Brain Teaser Challenge - "January" 2010†

Parker Peter was a science nerd. One day his school went for a field trip to a laboratory where they experiment with genetically altered earthworms. As the students were visiting the specimen cases, he discovered that one of the slithering mutants had escaped. Then while he was distracted taking pictures of the lab assistants, the errant annelid managed to sink its fangs (I did say it was a mutant, right) into the unsuspecting Parker. Naturally, Parker experienced only mild side effects as his body was transformed into that of a superhuman with all of the powers of a very large earth worm.

Aside from the ability to asexually reproduce, Wormboy also gained the ability to flatten his body so he could slide under the door to enter a locked room and borough in the soil. His arch enemy, The Bass Fisherman, discovered that passing an electric current through the ground would force Wormboy to come to the surface and reveal his whereabouts. BF decided to measure the bulk resistivity of the soil with four probes 1 cm apart and got 20 ohms. What is the bulk resistivity of this soil?

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† Our friend Butch volunteers a bit too much, he never quite catches up to the current month.

Brain Teaser Challenge - "December"†

Space travel has been the spark of imaginary adventures for over a hundred years. Jules Verne wrote "From the Earth to the Moon" in 1864. A popular film today is "Avatar" which takes place on a hypothetical planet some distance away where a very valuable mineral (unobtainium) is in abundance. One of the things that always bugs me about these science fiction stories is that they always underestimate the sophistication of future technology. Avatar is supposed to take place over 140 years into the future, and the military is still flying around in a type of helicopter and firing weapons that have chemically propelled bullets. And the worst thing is that they miss the target most of the time (also true in Star Trek). I am quite confident that in 100 years we will have fire control systems in handheld weapons that will ensure better accuracy, if only to conserve energy. I can imagine that many of you are hoping that in 100 years the whole notion of weapons is obsolete.

Today we improve the accuracy of air dropped ordnance, and reduce collateral damage, by using a target designator system. Can anyone tell me how these work?

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† Our friend Butch volunteers a bit too much, he never quite catches up to the current month.

Brain Teaser Challenge - "November"†

by Butch Shadwell
Fred Jones was in his last term as an EE undergrad at Whatsamatter U. For his senior project he decided to build a codec that would send 8 bit PCM audio at 2.5 kilobytes per second. It seemed to work pretty well on most male voices, but there was weird distortion with music and some women. Fred may have fallen asleep in his DSP class. What do you think could be his problem? Fred often preferred to be called Stanley Smith for some odd reason, but I am not sure why I am telling you his alternate identification. I have to stop with the clues.

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† Our friend Butch volunteers a bit too much, he never quite catches up to the current month.

Brain Teaser Challenge - "October"†

by Butch Shadwell
When I got started in this business we used multi-meters with a d'Arsonval meter movement that was powered by the signal that was being measured. Of course the voltage that one read from the meter needle movement could be off a bit depending on the source impedance of the signal. They used to rate the meters input resistance in ohms per volt. Some would be 10,000 ohms/v or even higher sometimes.

If I had a multimeter rated at 1000 ohms per volt, set on the 10 volt range, what voltage would I read from the dial if I measured the voltage at the middle node of a voltage divider composed of two 10,000 ohm resistors in series, across a solid 5 volt DC supply? Later I bought a VTVM or vacuum tube volt meter, with a fixed input resistance of 11 megaohms.

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† Our friend Butch volunteers a bit too much, he never quite catches up to the current month.

Brain Teaser Challenge - "September"†

by Butch Shadwell

Little Schlomo had nothing on his mind as he rolled the wheel down Pearl Street with his stick. The sound this perfect circle made as it rumbled along, drew his thoughts away from here and now. It was 1889, and for a ten year old in New York, life was lived in the street, and things were hard. Uncle Lenny, who had been living with his family for as long as he could remember, was sure his ship would come in any day now. Even though he knew it was rubbish, sometimes Schlomo would enjoy listening as his uncle would explain his latest get rich quick scheme. It was on a Tuesday, as he heard his Uncle Lenny describe his new electric light business. As you know, light bulbs were pretty expensive, about a dollar a piece, and they didn't really last that long. Lenny's idea was to sell folks lower voltage light bulbs which were a little cheaper and would last a little longer. He planned on buying transformers to reduce the voltage. What turn ratio did he need to run 25 volt bulbs? Hope you remember your electrifying history.

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† Our friend Butch volunteers a bit too much, he never quite catches up to the current month.

Brain Teaser Challenge - August

Sorry I missed a month with the BTC. My biggest vice is that I volunteer too much, and my volunteer work has been dominating my time. I guess this column is one of my volunteer jobs, now that I think about it. Anyway, some folks have asked me to mention that one of my big volunteer jobs is as the new international chair of the Humanitarian Technology Challenge, Reliable Electricity Committee. This project is sponsored by the United Nations Foundation and the IEEE. We are a large group of volunteer professionals and academicians who are dedicated to finding better ways to help people in need by the application of technology. These could be disaster victims or people who have never had infrastructure of any kind. Lighting, better food and water, communications, and better medical care are among our objectives.

I was recently asked about consulting on a project to collect deuterium from the ocean. We all know that deuterium is found in much higher concentrations in the sea than in the atmosphere. Perhaps the heavier molecules find it harder to make the transition from liquid to gas phase on the surface, so most of the evaporation is of the lighter isotopes. So the problem today is - how big a container do I need to hold 1 mole of H2 at STP? Don't light a match.

Reply to Butch Shadwell at b.shadwell@ieee.org (email), 904-410-9751 (fax), 904-410-9750 (v), 3308 Queen Palm Dr., Jacksonville, FL 32250-2328. (http://www.shadtechserv.com) The names of correct respondents may be mentioned in the solution column.

Brain Teaser Challenge - "June"

I attended a conference recently at the National Academy of Sciences in Washington DC, called the Humanitarian Technology Challenge. It was sponsored by the IEEE and the United Nations Foundation, among others. The objective was to organize volunteers from around the world to come up with better ways to apply technology to relieving human suffering.

Even though I am not really a power guy, I found myself engaged in a number conversations about power quality. We were talking about the amount of energy that gets converted to heat from harmonic distortion of the power waveform. Your challenge this month, should you choose to accept it, is to explain why most of the harmonic energy you find on the power mains is in the odd harmonics of the fundamental?


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Brain Teaser Challenge - "May"

I just got back from the international science and engineering fair in Reno a couple of weeks ago. What an amazing event! This was my third one in a row and it never fails to impress me. The really impressive part is not that the projects are so technically advanced, though many are, it is that these 1500 kids from all over the globe are so uniformly wonderful. Great looking kids, very polite, articulate, most of whom for which English is not the first language, it is amazing. In my opinion there is no other event that so clearly demonstrates that there is great hope for the human race. And even though every one is a fierce competitor, they consistently look after each other and help each other when they can.

I helped to escort ten kids from my community to the fair. As you can imagine I took a lot of pictures and HD video. Most images and video stored and reproduced digitally, such as JPEG and MPEG, use a lossy type of data compression. This is accomplished through a mathematical transform that converts the image information into coefficients of sinusoids at various frequencies. Can you name this mathematical transform?


Reply to Butch Shadwell at b.shadwell@ieee.org (email), 904-410-9751 (fax), 904-410-9750 (v), 3308 Queen Palm Dr., Jacksonville, FL 32250-2328. (http://www.shadtechserv.com) The names of correct respondents may be mentioned in the solution column.

Brain Teaser Challenge - "April"

I recently had to spend the night in the hospital. I didn't really feel that sick, but I had had some strange symptoms earlier and they wanted to do some tests to try to understand what had happened. I left the next day having had a very bad night's sleep and a huge barrage of tests. Though they were efficient and thorough, no one really knew what had caused my symptoms two days prior. I think this happens a lot in medicine. That is, they see some symptoms and they do their best to explain them. Then for all their best efforts and the latest technology, no one really knows. I feel blessed that no one suggested treating me for their best guess of what the problem might be.

In an earlier part of my career I did R&D in nuclear medicine, specifically gamma imaging. This is not taking pictures of gamma rays, but rather using gamma rays to take pictures inside of your body. Technetium-99m is a common radionuclide used in such imaging. As it turns out, most of the technetium used in medicine is harvested from a device called a cow as a by-product of another radionuclide called molybdenum-99. Our question this month is how does molybdenum-99 become technetium-99m? Hope you don't glow in the dark.


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Brain Teaser Challenge - "March"

These brain teasers get printed in newsletters around the world. In some of these places English is not the first language. I don't think anyone is doing an official translation. So I sometimes wonder if those readers having to translate it for themselves have a hard time making sense of my stories and humor. To be fair I have considered sending out the column alternately in Hindi, German, Chinese, etc., so as not to show favoritism to the native English speakers. Then I remembered that I am not really fluent in all of these languages and I don't even own an English-Chinese dictionary.

Anyway, let's get to the problem. I attended a conference on weather modeling the other day, a very interesting physics and math problem domain. These calculations are sometimes done in order to predict the path of hurricanes and tornadoes. So, after a 100 pound woman is airborne, how long does it take her to get from 0 to 30 MPH if she has a constant net horizontal accelerating force from the wind of 100 pounds(force). Obviously the wind is building during her entire flight. You can ignore wind drag and all other forces for this problem. I am using English units in order to add to the challenge, maybe metric next time.


Reply to Butch Shadwell at b.shadwell@ieee.org (email), 904-410-9751 (fax), 904-410-9750 (v), 3308 Queen Palm Dr., Jacksonville, FL 32250-2328. (http://www.shadtechserv.com) The names of correct respondents may be mentioned in the solution column.

Brain Teaser Challenge - "February"

I am on an astrophysics blog site, and occasionally am asked to add a little extra physics expertise to the discussion. In one discussion a blogger asked about the possibility of having a hollow earth. Letís discuss a few things about the real earth first. Most of the heaviest elements that are found on the earth are concentrated toward the center of our planet, due to their higher density. These heavier elements also happen to be the ones that are radioactive. Most scientists today believe that the heat that keeps the center of the earth molten is generated by the nuclear decay of these heavy elements and probably a slow rate of nuclear fission too. So the center of the planet is quite hot and has a deadly level of ionizing radiation. It is actually a much more hostile environment than outer space. Even if we could open up an empty sphere, it would be a very uncomfortable place to sit.

The question I was asked to comment on in this blog thread was, what kind of gravitational forces would one feel in this hollow earth scenario? Imagine the sphere is relatively small, say eight feet in diameter. Donít forget your lead underwear and a high power air conditioner.


Reply to Butch Shadwell at b.shadwell@ieee.org (email), 904-223-4510 (fax), 904-223-4465 (v), 3308 Queen Palm Dr., Jacksonville, FL 32250-2328. (http://www.shadtechserv.com) The names of correct respondents may be mentioned in the solution column.

Brain Teaser Challenge - "January"

by Butch Shadwell
Have you ever wanted to be a tap dancer? I hadn’t thought about it much until I saw Michael Flatley and his team in River Dance. It is literally poetry in motion. As I watched the show I could feel the Irish branch of my family tree swaying to the music.
Some of you may recall that I am a bit of a thespian. I have been in over 65 shows including 6 musicals. Though I have done a little tripping over the floor boards, I haven’t ever done any tap. However, I have seen how they mike tap performances. They use a device known as a PZM or pressure zone microphone. This type of mike has a design that limits how much sound is generated by vibration or movement of the microphone assembly itself. There is a small pressure zone sensor that can pick up sounds that are carried from other directions than the mounting structure.
In a condenser microphone element if the increasing sound pressure increases the capacitance, what kind of voltage change is observed on the microphone element as a high pressure wave passes?
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Brain Teaser Challenge - November

by Butch Shadwell

I was just watching one of those reality shows on TV. This one had a dozen American city girls trying to win the heart of an Australian fellow from the outback. It was very amusing. These girls came from all sorts of backgrounds and educational experience.
Some of the young debs were upset that they could not plug in there hair dryers while living in the bush. One even had to redo her own nails … a first for her. As luck would have it, one girl had been in the Girl Scouts and one of her merit badges was in electricity. The producers of the TV show found a car battery and a power inverter to aid with the hair blowing emergency. This inverter produced a 60 Hz sine wave at 120 vrms, 15A max. The instructions said that it will not handle loads with a PF less than 0.9. If the hair dryer says that it draws 1000W or 1200 VA, will the inverter carry the load? For extra credit what is the angle between the current and voltage waveforms on this appliance? Our Girl Scout got it right.
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Brain Teaser Challenge - October*

by Butch Shadwell

Once upon a time there lived a great green ogre in the woods at the end of the dale. From birth the children of the village were told stories of this horrible creature and what happens to those who venture too close. Because everyone in the village had been so indoctrinated from birth, no one still living in the village had been into the woods to see if the ogre was still there. The stories that had been passed down made such a journey unthinkable.
One day the people of the village were threatened with destruction as the sun was getting cooler and the winter was colder than any they could recall in over a hundred years. To get fuel to heat their homes folks had to chop trees closer and closer to the dreaded ogre’s lair. One day the inevitable confrontation occurred. As one woodcutter ventured further into the woods than anyone had before he came upon a small house. The woodcutter screwed up his courage and knocked on the door. To his relief, it was not an ogre who answered, but an average built older man with circular spectacles. Upon entering the home the woodcutter was amazed how comfortable the temperature felt, and at the array of unusual gadgets about the room.
It turns out that this wood was home to an engineer. The rumors of an ogre were started over the fact that many of the village people were afraid of math and science. It was difficult and better kept at a distance. After hearing of the village’s problems with the weather, the engineer decided to help. He told them about insulation and how to store heat in water during the day so they could use it at night. If a villager was able to heat 10000 liters of water during the day using his solar panels to a temperature of 60 degrees C, how many BTUs would be released as heat as the water cooled to 20 degrees C? It’s funny sometimes how things we fear can be worth getting to know better.
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* We seemed to have gotten behind on the challenges and answers. As of November, the October edition was the last one that Butch had sent out. Figure that one out:) - Webmaster.

Brain Teaser Challenge - September*

by Butch Shadwell

Certain times of year you can see many small meteors falling to earth, streaking to the surface from somewhere out in space. There is a theory that in fact life on this planet may have been seeded through DNA from space. The first microbes would have been based on these biological codes and then more complicated organisms evolved as different genes were expressed.
The thing about DNA is that most of it is not used in the life span of most organisms. Different genes only express themselves in the physiology of the organism when they are activated by chemicals in the vicinity. Your genome may include genes for a hairy body and arms that reach your knees, but these do not express themselves in most of us (rotten luck Fred).
Electrophoresis is a technology developed many years ago to sort protein molecules based on their mass. It involves straightening and coating each molecule with a negatively charged chemical, then placing the samples into a gel. Then an electric field is applied. The smaller molecules are more mobile in the viscous gel and so migrate more quickly toward the positive electrode. The result is that you get bands made up of molecules of the same mass at various distances from the starting point.
Your chemistry question today is: what does it mean if some of these molecules are isomers?
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* We seemed to have gotten behind on the challenges and answers, so here is the last few. As of October, the September edition was the last one that Butch had sent out. Figure that one out:) - Webmaster.

Brain Teaser Challenge - August*

by Butch Shadwell

I am so tired of all of the typographical errors and occasional grammatical faux pas that I read in these columns. I think somebody should do something about it.
Over the years I have invented quite a number of new technologies, circuits, systems, algorithms, etc. A small percentage of them have been patented with the US Patent and Trademark Office. The thing is that whenever I am filing for a patent on something, I suddenly find that I have a lot of writing to do. And it’s not only technical writing, but rather a strange legalistic version of a technical description. Another thing about writing patents is that you need to describe every detail of your invention so that someone with ordinary skill in the art can make one for themselves. The problem arises when you find out that the patent examiner assigned to review your claims, may not have that skill level. So you have to keep on writing.
I used to do R&D in electronic warfare. I designed a circuit once that used the voltage across a diode junction to get the log of an input sine wave function. That signal was amplified 2X and then that voltage was applied to the base of a bipolar transistor, where the collector current is proportional to antilog of the change in voltage applied to the base. What does the voltage across the collector resistor look like? In the old days we did some pretty cool math with analog components. Assume that all four quadrants are covered.
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* We seemed to have gotten behind on the challenges and answers, so here is the last few. As of September, the August edition was the last one that Butch had sent out. Figure that one out:) - Webmaster.

Brain Teaser Challenge - July*

by Butch Shadwell

We bought a new 61” HDTV last Christmas. It is the DLP type, though it has some interesting innovations. Instead of the usual projector lamp and color wheel for the light source, this set uses three high output LEDs (red, green, and blue). No color wheel and motor and no projector lamp to replace. Incase you are not familiar with DLP TVs, DLP stands for digital light processing. It is based on the use of a MEMS (micro electro mechanical system) device with 2,073,600 tiny mirrors that can be electro-statically moved. The mirrors are adjusted 360 times per second successively displaying the red, green, or blue components of the image, so that we get up to 120 complete display frames per second. The amount of red, green or blue light that is added to an individual pixel (picture element) by its respective mirror, is controlled by how long the mirror allows that color light to project to the screen. Each mirror pulse width modulates the light to control how much red is blended with how much green and blue. Your eye integrates these pulsing light sources into 10,000 levels of brightness for each of the three color components.
Let’s say that my high output LEDs have a forward voltage drop of 4 volts at 25 degrees C at the junction and the forward voltage drops 3mV per degree C. Then I supply forward current to one of these LEDS through a 100 ohm resistor and a 10VDC source. So tell me the current through the LED when the junction gets up to 100 degrees C? I know this is a simple one, but I have been struggling with writers block. Good luck.
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* We seemed to have gotten behind on the challenges and answers, so here is the last few. As of September, the July edition was the last one that Butch had sent out. Figure that one out:) - Webmaster.