Question

Variations in the resistivity of blood can give valuable clues to changes in the blood's viscosity and other properties. The resistivity is measured by applying a small potential difference and measuring the current. Suppose a medical device attaches electrodes into a 1.5-mm-diameter vein at two points 5.0 cm apart.

Required:
What s the blood resistivity if a 9.0 V potential difference causes a 230μA current through the blood in the vein?

Answer 1

Answer:

 ρ= 1.378 10⁴ Ω / m

Explanation:

Let's use ohm's law

          V = i R

           R = V / i

let's calculate

           R = 9.0 / 230 10⁻⁶

           R = 3.9 10⁴ Ω

now we can use the definite of resistance

           R = ρ $\frac{L}{A}$

the area of ​​a circle is

           A = π r² = π (d/2)²

           ρ = R A / L

           ρ = π R $\frac{d^2}{4L}$

let's calculate

          ρ = π 3.9 10⁴  $\frac{(1.5 \ 10^{-3}^2 }{4 \ 5 \ 10^{-2}}$

          ρ= 1.378 10⁴ Ω / m