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Chapter 22 - 22.46

46. The charge dq within a thin shell of thickness dr is ρAdr where A =4 πr 2 .Thus,with ρ = b/r ,wehave

q =

rdr =2 πb r 2 −

r 1 .

With b =3 . 0 µ C / m 2 , r 2 =0 . 06 m and r 1 =0 . 04 m, we obtain q =0 . 038 µ C.

dq =4 πb r 2

r 1