October 01, 1997 Filed in: Demo Corner
John Wylie, Toronto French School
Here are two tricks, sorry, demonstrations that you can store away for when you have a few minutes to kill and all you have available is a metre stick, or when you just feel the need to show off in front of impressionable young students. They both are opportunities to prove that a knowledge of physics is better than being young and co-ordinated. Read More...
June 01, 1997 Filed in: Demo Corner
Alan Hirsch, Port Credit SS, Mississauga
What physics toy have you seen that can attract the attention of every passerby in a mall during the December shopping rush? And what toy can you expect your physics students to exclaim “hey, cool” when they see it? The answer to each of these questions is the same: The Levitron
: The Amazing Antigravity Top. Read More...
March 01, 1997 Filed in: Demo Corner
John Pitre, Department of Physics, University of Toronto
When polarized light is discussed, polarizing plastic sheet filters are always mentioned. During manufacture, this material which contains
long chain molecules is mechanically stretched into sheets resulting in the alignment of the molecules. Electrons can travel along the axis of the molecules but cannot jump from molecule to molecule. When light is incident on a polaroid sheet, the component of the electric field which is parallel to the axis of the long chain molecules causes the electrons to move, and that component is absorbed; the component which is perpendicular to the axis of the molecules is unaffected. Thus, polaroid sheets have a preferred direction, or transmission axis, which is perpendicular to the axis of the long chain molecules. 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...