Category Archives: Science fair ideas

Science Fair Idea: Airfoils

1941SepPS1If Junior likes playing with matches, and the due date for the science fair project is rapidly approaching, then the perfect project can be found in the September 1941 issue of Popular Science. This experiment answers the question, “which surface provides the least wind resistance,” and it turns out the answer is the airfoil.

Junior can easily demonstrate this with the self-explanatory experiment shown here. With the piece of cardboard flat, drag is produced, and when you blow toward the flame, it actually moves back toward you. But when the card is bent into a teardrop shape, scientifically known as an airfoil, then the air blows the flame away.

1941SepPS2



Science Fair Idea: Clothing to Keep You Cool

1941AugPSsciencefairIf Junior just remembered that the science fair project is due tomorrow, and it hasn’t even been started, you’ve come to the right place. This last-minute experiment from 80 years ago will prove an important scientific principle, you have everything you need around the house, and the teacher will be suitably impressed at Junior’s ingenuity. The teacher needn’t suspect that the project was put off until the last minute.

This project answers the simple question, “what kind of clothing keeps you cooler?” It turns out that it’s light colored clothing. All you need is a couple of pieces of cardboard, a table lamp, and a little bit of wax. If you can’t find any wax around the house, you can always go to the closest all-night supermarket and buy a package of birthday candles.

While you are out buying the wax, Junior should cut out the two small human figures, one from a piece of white cardboard, and one from a piece of black cardboard. If you can’t find any black cardboard, just make the both out of white cardboard and color one with a black magic marker. The arms should be made separately, and the arm is attached with a small drop of wax. If Junior is not old enough to play with matches, then an adult should light the candle and place a drop of wax in the correct spot.

Then, you stand up both of the figures and shine a lamp on them. You want the hottest lamp you can find, so don’t mess around with energy-efficient bulbs.

Eventually, one of the figures will get hot enough that its arm will fall off. Unless the laws of physics have changed in the last 80 years (hint: they haven’t), it will be the one in dark clothing. Junior has proven that you will be cooler if you wear light clothing on a hot day.

The experiment appeared in the August 1941 issue of Popular Science.



Science Fair Ideas: Center of Mass & Sound Waves

1936AugPSIf Junior just announced that the science fair project is due tomorrow, but the project hasn’t even been started, there’s no need to panic. Thanks to these simple projects from 85 years ago, it’s still possible to get an A on the assignment, and the teacher will assume that many weeks of planning went into the project.

Shown above is a simple method of determining the center of gravity (or, since the teacher will prefer the more scientifically accurate term, the center of mass) of an object. Cardboard is used, but any similar substance of uniform thickness will work fine. After the pattern is cut out, the design is hung by one edge. A plum line (which is just a piece of string, with a weight on one end) is hung from the same point, and it is traced on the item. Then, it’s hung from another edge. Where the two lines intersect, that is the center of mass.

The other project, shown below, gives a visual indication of sound waves. All that’s needed is a couple of cardboard tubes, a balloon, and some sand. Both projects appeared in the August 1936 issue of Popular Science.

1936AugP2S

 



1941 Optical Communicator

1941AugPS1Eighty years ago, this well dressed gentleman was sending a message through this light beam transmitter, as described in the August 1941 issue of Popular Science.

The magazine was a bit prophetic, since there was more experimentation with the idea after Pearl Harbor. When hams were ordered off the air for the duration of the war, optical communications was one of the ways they continued to practice their hobby (along with carrier current communications.)

The idea is simplicity itself, and it’s an idea that I independently invented as a youngster 30 years later, and I know others did as well. The light beam of a flashlight is modulated with an audio signal by wiring the light in series with the secondary of a transformer. The primary of the transformer is wired with a buzzer and key to send Morse code. When I did the same thing, I hooked the transformer primary to the output of a transistor radio or other audio amplifier, allowing voice signals to be sent.

The receiver is an audio amplifier, with a photoelectric tube hooked to the input. In my later experiments, I used a solar cell hooked directly to the input of an amplifier, which didn’t seem to mind the small DC voltage.

The student looking for an interesting project for a science fair could easily duplicate this experiment with modern equipment, at very low cost.  It’s an easy demonstration of a communications device dependent only upon light.

1941AugPSRx1941AugPSTx



1911 Homemade Alarm Clock

1911JunePopElec110 years ago, a young John Long of Leechburg, PA, sent in this self-explanatory idea for building an alarm clock to the “Young Edisons” department of Popular Electricity magazine.

The magazine carried the feature of letters from readers of its Junior Department. Letters were to accurately and briefly describe experiences in the making and operation of electrical devices and the performance of electrical experiments. The magazine asked readers, “see how good an ‘engineering report’ you can make of your investigations.”

Young Mr. Long constructed this alarm switch with a battery, door bell, and pocket watch.

Some links on this site are affiliate links, meaning this site earns a small commission if you make a purchase after clicking on the link.

Human Reflex Science Fair Project

1941JunePSIf Junior is looking for an interesting demonstration for the first post-COVID science fair, he or she can’t go wrong with this illustration of how human reflexes work.  If you touch a hot stove, your body needs to react before the brain kicks in.  Therefore, you are hardwired to jerk your hand away.

This demonstration illustrates the principle.  A flame is brought close to a simulated human hand, but as soon as it comes into contact with the simulated nerve, the solenoid energizes and jerks the hand away.

The idea appeared 80 years ago this month in the June 1941 issue of Popular Science.  For the young scientist wishing to duplicate the project, all of the parts are readily available on Amazon:  This switch will kick in at 40 degrees Celsius, an uncomfortably warm, but not dangerous temperature.  This 3-volt solenoid will reliably move the hand.  And there’s no need for the old-school dry cell batteries shown above.  Alkaline D cells will work very well, especially if you have a battery holder for them.   And while Junior can make the hand out of cardboard, he or she will be virtually guaranteed the blue ribbon with a realistic looking plastic hand.

Some links on this site are affiliate links, meaning this site earns a small commission if you make a purchase after clicking on the link.

Homemade Cardiac Monitor: 1961

1961JunePEIf Junior is looking for a spectacular science project in the field of biomedical engineering, this one is a sure winner.

Sixty years ago, the June 1961 issue of Popular Electronics showed how to construct this simple cardiac monitor. The circuit was simple, amounting to a 4 transistor audio amplifier. The diagram called for 2N279 transistors, which are apparently unobtainium today, but this substitution guide lists the 2N2431 as equivalent, and it is available at a reasonable price.

The input comes from two electrodes, one of which is placed on each arm. In this position, they will pick up the currents from the heart, which are alternating currents of up to 100 kHz. The audio portions will be audible in the headphones, and also displayed on the meter. The magazine notes that you are not hearing the actual sound of the heart, merely the amplified voltage sent to the heart muscle. Other muscles can be monitored by placing the electrodes on either side of the muscle in question.

The electrodes are simply pieces of metal placed on the body. Prior to placing them, the skin needs to be scrubbed to improve the conductivity. This is done by scrubbing with Lava soap
or Ajax cleanser. (However, since Ajax is now billed as “non-scratching”, I’m not sure it would still work.) The article notes that the device is completely safe, even for children. First of all, it runs off only three volts. And the connection to the electrodes goes through a capacitor, so even that voltage has no pathway to the body.

More advanced versions are available today, but the advanced student will almost certainly bring home the blue ribbon in the science fair by building the medical device at home.

1961JunePE2



Homemade Boxes

1921MayPSA hundred years ago this month, the May 1921 issue of Popular Science showed how to make your own boxes. According to the item, it was frequently the case that you needed a box, but didn’t have one of the proper shape and size. With a piece of stout paper, it was possible to make one yourself capable of containing solids, even paper. And if you needed a container for liquids, the same could be done with parafined paper (what we would call wax paper today).

In addition to the practical uses around the house, the younger student looking for a science fair project could compare the qualities of various types of paper in forming boxes.  Of course, if one needs a box with a lid, a second, slightly larger, box could be made to slip snugly over the first.

The idea had been sent in to the magazine by one Peter P. Lembo.



1941 Electrical Science Fair Ideas

1941AprilPSbuzzerIf Junior wants to take home the Blue Ribbon in the science fair, there’s plenty of inspiration to be found in the April 1941 issue of Popular Science. Some of these ideas might look difficult to some kids today, but the smart students will realize that they are really quite simple. One or more of these ideas is sure to impress the judges.

The idea shown above is a simple buzzer. When the battery is connected, the electromagnet pulls the strip of metal away from the screw. This breaks the contact, and the strip snaps back into place, and the whole process is repeated.

1941AprilPSthermostatShown at left is a simple thermostat.  It’s made of a strip of iron and a strip of copper or brass, bolted together.  When the temperature changes, they expand or contract unequally, causing it to bend to one side.  Simply add an electrical contact at just the right spot, and a circuit will turn on or off at a given temperature.

The self-explanatory experiment to the right uses a thin strip of foil to demonstrate1941AprilPSfuse how a fuse works.  Simply cut it narrow enough so that it blows when a short-circuit is applied.

The experiment shown below is similar to one we featured recently.  It uses a transformer designed to convert 120 volts to 6 volts, but shows that the process can be reversed to change a low voltage to a high voltage.  As in the experiment we showed earlier, a wire is run along a file to create a pseudo-alternating current at the low voltage.

1941AprilPStransformer

The final experiment is also similar to one we’ve shown previously.  A homemade microphone is made by balancing a pencil lead on two razor blades.

1941AprilPSmicrophone

Even though all of these experiments use the old-school large dry cells, they will work just as well with alkaline D cells.  The hookup will be easier if you purchase battery holders.  And don’t forget some wire.

Some links on this page are affiliate links, meaning this site earns a small commission if you make a purchase after clicking on the link.



High School, 1946

1946Apr22LifeShown on the cover of Life Magazine 75 years ago today, April 22, 1946, is Marilyn Rights, a junior at Denver East High School, in her Latin class. She would have been in seventh grade for Pearl Harbor, and most of her high school career took place during the war. The magazine profiled the school, and also took a look at the tension between two competing points of view.

1946Apr22LifeTyping One view, championed by the National Education Association, called for more practical program for high school. Harvard University, on the other hand, called for more emphasis on cultural and academic subjects. The magazine’s focus was on how well the school was measuring up under the two competing plans. Harvard would be pleased to see Miss Rights’ studious attack of Latin, whereas the NEA would probably be pleased with the typing class shown here. The magazine noted that the class was one of the most popular at the school. While it was originally intended for “commercial students,” it was open to other students who learned typing in order to prepare neater homework.

1946Apr22LifeColdCreamAt least one of the courses, practical chemistry, allowed students to learn about cosmetics by manufacturing their own cold cream, probably with a formula such as this one involving borax.

The psychology class appears to be much more interesting than the one I took in college. Here, we1946Apr22LifeMovie see the class on a field trip to see Ingrid Bergman in Spellbound, which deals with psychiatry. They discussed the film in class, and were critical of its superficial psychiatric approach. Those same students were also engrossed in the simple science experiment shown below, demonstrating how sound is transmitted to the ear. The spoon was tapped to the desk to make it vibrate, and the string held to the ear to demonstrate how the vibrations traveled through the string. In fact, elementary students looking for a simple experiment for the science fair can conduct this experiment, which you can see described at this site.

1946Apr22LifeSpoon

Another interesting activity in the psychology class is shown in the sociogram of the class below. Each student was asked to name their two best friends in the class, and these links were plotted on the chart. This revealed that the class consisted of four distinct “cliques,” which were largely independent. Girls 12 and 15 were revealed to be the most popular, with four students each identifying them as a friend. Interestingly, each was member of a separate clique. Girl 25 is identified as a “typical lonely student,” who chose students 4 and 11 as her best friends, but was herself chosen as best friend by no other student. Interestingly, though, she is the only student who links two cliques. One of her friends, 11, is a member of the clique at the left, and her other friend, 4, is a member of the lower clique.

1946Apr22LifeSociogram