*University of Lagos*
*Faculty of Engineering*
*Department of Electrical and Electronics Engineering*
*Electrical Engineering Materials (EEG 215) Mid-Semester Test*
*Instructions: Write out only the correct option for each question*
*Time allowed: 15 Minutes*
A copper wire of 2mm diameter with conductivity of 5x10^7 Siemens/m and electron mobility of
0.0032 m2/V-S is subjected to an electric field of 20mV/m. Use the information to answer
questions 1-4.
1. The change density of free electrons is
A. 1.132x10^(29)/m^3
B. 1.232x10^(27)/m^3
C. 1.332x10^(25)/m^3
D. 1.432x10^(23)/m^3
2. The current density
A. 1.16x10^(6)A/m^2
B. 1.26x10^(5)A/m^2
C. 1.36x10^(4)A/m^2
D. 1.46x10^(3)A/m^2
3. The current flowing in the wire is
A. 3.67 A
B. 3.76 A
C. 2.67 A
D. 2.66 A
4. The electron drift velocity is
A. 64m/s
B. 62m/s
C. 60m/s
D. 58m/s
5. An aluminum cable has a resistance of 27Ohm at a tempt of 35°C. If the temperature
coefficient of at 0°C is 0.0038/°C, the resistance at 0°C is
A. 23.83 Ohms
B. 23.03 Ohms
C. 22.83 Ohms
D. 22.03 Ohms
6. Which of these is NOT true about the classical free electron theory?
A. It is used to explain the electrical conductivity of semiconductors and insulators
B. It is used to verify Ohm's
C. It is used to derive Widemann-Franz law
D. It is used to explain the optical properties of metals
7. Which of the following is NOT a physical properties of metals?
A. At high temperature, resistivity is proportional to fifth power of absolute temperature.
B. High electrical and thermal conductivity
C. Obey Ohm's law
D. Resistivity is inversely proportional to the pressure in many metals.
8. The resistance of an electrical conductor does not depend on
A. Length of the conductor
B. Strength of the conductor
C. Type of material
D. Cross sectional area of the conductor
9. Use the Fermi distribution function to obtain the value of F(E) for E-Ef = 0.01eV
A. 0.3589
B. 0.3398
C. 0.3278
D. 0.3198
10. The correct value of Lorentz number as based on quantum theory is
A. 2.44x10^(-8) WOhm/K^-2
B.2.45x10^(-8) WOhm/K^-2
C.2.44x10^(-6) WOhm/K^-2
D.2.45x10^(-6) WOhm/K^-2
11. The Fermi distribution function can be described by
A. F(E)= 1/(1+(exp(E-Ef)/KT))
B.F(E)= 1/(1+(exp(Ef+E)/KT))
C.F(E)= 1/(1-(exp(E-Ef)/KT))
D. F(E)= 1/(1-(exp(E+Ef)/KT))
Answers:
1. A
2. A
3. A
4. A
5. A
6. A
7. A
8. B
9.
10. A
11. A