2002. 4.18
1.Please give the definitions of electric and magnetic dipole ρ and μ.
(Indicate their direction)(10%)
Consider a magnetic dipole μ in magnetic field B. Show that the energy
difference of the states between the maximal and minimal values is 2μB.
(10%)
2.Please give two methods to distinguish electric dipole from monopole.
(10%)
3.Two parallel-plate capacitors have the same plate area A and separation d,
but the dielectric constants of the materials between their plates are
κ+Δκ in one and κ-Δκ in the other.
(a)Find the equivalent capacitance when they are connected in parallel.
(b)If the total charge on the parallel combination is Q, what is the charge
on the capacitor with the larger capacitance?
(15%)
4.Find an expression for the magnitude E of the induced electric field at
points within the magnetic field, at radius r from the center of the
magnetic field.
(10%)
5.Please derive the number density n of charge carriers with charge e in
conducting strip of thickness ι carrying a current I placed in a magnetic
field B, creating a potential difference V across the strip.(Hall effect)
(15%)
6.A particle of mass m, positive charge q, and initial kinetic energy K is
projected (from a large distance) toward a heavy nucleus of charge Q that is
fixed in place. Assuming that the particle approaches head-on, how close to
the center of nucleus is the particle when it comes momentarily to rest?
(10%)
7.Please describe and explain the three different conduction behavior in
conductor, insulator, and semiconductor by using the concept of the energy
band.(9%)
How is the temperature dependence of the conductivity for each type?(6%)
Why?(5%)
8.Good luck!!!! (Total 100%)
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