Find the radius of the unmyelinated axon (m) with space parameter A = 15 mm, (Resistance of a unit area of the membrane, R, =0.2 Q.m, Resistivity of axoplasm, p. =2 0.m).

How much current will be flowiing through a 40.0 length of copper wire with  a radius 4.0 mm if it is connected to a source supplying 16.0 V? ( The resistivity of copper is 1.68E-8 ohm m)

A certain single ion channel is selectively permeable to K+ and has a resistance of 1.15 GΩ , therefore a current of potassium ions through the channel is possible. During an experiment, the channel is open for approximately 1.50 ms while the voltage across the channel is maintained at 89.5 mV. How many K+ ions, ?, travel through the channel during this time?

Assuming a constant temperature coefficient of resistivity, what is the maximum percent decrease in the resistance of a constantan wire starting at 20.0oC ?