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EKT101 Electric Circuit Theory
Semester 1, 2012/2013
Assignment 3
CHAPTER 6 - SINUSOIDAL STEADY-STATE ANALYSIS
Q1.
Determine the Vo in the figure 1 using the following method;
a. Nodal analysis
b. Mesh analysis
Figure 1
Q2.
Find the Thevenin and Norton equivalent circuits at terminals a-b for each of the circuits in
Figure 2 (a) and (b).
Figure 2
Q3.
Find the Thevenin and Norton equivalent circuits for the circuit shown in Figure 3.
Figure 3
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EKT101 Electric Circuit Theory
Semester 1, 2012/2013
CHAPTER 7 - AC POWER ANALYSIS
Q1.
Given the circuit in Figure 1, find the average power supplied or absorbed by each element.
Figure 1
Q2.
Given Vs = 2030V, R1 = 5Ω, R2 = 8Ω, XL = j4Ω, XC = -j6Ω in the circuit shown in Figure
2, find the average power dissipated by each element and the complex power.
Figure 2
Q3.
Determine the maximum average power transfer in Figure 3 if is  5cos 40t A and the value
of inductor is 7.5 mH, the resistor, R1 is12 ohm, the resistor, R2 is 8 ohm and the capacitor is
40 mH.
Figure 3
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EKT101 Electric Circuit Theory
Q4.
Semester 1, 2012/2013
Find the value of ZL in the circuit of Figure 4 for maximum power transfer.
Figure 4
Q5.
Assuming that the load impedance is to be purely resistive, what load should be connected to
terminals a-b of the circuits in Figure 5 so that the maximum power is transferred to the load?
Figure 5
Q6.
For the circuit in Figure 6, calculate the following:
(a)
The power factor
(b)
The average power delivered by the source
(c)
The reactive power
(d)
The apparent power
(e)
The complex power
12045ºV
Figure 6
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EKT101 Electric Circuit Theory
Semester 1, 2012/2013
CHAPTER 8 - THREE PHASE CIRCUITS
Q1.
A balanced delta-connected load has a phase current IAC = 10-30 A.
(a)
Determine the three line currents assuming that the circuit operates in the positive
phase sequence.
(b)
Calculate the load impedance if the line voltage is VAB = 110 0 V.
Q2.
A balanced three-phase wye-delta system has Van = 1200˚ V rms and ZΔ = 51+j45Ω. If the
line impedance per phase is 0.4 + j 1.2, find the total complex power delivered to the load.
Q3.
A balanced delta-connected load is supplied by a 60-Hz three-phase source with a line
voltage of 240V. Each load phase draws 6 kW at a lagging power factor of 0.8. Find:
(a)
the load impedance per phase
(b)
the line current
(c)
The value of capacitance needed to be connected in parallel with each load phase to
minimize the current from the source.
Q4.
A balanced wye load is connected to a 60-Hz three-phase source with Vab = 2400˚V. The
load has lagging pf =0.5 and each phase draws 5 kW.
(a)
Determine the load impedance, ZY.
(b)
Find Ia, Ib, and Ic.
Q5.
A balanced wye-connected load with a phase impedance of 10 - j16 is connected to a
balanced three-phase generator with a line voltage of 220 V. Determine the line current and
the complex power absorbed by the load.
Q6.
Three equal impedances, 60 + j80  each, are delta-connected to a 230-V (rms) three-phase
circuit. Another three equal impedances, 40 + j10  each, are wye-connected across the same
circuit at the same points. Determine:
(a)
the line current,
(b)
the total complex power supplied to the two loads,
(c)
the power factor of the two loads combined.
Q7.
The total power measured in a three-phase system feeding a balanced wye-connected load is
12 kW at a power factor of 0.6 leading. If the line voltage is 208 V, calculate the line current
IL and the load impedance ZY.
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