Lecture 2 - AC and DC Circuit Analysis
Lecture 2 - AC and DC Circuit Analysis
Lecture 2 - AC and DC Circuit Analysis
INTRODUCTION
TYPES OF ELECTRIC CURRENT
• Direct Current – flows in one direction and energy
transfer takes place unidirectional
• Alternating Current – one in which the direction
alternates regularly
OHM’S LAW
•
OHM’s LAW relates the three basic electrical quantities:
current, voltage and resistance.
“The current flowing in a circuit is directly proportional
to the voltage and inversely proportional to the
resistance.”
OHM’S LAW
•
Electrical Power is defined as the time rate at which
charged Q is forced to move by the applied voltage.
Parallel Circuit
VOLTAGE DIVIDER RULE
•
CURRENT DIVIDER RULE
DELTA AND WYE CIRCUITS
• – Wye transformations
Delta
Wye – Delta transformations
SAMPLE PROBLEMS
1. A 50-ohm resistor is in parallel with 100-ohm
resistor. Current in 50-ohm resistor is 7.2 A. How will
you add a third resistor and what will be its value if
the line-current is to be 12.1 A?
a. 360 ohms
b. 277 ohms
c. 156 ohms
d. 450 ohms
2. What is the power dissipated by R2, R4, and R6?
• network
A is defined as the interconnection of
components.
A branch represents a single element.
A node is the point of connection between two or more
branches.
A loop is any closed path in a circuit.
A mesh is a loop which does not contain any other loops
within it.
ELECTRICAL NETWORK LAWS AND THEOREMS
Superposition Theorem
• In a network with two or more sources, the current
or voltage for any component is the algebraic sum of
the effects produced by each source acting
separately.
Thevenin’s Theorem
• The entire network connected to the load can be replaced by
a single voltage source Vth in series with a single resistance Rth
connected to the same terminal.
Norton’s Theorem
• The entire network connected to the load can be
replaced by a single current source ISC in parallel with
a single resistance RO.
11. Find the Thevenin equivalent (VTH and RTH) between
terminals A and B of the circuit given below.
a. 4.16 V, 120 Ω
b. 41.6 V, 120 Ω
c. 4.16 V, 70 Ω
d. 41.67 V, 70 Ω
12. A certain current source has the values IS = 4 µA
and RS = 1.2 MΩ. The values for an equivalent voltage
source are
a. 4.8 μV and 1.2 M Ω
b. 1 V and 1.2 M Ω
c. 4.8 V and 4.8 M Ω
d. 4.8 V and 1.2 M Ω
13. Calculate Iab and Vcg for the circuit below.
a. 0.931 A, 6.62 V
b. 0.113 A, 2.26 V
c. 0.313 A, 2.26 V
d. 0.391 A, 6.26 V
14. Find the current through R2 of the given circuit.
a. 30.7 mA
b. 104 mA
c. 74 mA
d. 134 mA
15. Referring to the given circuit, the voltage and
current for the load resistor, RL, is
a. 450 mV, 4.5 mA
b. 4.50 V, 45 mA
c. 4.50 V, 4.5 mA
d. 450 mV, 45 mA
AC Circuits
•
Peak Value is the maximum value of a waveform of one alternation either negative or
positive alternation.
Peak-to-Peak Value is the magnitude of the waveform from the peak of the positive
alternation to the peak of the negative alternation.
Average Value is the average of ALL the instantaneous value during ONE alternation.
• Capacitive Reactance
2. Reactive Power
• the power consumed by the reactive component
3. Apparent Power
• vector sum of the true power and reactive powers.
16. What is the peak-to-peak voltage of the waveform
in the given circuit?
a. 2 V
b. 4 V
c. 6 V
d. 8 V
17. A half-cycle average voltage of 12 V is equal to what
rms voltage?
a. 13.33 V
b. 8.48 V
c. 18.84 V
d. 7.64 V
18. What is the total current?
a. 56.6 mA
b. 141 mA
c. 191 mA
d. 244 mA
19. What is the total current?
a. 15.6 mA
b. 17.8 mA
c. 21.9 mA
d. 26.0 mA
• Referring to the given figure, determine ZTH as seen
20.
by RL if R1 is changed to 3.3 kΩ.
a. 1488
b. 3859
c. 5180
d. 1828
21. A 9 mH coil is in parallel with a 0.015 μF capacitor
across an 18 kHz ac source. The coil's internal
resistance, RW, is 60 Ω. The circuit impedance is
a. 1,389 Ω
b. 1,734 Ω
c. 290 Ω
d. 1,018 Ω
22. A 15 resistor, an inductor with 8 inductive
reactance, and a capacitor with 12 capacitive reactance
are in parallel across an ac voltage source. The circuit
impedance is
a. 12.7 ohms
b. 127 ohms
c. 4,436 ohms
d. 6,174 ohms