The damage caused by electricshock depends on the current flowing throughthe bod

Question

The damage caused by electricshock depends

on the current flowing throughthe body;

1 mA can be felt and 5 mA ispainful. Above

15 mA, a person loses musclecontrol, and 70

mA can be fatal. A person withdry skin has a

resistance from one arm to theother of about

1 × 105 . When skin is wet, the resistance

drops to about 4700 .

What is the minimum voltageplaced across

the arms that would produce acurrent that

could be felt by a person withdry skin?

Using the same electricpotential as in Part 1,

what would be the current if theperson had

wet skin?

Answer in units of mA.

Explanation / Answer

Resistance with dry skin, R1 = 1 X 10 5 Resistance with wet skin, R2 = 4700 current to be felt , i = 1 mA = 1 X 10 -3 A   dryskin: voltage, V = i R1 = 1 X 10 -3 * 1 X 10 5 =  100 volts    Wetskin:    current, i = V / R2 = 100 / 4700= 0.0213 A = 21.3mA    current, i = V / R2 = 100 / 4700= 0.0213 A = 21.3mA

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