课程名称︰电磁学一 课程性质︰必修 课程教师︰张宏钧、江衍伟、林怡成、林晃岩 开课学院：电机资讯学院 开课系所︰电机工程学系 考试日期（年月日）︰2012/06/22 考试时限（分钟）：100min 是否需发放奖励金：是（如未明确表示，则不予发放） 试题 : Final Exam (10:20am-12:00noon) 1.(5%) What is the definition of the magnetization vector in a magnetic material in terms of magnetic dipole moments? 2.(5%) For a material medium with permittivity ε, permeability μ, and conductivity σ, what is its complex intrinsic impedance? 3.(8%) Find the unit vector normal to the surface y = x^2 at the point (3,9,3) 4.(27%) Consider a source consisting of an infinite sheet lying in the xy-plane in free space. A uniformly distributed current Js(t) flows on this infinite plane sheet. (a)(20%) The source generates sinusoidally time-varying uniform plane waves propagating in the ±z-direction in free space. Consider the +z propagatiion having the following characteristics: f = 200MHz and polarization is left circular with the electric field at z = 0+ and t = 0 having an x-component equal to -2E0 and a y-component equal to 1.5E0. Please write the expressions for the electric-and magnetic- field intensities for this wave. (b)(7%) What is the expression for Js(t). 5.(20%) Consider a uniform electromagnetic wave propagating in a uniform material with intrinsic impedance expressed as η = |η|exp(jθ) along the negative z-direction. The electric field at z = 0 is found to be H(0,t) = H0cosωt ax H/m, where ω is the angular frequancy. The propagation constant of the wave is expressed as γ = α + jβ. (a) Give the expression for H(z,t). (4%) (b) Give the expression for E(z,t). (6%) (c) Give the expression for the instantaneous Poynting vector. (4%) (d) What is the time-varying power flow per unit area along the z-direction? (6%) 6.(15%) Consider two infinitely long, straight-line charges of equal and opposite uniform and passing through x = b and x = -b, respectively, as shown in the figure. If the potential is zero at the point (0,b,0) and is 1V at (b,b,0), what are the values for the potential at the points (2b,b,0) and (b,2b,b), respectively? 第六题的图与课本FIGURE 5.14(b)完全同 7.(20%) Consider a coaxial-line structure. The inner conductor has a ring-shape cross-section, that is, it is a solid cylindrical conductor of radius a with that part of r < r0 removed and replaced by air, where the radius r0 < a. A current I(Amp) flows with uniform volume density J = J0 az (Amp/m^2) along the infinitely long inner conductor and returns with uniform surface density in the opposite direction along the surface of an infinitely long, perfectly conducting cylinder of radius b(>a) and coaxial with the inner conductor. Please find the internal inductance per unit length of the inner conductor. --

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