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ERIC Number: EJ1046786
Record Type: Journal
Publication Date: 2014-Dec
Pages: 2
Abstractor: As Provided
ISSN: ISSN-0031-921X
A Well-Known but Still Surprising Generator
Haugland, Ole Anton
Physics Teacher, v52 n9 p532-533 Dec 2014
The bicycle generator is often mentioned as an example of a method to produce electric energy. It is cheap and easily accessible, so it is a natural example to use in teaching. There are different types, but I prefer the old side-wall dynamo. The most common explanation of its working principle seems to be something like the illustration in Fig. 1. The illustration is taken from a popular textbook in the Norwegian junior high school. Typically it is explained as a system of a moving magnet or coils that directly results in a varying magnetic field through the coils. According to Faraday's law a voltage is induced in the coils. Simple and easy! A few times I have had a chance to glimpse into a bicycle generator, and I was somewhat surprised to sense that the magnet rotated parallel to the turns of the coil. How could the flux through the coil change and induce a voltage when the magnet rotated parallel to the turns of the coil? When teaching electromagnetic induction I have showed the students a dismantled generator and asked them how this could work. They naturally found that this was more difficult to understand than the principle illustrated in Fig. 1. Other authors in this journal have discussed even more challenging questions concerning electric generators.
American Association of Physics Teachers. One Physics Ellipse, College Park, MD 20740. Tel: 301-209-3300; Fax: 301-209-0845; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Descriptive
Education Level: N/A
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A
Grant or Contract Numbers: N/A