.boxed { border: 1px solid green ; }
Electricity

Equity Through Understanding: Electric Current & Potential Difference

Dave Doucette,OCT
Richmond Hill HS (retired)
STEAM Education Consultant, FAST Motion Studios, Toronto
doucettefamily@sympatico.ca

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...

Controlled Experiments with Three Factors in SPH4C Grade 12 College Physics

Tim McCarthy, Teacher, St. Ignatius of Loyola Catholic Secondary School
mccarthyt@hcdsb.org

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...

Intersection Traffic Signals: Coding to Control Series and Parallel Circuits in Grade 12 College Physics and Grade 11 University Physics

Tim McCarthy, Teacher, St. Ignatius of Loyola Catholic Secondary School, Oakville, ON
mccarthyt@hcdsb.org

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...

Light ’Em Up!!! – Electric Greeting Cards for the Grade 9 Electricity unit

Andrew Moffat, Teacher Bishop Strachan School
amoffat@bss.on.ca

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...

Learning the Current Electricity Ropes

Chris Meyer, President OAPT
christopher.meyer@tdsb.on.ca

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...

Visualizing Static Electricity

Chris Meyer, President, Ontario Association of Physics Teachers
Christopher.meyer@tdsb.on.ca

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...

The End of Conventional Current

Chris Meyer
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...

Hands-On Fields

Roberta Tevlin
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...

LEDs: An alternative to traditional bulbs

David Gervais
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...

Metal Leaf Electroscope Simulator

Matthew Craig, Teacher at the Community Hebrew Academy of Toronto
matt.simon.craig@gmail.com

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...

Animating Graphs to Animate Discussions about Electrical Energy

Roberta Tevlin, Teacher at Danforth CTI
roberta.tevlin@tdsb.on.ca

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...

Making Speakers

Bonnie Lasby Physical and Engineering Science Dean’s Office University of Guelph
blasby@uoguelph.ca

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...

Wire Fire!

Joanne O’Meara, Department of Physics, University of Guelph
omeara@physics.uoguelph.ca

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...

Induction Puzzle

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...

The World’s Simplest Motor

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...

An Electric Guitar Pickup

Peter Scovil, Waterford, ON
petescov@enoreo.on.ca

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...

The Neon Lamp Flasher

John Childs, Grenville Christian College, Brockville
jchilds@grenvillecc.ca

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...

Lenz’s Law with Plumbing Pipes

John M. Pitre, Department of Physics, University of Toronto
pitre@faraday.physics.utoronto.ca

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...

A Multi-Purpose Instrument

Tomasz Dindorf and Wojciech Dindorf
Donaufelderstr. 252/24, 1220 Wien, Austria

(Editor's note: This article is reproduced, with permission, from a delightful little book, "The Sun on the Floor -Physics experiments that can be performed at home." This 68-page book describes 58 experiments that can be accomplished with simple apparatus. There are many drawings and photographs to illustrate the experiments. A single copy of the book can be ordered for only $10 U.S. from the authors at the address above, and 20 copies can be obtained for $100 U.S.) Read More...

Demonstrations with a Tesla Coil

Roland Meisel, Ridgeway Crystal Beach High School
rollym@iaw.on.ca

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...

Big Ben — Lenz’s Law and the Cow

John Childs, Grenville Christian College, Brockville

Two demonstrations from John Childs. Read More...

Electric Hotdog

Roland Meisel, Ridgeway Crystal Beach High School
rolameis@village.ca

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...

A Not-so-Serious Parallel Circuit

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...

The World’s Simplest Speaker

Frank Allan, Science Co-ordinator, Ottawa Board of Education

The world’s simplest speaker can be constructed in a matter of seconds. Read More...

The World’s Simplest Motor

Robert Ehrlich, Physics Department, George Mason University

The world's simplest motor can be constructed in less than five minutes. Read More...

The D.C. Motor

Peter Scovil, Waterford District High School

Have you had difficulties explaining to students the complexities of the D.C. motor? Read More...

Electrostatics with Ping Pong Balls

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...

The Electrostatic Precipitator

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...
©Ontario Association of Physics Teachers Contact the Newsletter