ASSIGNEMENT 1
Electronics Principles: ELPH501
Part A: Electronic circuits
Question 1. [10 Marks]
A combination circuit is shown in the diagram
at the right. Use the diagram to answer the
following questions.
a. The current at location A is _____ (greater
than, equal to, less than) the current at location
B.
b. The current at location B is _____ (greater
than, equal to, less than) the current at location
E.
c. The current at location G is _____ (greater than, equal to, less than) the current at location
F.
d. The current at location E is _____ (greater than, equal to, less than) the current at location
G.
e. The current at location B is _____ (greater than, equal to, less than) the current at location
F.
f. The current at location A is _____ (greater than, equal to, less than) the current at location
L.
g. The current at location H is _____ (greater than, equal to, less than) the current at location
I.
Question 2. [15 Marks]
Analyze the following circuit and determine the values of the total resistance, total current,
and the current at and voltage drops across each individual resistor.
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Part B: Semiconductors
Question 3. [10 Marks]
A semiconductor of composition 20%Na2O-80%SiO2 and a density of approximately 2.4g.cm3
has a conductivity of 8.25x10-6 (Ω-m)-1 at 150oC. If the conduction occurs by the diffusion of
Na+ ions, what is their drift mobility (μ)?
Data: Atomic masses of Na, O and Si are 23, 16 and 28.1 respectively.
Question 4. [15 Marks]
Suppose that the electrical conductivity of the semiconductor MgO is determined primarily by
the diffusion of Mg2+ ions. Estimate the mobility of Mg2+ ions and calculate the electrical
conductivity of MgO at 1800oC.
Data: Diffusion Constant of Mg in MgO = 0.0239 cm2/s; lattice parameter of MgO,
a=0.396x10-7cm; Activation Energy for the Diffusion of Mg2+ in MgO = 79,000cal/mol;
k=1.987cal/K=k-mol; For MgO, Z=2/ion; q=1.6x10-19C; kB=1.38x10-23J/K-mol
Hint: First calculate the diffusion coefficient D.
Know that MgO has 4 Mg2+ and 4 O2- Per cell.
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