Category Archives: Science fair ideas

1948 Homemade Transistor

1948OctRadioNewsShown here is a crude but functional homemade transistor from 1948, from the October 1948 issue of Radio News.  While the author had not yet used the fragile device in a working circuit, he did note that he achieved amplification by a factor of up to 50.  The transistor was very unstable at that high amplification, but it did work reliably amplifying by a factor of 15.

The transistor was made of a 1N34 germanium diode carefully broken open.  One lead was kept intact, and the other two contacts were made by making cat whiskers out of filaments of old tubes.

The article cites some 1920s articles where the authors made “amplifying crystals” by a similar means.  By applying the techniques in this article, the advanced student could prepare a science fair project that his or her teacher would probably declare impossible–making a homemade transistor.



Science Fair Idea: Trajectory of Moving Object

1943OctPS2If Junior needs to quickly put together a science fair project, this idea from the October 1943 issue of Popular Science will demonstrate some meaningful science with minimal preparation.  It makes use of two marbles and an old hacksaw blade, although with a bit of ingenuity, substitutions can be made to take advantage of available materials.

The two marbles are placed at the edge of a table and whacked as shown in the illustration.  Obviously, one of them flies off the table much faster and further than the other one.  But by listening to the sound of them hitting the floor simultaneously, it is clear that they are traveling downward at an identical rate.

If the teacher requires a question to be answered by the experiment, it can be something along the lines of:  “Does horizontal velocity of a projectile affect the rate of descent due to gravity?”

Junior will walk away with the blue ribbon, and the teacher will be none the wiser that he waited until the last minute.



Distilling Water

1928OctRadioNewsIf you need some distilled water, it’s usually a pretty easy matter to go to the local supermarket and buy a convenient gallon jug. Or, if you’re willing to pay for the convenience, you can even order it on Amazon.

But it’s also easy to whip up a small batch at home, as shown in this self-explanatory photo from Radio News, October 1928.  The hanging container is filled with cold water, preferably ice water.  It should be as thin as possible.  The spout of the kettle is directed at this container, and the distilled water drips onto a plate below.

The idea was sent in to the magazine by  one C.A. Oldroyd.

If the aspiring young scientist needs distilled water for a science fair project, adding this method to the project will almost guarantee the elusive blue ribbon.



1948 Periscope

1948OctBLFor anyone desiring to see around corners, the periscope is the ideal solution to the problem. 70 years ago this month, the October 1948 issue of Boys’ Life showed how to make this simple but effective model.

In addition to a small wood block, only two parts were necessary.  And if you can’t find them locally, you can order them on Amazon:  Two two-inch mirrors and an 18 inch, 2 inch diameter mailing tube.  For making the precise 45 degree cuts, a miter saw was recommended.  Rounding out the bill of materials was some glue, and black shoe polish to paint the interior angles to reduce glare.

For older scouts, the completed periscope could be a useful tool for any number of purposes.  And for younger students, the project could serve as the basis for an interesting science fair project.

And for the more impatient modern youth, another option is to simply buy the genuine plastic periscope shown here.

 



Wood Burning USB Charger

We recently featured a 1958 Soviet kerosene powered radio and lamented the fact that similar products are not available today.  It turns out, however, that we were wrong.

LufoFirst, a Facebook comment to our original post alerted us to the Lufo lamp, shown here.  This is a kerosene lantern, apparently developed as part of a UN project to provide radio receivers for Africa.  The heat from the lamp operates a Peltier effect device which powers the built-in AM FM radio.

These don’t appear to be manufactured currently, but they are reportedly available in Europe if you look hard enough.

There is, however, one device on the market currently, and it doesn’t even require kerosene!  At Amazon, you can purchase a wood-powered USB charger that uses the same principle. You can then charge your phone using sticks gathered from your yard.

The USB charger appears to be a bit of an afterthought, but also appears to be fully functional. It appears that the Peltier device power supply is intended mostly to power an internal fan that increases the efficiency of the stove. But it also provides usable power, which is available from the USB socket.

The stove also includes an internal 2600 mAh lithium-ion battery to store the charge. According to the Amazon reviews, the stove itself works extremely well.  According to one review, the stove will boil a pint of water in about four minutes, which is quite good for a stove burning nothing but small twigs.   The stove is useful for charging a phone or other device. The fan speed appears to be a trade-off. With the fan on high speed, the stove runs most efficiently, but it also uses most of the current that is produced. It appears that the best compromise for generating electricity is to run the fan on low speed.

For the do it yourselfer, it seems that producing a similar device should be relatively easy and inexpensive.  The Peltier elements are readily available on Amazon.  You can also order direct from China with free shipping at this link.  They’re normally intended for use in applications such as 12-volt coolers, where an electric current is run through the device, where it produces a difference in temperature between the hot side of the device and the cold side.  But this is a case where the physics works the same with a minus sign in front of the equation:  If you generate a difference in temperature, this will cause electric current to flow.

You’ll probably need more than one, and you’ll probably have to experiment with wiring them in series (to increase voltage) and parallel (to increase current) to get sufficient power.  You’ll also need some kind of heat sink mounted on the cold side.  The device will have maximum output when the temperature difference between the two sides is greatest.  So you need to get one side as hot as possible while keeping the other side of the thin device as cool as possible.

Once you have sufficient voltage and current, you can hook the output to a 12 volt USB charger.  Even if you don’t have a full 12 volts, most such chargers are little more than a voltage regulator, so as long as your output is more than 5 volts, you should have a fully functional USB power connection.

To use your new power supply to listen to the radio, you could add the small portable shown here.  When batteries are available, you can use standard AAA batteries.  During the day, you can run it with the built-in solar cell.  And at night, you can plug it in to your wood burning charger with its USB port.

Of course, most of our readers will want to listen to shortwave, and will probably opt for this inexpensive USB-powered receiver  which tunes AM, FM, and 4.75-21.85 MHz shortwave.

In addition to being useful for camping or emergencies, such a project would be excellent for a science fair project.



Science Fair Project: Electricity Through Glass

1938SepPSIf you’re looking for an interesting but slightly dangerous experiment for your science fair project, you’ve come to the right place, with this project from the August 1938 issue of Popular Science. With just a few odds and ends from the hardware store, you’ll be able to cause an electric current to flow through glass.

You’ll need some copper wire (which can be cannibalized from the electric light you’ll be using, as well as some glass tubes.  If you can’t find the glass tubing locally (or “borrow” a couple from your science teacher), then one of the least expensive options appears to be these reusable glass drinking straws from Amazon or these glass test tubes.

You’ll need a lamp cord similar to the one shown here, or you can simply use a normal desk lamp.  Cut one of the two wires leading to the lamp (or plug it into an extension cord and cut one of those two wires), and strip the insulation off the end of the two wires.  Insert each wire into a glass tube.

Of course, glass is an insulator, so the lamp won’t work when plugged in.  But when you hold the two glass tubes next to each other and heat them in a bunsen burner, electricity will begin arcing through the molten glass, and the light will come on.

It appears that what’s happening is that an oxide of the copper is mixing with the molten glass, and the current is using this as an electrical path.  When you remove the glass from the flame, the light will stay lit until the glass again solidifies.

Warning:  This experiment uses household electricity, which can kill you if you’re not careful.  Don’t work in a wet area or anyplace where you can touch a metal object.  Whatever you do, don’t let anyone touch either of the two exposed wires.  When you’re done with the experiment, cut the plug off your modified cord so that some younger kid won’t plug it in and get electrocuted.  Do this experiment only with adult supervision.

 



1978 Solar Oven

1978AugBLForty years ago this month, the August 1978 issue of Boys’ Life carried these plans for a solar oven. According to the magazine, the oven would reach 200 degrees, “hot enough to cook a meat loaf or bake breads in several hours.” The inner and outer boxes were insulated with fiberglass insulation and sealed air tight. The inside of the inner box was painted black with a “non-lead” paint. Four shiny aluminum panels could be used to direct heat into the oven.

A suggested improvement to increase efficiency was to use a double layer of glass with an air gap between the two panes.

If you would prefer to have someone else do the construction work, the solar oven shown at left is you can find  this solar oven Amazon which appears to have good reviews.

 



1968 Radio Shack Battery Kit

1968AugRadioTVExpFifty years ago, the August 1968 issue of Radio-TV Experimenter showed this interesting offering from Radio Shack, a hobbyist kit for assembling two D-cell flashlight batteries.

By all appearances, the finished product is identical to the store’s pre-manufactured “heavy duty” carbon-zinc battery. The only difference is the price, as you apparently had to pay a small premium for the privilege of putting it together yourself:  The kit cost $1.25 for two batteries, but the manufactured article, as shown below in the 1968 Radio Shack catalog, were available four for 98 cents.

1968RScatalogbatteries

Despite the slight extra charge, there is something alluring about making a product at home that’s indistinguishable from the factory version (as is the case with this currently available AM-FM radio kit).  For students thinking about making a homemade battery today, see our earlier post about making a reasonably useful battery suitable for emergency use, or this hundred year old idea for making a homemade flashlight, battery and all.



1938 Pyro Pantagraph

1938AugRadioCraftThis ad for the Pyro Pantagraph appeared 80 years ago this month in the August 1938 issue of Radio Craft. For a mere $2.75, the enterprising young man or woman could go into business and “burn your way to extra dollars.” The burning tool was designed to burn designs onto leather, wood, cork, bakelite, or even gourds. The electric pencil plugged in to any 110 volt outlet, with “plug and cord furnished as part of equipment.”

Pantograph. Wikipedia animation.

But what made the set special was the pantograph, which allowed designs to be reproduced in the original size, enlarged, or reduced, as illustrated by the animation here.

As far as I know, the Pyro Pantagraph is no longer available, but inexpensive wood burning tools such as the one shown here are readily available, as is a pantograph such as this one.  Most modern pantographs appear to be made of plastic, so you’ll need to figure out a way to affix the burning tool.  And most of the negative Amazon reviews are fixated on the fact that the instructions are in Chinese.  But we’re confident that our readers are smart enough to figure these things out themselves, and have no need for the instructions.  You can still burn your way to extra dollars, or this could be the basis for a most interesting science fair project.



More Planning Advice for Time Travelers

Admittedly it’s unlikely that you’ll need the information, but we occasionally provide useful advice to keep in mind in case you’re ever inadvertently subjected to time travel. If you get caught in a time warp, the experience will be much less unpleasant if you do some minimal preparation.

For example, if you get sent back to the past, your situation would be much improved if you could “invent” some modern technology. Columbus could use some better navigational tools to determine that he had not, in fact, reached India.  Louis XVI would have been more likely to keep his head with a telegraph to better manage the affairs of his kingdom.  Just about wherever and whenever you arrive, you’ll have similar opportunities involving people who would be willing to pay handsomely for bits of technology that you can invent.

We’ve previously written about the importance of having a WikiReader, which holds the contents of the English Wikipedia in a handheld device.  And we’ve written about how to make the most difficult component of a radio receiver, the earphone, from scratch.

We’re confident that most of our readers will do well if they’re ever whisked back into time.

How to Figure Out the Date

In many situations, you’ll be able to determine the date easily.  If you’re in an urban area in the past few centuries, you can simply peek at a newspaper.  You can even  ask people on the street what year it is.  They might give you a funny look, but if more than one person gives you the same answer, it’s a safe bet that they’re telling the truth.  If they’re not clear on the concept of the A.D. scale, then you can determine things such as the name of the king, and use your WikiReader to figure out the year.

But in some cases, this information might not be quite so convenient.  Fortunately, the night sky provides a convenient clock, and with a bit of number crunching, you should be able to figure out the date.

Determining the Day of the Year

The first step is to determine the day of the year, and this is quite easy.  You simply observe the local sunrise and sunset times.  The sunrise and sunset times will be the same from year to year, so you can use a reference for any year.  Just note the time of sunrise and sunset, and see which day they correspond with.  You’ll probably come up with two possible dates, so you might need to check again to see whether the days are getting longer or shorter.  In the Northern Hemisphere, if the days are getting longer, then the date is after December 21 but before June 21.  If the days are getting shorter, then it’s after June 21 but before December 21.  The best source of sunrise and sunset times is probably the Old Farmer’s Almanac, although this information should be available in many places.  You can probably find it somewhere on your WikiReader.  Remember, the year of your source is unimportant, since the data will be about the same from year to year.

Determining the Year

The planets. NASA image.

The planets. NASA image.

Now that you know the month and day, you can move to the next step, namely, figuring out what year it is.  For this, you can use the planets.  The planets Mercury, Venus, Mars, Jupiter, and Saturn are all visible to the naked eye.  On any given date, each one of them is supposed to be in a particular spot in the sky, in one of the twelve constellations of the zodiac.   You start by finding these planets and noting what constellation they are in.

At this point, you can go to a website such as Your Sky, start punching in the various possible dates, and see which one corresponds to the observed data.  When you get a match, you know the exact date, at least within a few days.  For example, currently (1 August 2018), Mercury is in Cancer, Venus is halfway between Leo and Virgo, Mars is right between Capricorn and Sagittarius, Jupiter is in Libra, and Saturn is between Scorpio and Sagittarius.

So if I knew it was August 1, I would simply use that date, and repeat the process with different years until I found that the planets matched up with what I was seeing in the sky.  In this case, as soon as I plugged in 2018, I would see that it matched, and know that I guessed the year correctly.

How To Do This Without the Internet

Of course, I’m sure that by now you’ve spotted a big flaw in this strategy.  If you have the internet available, then you can just ask the internet what date it is.  But that website, and others like it, merely employ a relatively simple computer program.  You can find all of the information you need to calculate the same positions by using a book such as Practical Astronomy With Your Calculator or Spreadsheet.  It will contain all of the information you need to do the calculations, either with a calculator or computer, or if all else fails, with pencil and paper.  You can buy the book now, before the time warp.

On the other hand, you’re probably thinking that the likelihood of needing such a book is quite small.  If you don’t get stuck in a time warp, then it’s money wasted, and I would have a hard time arguing with you.  In fact, if you get sent back along with a public library, you’ll probably be able to find a similar book there.

You'll want to use the full size version of this chart, which is available, along with complete instructions, at this link.

You’ll want to use the full size version of this chart, which is available, along with complete instructions, at this link.

But there’s still a minimal level of preparation with practically zero cost!  I found this homework assignment from a college astronomy course.  If you print this out before getting sent back in time, it actually includes all the information you will need to calculate the positions of the five visible planets!  It uses a graphical method:  Right there on the worksheet it gives the position of the planets as of a certain date.  You simply calculate how many times each planet will need to go around to reach that date.  After you do the division, the remainder is the portion of one orbit the planet is away from that spot.  You plot the position of both that planet and the Earth on the provided graph, and you can then see where in the sky the planet is located on a given date.

This method is not as precise as the computer programs, but those computer programs are designed to show you exactly where to point your telescope.  You don’t need that level of precision.  By graphing the general location of several planets, you will be able to confirm what year it is.

You should download (or better yet, print) that worksheet now, before the time warp.

Checking Your Work

PrecessionOfEquinoxesTo confirm that you’ve picked the correct year, you might want to use another method.  It’s possible, for example, that all of the planets were in the same position in the sky on today’s date millions of years ago.  The best way to check your work is to use the precession of the equinoxes.  Simply put, the star Polaris is currently located at the North Celestial Pole.  In other words, all of the stars in the sky seem to revolve around this point.  But the celestial pole moves over time, following a 26,000 year cycle.   You’ll want to print the handy chart shown here.  Match up the pole star with the chart, and you’ll know where you are in the cycle.  For example, if you discover that Vega is the pole star, that means the year is approximately 11,000 BC (or maybe 12,000 AD).