ECE 307 – Exam 3 – Spring 2003 – Date – Name (print):
This test is closed book and closed notes. SHOW ALL WORK. Partial credit may be
given. Work the problems according to the method specified. Be sure to specify whether
your answers are in degrees or radians. Please be sure to BOX IN your answers.
1 Power Calculation (25 points)
You are a non-electrical engineering employee working for an electronics manufacturer that
has been producing defective DVD players. Your boss decides that, although EE is not your
focus area, since you have obtained a quality engineering education from South Carolina’s
most prestigious university, that you should lead the R&D team that is investigating the
defects in the DVD player’s design. You are presented with a capacitor (C= 2 mF), resistor
(R= 2 Ω), and an inductor (L= 20 mH) that are connected in series. This series connection
of elements is connected across a voltage source with v(t) = 10√2sin(120πt+π
2) One of your
EE colleagues has determined this voltage phasor to be 106π
2, but you know that this is not
the case. Find his mistake and finish the job that he doesn’t seem capable of doing, and
you’ll be up for promotion by the end of the month.
(A) Write the voltage source as an RMS voltage phasor.
(B) Find the current that flows through the series connection of elements. Express this
current as an RMS current phasor and as a function of time.
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