课程名称︰电磁学 课程性质︰必修 课程教师︰陈政维 开课学院：理学院 开课系所︰物理系 考试日期（年月日）︰97/06/23 考试时限（分钟）：120 分钟 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : 1.What are the skin depth of (a) silver and (b) water for a microwave with a frequency of 10^10 Hz ? (Both Ag and ater are non-magnetic ; the dielectric constant for Ag and water are 1 and 80 ; the resistivity for Ag and water are 1.59x10^-8Ω-m and 2.5x10^5Ω-m) 2.An insulating circle ring of radius b lies in the xy plane , centered at the origin. It carries a linear charge density λ=λ0sinΦ, where λ0 is a constant and Φ is the usual azimuthal angle. Charge the power radiated by the ring if it ratates at a constant angular velocity ω about the z-axis. 3.(a)Suppose we have a rectanglar wave guide with height a and width b (a>b), please derive the solution for the TEmin modes. (b) Let a=2.28 cm and b=1.01 cm , and the deriving frequency is 1.70x10^10 Hz, what TE modes will propagate in this waveguide? 4.Please find the resulting electric and magnetic fields of an infinite straight wire that carries the current I(t)=0 for t<=0 and I(t)=Io for t>0. The wire is electrically neutral and Io is a constant. 5.A paticle of charge q is traveling at constant speed v along the x axis. Calculate the total power passing through the plane x=a, at the moment the particle itself is at the origin. 6.With the inclusion of the radiation force, Newton's second law of a charged particle becomes a=τ(da/dt)+F/m, where F is the external force acting on the particle and τ=μoq^2/6πmc. If a particle is subjected to a constant force F, beginning at time t=0 and last until time T. Exclude the runaway solution, calculate (a) the work done by the external force and (b) the total energy radiated. --

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