Physics Help: Calculating Electric Shock Voltage/Current

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Homework Help Overview

The discussion revolves around calculating the voltage and current related to electric shock, specifically focusing on the effects of skin resistance in different conditions (dry vs. wet skin). The original poster presents a problem involving the application of Ohm's law to determine the minimum voltage required to produce a perceivable current through the body.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the application of Ohm's law (I=V/R) to find the voltage and current. There are attempts to clarify the calculations made for both parts of the problem, with some questioning the original poster's methodology and unit conversions.

Discussion Status

There is ongoing clarification regarding the calculations, with participants pointing out potential errors in unit handling and formula application. Some participants express concern over the accuracy of the resistance values provided in the problem statement, suggesting that the assumptions may need to be revisited.

Contextual Notes

Participants note that the resistance values for wet skin may vary significantly and that the original problem may not reflect safe handling practices regarding electricity.

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Physics help, urgent!

Homework Statement




The damage caused by electric shock depends
on the current fowing through the body;
1 mA can be felt and 5 mA is painful. Above
15 mA, a person loses muscle control, and 70
mA can be fatal. A person with dry skin has a
resistance from one arm to the other of about
70000 ohms *. When skin is wet, the resistance
drops to about 5000 ohms .
a.)What is the minimum voltage placed across
the arms that would produce a current that
could be felt by a person with dry skin? An-
swer in units of V.
b.) Using the same electric potential as in Part 1,
what would be the current if the person had
wet skin? Answer in units of mA.

Homework Equations



I=V/R

The Attempt at a Solution



I got part a right. It's 70 V.
For b.) I did 5000/70. but it wasn't right. Can someone help?
 
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upside down?

Compare what you did to the formula.
 
answer why you tried 5000 / 70 ?

what does "Part 1" refer to?
 
whoops

I should have done 70/5000 because V=70 and R=5000.
I got .014 but it is still wrong.

Part 1 means part a.
 
Make sure you follow directions and give the answer in the correct units.
 
...

I got .014 mA. Can someone explain what I'm doing wrong?
 
Check your units. Volts/Ohms = Amps.
 
WARNING!
I know this has nothing to do with the question, but the question is quite simply dangerously wrong. Wet or broken skin is closer to 1000 Ohms and a wound can be lower. No one should handle electricity based on the information in the question. Source: NIOSH
 


hey can u play explain to me how u got part a?
 
  • #10


victorlee2 said:
hey can u play explain to me how u got part a?
Use Ohm's law, the formula given in post #1.
 

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