21_Chapter 15 HomeworkCH15 Electric Forces and Electric Fields

21_Chapter 15 HomeworkCH15 Electric Forces and Electric Fields

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Electric Forces and Electric Fields 21 (c) Outside the spherical dome, 2 e kq E r = . Thus, at 4.0 m r = , () ( ) 92 2 4 2 8.99 10 N m C 2.0 10 C C 4.0 m E ×⋅ × == 5 1.1 10 N × 15.35 For a uniformly charged sphere, the field is strongest at the surface. Thus, max max 2 e E R = , or ( ) ( ) 2 6 2 3 max max 2 2.0 m 3.0 10 N C 1.3 10 C 8.99 C e RE q k × = × 15.36 If the weight of the drop is balanced by the electric force, then mg or the mass of the drop must be q E eE ( ) ( ) 19 4 16 2 1.6 10 C 3 51 0 k g 9.8 m s eE m g ×× × But, 3 4 3 mV r ρρ π    and the radius of the drop is 13 3 4 m πρ r = 16 7 3 35 10 kg 5.2 10 m or ~ 1 m 48 5 8 k gm rr µ  ×  ×  15.37 (a)
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This document was uploaded on 10/20/2011.

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