中原大學九十二學年度碩士班入學招生考試

1.	Derive the wave equation of the electric part in the source-free medium with its permittivity ,permeability and conductivity .And interpret the term in the equation involving the conductivity.(5%)
2.	For one-sided abrupt p+n-junction of semiconductor with permitt s and doping concentration NA>>ND in consideration of x-direction.
	i)	Using the Poisson's equation to solve the depletion-layer width w for the reverse-biased voltage VR.(5%)
	ii)	How to determine the built-in potential Vbi in terms of edpletion-layer capacitance per unit area C5%)by plotting the straight line of(1/C')2 vs.VR.(5%)
3.	Steady(DC-)current flows through two different lossy dielectric materials 1,1 and 2,2,respectively.Prove the condition for the parameters of the both media that there exists no surface charge density si=0 at the interface.(15%)
4.	Illustrate the Hall-measurement schema for the n-type rectangular sample of length ,width w and thickness t,note the polarity of applied voltage V and Hall-voltage VH as well as the direction of current flow I(or ).(10%)And derive to obtain the electron-mobility n.(10%)
5.	Two parallel cylindrical conductors(transmission lines)each of radius a and length ,separated by distance d(d>>a),that are buried in the soil of parameter ,and.
	i)	Solve in between the inductance L and the capacitance C.(15%)
	ii)	If the electrodes are connected to an ohmmeter for measuring the resistance R=1.47k and the given pair of copper rods,each of which is 5 mm in diameter, 15 cm in length and 2 cm in spacing.Calculate the corresponding conductivity of the soil.(10%)
	iii)	What is the product of L and C.(5%)
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