4. Figure in the below shows a cross section of a hollow cylindrical conductor of radii a and b, carrying a uniformly distributed current i. a) Show that the magnetic field magnitude B(r) for the radial distance r in the range. b < r < a is given by b) Show that when r = a, this equation gives the magnetic field magnitude B at the surface of a long straight wire carrying current i; when r = b, it gives zero magnetic field; and when b = 0, it gives the magnetic field inside a solid conductor of radius a carrying current i. c) Assume that a = 2.0 cm, b = 1.8 cm, and i= 100 A, and then plot B(r) for the range 0 < r < 6 cm .

4. Figure in the below shows a cross section of a hollow cylindrical conductor of radii a and b, carrying a uniformly distributed current i. a) Show that the magnetic field magnitude B(r) for the radial distance r in the range. b < r < a is given by b) Show that when r = a, this equation gives the magnetic field magnitude B at the surface of a long straight wire carrying current i; when r = b, it gives zero magnetic field; and when b = 0, it gives the magnetic field inside a solid conductor of radius a carrying current i. c) Assume that a = 2.0 cm, b = 1.8 cm, and i= 100 A, and then plot B(r) for the range 0 < r < 6 cm .