ECET 3000 Electrical Principles ___________________________Homework # 2 – Due: 15 June 2016
Instructions – Complete the following problems and place your final answers in the blanks provided. Be sure to
show all of the work required to obtain the final solutions. You may complete this assignment in the
space provided after each problem statement on this handout as long as you write neatly and that your
work is well organized.
Problem #19) Given the following DC circuit, determine the voltage across the 115Ω resistor, V A , using the
Superposition Theorem. (You may use the space on the next page when completing this problem)
30
+
VA
V1
V1  120 volts
40
+
115
+
V2
V2  60 volts
-
VA = ______________________ (V)
Problem #21) Given the following circuit with load resistor RL:
10
15V
20
40
a
RL
b
a) Determine the Thevenin’s Equivalent Circuit for the network as “seen” by the load
resistor connected to terminals “a” and “b”.
b) Determine the power supplied to the resistor using both the original circuit and the
Thevenin’s Equivalent Circuit if RL = 52Ω.
Problem #22) Determine the Thevenin’s equivalent circuit for the network shown in the figure below with
respect to terminals “a” and “b”. Also, if a single resistive load is connected to the circuit at
terminals “a” and “b” in order to transfer maximum power to that resistor from the circuit,
determine the maximum amount of transferred power that could be achieved.
100
75
a
18V
40
50
b
Problem #23) Given the following DC circuit that is operating at steady-state:
IDC 60
100
24V
+
Ohms
Ohms
40uF
VR
120
Ohms
20mH
Determine IDC and VR in the circuit as shown.
Problem #24) Given the following DC circuit that is operating at steady-state, determine the DC currents I S and
I C as shown in the circuit:
IS
60
Ohms
20V
80
40 Ohms
IC
Ohms
40uF
20mH
Problem T/F) Specify whether each of the statements are TRUE or FALSE.
__________ The series equivalent resistance of multiple resistors in series will always be greater than the
resistance of any of the individual resistors.
__________ Kirchhoff’s Voltage Law states that the sum of voltages across a set of series resistors will
always equal zero.
__________ The parallel equivalent resistance of multiple resistors in parallel will always be greater than the
resistance of any of the individual resistors.
__________ An ideal switch in the “off” position appears to be an “open-circuit”.
__________ Within a circuit, parallel resistors must have the same current flowing through all of them.
__________ If two resistors having the same resistance value are in parallel with each other in an active
circuit then the two resistors will have the same magnitude currents flowing through them.
__________ According to Kirchhoff’s Current Law, if all of the currents for a given node are defined in a
direction such that they are all “entering” the node, then the sum of these currents must be zero.
__________ Given a set of parallel resistors, if additional resistors are added to the parallel combination then
the total equivalent resistance will decrease.
__________ Given a circuit containing a single voltage source and one or more resistors, current will flow
“out of” the positive terminal of the voltage source.
__________ There is never a potential difference (voltage) across an idea wire.
__________ If two resistors are in series with each other in an active circuit then the two resistors will have
the same magnitude currents flowing through them.
__________ The direction of the voltage rise across a resistor will always be opposite compared to the
direction of current flowing through the resistor.
__________ Any two elements within a circuit that are connected across the same two nodes are said to be in
parallel with each other.
__________ Nodal Analysis of a circuit utilizes a set of Kirchhoff’s Voltage Law equations specified in terms
of node voltages.
__________ Setting a load resistor connected to a specific circuit equal to the circuit’s Thevenin’s Equivalent
Resistance will result in a maximum power transfer to the load resistor from the circuit.
__________ Setting a load resistor connected to a specific circuit equal to the circuit’s Thevenin’s Equivalent
Resistance will result in a maximum voltage across the load resistor.
#19) V A1  59.68 volts
Answers:
V A2  22.38 volts

V A  V A1  V A2  37.3 volts
Rth = 28
a
Vth = 12V
21)
b
Pload  1.17 watts
(same for both the original circuit and the equivalent circuit)
______________________________________________________________________________________
Rth = 33.7
a
RL  RTH  33.7 I 
22)
Vth = 1.675V
1.675
 0.02484 A
33.7  33.7
PL  I 2  RL  (0.02484) 2  (33.7)  0.0208W  20.8mW
b
______________________________________________________________________________________
23)
IDC 60
Ohms
24V
100
+
Ohms
VR
120
Ohms
-
Cap.  Open Ckt. at steady-state (remove from ckt.)
Ind.  Short Ckt. at steady-state (replace with “ideal”
wire)
VR  0 volts (no voltage across an "ideal" short - ckt.)
24V
24
I DC 

 0.15 amps
(60  100) 160
______________________________________________________________________________________
24)
I S  0.2 amps, I C  0 amps
True/False) T, F, F, T, F, T, T, T, T, T, T, T, T, F, T, F