Electric Forces and Electric Fields21(c) Outside the spherical dome,2ekqEr=. Thus, at 4.0 mr=, ()( )922428.9910 N mC2.010CC4.0 mE−×⋅×==51.110 N×15.35For a uniformly charged sphere, the field is strongest at the surface. Thus, maxmax2eER=, or ( )( )2623maxmax22.0 m3.010 N C1.310C8.99CeREqk−×=×15.36If the weight of the drop is balanced by the electric force, then mgor the mass of the drop must be q EeE( )( )1941621.610C3510 kg9.8 m seEmg−−××≈×But, 343mVrρρπand the radius of the drop is 1334mπρr=167335 10 kg5.210mor~ 1 m4858kgmrrµ−−××15.37(a)
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