This article was posted 12/28/2005 and is most likely outdated.

A Look at Electrical History - A Visit with Charles Dalziel
 

 
Topic - History
Subject - A Look at Electrical History - A Visit with Charles Dalziel

December 28, 2005

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A Look at Electrical History - A Visit with Charles Dalziel

The year is 1941. You are an assistant professor of Electrical Engineering at the University of California, Berkeley. You are awarded a grant by the California Committee on Relation of Electricity to Agriculture. Purpose: To find the effects of sub lethal electrical currents on the human body. He decided to use healthy human subjects. The subjects are given physical examinations and electrocardiograms. Only subjects in good physical condition are used.ss

Subjects grasp a 12 inch length of bare copper No. 6 wire in one hand and the other hand is placed on a brass plate. Current is passed through the person from the left hand to the right hand. The subject is asked to drop the wire. After dropping the wire the experiment is repeated using more current, again and again, until the subject can no longer keep his hand on the eight inch diameter brass plate.

Assistants are then used to hold the subjects hand on the brass plate and the experiment continues until the subject can no longer drop the wire because he cannot let go. This experiment is repeated with 28 subjects and the maximum let-go currents are tabulated and analyzed.

Frequencies were changed from 60 cycles per second to 180 cps, then 500 cps, then to 1000 cps and the experiments are repeated. It was found that the average 60 cycle let-go current for men is 16 milliamperes and the average let-go current for women is 11 milliamperes.

Your name is Charles Dalziel and you have just begun. You will establish criteria on fibrillation currents using dogs, pigs, calves, and sheep. You become the authority on dangerous electric currents. Your experimentation will establish the principles for protecting persons from the hazards arising from the use of electricity, and your findings will be used for the notes to the Tables in Article 725 of the National Electrical Code.

© 1996 Gerald Newton. All rights reserved.

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Comments
  • Very interesting article. Would it be ok to use this in our company newsletter?

    Mary Larson
    Reply to this comment

  • An excellent article it always amazes me how much current the average person believes they can with stand safely. Most feel that only current approaching 15 amperes should be a concern. Probably because of your typical 15 amp. lighting circuits in houses.

    Jim Yancey-NCDOI Engineering Code Consultant

    Jim Yancey
    Reply to this comment

  • I appreciate this article and the extensive study. I can see the background now of tool safety limits and gfci settings. Thanks

    Jim
    Reply to this comment

  • I heard of Mr. Dalziel but not this detailed study of electrical shock hazzard. Thanks. Les Vass

    Les Vass
    Reply to this comment

  • Mr. Dalziel's study has provided excellent guidelines towards todays safety requirements when dealing with electricity.

    His data on capacitive discharge energies appears to be somewhat limited. I believe there are further studies within this area, especially as it pertains to back EMF's and the fatal cardiac arrests (deaths).

    If someone is electrocuted [1.] NEVER assume he/she is clear or disconnected from the flow of electricity - do not attempt to pull them away without some insulation to protect oneself. [2.] Do not go back to the Main switch and disconnect power, especially in large or commercial buildings - the energy from the back EMF stored in the system wires etc.. is likely to kill them. One must assume (high possibility) they are still alive.

    In other words "remove the victim by pulling (rubber hose pipe)them away from the electrical path or knocking them off (wooden chair or similar) the electrical connection.

    Richard Soundy

    Richard Soundy
    Reply to this comment

  • I have been attempting to learn and teach myself about old electrical codes. This is by far one of the most interesting articles i have read to date. I will look forward to reading his research.

    James Campbell
    Reply to this comment


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