課程名稱︰電磁學下
課程性質︰物理系必修
課程教師︰陳政維
開課學院：理學院
開課系所︰物理系
考試日期（年月日）︰99.4.19
考試時限（分鐘）：08:10~10:20
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題︰
1.Please calculate the ratio of displacement current to conduction current of
(a)silver and (b)water for a microwave with a frequency of 10^10 Hz.
(Both Ag and water are non-magnetic;the dieletric constant for Ag and water
are 1 and 80;the resistivity for Ag and water are 1.59×10^-8Ω/m and
2.5×10^5Ω/m) (10pts)
2.What are the skin depths of (a) silver and (b) water for a microwave with a
frequency of 10^10 Hz? (15pts)
3.Calculate the reflection coefficient for light at an air-to-silver at an
optical frequency?
(ω=4×10^15/s) (10pts)
4.It should be noticed that theMaxwell stress tensor T must be integrated over
the full closed surface to have the proper effect.
(a)the force between two point charges q,seperated by a distance 2a
by integrating T over the plane equidistance between the two charges.
(b)The force exerted on the (infinite)planar surface of a dieletric of
permittivityεby apoint charge q a distance d away. (20pts)
5.A longcoaxial cable,of length l,consists of an inner conductor (radius a)
and an outer conducter (radius b).It is connected to a battery at one end
and a resistor at the other.The inner conductor carries a uniform charge per
unit lengthλ,and a steady current I to the right;the outer conductor has the
opposite charge and current.What is the electromagnetic momentum stored in
the field? (10pts)
6.The intensity of sunlighthitting the earth is about 1300W/m^2.What pressure
does it exert if the sunlight strikes a perfect reflector. (10pts)
7.Imagine an iron sphere of radius R that carries a charge Q and a uniform
magnetization M=Mz.The sphere is initially at rest.Please compute the
angular momentumstored in the eletromagnetic fields. (15pts)
8.Please derive theFresnels equation for the case of polarization
perpendicular to the plane of incidence.
(You can use the following parameters:n1,n2,μ1,μ2,ΘI,ΘT) (10pts)
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