Question

The damage caused by electric shock depends on the current flowing 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 60000 ω. when skin is wet, the resistance drops to about 4900 ω. what is the minimum voltage placed across the arms that would produce a current that could be felt by a person with dry skin? answer in units of v.

Answer 1

We can solve the problem by using Ohm's law.

The resistance of the person, with dry skin, is $R=60000 \Omega$. In order to be felt, the current must be at least 
$I=1 mA=0.001 A$

Ohm's law gives us the relationship between current and voltage:
$V=IR$
where 
I is the current
R the resistance 
V the voltage

Using the data of the problem, we find that the minimum voltage needed is
$V=IR=(0.001 A)(60000 \Omega)=60 V$