Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Electrical sockets
Name: N/A
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: N/A


Question:
Recently I used a multimeter to test resistance between the left and right hand of student. It came out to be about 200 k . Using ohm's law I found that current drawn from a 120 V socket would be about 0.0006 A, hardly noticeable. Yet I know that more current than that would be drawn. What am I not taking into account?



Replies:
Well, I just checked my own, and it is even higher! Yet, I am not going to stick my fingers in the socket. The surface area of contact is important (multimeter probes provide a pretty small contact area), but even more important is the amount of moisture on the skin's surface. Try it with sweaty hands, and you will see at least an order of magnitude reduction...now we are talking about 6 millimps (milliamps), which is noticeable and is of the same order of magnitude as potentially fatal shocks. I also recall that as soon as a small amount of current is passed, the resistance of the skin drops rapidly...do not remember why. If you want to pursue this, get back to me and I will check with our electrical safety engineer for details. --Gary

gary e myers



Click here to return to the Physics Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory