December 08, 2019 Filed in: Articles
President, Ontario Association of Physics Teachers
Hybrid Teacher-Coach for Science, Toronto District School Board
I have a question for you to think about, which I have chosen for two reasons: first, it is about electric circuits, which are fun; second, answering this question well requires thinking carefully about how we describe circuits. If you work through it carefully, you should discover one important reason why many students and teachers get tripped up when thinking about electric circuits. Now, I don’t want you getting bogged down in the weeds on this, so let’s start by assuming the devices are ohmic, meaning they faithfully obeys Ohm’s law. My question is this: Which bulb would be brighter: a 10 Ω bulb or a 20 Ω bulb?
Take a few minutes to think about this question. What assumptions are you making about the circuit in which this bulb is found? Can you think of an example where either answer is the correct one? Keep thinking! And when you are ready for the full discussion, read on! Read More...
October 13, 2019 Filed in: Articles
Richmond Hill HS (retired)
STEAM Education Consultant, FAST Motion Studios, Toronto
A 2016 paper1
surveying Purdue University electrical engineering undergraduates discovered “…seniors were more confused than novices about physical concepts such as charge, current and electrical field.” The study did not reveal precise reasons but did caution that well-intentioned but incorrect analogies “usually transform into foggy concepts students carry towards graduation (p4).” This echoed a 2008 engineering-science paper2
investigating obstacles to concept attainment of direct current. One barrier was weak modeling of the phenomenon, “…and identified the cause of this deficiency as lack of direct experience which can be remediated by creative instructional design.”
The actual mechanism of potential difference and direct current involves surface charge distribution. The challenge to develop this conceptual foundation is its invisible nature. Students cannot directly observe charge and ‘creative instructional design’ is needed to carefully scaffold inferences from static to moving charge. This paper suggests a series of activities to create the experiential background necessary for robust modelling of surface charge distribution. This conceptual foundation will be applied to series and parallel circuits to reinforce Kirchhoff’s laws. Read More...
May 05, 2019 Filed in: Articles
Tim McCarthy, Teacher, St. Ignatius of Loyola Catholic Secondary School
Controlled experiments with three factors are a great way for physics students to practice identifying and testing factors that may affect a situation. They provide an excellent opportunity to practice the Scientific Investigation Skills found in Strand A. The students are provided with a situation, brainstorm possible factors that may affect the situation, reduce the list of factors to three that can be tested in the physics lab, develop hypotheses, design procedures to test the factors, test the factors, analyze the data, perform experimental error analysis, and draw conclusions on the effects the three factors have had on the original situation.
My struggle has been to find situations that easily fit this format and that also match the curriculum specific expectations. I have created one three-factor controlled experiment for each of the six units in my 12C physics course. The three-factor experiment in the first unit is used as assessment for learning (formative) to teach the students how to do a controlled experiment. The remaining five experiments are used as assessment of learning (summative). Simulations are used for some experiments as I do not have the necessary equipment to perform all them in the lab. Read More...
April 21, 2019 Filed in: Articles
Tim McCarthy, Teacher, St. Ignatius of Loyola Catholic Secondary School, Oakville, ON
Coding is an important skill for physics students to learn. Grade 12 College and Grade 11 University physics students must build series and parallel circuits, so why not use coding to control them and model an everyday, real-world situation? This can be done by first using TinkerCAD simulations, followed by construction of the simulation using real components; Arduino UNO R3 microcontroller boards, breadboards, LEDs, resistors and wires. Students have a high level of satisfaction as they complete a task that is brand new to most and learn skills that they are likely to need in their post-secondary education. Read More...
April 14, 2019 Filed in: Articles
Andrew Moffat, Teacher Bishop Strachan School
Students often struggle with the “Physics” unit in grade 9 Science — electricity. This can lead to a negative association with Physics and fewer students taking grade 11 and 12 Physics. At our school we have tried to make the electricity unit (and specifically the idea of circuits) more fun and engaging by having students create an electric greeting card consisting of LEDs and a battery. This can be done for around $2 per student. Read More...
December 08, 2018 Filed in: Articles
Chris Meyer, President OAPT
Electricity is almost always invisible; we never get to see electrons doing their thing. Only occasionally do we observe some by-product of electrical shenanigans like a spark, a glow, or a warm battery. This makes learning about electricity tough. As a result, many students (and even some teachers!) don’t develop a clear mental model representing how electrons move in a circuit. There are two important ideas are often missing from our mental models. Read More...
November 25, 2018 Filed in: Articles
Chris Meyer, President, Ontario Association of Physics Teachers
Static electricity might very well be the most important topic taught in high school science. Exploring static electricity teaches us how charged particles behave, which becomes the basis for understanding the structure of the atom, chemical reactions, the behaviour of complex biological molecules, cells, and even human thought. Static electricity is challenging to understand because it is invisible; we can’t see the particles doing their thing. As a result, we need to help students construct concrete, visual models of charged particles and provide students with visual ways of verifying their understanding of static electricity. Read More...
June 17, 2018 Filed in: Articles
President, Ontario Association of Physics Teachers
Time to Let Go
It’s time! Conventional current, the mysterious flow of positively charged particles in current electricity, has outlived its usefulness. This model hinders the development of clear physical understanding and places an additional, unnecessary conceptual burden on all our students. We ought to let the few students who pursue the electrical trades, electrical engineering, or physics deal with this awkward relic. Use electron current in high school. It’s time to let go of the ghosts from our disciplinary past and focus on improving our students’ learning. Read More...
June 04, 2018 Filed in: Articles
Teacher at Danforth CTI, Manager OAPT Newsletter
The concept of fields is fundamental to our modern understanding of physics and the Ontario curriculum dedicates one of the five units in 12U physics to Gravitational, Electric and Magnetic Fields. I have struggled for many years to find ways to make this important but abstract concept more tangible to my students. Here is what I have come up with so far. Read More...
May 27, 2018 Filed in: Articles
STAO Safety Chair
The traditional incandescent bulbs used for teaching series and parallel circuits are rated for 3 V or 6 V. The problem is that many power supplies can generate 12 to 15 V. As a result, it is common to have many blown bulbs. With several sections teaching this unit, bulbs can quickly become in short supply. Each bulb replacement can cost $1.00 each, and often are included in the general department order at the end of each semester. For those teachers using breadboards, traditional bulbs are also not easily adapted to fit into the small holes. LEDs are a great alternative for many reasons. Read More...
January 28, 2018 Filed in: Articles
Matthew Craig, Teacher at the Community Hebrew Academy of Toronto
I’ve been programming a suite of PC/MAC/Android simulations designed for teaching the Ontario curriculum for science and physics. One topic for which I have never had an effective simulation is the metal-leaf electroscope for grade 9 science, and revisited briefly in grade 12 physics.
The electroscope simulation I have developed is a very simple simulation that can be used to show induced charge separation, charging by contact, charging by induction and grounding. Read More...
December 18, 2015 Filed in: Articles
Roberta Tevlin, Teacher at Danforth CTI
One of the biggest problems facing the world right now is how to generate the electricity that we want without destroying the environment. This is a very complicated problem and we are supposed to help our students understand this issue in all four grades in high school: grade 9 Science (Electricity), grade 10 Science (Climate Change), grade 11 Physics (Energy and Society) and grade 12C Physics (Energy Transformations). This summer I found a great tool to help with this. Read More...
November 01, 2009 Filed in: Demo Corner
Bonnie Lasby Physical and Engineering Science Dean’s Office University of Guelph
I prefer to do this as an activity as opposed to a demonstration, and have found that it works very well for students in Grades 7 to 12 visiting the University. I start with a discussion about sound and then compare a speaker to the human ear. In the discussion on speakers, I also talk about magnets and how they work, and I explain the difference between permanent magnets and electromagnets. After this discussion, I explain how to make speakers using a plastic cup, a magnet, and a coil of wire. Each student makes his/her own speaker and then tests it. Read More...
February 01, 2009 Filed in: Demo Corner
Joanne O’Meara, Department of Physics, University of Guelph
This demonstration is a nice way to illustrate the P
= I 2R
relationship that is discussed in electric circuits. Figure 1 illustrates the equipment: a Variac transformer takes the wall output of 120 V and generates a variable voltage from 0 to 140 V. This is then sent through a Hammond Manufacturing transformer (167X5), converting down to 5 V output. We use this second transformer in order to increase the current through the wires. The output from the second transformer is connected to three wires in series: approximately 10 cm in length of each of ~18 gauge Nichrome, steel and copper. A piece of folded paper is placed on each wire. Read More...
September 01, 2006 Filed in: Demo Corner
Leigh Palmer, Simon Fraser University
Here's a demonstration that will make your students think more carefully about the meanings of the terms voltage, electromotive force, and potential difference. A transformer is necessary for the demonstration. Read More...
March 01, 2006 Filed in: Demo Corner
John Pitre, University of Toronto
In the December 2004 issue of The Physics Teacher
, Christopher Chiaverina described a motor consisting of four components: a battery, a cylindrical rare earth magnet, a small piece of copper wire, and a steel nail. Since I know that many of our members do not have ready access to this journal, I have essentially reproduced his article here. Read More...
January 01, 2001 Filed in: Demo Corner
Peter Scovil, Waterford, ON
I like music, and enjoy playing the guitar, so the following demo caught my eye (or ear?). It was in the Jan. '95 issue of The Physics Teacher
(p.58) by G.R. Davies of South Africa. It is a good example of electromagnetic induction that is easy for students to understand. Read More...
December 01, 1998 Filed in: Demo Corner
John Childs, Grenville Christian College, Brockville
This simple little homemade device can provide a very effective demonstration of AC current, it’s fun, and it’s cheap! All you need is a little neon lamp, a resistor and an AC cord. Solder one leg of the neon lamp in series with a 10K, 1/2 watt resistor, and then attach to the AC cord. Heat shrink tubing is excellent insulation for this construction, otherwise use carefully applied electrical tape. Be sure to insulate throughly, you have AC power here. Read More...
June 01, 1998 Filed in: Demo Corner
John M. Pitre, Department of Physics, University of Toronto
In the January 1997 issue of The Physics Teacher
, two articles appeared detailing the use of rare earth magnets to demonstrate Lenz’s Law in the classroom. The principle involved is that a permanent magnet falling through a tubular conductor will induce a current in the conductor and hence a magnetic field which will oppose the magnetic field of the permanent magnet and thus slow its rate of fall. This article gives variations of the methods discussed in those papers. Read More...
January 01, 1997 Filed in: Demo Corner
Roland Meisel, Ridgeway Crystal Beach High School
A Tesla coil circuit generally consists of some sort of step-up transformer along with a tuned oscillator. The B-10 coil sold by Cenco Scientific is a compact device which produces 40-50 kV at frequencies of 3-4 MHz. The schematic diagram shows an inductance connected to an AC circuit. As the AC goes through its cycle, the inductance builds up a high reverse potential (similar to the arcing at the commutator of an electric motor) which can exceed the breakdown resistance of the spark gap in the oscillator circuit. When this happens, the resistance across the gap drops effectively to zero, and causes the tuned circuit to “ring” electrically, much like hitting a tuning fork. A high-voltage high-frequency AC potential is induced at the tip. This is the “simple” explanation which high school students can usually follow. For those who wish to see the differential equations describing what is going on, may I suggest an advanced book on electrical physics! Read More...
November 01, 1995 Filed in: Demo Corner
John Childs, Grenville Christian College, Brockville
Two demonstrations from John Childs. Read More...
January 01, 1995 Filed in: Demo Corner
Roland Meisel, Ridgeway Crystal Beach High School
A current can be run through a hotdog in order to cook it. There are commercial hotdog cookers that make use of this principle. I use it near the end of the unit on resistance in the Grade 12 Physics course. Read More...
January 01, 1992 Filed in: Demo Corner
Peter Zuech, Mother Teresa S.S., Scarborough
This idea was born while watching the Tonight Show. A popular entertainer demonstrated a wooden board upon which four coloured light bulbs in sockets were mounted along with a corresponding set of four coloured switches. No matter how the bulbs were rearranged in the sockets, the blue switch turned the blue bulb on and off, the red switch operated the red bulb, and so on. Johnny examined the bulbs, found them to be “normal” and was convinced that it was magic. Unable to determine how the four-bulb unit operated, we designed a simpler two-bulb version for use as a discrepant event in current electricity. Our unit used two white bulbs but coloured ones could be used as in the original unit. The only skills required to construct the unit are an ability to solder and the willingness to tinker a little. Read More...
March 01, 1991 Filed in: Demo Corner
Frank Allan, Science Co-ordinator, Ottawa Board of Education
The world’s simplest speaker can be constructed in a matter of seconds. Read More...
December 01, 1990 Filed in: Demo Corner
Robert Ehrlich, Physics Department, George Mason University
The world's simplest motor can be constructed in less than five minutes. Read More...
December 01, 1989 Filed in: Demo Corner
Peter Scovil, Waterford District High School
Have you had difficulties explaining to students the complexities of the D.C. motor? Read More...
May 01, 1989 Filed in: Demo Corner
Gyula Lorincz, University of Toronto
Many of our old favourite electrostatics demonstrations can be improved using ping pong balls painted with graphite to replace pith balls. In particular, a simple but very sensitive electrostatic torsion balance can be used to demonstrate both the attraction of opposite charges and the repulsion of like charges. Read More...
September 01, 1988 Filed in: Demo Corner
Roland Meisel, Ridgeway-Crystal Beach High School
An electrostatic precipitator can be assembled in less than half an hour using parts commonly found around the science department in a high school. I have used it as a demonstration in classes ranging from grade 10 general science to grade 13 physics. In addition, it has spawned several senior science projects using it as an investigative tool. Read More...