Bell’s experiments and our understanding of the telephone principles are perhaps a sideshow to the mainstream of curriculum we see in STEM. We don’t see much in textbooks anymore about the technology or the science of the phone as most have moved into the digital age and do not use the same technology. It is unfortunate as this small piece of the history of science has a wealth of both drama and deep meaning for students in STEM. Even though it is an old story, the progression of Bell learning the STEM disciplines to solve the problem is the same. 

When we consider the goals and aims of STEM, the standards are something we should examine. Of particular value in relationship to the NGSS standards (Links to an external site.)

Consider the stated standards about energy:

4-PS3-2 Energy (Links to an external site.) Make observations to provide evidence that energy can be transferred from place to place by sound, light, heat, and electric currents. Grade: 3-5

4-PS3-3 Energy (Links to an external site.) Ask questions and predict outcomes about the changes in energy that occur when objects collide. Grade:  3-5

4-PS3-4 Energy (Links to an external site.) Apply scientific ideas to design, test, and refine a device that converts energy from one form to another.* Grade: 3-5

MS-PS3-5 Energy (Links to an external site.) Construct, use, and present arguments to support the claim that when the kinetic energy of an object changes, energy is transferred to or from the object. Grade: Middle School (6-8)

HS-PS2-5 Motion and Stability: Forces and Interactions (Links to an external site.) Plan and conduct an investigation to provide evidence that an electric current can produce a magnetic field and that a changing magnetic field can produce an electric current. Grade: High School (9-12)

HS-PS3-1 Energy (Links to an external site.) Create a computational model to calculate the change in the energy of one component in a system when the change in energy of the other component(s) and energy flows in and out of the system are known. Grade:  High School (9-12)

HS-PS3-3 Energy (Links to an external site.) Design, build, and refine a device that works within given constraints to convert one form of energy into another form of energy.* Grade:  High School (9-12)

HS-PS3-5 Energy (Links to an external site.) Develop and use a model of two objects interacting through electric or magnetic fields to illustrate the forces between objects and the changes in energy of the objects due to the interaction. Grade: High School (9-12)

Now consider the energy transformations we have examined in this series of explorations.  Watch this powerpoint to hone in on the principles here.

Link to Powerpoint

So, in the case of transforming any energy into a different form, like the telephone, we lose some to heat or other kinds of energy that what we had expected. (The incandescent light bulb, for example, is more a producer of heat than light. SEE: Light Bulb Heat (Links to an external site.) for an experiment that you can do to calculate the efficiency of an small light bulb.)

Once you have some sense of how energy transformations occur, examine this video:

Where is the energy coming from? 

MORE INFORMATION>> We travelled through Bell’s experiments and electromagnetic interactions a bit too fast perhaps and missed some fundamentals.  Here are some things we should have in our understanding:

  1. When a magnet and a coil of wire interact, electrons will flow in a circuit.

2. The magnet must be in motion to make this so.

3. This is an induced current. The magnetic lines of force that cut across the copper wires “push” an electron flow (more accurately create an Electromotive Force).

4. In our experiments we moved the coil instead of the magnet.

In our example we used a speaker.  The coil was attached to the diaphragm and it moved from the push of our voice.

The speaker cone pushes the coil (voice coil) against the magnet. This produces a weak electrical pulse.

Now, in a very real sense since we are making electricity, we say we are generating electricity like a generator on a power supply or an alternator on a car. Instead of sound we can move the coils or the magnets to create electricity for use. 

In the diagram above, if we rotate magnets in the area where there is a coil of wire, it will generate an electric current. If we spin this magnet with a propeller we have a wind generator, if it is propelled by a turbine, a hydroelectric generator, etc. The principle is the same throughout, a moving magnetic field near a coil of wire will cause a current flow.  The magnet or coil must be moving!

Here is a video to help:

PLEASE RESPOND: How would you debunk this hoax in terms of what we know about energy creation and transformation?

Move on to Option Exploration