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ERIC Number: EJ1037711
Record Type: Journal
Publication Date: 2014-Sep
Pages: 3
Abstractor: As Provided
Reference Count: 7
ISSN: ISSN-0031-921X
Measuring "c" with an LC Circuit
Doran, Patrick; Hawk, William; Siegel, P. B.
Physics Teacher, v52 n6 p368-370 Sep 2014
Maxwell's discovery of the relation between electricity, magnetism, and light was one of the most important ones in physics. With his added displacement current term, Maxwell showed that the equations of electricity and magnetism produced a radiation solution, electromagnetic (EM) radiation, that traveled with a speed of c=1/v(e0µ0). The constant e0 is the permittivity of free space from electrostatics, and µ0 is the permeability of free space from the magnetic interaction. There are a number of classroom experiments that directly measure the speed of light and EM radiation by dividing distance traveled by time. It is also possible to measure c using standing waves in a microwave oven. These are excellent experiments, but do not demonstrate the relationship between c, e0, and µ0. One can also measure the permittivity of substances in the classroom; however, the quantity that is relevant for the speed of EM radiation is the product of e0 µ0. The product e0 µ0 is interesting since its units are "time[superscript 2]/length[superscript 2]," and its value is the same for any choice of charge units. We present an experiment for the student laboratory to measure this product.
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