Kirchhoff voltage law corrected for radiating circuits

 The power spectrum showing its line width as function of the total resistance that include magnetic and electric radiation

The power spectrum showing its line width as function of the total resistance that include magnetic and electric radiation

Vitor Lara, Kaled Dechoum
When a circular loop composed by a RLC is put to oscillate, the oscillation will eventually vanish in an exponentially decaying current, even considering superconducting wires, due to the emission of electric and magnetic dipole radiation.
In this work we propose a modification on the Kirchhoff voltage law by adding the radiative contributions to the energy loss as an effective resistance, whose value is relatively small when compared to typical resistance value, but fundamental to describe correctly real circuits.
We have also analysed the change in the pattern of the radiation spectra emitted by the circuit as we vary both the effective and electrical resistance…
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A Tiny Speaker Printed on a Single Sheet of Paper

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Coralie Gourguechon created a paper speaker and amplifier. Image: Coralie Gourguechon

If you’re the tinkering type, you’ve probably deconstructed a fair number of electronics. It doesn’t take a genius to tear apart a radio, but once you get past the bulk of plastic packaging and down to the guts, you begin to realize that reading the mess of circuits, chips and components is like trying to navigate your way through a foreign country with a map from the 18th century.
But it doesn’t have to be so complicated, says Coralie Gourguechon. “Nowadays, we own devices that are too complicated considering the way we really use them,” she says. Gourguechon, maker of the Craft Camera, believes that in order to understand our electronics, they need to be vastly simpler and more transparent than they currently are.

Which is why the France-based product designer decided to totally deconstruct them. In her most recent project, Gourguechon has created a series of paper electronics—an amplifier, speaker and radio—stripped down to their most basic components and fitted onto a single sheet of paper. “The idea was that the sheet of paper become the object, with no complicated assembly needed,” she says.

The anatomy of each gadget’s operating system is outlined in bold icons, like an anatomical roadmap that teaches users how to build the object. Each graphical representation has a function: the circuit icons teach users what connects to what, the anatomical chart shows the inner workings of the components and the patterns of the paper modules help users to shape their own paper circuit. “I saw this as a map, that could help for the assembly of the product, or in order to repair it,” she says.

All of the components are linked together through a series of lines that are printed with conductive ink, which allows the paper electronics to actually function. To turn the speaker on, for example, you pop out the sound cone in order to amplify your input. To close the circuit and turn it off, you simply lay the cone flat.

It’s hard to believe, but the devices are totally functional, if a little on the weak side. “It does sound quite good considering the simplicity of the device; of course it’s not as clear as a regular speaker, the sound is lower and low frequencies do not go out very well.”

Though this is just a prototype, Gourguechon says that she can envision a day where paper electronics could be part of a massive database of pattern modules that users could simply print out and assemble. I’m particularly interested into open systems and about the oncoming technologies that could help building this alternatives,” she says. I’m looking forward to the progress of printed electronics, both 2D and 3D. I hope that we will find an effective way of solving the problem of electronic waste, which is growing quickly.”

The Motion of a Pair of Charged Particles

chargeJ. Franklin, C. LaMont
We re-visit the problem of two (oppositely) charged particles interacting electromagnetically in one dimension with retarded potentials and no radiation reaction.
The specific quantitative result of interest is the time it takes for the particles to fall in towards one another.
Starting with the non-relativistic form, we answer this question while adding layers of complexity until we arrive at the full relativistic delay differential equation that governs this problem.
That case can be solved using the Synge method, which we describe and discuss.

Experimental determination of circuit equations

Jason Shulman, Frank Malatino, Matthew Widjaja, Gemunu H. Gunaratne
Kirchhoff’s laws offer a general, straightforward approach to circuit analysis.
Unfortunately, use of the laws becomes impractical for all but the simplest of circuits. This work presents a novel method of analyzing direct current resistor circuits.
It is based on an approach developed to model complex networks, making it appropriate for use on large, complicated circuits. It is unique in that it is not an analytic method.
It is based on experiment, yet the approach produces the same circuit equations obtained by more traditional means.

New insights into what triggers lightning

What initiates a lightning strike? In the image above, multiple cloud-to-ground and cloud-to-cloud lightning strikes are observed during a night-time thunderstorm. (Courtesy: NOAA)

What initiates a lightning strike? In the image above, multiple cloud-to-ground and cloud-to-cloud lightning strikes are observed during a night-time thunderstorm. (Courtesy: NOAA)

Cosmic rays interacting with water droplets within thunderclouds could play an important role in initiating lightning strikes. That is the claim of researchers in Russia, who have studied the radio signals emitted during thousands of lightning strikes. The work could provide new insights into how and why lightning occurs in the first place.
Although most people have witnessed a flash of lightning during a thunderstorm at some point in their lives, scientists still do not completely understand what triggers the discharge in the first place. Lightning has been studied for hundreds of years, yet while many possibilities for observation are available – there are about 40 to 50 lightning strikes per second across the globe – predicting the onset of a strike is difficult…. Read more at

How To Steer Sound Using Light

The ability to create phonons and then steer them using laser beams could lead to a new generation of applications, say physicists

Zap an optical fibre with a couple of laser beams and the resulting interference pattern causes an interesting effect–it squeezes the material, an effect known as electrostriction. This creates a compression wave called a phonon, a packet of sound, which travels along the fibre.

Not to be outdone, phonons also influence light because they change the refractive index of the material. This bends light and alters its frequency, an effect known as Brillouin scattering.

After that, things get complicated. This mechanism sets in train a complex set of feedback effects in which photons generate phonons which influence the photons and so on.

The problem is understanding what’s going on. The ability to influence sound with light, and vice versa, could have interesting applications. But without an accurate model of this phenomenon, it’s hard to exploit.

That looks set to change. Until now, physicists have sought to understand the phenomenon by assuming the phonons have a particular form and working out how this influences the incident light. In other words, they ignore feedback effects.

Today, Jean-Charles Beugnot and Vincent Laude at Université de Franche-Comté in Besançon, France, take a more detailed at look the problem.

For the first time, these guys simulate how light generates phonons inside an optical fibre and how the phonons then interact with the light that generated them. They then test their ideas by measuring the way phonons scatter light in two types of fibre.

Their conclusion has interesting implications. They say that the light ends up guiding the phonons that it creates. In other words, it’s possible to create and then steer sound using light. “The phonon wavepacket generated via [electrostriction] is naturally guided by the light that gave it birth,” say Beugnot and Laude.

These guys aren’t very forthcoming with potential applications but it doesn’t take much imagination to speculate. Engineers already use light to reduce vibrations in mirrors, cooling them close to absolute zero.

Beyond this,the most exciting application is in information processing. In this field, there is  growing interest in controlling phonons because they are essentially noise generated by heat.

Controlling phonons would allow them to be steered away from sensitive areas. More ambitious still is the possibility of computing with phonons, with various groups around the world working on phonon diodes and transistors, the building blocks of logic gates.

Progress so far is tentative but that could soon change. Other suggestions in the comments section please.

Ref: Electrostriction And Guidance Of Sound By Light In Optical Fbers

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