Figure P27.8 represents a section of a circular conductor of non-uniform diameter carrying a current of 5.00

Question:

Figure P27.8 represents a section of a circular conductor of non-uniform diameter carrying a current of 5.00 A. The radius of cross section A1 is 0.400 cm.
(a) What is the magnitude of the current density across A1?
(b) If the current density across A2 is one-fourth the value across A1, what is the radius of the conductor at A2?

Ag A1