CE 403 Optional FE review
Chris Rehmann
Electricity and magnetism
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Charge, energy, current, voltage, power
Work done in moving a charge in an electric field
Force between charges
Current and voltage laws
Equivalent circuits
Capacitance and inductance
Reactance and impedance, susceptance, and
admittance
• AC circuits
• Basic complex algebra
AUC practice exam #105
Problem 12: Forces on charges
Three point charges in a vacuum are arranged in a
straight line. Find the force on point charge A.
A
400 mC
3m
B
-200 mC
4m
C
800 mC
USF Problem 2.2
Example 2.2 from USF FE question of the day
Problem 1: Resistor
A cylindrical resistor is redesigned so that its length is 4
times larger and its diameter is 2 times larger. The
original resistance is 100 kW. What is the new resistance?
a. 100 kW
b. 400 kW
c. 800 kW
d. 1600 kW
arcolresistors.com
AUC practice exam #106
Problem 2: Resistor
What is the current in the circuit below and what is the
power dissipated in the resistor?
a. 12 A and 4 W
b. 2.5 A and 30.1 W
c. 360 A and 9.2 W
d. 0.4 A and 4.8 W
12 V
30 W
Problem 3: Resistors in series
What is the voltage across resistor 2?
a. 3 V
b. 9 V
c. 12 V
d. 30 V
V =12 V
R1 = 10 kW
R2 = 30 kW
Problem 4: Resistors in parallel
What is the current through resistor 2?
a. 0.3 mA
b. 0.4 mA
c. 1.2 mA
d. 1.6 mA
V =12 V
R1 = 10 kW
R2 = 30 kW
Problem 4a: More resistors
What is the current through resistor 2?
a. 0.0 mA
b. 0.3 mA
c. 0.4 mA
d. 1.2 mA
V =12 V
R1 = 10 kW
R2 = 30 kW
AUC practice exam #107
Problem 5: More complicated case
What is the current through resistor 1?
Vb
Va
R1
R3
R2
Va = 32 V
Vb = 20 V
R1 = 2 W
R2 = 4 W
R3 = 8 W
AUC practice exam #103
• Capacitors have places separated by a
dielectric material.
• An electric field forms across the dielectric
material.
• Charge is separated, and energy is stored
Problem 6: Capacitance
Two square parallel plates (0.04m x 0.04 m) are
separated by a 0.1 cm thick insulator with a dielectric
constant of 3.4. The plates are connected across 200 V.
a. What is the capacitance?
b. What charge exists on the plates?
Ex. 46.1 of Lindenburg, EIT Reference Manual, 8th edition
Problem 7: RC circuit #1
The capacitor is initially uncharged, and the switch is set
to position a at t = 0.
a. What is the time constant of the circuit?
b. What is the current 1 ms after the switch is closed?
c. What is the energy in the capacitor at that time?
a
R
b
V
C
R = 2 kW
C = 1 mF
V = 10 V
Problem 8: RC circuit #2
If after a long time the switch (in #7) is set on position b,
then when is only 1% of the steady state charge
remaining?
a
R
b
V
C
R = 2 kW
C = 1 mF
V = 10 V
Problem 9: Equivalent capacitance
Determine the equivalent capacitance.
C2
C1
V
C3
C1 = 10 mF
C2 = 5 mF
C3 = 4 mF
Problem 10: Steady state RC circuit
Example 2.1 from USF FE question of the day
AUC practice exam #108
Problem 11: LR circuit
a. What is the time constant of the circuit?
b. What are the voltages in the resistor and inductor and the
energy in the inductor 1 ms after the switch is set to a?
c. When is the voltage across the inductor 1% of the voltage V
when the switch is set to b after steady state is reached?
a
b
V
R
L
R = 2 kW
V = 10 V
L=4H
Problem 11: LR circuit
a. What is the time constant of the circuit?
b. What are the voltages in the resistor and inductor and the
energy in the inductor 1 ms after the switch is set to a?
c. When is the voltage across the inductor 1% of the voltage V
when the switch is set to b after steady state is reached?
a
b
V
R
L
R = 2 kW
V = 10 V
L=4H
Problem 13: Phasor form
Express 6 + j 7 in phasor form.
Problem 14: Phasor form
Express (13 + j 17)/(15 – j 10) in phasor form.
Problem 15: AC circuit—resistance only
How is VR related to V? What is the impedance V/I? Does
the current lead or lag the voltage VR?
R
V = Vmsinwt ~~
Problem 16: AC circuit—capacitance only
Find the maximum current in the circuit if C = 150 mF, Vm
= 300 V, and the frequency is 60 Hz.
C
V = Vmsinwt ~~
Problem 17: AC circuit—inductance only
Find the maximum current in the circuit if L = 60 mH, Vm
= 300 V, and the frequency is 60 Hz.
L
V = Vmsinwt ~~
Problem 18: Average power in AC circuit
A circuit has a load of 150 W and a voltage V = Vmsinwt
with Vm = 170 V and f = w/2p = 60 Hz. What is the
average power?
Problem 19: Resonance in an AC circuit
At what frequency does resonance occur if C = 150 mF, L
= 4 mH, and R = 150 kW?
L
C
V = Vmsinwt ~~
R
AUC practice exam #111
AUC practice exam #110