A Child’s Magnetism
Our Earth’s magnetic field is one of the planet’s fundamental properties. It is a property on which all life depends, and a property which more than a few animals and insects sense directly and by which they navigate. Plants also respond to it. Through instrumentation, we humans have learned to use it as well. Magnetism permeates our technologies, literally. Magnetism is, in fact, one of the natural world’s primordial forms of Energy.
Yet in most primary classrooms of any type, a child is likely to find little more than a bar or horseshoe magnet in a basket of random objects…or perhaps a compass, or some magnetic letters. Another occasionally encountered design is that of construction sets in which magnetism is the method of connecting the structural pieces. Such things do more to obscure the properties of magnetism than to reveal them. A magnet is more than a piece of sticky metal, or even more confusing, a piece of sticky metal hidden inside a piece of colored plastic.
The Montessori Method teaches the primary child about the Earth extensively: the natural world, its general appearance and geography, its position in the Solar System, birthdays as they relate to a trip around the sun, land and water forms, weather, and the inhabitants of the biosphere, all creatures great and small. However, the primary curriculum does not recognize magnetism per se, as if the magnetic field to which animals and plants react is in some way less natural than the creatures themselves. And yet, the method is quite easily adapted to the presentation of magnetism, just as it can be adapted to the presentation of electricity; see A Child’s Electricity.
What are the basic properties of magnetism and how can they be presented in a primary, or early elementary, classroom? How can they be related to other aspects of the child’s natural and human-made world? How does magnetism work with the other forms of Energy described in A Child’s Physics?
Magnetism is Tactile
The hand is the tool of the intellect and the beauty of a magnetic field is that the child can feel it. Therein lies the wonder, the point of interest. A magnetic field is invisible to the eye but real to the hand, which is why painting one magnetic pole red and the other blue is one of the last things we should do. Remove the visual clues.
Let the child use actual magnetic interactions to realize the existence of the extrasensory field and from these experiences construct an awareness of magnetic properties. Provide exercises that reinforce the sensation of a field effect.
Magnetism is like angular momentum. You’ve got to hold a spinning gyroscope in your hand and try to turn it to really get what’s happening. No amount of math provided later in education can have the impact of two magnets that cannot be forced to touch, or the surprise and delight at the acceleration of two magnets as they approach and click. Without that experience, the math will be empty. If that experience is delayed, it will eventually seem trivial.
There are a number of magnetic desk toys, many of which are, frankly, pretty cool and over time these can supplement classroom materials. A few, like a levitating magnetic top, can develop advanced fine motor skills while combining multiple concepts: in the case of the top, the stability of angular momentum in a magnetic field. Others can confuse, obfuscate and seem like magic. Primary teaching materials should reveal basic physical realities in simple, independently repeatable demonstrations.
The Primary Aspects of Magnetism
Remember not knowing and begin with…
Action at a distance: the presence of a real, invisible field of force. This is the magnetic counterpart to the electrostatic force field demonstrated in
A Child’s Electricity.
Isolated Attraction: the idea that a magnet pulls.
The simplest thing to do is to hang a ferromagnetic object, like a paper clip, and then move it with a hand held magnet. Banana hooks are inexpensive and and can be visually appealing. Like a set of graded tuning forks, or a set of glass lenses, they compliment the Montessori equipment aesthetic.
The child can also fix the magnet to the base and defy gravity. Then, take the object out of the field and put it back. It’s that simple, interesting and challenging. Presented in the sensitive period this activity will produce the spontaneous, sustained repetition that is the hallmark of Montessori design.
Hanging a metal chain provides the experience of a magnetically sustained oscillation and so provides another example of the transverse wave concept, also presented in the vibrating rod and the slinky exercises. It presents the possibility of containing a sustained, stable Motion within a magnetic field. The manual dexterity required, the ability to manipulate an object magnetically without actually touching it is a challenging and stimulating control of error. It is also the fundamental phenomenon underlying a myriad of scientific and industrial equipment.
Isolated repulsion: a magnet can push
Magnets not only pull, they push, and that field effect can be isolated as well. Two ring magnets on a straw will do, but a proper shelf work might look more like this magnet bouncer. Again, the essence of this work is manual dexterity developed through real action.
While the magnet stacker, below, is focused on process, the magnetic bouncer, like the plasma ball in A Child’s Electricity, is impressionistic. One of the basic impressions to be gained is the consistency of magnetic interaction. When released, the magnets will return to the same point of equilibrium for any given orientation of the bouncer.
Polarity
The universality of magnetic dipoles is one of our fundamental scientific assumptions. As far as we know, there is always a north and a south. But they are not red and blue. The idea of a polarity exercise is that opposition and attraction be rediscovered through the hands in each use.
A magnet stacker is a common enough toy, usually presented in arbitrary numbers, distracting materials and colors with no regard to control of error or containing the pieces of the work within the exercise. The design above illustrates simplicity, isolation of idea and independent control of error. It can stand alone in any type of classroom, but again, integrates well with the larger Montessori equipment set.
Interaction with Elements and complex materials
The basic idea is that, while magnets do attract, they do not attract everything. If you give a child a magnet and an identically, or even randomly shaped piece of iron, the child has no way of telling which actually has the attractive force.
This exercise presents elemental materials, additionally described in A Child’s Elements, in comparison to complex combinations of elements in a consistent shape and size. This design uses the idea of tablets, like the Montessori baric tablets, in order to isolate the concept which is the variability of magnetic interaction. Shown here are tin, copper and acrylic plastic. Other materials like glass and wood can be easily added to a the set. It is important that conversation include which of the materials are elements and which are combinations. This exercise is the opposite of the basket of random objects approach to magnets. The idea is to isolate the relationship between the material and the magnetic field. The child’s attention is drawn to the material by eliminating differences of shape and function.
At the primary level, the first differentiation is between ferromagnetic and non-ferromagnetic materials. Either the material reacts to a magnet or it doesn’t. Diamagnetic materials represent an advanced concept requiring the idea of Induction, which is introduced below and also occurs in A Child’s Electricity.
Ferrofluid
It is important that different forms of energy be shown in relation to different states of matter. Just as we show the child that water conducts electricity and that tubular circuits conduct the flow of water, we want to show that magnetic fields flow through and can shape liquids.
This develops the visualization of the field and awareness of states of matter. It is analogous to using sand to reveal the vibration of a drum head. The example shown here is for DYI enthusiasts. There are commercially produced items that are relatively inexpensive and readily available.
If the teacher is open to the use of video, the child’s experience can be enhanced by the presentation of Ferrofluid Sculpture, which can be quite beautiful.
Shape of the field versus shape of the magnet
Magnets should also not be presented in only one shape. Doing so encourages the mistaken assumption the the shape of the object reveals the orientation of the field. It does not.The goal is that the child recognize the existence of the field and begin to visualize it.
There are any number of simple devices available that will display the presence of a magnetic field, usually through the use of contained iron filings. Most of these are just fine as visual reinforcements, but once you’ve moved the magnet around a little bit, that’s about it for the activity.
The goal is to provide an interactive exercise, a process that has a goal, that encourages repetition, and has a control of error. The bowl uses ellipsoidal magnets and develops the awareness that the polarity happens to exist through the short axis of the object.
The addition of a spherical magnet further develops the idea of field as related to shape. It offers another dynamic game of skill and presents the idea of induced motion decreasing to equilibrium.
Imaging and Measurement
Magnetic imaging is a major tool in modern technology. The easiest way to introduce magnetic imagery is with magnetic viewing film. It can be used to reveal magnets inside common objects, like toys, refrigerator stick-ons or….
Magnetic film is somewhat vulnerable, so a suggested shelf work is to contain a large piece in a freestanding plastic picture frame, also how colored filters are presented in A Child’s Light. This frees the child to use both hands behind the film to manipulate and examine various objects.
Images do have to be erased
and this presents a rather entertaining process in itself. Keep a rectangular ceramic magnet on hand as an eraser and erase by passing the magnet over the film, again, without touching it.
Touching it creates a new image. A gentle sweeping gesture clears the film. So it’s a practical example of action at a distance.
As discussed in A Child’s Extrasensory Experience, the basic goal in the presentation of any form of energy is the child’s conscious awareness of its existence as such, which viewing film reinforces. The second goal is realize that the energy can be measured or quantified. This under standing can be approached by giving the child an instrument that reacts to the particular energy, associating numbers and language, and this can be done before the child can understand the technical definition of the units or do any math at all. You don’t have to understand the effect of the gravitational constant on a given mass to see that the scale says you weigh 30 pounds. Likewise, you don’t have to know the definition of a Tau (a Tesla) to use a field meter and determine that one magnet shows larger numbers than another or is changing distance and direction.
A teacher can choose from a number of inexpensive hand held meters. However, if a teacher is open to the use of video displays and has used magnetic film to look at an Ipad, then that teacher already has a magnetic field sensor in her classroom. There are a few apps that are simple to use and clear in their displays. The child need only manipulate a magnet near the Ipad, circling and flipping, approaching and receding, to see the field being indicated and measured.
Deflection of a rolling ball
The simple realization that a magnetic field can alter the course of a moving object is also import. It has a fundamental application in our technologies, appearing in motors, switches, speakers and guidance, like bullet trains. Classroom design begins with the simplest, most self-evident example. So, we roll a steel ball past a magnet. Again, this exercise requires a good deal of manual dexterity and the ability to visualize the field.
Using a shallow flat bottom bowl and simply releasing a steel ball from a point on the side regulates velocity, drawing attention to the position of the magnet’s field relative to the expected path of the ball.
The exercise is to hold the magnet in a position that will deflect the ball without capturing it. Deflection is the goal. There will be many angles of deflection, but there is a sweet spot where the ball rolls away in a curve and returns to the hand in almost the same curve. Capture is the control of error. By deliberately deflecting the ball, the magnet becomes an intentional tool. As with the other exercises, development of eye-hand coordination is one of the benefits.
Motion of a magnetic field in a conducting material
The first step in this idea is to show that the behavior of a magnet and a conductor change if they are in motion relative to each other. The physical phenomenon in use here is that of Eddy Currents. The realization being developed is that the magnet acts differently on a conducting material when it is moving. In a primary classroom the conductors will be the elements, Copper and Aluminum, as described in A Child’s Elements. The geometric forms will be sheets and tubes. It is worth mentioning that, from a Practical life aspect, copper and aluminum also provide finger prints and tarnish, and so ready opportunities to polish and observe simple chemical reactions.
The magnetic tablet work will have shown that copper and aluminum are not attracted by stationary magnets. This exercise is simply to compare dropping a magnet down a plastic tube with dropping it down a copper tube.
The dexterity involved requires holding the tube in one hand and both dropping and catching the magnet in the other. The child will not be able to catch the magnet falling at a normal rate through the plastic tube. The magnet falling in slow motion through the copper tube can be caught. A variation is to keep the magnet floating in the tube by tilting the tube back and forth. All of this motion can be made visible by wrapping viewing film around the tube.
The aluminum sheet is used to compare the difference between sliding down aluminum and sliding down plastic. Eddy currents, not friction, slow the magnet on the aluminum.
The point of the exercises, which should also be a point of conversation while presenting them, is that the magnet is doing something to, causing something to happen in, the material because it is moving. This recognition of the effect of Motion and in turn, Magnetism and Electricity, is the perception of Energy as such, one of fundamental goals described in A Child’s Physics.
Induction
Induction is a dynamic phenomenon. Induction occurs when magnetic fields, conducting materials and electric currents combine through the energy of Motion. If a field moves in an isolated solid conductor, swirls or eddies, of electric charge and their associated magnetic fields arise. These are the eddies that slow the magnet in the tube and on the sheet. If a field passes through a length of thin conducting material arranged in a closed circuit, an organized electric current arises. When a current passes through a conductor, a magnetic field arises. If that conductor is wound into a coil, it becomes one of the key inventions of the nineteenth century and is absolutely fundamental to our technological culture.
The introduction of this additional geometric solid into the primary classroom is as easy as any other shape. Coils should be in every primary geometric solid set because of the ubiquitous role they play electrically, mechanically and even biologically in the double helix of DNA.
A tube is a modification of a cylinder . A coil is a modification of a tube. And so a simple presentation of induction is to drop a magnet down a coil just as we drop it down an eddy current tube.
A coil can be easily hooked up to a diode or a meter to form a closed circuit and the exercise is well within the primary child’s abilities. It’s a good example of assembly and disassembly as part of the process of the work. You need to pinch an alligator clip and turn a thumb screw. Then drop the magnet in the hole, and the meter jumps or the diode flashes. It does need to be a clean drop. Missing is the control of error. The moving magnet induces an electric current, which then is transformed either into Motion or Light.
This can also be shown by just sweeping the coil relative to the magnet, as shown with the snap circuit set in A Child’s Electricity. It doesn’t matter which one moves, or if both do.
Electromagnets
In addition to exciting a coil with a magnet, we can put a current through a coil creating an electromagnet, and then use that magnet to pick things up and move them from one cup to another.
This is the magnetic equivalent of a spooning exercise. All it takes is a battery and a wire coiled around a bolt or a nail. Holding the wires pinched against the ends of the battery is the control of error. It can also be done with a Snap Circuit set.
Ambitious DYI teachers can consider fashioning a handle to hold a battery and a coil, offering a magnetic hand tool that involves a process of assembly.
A Homopolar Motor
The homopolar motor is, historically, the first electric motor to have been invented. Designs for this type of motor are all over the internet, but they tend to be delicate. The trick is to find a form suitable for a primary classroom.
The answer is to make the armature out of heavy gauge copper wire. It requires adult hands to bend the basic shape which will then be durable and remain relatively stable, while being capable of the inevitably necessary fine adjustments made by the child. Combine it with a larger C battery, rather than AA.
The lesson of the motor is the combination of the basic elements that have been presented in Magnetism and Electricity into a self-sustaining electromechanical motion. But instead of just giving the child a pointless and unexplained toy, we are able to present a magnet, a source of electricity, a conductor and, incidentally, another example of assembly. We have established the ideas and the language to be able say that electricity, a current, moves from the battery through the magnets, then through the copper armature back to the battery. This is a complete, closed circuit. The copper armature becomes an induced electromagnet and pushes against the permanent magnet. And so it spins.
We place in the child’s hands an invisible field of force, Magnetism, which both attracts and repels. We combine it with different materials and states of matter and motion. We measure it, create images with it, and and talk about it, using the pertinent language. We transform it into other forms of energy. Finally, we show its unique connection through Induction to another fundamental energy, Electricity.
Each of these ideas is simple, which is why they belong at the primary level. They are the building blocks out of which can come a concrete understanding of so much of the technological cacophony the child encounters.
From these small and simple experiences the child can build an awareness and make sense of an unseen energy that permeates the natural world and guides so many of its inhabitants.
