Most of the resistance of the human body comes from the skin, as the interior of

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Most of the resistance of the human body comes from the skin, as the interior of the body contains aqueous solutions that are good electrical conductors. For dry skin, the resistance between a person s hands is measured at typically 500 k ohm. The skin varies in thickness, but on the average it is about 2.0 mm thick. We can model the body between the hands as a cylinder 1.6 m long and 14 cm in diameter with the skin wrapped around it. What is the resistivity of the skin ohm. m Compare your answer with the internal resistivity of the body, approximately 4.8 ohm middot m. P skin/p interior = How do you explain the fact that the resistance of the skin is about 1000 times greater than the internal resistance of the body, even though the resistivity of the skin is only about 60 times that of the interior of the body The skin is constantly moistened by biological processes. The skin has a smaller cross sectional area. Charges can only exist on the surface of conductors. The resistance of an object scales exponentially with respect to the resistivity of the material out of which it is made. A 3.0 MU F capacitor is put across a 9 V battery. After a long time (~20 time constants), the capacitor is disconnected and placed in series through an open switch, with a 225 ohm resistor, Determine the charge on the capacitor before it is discharged. C What is the initial current through the resistor when the switch is closed A At what time will the current reach 37% of its initial value An ultracapacitor is a very high-capacitance device capable of storing much more energy than an ordinary capacitor. It is designed so that the spacing of the plates is around 1000 times smaller than in ordinary capacitors. Furthermore the plates contain millions of microscopic nanotubes, which increase their effective area 100,000 times. If the plate separation and effective area of a 30 mu F capacitor are changed as described above to make an ultracapacitor, what is its new capacitance F How much energy does the ultracapacitor store if charged to 1.5 V Compare this to the energy in an ordinary 30 mu F capacitor at that potential, union_ultracapacitor = J union_ultracapacitor/union_capacitor = Compare the energy stored in the ultracapacitor to that of the AAA battery, which contains 6750 J. union_ultracapacitor/union_battery = If the ultracapacitor is to take 1.0 min to decrease to 1/e of its initial maximum charge, what resistance must it discharge through

Explanation / Answer

8. we know that equation R=(L)/A .

hence resistivity = R*A/ L

surface area = 2pi*r*h + 2pi*r2 =0.73 m2

resistivity = R*A/ L = 500 x 103 * 0.73 / 1.6 = 228.125 x 103 ohm. metre ........Ans.

skin/ interior = 228.125 x 103 /4.8 = 47.52   Ans.

other questions are not clear appearing

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