EPA photo.

Here’s an idea for students looking for an interesting science fair project, or for those who are simply nosy and want to see if their neighbors are wasting energy.

For those of us who live in cold climates, it’s easy to keep track of how much energy your neighbors are using for heating. For any house with a conventional gas, oil, or coal furnace, there’s an easy indicator telling you exactly when their furnace is running. There’s a vent on the roof of the house, and when the furnace is running, you can see steam rising from it. When the furnace is turned off, the steam quickly disappears. (The water vapor might not be visible when the temperature is high enough, but on cold days, the effect is readily apparent.)

Furnace is on.

This means that just by looking at a house, you can tell if the furnace is on. By keeping an eye on it for a few hours, you can determine what percentage of the time the furnace is running. Families who are conserving energy by turning down the thermostat a few degrees, or those who have well insulated houses, will have the furnace on fewer minutes per hour, saving money and energy.

For a science fair project, the student is usually expected to design an experiment that answers a question. The easiest question would be, “how does temperature affect fuel consumption.” By monitoring on different days with different temperatures, you can make a chart showing that when the temperature goes down, the amount of time the furnace runs, and hence the amount of fuel burned, goes up. Or you could compare different houses, and answer the question of whether a _____ house uses more energy than a ____ house. You can fill in the blanks as you please.

Furnace is off.

Since numerous chimneys are probably visible from your house, you can conduct the entire experiment from the comfort of your own home.

We would be hard pressed to come up with any scientific principle that is established by this demonstration, but it’s a clever illusion, and if Junior’s teacher is the charitable sort, we’re sure that this project would be a most welcome diversion at the next science fair.

The light bulb seemingly glows without being hooked up to anything. As you can see from the diagram, this is accomplished by taking the base from a burnt out bulb and carefully attaching it to another bulb.

The idea appeared 75 years ago this month in the February, 1946, issue of Popular Science.

The young scientist wishing to create a simple but spectacular science fair project is almost assured of taking home the blue ribbon by duplicating the 1919 experiment of German scientist Heinrich Barkhausen establishing the domain theory of magnetism. When a piece of ferrous material is magnetized, it does not magnetize evenly. Instead, tiny pieces of material are magnetized together in discrete pieces. This is known as the Barkhausen effect.

Barkhausen on 1981 East German stamp. Wikipedia image.

To prove this, a coil is wrapped around a piece of iron, and the coil is connected to the input of an audio amplifier. As a magnet is brought toward the coil, static is heard in the speaker. But if the iron core is removed and the experiment repeated, the static is absent. A simulation of the effect can be found at this link.

Replica of Barkhausen’s experiment. Wikipedia photo.

Full instructions can be found in the January 1941 issue of Radio & Television magazine. You will need 38 gauge or smaller enamel wire to wind the coil, as well as an audio amplifier and speaker.

If Junior is looking for a science fair project, the teacher probably wants the students to create an experiment to answer some question. Often, the student is required to submit the question for approval. If the teacher deems the question to be appropriate, then the students are allowed to proceed with the experiment.

Occasionally, teachers have been known to be nitpicky with this process, rejecting questions based upon their personal perception of scientific merit. Therefore, there might be some advantage to proposing a question that the teacher doesn’t understand. Then, they can’t reject the question without revealing their own scientific ignorance.

We can guarantee that Junior’s teacher has never heard of ferroresonance. Therefore, if Junior proposes a project involving ferroresonance, then the teacher is bound to accept. Junior’s question could be something along the lines of: “Can non-linear inductance be used to make a ferroresonant relaxation oscillator?” It turns out that the answer is yes, according to the January 1961 issue of Popular Electronics, and it can be proven by the experiment shown here.

M. Boucherot. Image courtesy of École supérieure de physique et de chimie industrielles de la Ville de Paris.

Ferroresonance was first described in 1907 by French electrical engineer Joseph Bethenod, and named by French engineer Paul Boucherot.

A circuit is resonant when the capacitive reactance and inductive reactance are equal. And normally, the reactance is dependent upon the frequency alone. But other factors, such as magnetic flux of the inductor, can cause non-linear effects at the time when the circuit is initially switched on.

The heart of this experiment is an old choke of more than 1 Henry, capable of handling at least 50 mA. I’m guessing that one could use an old power transformer. Remove the frame to reveal the “E” shaped core inside. From another old transformer, obtain a section of laminations, which will be laid on the top.

According to the magazine, “the point of adjustment is quite critical and requires a bit of patience.” The loose section starts completely on top of the “E”. With the switch on, the bulb should not light. That section is slowly moved, about 1/32 of an inch at a time, with the switch turned off after each move. At the critical point, the bulb will flash on and off at intervals of about 1 second.

Junior will thus have demonstrated that by varying the magnetic flux, he has introduced a non-linearity which causes the circuit to flash.

It should be noted that this experiment involves 120 volt electrical current, so proper precautions should be taken.

The magazine doesn’t show all of the construction details, but if you want to be accused of Russian meddling in the science fair, here’s the project for you. For the young Soviet comrade wishing to take home the blue ribbon in the oblast science fair, the November 1970 issue of Юный техник (Young Technician) magazine gave enough information to build a fax machine. Apparently, it was called a “phototelegraph-integrator”, since that is the title shown here.

Both of the drums are spinning at exactly the same speed.  A scanner is moving across one of them, and a printing element, such as a pen, is moving across the other one, at exactly the same speed.  One of the machines scans a picture of the word Mir (peace), and this is transmitted to the printer, which makes an exact facsimile.

The bright American student can also build a device that can transmit pictures through a wire. The key is to have two drums that are spinning at exactly the same speed. The easy way to accomplish this, for demonstration purposes, is to simply have both of them revolving together on the same shaft. Both of them need to have something that moves along the drum at exactly the same speed. The easy way to do this, for demonstration purposes, is to have the sending and receiving elements connected together with a shaft.

One of those elements needs to have a method to detect the picture. In a fax machine, that’s done with light. But an easy way to do it, for demonstration purposes, is to create the image using aluminum foil. Then, the sensor can be nothing more than a piece of wire that comes into contact with the foil.

This wire is hooked to a circuit which operates a solenoid. The solenoid raises and lowers a pen which comes into contact with the other drum. Whenever the wire on the sending drum comes into contact with the foil, the circuit is closed, and the pen starts drawing on the other drum.

Turn the drum while slowly moving the two sensors. The result will be a drawing exactly the same shape as the piece of foil.

The crude drawing below shows the general idea. An advanced student should be able to work out the invariable bugs and build their own fax machine. When you take home the blue ribbon, the other students will probably accuse you of winning due to Russian meddling. When they do, point out that there was nothing in the rules prohibiting it.

This young woman undoubtedly took home the blue ribbon in the 1960 science fair. And she certainly earned herself considerable street cred as a mad scientist by putting together this Jacob’s ladder, by carefully following the plans in the November 1960 issue of Electronics Illustrated.

As revealed by the schematic diagram below, the circuit is simplicity itself. It simply takes normal household current and runs it into a transformer which steps it up to 12,000 volts, which is fed into two electrodes. One way or another, there is going to be an arc between the two conductors. It will follow the path of least resistance, and thus starts out at the bottom, where the two metal rods are closest together.

The arc heats the air right above it, which ionizes the air. The ionized air thus becomes the new path of least resistance, and the arc moves upward. The process repeats until it reaches the top, at which point a new arc forms at the bottom.

The critical component, of course, is the high voltage transformer. In 1960, it was available in the form of a neon light transformer, for $12 plus shipping. Of course, neon signs still exist, and you can buy the transformers on Amazon.  This modern replacement is rated at “only” 10,000 volts, but it seems like that should be sufficient.

The 1960 article includes a number of important safety features. First of all, the electrodes are safely behind a sheet of 1/32″ clear acetate. This also appears to be available on Amazon.

And the choice of switch ensures that the device isn’t turned on accidentally. The power switch is a momentary switch, meaning that when you let go of the switch, it turns off. It’s a SPDT switch, meaning that when it’s off, another contact is energized. This is wired to a green pilot light that indicates that the device is plugged in. The switch has a safety cover, meaning that one needs to consciously lift the cover to flip the switch.

The article begins by saying that “if the directions given in this article are followed to the letter, there is no danger of shock. Don’t take short-cuts or omit the built-in safety features of this model; it is poor economy to leave out relatively inexpensive components that might prevent a nasty shock.”

These days, when one reads safety warnings, there’s a tendency to ignore them. But in 1960, when a warning like this was included, it’s because the activity in question was, indeed, dangerous, and you really needed to be careful. So I believe this project is suitable for mature students, working under the supervision of a competent adult. But this contraption is potentially lethal, and great care must be taken in its construction and use.  In 2016, a Michigan teen was killed trying to build one, and we don’t want any of our readers to suffer the same fate.  So please be careful.