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Introduction
- Resonance is a common thread which runs through almost every branch of
physics, and yet a lot of people have never studied it. Without resonance we wouldn't have radio, television, music,
or swings on playgrounds, not to mention cool gismos like Tesla coils. Of course,
resonance also has its dark side. It occasionally causes a bridge to collapse, a
helicopter to fly apart, or other inconveniences. Unlike black holes, time
travel, and quantum mechanics, resonance is common place and easy to observe.
Yet, it is one of the most striking and unexpected phenomenon in all of
physics.
The following site is the most comprehensive site on resonance
available on the web. Its information is intended especially for use by high school
students, teachers, home schools, and anyone interested in the subject. Suggestions for
quick demos are included in many of the sections and are noted on the contents
page. More elaborate demos and lab experiments are described in separate
sections which contain the word demonstration in the title.
The materials and parts specified in the
demonstrations are based on items commonly found in the United States since that
is where the demonstrations were built and tested. However, we sincerely hope
our international readers will be able to gain some useful ideas.
- Resonance Basics
- Nikola Tesla - Master of Resonance:
Tesla was a genius who was obsessed with resonance. No discussion of
resonance could be complete with out talking about Tesla.
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- The ABC's of Resonance: Find out
what resonance is and why it happens.
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- Vibrations/Oscillations
- Playground Swings: This is the example Tesla used when he
gave explanations of resonance. (Demo)
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- Sound
- An Incredibly Irritating Resonance Demonstration: This
easy-to-do demo creates an unexpected, incredibly ear splitting, and
annoying sound. It's one of the most dramatic high school physics
demos available.
- Electrical/Magnetic Resonance--at
the foundation of wireless communication.
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- Electrical Circuits Anything
which moves can potentially resonate, even
the electrons in a circuit.
Crystal Radio Demonstrations
Crystal radios are simple circuits designed to resonate at
the same frequency as the radio station they're tuned to receive.
How Antennas Work
You guessed it. They resonate (at least the most efficient ones do).
Standing Electrical Waves Demonstration
Actually see standing electrical waves using an ordinary
florescent tube.
Antenna Demonstrations Shows
that simple antenna's work best when their length is adjusted so that they
resonate. Also shows that simple antennas emit polarized waves.
For more information about wireless communication
and the electromagnetic spectrum visit
The Hidden World of the
Electromagnetic Spectrum.
- Appendix
- References
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- The Dark Side of Resonance,
- The Tacoma-Narrows Bridge
Every powerful phenomenon in nature has its dark
side and resonance is no exception. It's best experienced in
moderation. Taken to an extreme, resonance causes things to break catastrophically.
For example, when an opera singer with a very loud voice hits the
right frequency she can cause a champagne glass to resonate and
break.
On the morning of November 7, 1940, the four month
old Tacoma Narrows Bridge began to oscillate dangerously up and
down. A reporter drove out on the bridge with his cocker spaniel in
the car. The bridge was heaving so violently that he had to abandon
his car and crawl back to safety on his hands and knees.
At about 11:00 the bridge tore itself apart and
collapsed. It had been designed for winds of 120 mph and yet a wind
of only 42 mph caused it to collapse. How could this happen? No one
knows exactly why. However, the experts do agree that somehow the
wind caused the bridge to resonate. It was a shocking calamity
although the only loss of life was the cocker spaniel.
View
NOVA videos of the collapse. (Follow the link and scroll down to
the bottom of the page) |
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