Microcontrollers in Physics education: a circuit simulation ... - ICL

Conference ICL2010
September 15 -17, 2010 Hasselt, Belgium
Children are also taught (in theory) that: “Electric current exists only in closed circuits.
Therefore, if the switch is off the circuit opens, and although a battery is connected to the
circuit, there is no forced movement of electrons. Consequently, when the circuit opens the
electrons move randomly and slowly (i.e. thermally) and the light bulb does not illuminate”.
In the emulator, in case the switch is open, no mater if the battery is connected to the device
or not, the LEDs spark randomly, and the light bulb does not illuminate. Incidentally, due to
the idiomatic use of the everyday language in Greece, the phrase “turn on the lights”
translates (literally) to “open the lights”, which is of course very close to “open the circuit”,
only to further confuse the students. The opposite phrase is used for turning the lights off,
thereby making the distinction between “scientific language” used at school, and “everyday
language” used at home, final! This is precisely what the teacher tries to avoid as it reinforces
the widely accepted opinion amongst pupils, namely that science is irrelevant to everyday life.
There is not much that an experienced teacher can do about it, except to learn to live with the
problem and try to clear out any confusion in the best possible way.
After all demonstrations have finished, all students (one pair at a time) experimented with the
new device. They were asked to try all possible switch and battery combinations and carefully
observe the results.
For the AC case an ordinary transformer that provides the circuit with 12V AC is used
Students learn that “in A.C. current the move of electrons changes from clockwise to counterclockwise,
and the frequency of the source will determine how many times per second this
direction of movement changes”. For the purpose of the emulator presented herein, when the
input of the board detects high frequency alternating current, the frequency is reduced (by the
embedded software program) so as the eye can see the change in the direction of the flow of
electrons. The directions of the electrons move changes from clockwise to counter clockwise
and the students can see clearly the change in the direction of the electron movement.
Although the alternating current is the type most commonly used everyday, since it is the
current that electricity-supply companies provide, it is common practice to postpone the
teaching of it for a while, and to only introduce it after the students had grasped the basic
concepts of electric circuits, and of DC electric current. The alternating current simulation
was not taught during the trial teaching sequence presented here, although there is a suitable
video available online. This was done for several reasons: a) AC current is even more difficult
for the students to understand, because they cannot distinguish the positive and negative pole
and normally the electric current direction changes so quickly from clockwise to counter
clockwise but the light bulb illuminate continuously. And b) AC current was not taught for
the time being (worried that this way one might encourage students to “experiment at home”
using power from an ordinary socket). This is because for this demonstration an ordinary
transformer that lowers the voltage to 12V AC should be used. The students participated in
the trial were young and not quite aware of the dangers involved when using the 220-Volt
sockets available at home. They are also unaware of the difference between the current
available in the sockets and the one provided by the transformer.
Therefore the teaching of alternating current was postponed for a later time, in order to avoid
students’ misunderstandings and prevent the acquiring of misconceptions.
4 The educational trial
This is the first trial of this new device and, therefore, the knowledge remaining to the
students when this new teaching procedure incorporating the new emulator device was
ICL 2010 Proceedings – Page 414
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