The resistivity of the body is a good measure of its overall composition. A measure of the resistance of the upper arm is a good way to estimate the percent fat in a person's body. Let's model a person's upper arm as a cylinder of diameter 8.0 cm and length 20 cm. We can model the composition of the arm by assuming that the muscle, far, and nonconductive portions (the bone) form simple regions. This simple model actually works quite well. For a typical adult, the bone has a cross-sectional area of 1.0 cm2; to a good approximation, the balance of the arm is fatty tissue or muscle.
A. Assume that the arm has 30% fat and 70% muscle. What is the resistance of the arm?
B. Now, assume that the arm has only 10% muscle. What is the resistance now?