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Electricity

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...
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