Ece 152: Electrical Engineering Materials Question Paper

Ece 152: Electrical Engineering Materials

Course:Bachelor Of Engineering In Electrical And Electronics Engineering

Institution: Moi University question papers

Exam Year:2008

ECE 152:ELECTRICAL ENGINEERING MATERIALS

QUESTION ONE
a. Enumerate the failures of free electron model (4mks)

b. What is the significance difference between quantized photons and electron distribution (2mks)

c.
i. give the important information that Fermi energy contributes in bans theory of solids (3mks)

ii. With your knowledge in quantized free electron theory show

E(PD)=(n/4.55*10^27)^2/3 (5mks)

QUESTION TWO
a. State the reason why the applied field only has an effect on the electron energy in between collisions (2mks)

b. From Drude's model show that electrical conductivity is given by;
s={(ne^2)t*E}/m (7mks)

c.
i. what was the most celebrated success of Dryer's model (1mks)

ii. List the successes of free electron model (4mks)

QUESTION THREE
a. Explain the term superconductivity as in electron of metals (4mks)

b. Discuss the occurrence of superconductivity (4mks)

c. The Fermi energy of a metal is 5eV. Calculate the magnitude.

i. momentum
ii. the wave vector
iii. the velocity of an electronp near the fermi surface.(6mks)

QUESTION FOUR
a. Sketch the graphs of states g(E), f(E)g(E) when T=0 and that of f(E)g(E) when T>0 against electron energy E (6mks)

b. Prove that the fermi level in an intrinsic semiconductor exists in the middle of the band gap (4mks)

c. Prove that polarization is given by
P=e(0)E{e(r)-1} (4mks)

QUESTION FOUR
a. List any four dielectric properties (4mkk

b.
i. What brings about Hall effect in conductors (1mk)

ii. Mention the three magnetic effects of free electrons (3mks)

c. What are the mobility and the density of doping of a semiconductor if a plate of gives a Hall voltage of 15mV when the. current through the plate is 48mA and the magnetic flux density at right angles to it is 0.10T? The plate has thickness of 2.0mm, a width of 4.0 mm and a length of 5.0mm. The current through the plate is produced by a voltage of 2.0Vbetween its ends. (6mks)

QUESTION SIX
a. Classify magnetism as per the susceptibility and atomic /magnetic behavior (5mks)

b. Discuss anti ferromagnetism as applied in magnetic materials (6mks)

c. A magnetic field of 200A/m is applied to a material which has a susceptibility of 1200.What will be the
i. Relative permiability
ii. intensity of magnetization
iii. Flux density (3mks)

Ece 152: Electrical Engineering Materials Question Paper

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