Question

A thin-walled metal spherical shell of radius a = 8 m has a charge qa = 23 C. Concentric with it is a thin-walled metal spherical shell of radius b = 7a and charge qb = 27 C. Find the electric field at points a distance r from the common center, where (a) r = 2.4 m, (b) r = 16 m, and (c) r = 84.0 m.

Answer 1

given

a = 8 m

q_a = 23 C

b = 7a

q_b = 27 C

(a) r = 2.4 m

using equation

E = Q / 4 _o r²

r = 2.4 < a

so

E = 0 N/C ( no electric field )

b )

r = 16 m

E = Q / 4 _o r²

= 9 X 10⁹ X ( 23 + 27 ) / 16²

E = 1.757 X 10⁹ N/C

c )

r = 84 m

E = Q / 4 _o r²

= 9 X 10⁹ X ( 23 + 27 ) / 84²

E = 6.377 X 10⁷ N/C