current density is unity.
9.20 In a dielectric ($\sigma$ = 10$^{-4}$ S/m, $\mu_r$ = 1, $\epsilon_r$ = 4.5), the conduction current density is given
as $J_c$ = 0.4 cos(2$\pi$ × 10$^8$t) A/m$^2$. Determine the displacement current density.
9.21 In a source-free region, H = H$_o$cos($\omega$t ? $\beta$z)a$_x$ A/m. Find the displacement current
density.
9.22 An ac voltage source is connected across the plates of a parallel-plate capacitor so that
E = 25sin(10$^3$t)a$_z$ V/m. Calculate the total current crossing a 2 × 5 m area placed per-
pendicular to the electric field. Assume that the capacitor is air filled.
