4. A parallel-plate capacitor has plates of area A separated by a distance s. Its dielectric has a conductivity σ=a+bx, where x is the distance to one plate and a uniform relative permittivity εᵣ. With an alternating voltage with the angular frequency ω across the electrodes, there is a current I flowing through the dielectric. What is the electric field in the capacitor?
(A)
(B)
(C)
(D) 
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統計: 尚無統計資料
統計: 尚無統計資料