Armor found to raise electrical capacitance


Medieval history met modern silicon last week when a man clad in a suit of armor took part in a light-hearted test to determine whether the metallic outfit would affect his body's electrical capacitance.

Mechanical engineering major Jason Hintersteiner `96, who helped design and assemble the capacitance demonstration that has been in Hayden Library for several months, had Carl West step up to the device while wearing a suit of armor. The suit was made by Mr. West himself, a fan of medieval topics and participant in the MIT Society for Creative Anachronism, which periodically meets for medieval-style "battles." The January 26 experiment was intended to see whether someone in garb that conducts electricity would be able to store more or less electricity in relation to his surroundings than someone in ordinary clothes.

"We decided that a conducting surface would provide an interesting check of our theoretical formula," said Mr. Hintersteiner, who worked out the formula for human-body capacitance as part of a UROP project with Professor John King of physics. The apparatus will eventually be moved to the third floor of the Infinite Corridor as part of the Corridor Lab, a series of several dozen displays around the Institute planned by Dr. King and the Edgerton Center that will demonstrate various scientific principles.

Mr. Hintersteiner first had to connect the many separate metal parts of the outfit together with a series of wires and clips to make it electrically continuous. Fully clad in his 65-pound suit (including metal gloves and slotted helmet), Mr. West the stepped on a platform and pressed a button to calibrate the measuring device and drain residual electricity from his body. After pressing another plate to "charge up" to 600 volts, he touched a button with his metal fist to measure his capacitance.

"It's a bit higher than we were expecting," Mr. Hintersteiner said as he jotted down readings averaging around 100 picofarads. Normal readings for a person of average height and weight are about 80 picofarads. Mr. West's readings were lower if he hunkered down and higher if he raised an arm, since capacitance with respect to the ground varies according to height."This shows that [capacitors are] not just little metal things that you plug into circuits. Anything can be charged," Mr. Hintersteiner said.

Dr. King envisions the construction and placement of Corridor Lab displays by technicians and students over a period of 10 years or so. Funding for the project, which could be viewed by the general public as well as the MIT community, would be supplied by MIT, the National Science Foundation and perhaps private donations. Some of the phenomena that may be included are pendulums; waves (such as those in radio, light and sound); signals and noise, and reflection, refraction and diffraction. The displays will use varied technology from the 19th-century optical lever to the microprocessor of today.

A version of this
article appeared in the
February 2, 1994

issue of MIT Tech Talk (Volume
38, Number
21).


Topics: Mechanical engineering, Physics, Students

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