In: Physics
A) The resistivity of blood is related to its hematocrit, the volume fraction of red blood cells in the blood. A commonly used equation relating the hematocrit h to the blood resistivity ρ (in Ω⋅m) is ρ=1.32/(1−h)−0.79. In one experiment, blood filled a graduated cylinder with an inner diameter of 0.90 cm. The resistance of the blood between the 1.0 cm and 2.0 cm marks of the cylinder was measured to be 246 Ω. What was the hematocrit for this blood?
B) When the starter motor on a car is engaged, there is a 310 AA current in the wires between the battery and the motor. Suppose the wires are made of copper and have a total length of 1.2 mm . What minimum diameter can the wires have if the voltage drop along the wires is to be less than 0.60 VV ? Express your answer in millimeters.
C) 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-mmmm-diameter vein at two points 5.0 cmcm apart. What is the blood resistivity if a 8.8 VV potential difference causes a 220 μAμA current through the blood in the vein? Express your answer in ohm meters.