- #1
sharkey1314
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Current Electricity -- current flowing through hand
i)For a layer dry skin 1mm thick, determine the resistance of a 1 cm^2 area of skin.
Resistivity of dry skin : 3 x 10^4 ohms m
[3.0 x 10^5 ohms ]
ii)A person, who is well-earthed, accidentally grabs a wire of diameter 0.4 cm at a potential of 50V. His hand makes contact with the whole circumference of the wire over a distance of 9cm.
The average thickness of skin of his hand is 1mm. Estimate the current flowing through him.
[1.89 mA ]
Resistance = resistivity(length)/area
V = IR
For i) , I managed to solve it.
Using the equation directly.
For ii), I couldn't get the answer.
First, I calculate the surface area of the cylinder ( wire ) where it is in contact with the wire.
Surface area = pi . diameter . length
= pi . (0.4 x 10^-2) . (9 x 10^-2)
= 0.0011309 m^2
Then I multiply this surface area with the resistance of dry hand obtain in i)
Total resistance = surface area x resistance of dry skin 1 mm thick, area of 1m^2
= 0.0011309 x 3.0 x 10^5
Next, I used V = IR. Sub in total resistance and P.D of 50 V
The answer I got was 0.147 A. Totally off.
Thanks for the time !
Homework Statement
i)For a layer dry skin 1mm thick, determine the resistance of a 1 cm^2 area of skin.
Resistivity of dry skin : 3 x 10^4 ohms m
[3.0 x 10^5 ohms ]
ii)A person, who is well-earthed, accidentally grabs a wire of diameter 0.4 cm at a potential of 50V. His hand makes contact with the whole circumference of the wire over a distance of 9cm.
The average thickness of skin of his hand is 1mm. Estimate the current flowing through him.
[1.89 mA ]
Homework Equations
Resistance = resistivity(length)/area
V = IR
The Attempt at a Solution
For i) , I managed to solve it.
Using the equation directly.
For ii), I couldn't get the answer.
First, I calculate the surface area of the cylinder ( wire ) where it is in contact with the wire.
Surface area = pi . diameter . length
= pi . (0.4 x 10^-2) . (9 x 10^-2)
= 0.0011309 m^2
Then I multiply this surface area with the resistance of dry hand obtain in i)
Total resistance = surface area x resistance of dry skin 1 mm thick, area of 1m^2
= 0.0011309 x 3.0 x 10^5
Next, I used V = IR. Sub in total resistance and P.D of 50 V
The answer I got was 0.147 A. Totally off.
Thanks for the time !