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

ρ= 1.378 10⁴ Ω / m

Step-by-step 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
`(L)/(A)`

the area of ​​a circle is

A = π r² = π (d/2)²

ρ = R A / L

ρ = π R
`(d^2)/(4L)`

let's calculate

ρ = π 3.9 10⁴
`((1.5 \ 10^(-3)^2 )/(4 \ 5 \ 10^(-2))`

ρ= 1.378 10⁴ Ω / m