Electronics 1 (PHYS2241)

BSc, Physics - PHYS

Semester: Second Semester

Level: 200

Year: 2017

Answers (200 )
REPUBLIC OF CAMEROON THE UNIVERSITY OF BAMENDA
Peace-Work-Fatherland P.O BOX 39 Bambili
School/Faculty: Science Department: Physics Lecturer(s): N.H. ALOMBAH
Course Code: PHYS2241 Course Title: ELECTRONICS 1
Date: 4-08-2017 Hall: ASANJI Time: 3hours
Instructions: Answer all questions.
SECTION A 15 MULTIPLE CHOICE QUESTIONS
Select the letter that corresponds to the best answer and write it down in your answer booklet.
1) Two initially identical samples A and B of pure germanium are doped with donors to
concentrations of 1 ∙ 10

and 3 ∙ 10

respectively. If the hole concentration in A is 9 ∙ 10

, then
the hole concentration in B at the same temperature will be
3 ∙ 10


7 ∙ 10


11 ∙ 10


27 ∙ 10


2) To forward-bias a P-N junction, diode,
an external voltage is applied that is positive at the anode and negative at the cathode
an external voltage is applied that is negative at the anode and positive at the cathode.
an external voltage is applied that is positive at the P-region and negative at the N-region
A and C above
3) In the forward region of its characteristics, a diode appears as a/an
OFF switch
high resistance
capacitor
ON switch.
4) A PN junction acts as: (A) a controlled switch (B) a bidirectional switch (C) a unidirectional switch
(D) a push button switch
5) The output of a half-wave rectifier is suitable only for
running car radios
running ac motors
charging batteries
running tape-recorders.
6) Nodal analysis can be applied for
(A) Planar networks (B) non-planar networks (C) both planar and non-planar networks (D) neither
planar nor non-planar networks
7) What should be done, if the dependent current and voltage sources are present in a circuit while
applying ‘Superposition Theorem’?
(A) Replace them by open circuit
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(B) Replaced them by short circuit
(C) Keep in their original forms
(D) None of the above
8) If there ‘b’ branches and ‘n’ nodes the number of equations will be:
(A) n-1
(B) b
(C) b-n-1
(D) b-n+1
9) An ideal current source has:
(A) Zero internal conductance
(B) Zero internal resistance
(C) Zero voltage on no load
(D) Zero ripple
10) For maximum transfer of power, internal resistance of the source should be:
(A) Equal to load resistance
(B) Less than that of the load
(C) More than that of the load
(D) Zero
11) The superposition theorem requires as many circuits to be solved as there are:
(A) Nodes
(B) Sources
(C) Nodes and Sources
(D) Nodes, Sources and Mesh
12) Which of the following is correct:
(A) Norton’s equivalent resistance is the same as Thevenin’s equivalent resistance
(B) Norton’s equivalent is the current equivalent of the network
(C) The load is connected in Parallel to the Norton’s equivalent resistance and Norton’s equivalent
current source
(D) All the above
13) “Maximum power output is obtained from a network when the load resistance is equal to the
output resistance of the network as seen from the terminals of the load”. The above statement is
associated with
(A) Millman’s theorem
(B) Thevenin’s theorem
(C) Superposition theorem
(D) Maximum power transfer theorem
14) In Thevenin’s theorem, to find the equivalent impedance,
(A) all independent current sources are short circuited and independent voltage sources are open
circuited
(B) all independent voltage sources are open circuited and all independent current sources are short
circuited
(C) all independent voltage and current sources are short circuited
(D) all independent voltage sources are circuited and all independent current sources are open
circuited
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15) “Any number of current sources in parallel may be replaced by a single current source whose
current is the algebraic sum of individual source currents and source resistance is the parallel
combination of individual source resistances”. The above statement is associated with
(A) Thevenin’s theorem
(B) Millman’s theorem
(C) Maximum powedr transfer theorem
(D) None of the above
SECTION B: give detailed solutions and explanations where necessary.
(1) What do you understand by the following: (a) open circuit (b) short circuit (c) Ground (d)
Zener Breakdown? (4mks)
(2) Distinguish between analogue and digital electronics giving examples (4mks)
(3) Obtain the node voltages
,
,
in the circuit shown below. (6mks)
(4) For the bridge circuit shown in the figure below, find the load
for maximum power
transfer and the maximum power absorbed bly the load. (6mks)
(5) (a) State the Thevenin and Norton theorems. (4mks)
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(b) Obtain the Thevenin and Norton equivalent circuits at the terminals a-b of the circuit in
the figure below. (6mks)
(6) What is rectification? Using a circuit diagram, explain full wave rectification, using
waveforms were necessary to explain. (6mks)
(7) Find

and in the circuit of the figure below. (6mks)
END
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