminosity variation of
the different bulb types. Use a sensitive film: the one used in the experiment had a
sensitivity of 1600 ASA and you must get as near as possible to the light source, possibly
at one end or the other of the bulb. Cameras with a vertical shutter are less suitable for
this experiment and cameras with a lens shutter are totally unsuitable for our purpose.
The original aim of the experiment was to assess if there was a color change in the light
emitted at the beginning or at the end of each pulse, specially in relation to fluorescent
lights, but it appears that such a color change does not take place. Of course there is no
use taking picturegrams of electronic fluorescent lights: they pulse at a much higher
frequency and cameras are not fast enough for them.
Update:
I was told that actually there is a change of colors in the traditional neon
lights. Probably the shutter speed I used was too slow hence I did some new
experiments with a video camera with a shutter speed set at 1/10000 of a second.
There is indeed a color change as you can see from the image on the side. The
left part of the picture is the neon normal color while on the right you can see
the color of the appliance that lasts for a very short time. A faithful color
reproduction was not possible: the original hue is more on the orange side
rather than a plain yellow.
Any plastic will deform easily
when it is pulled or stretched. If you cut thin strips of plastic 6mm wide and 100mm long
out of any thin plastic material, it will reach a length 3 times as long once it is
stretched. This operation can be done manually with a bit of practice. The width of the
stretched plastic will tend to decrease, two to 3 times the original width and the
thickness will normally decrease as well, but not always: if the stretching operation is
made with video tapes, you will find that the actual thickness is almost double the
original. The substantial difference between the unstretched and stretched tape is that
the latter is mechanically more stable and it will not deform easily and could become the
ideal medium for audio and video tapes. I was surprised to find the normal tapes, both
video and audio, can be easily stretched meaning that they did not go any pre-stretching
operation. Suitable plastics could be cut with predetermined width and thickness, then
stretched under controlled thermal conditions thus obtaining a thin film with excellent
mechanical properties. The resulting tape will be thinner than current tapes meaning that
you may have longer reels with a higher recording quality due to the more stable plastic
support. Stretching speed and temperature are the two important parameters that will
influence the quality and dimension of the end product and a good deal of experimentation
must be carried out with different types of plastic material although I expect that the
recording tape already in use is a good starting point.