Let inner conductor at reza have drange to on it, " outer :" r= 3a 20 Use Gauss' law to find held in dielectric at zac re 30. $ Dids = Q where 5 is spherical surface of radius r in dielectric and note , lay symmetry, D CP ) = D(r ) ar ! . D ( r ) . 4trz = Q = D ( " ) = 40re Q AD E = -D = Q ar " Potential difference between inver router corderstars is r= 20 20 V = - Eidr = - - ardr r=3a 3a :dr Q for Q Q ATTE ( za - 3a ) Q 24 rea ! Capacitance is C = Q Q 24 TE a 2/24TEA