Your Name:
(lpt)
50
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.
Prelim
1
ECE 2100, spring 2011, Professor Molnar
The exam will last 2.5 hours, you are permitted 1 singlesided 8.5"x 11" crib sheet to be
turned in for 5pts. You may also use a calculator. Scrap paper is provided and should
be attached: show your work for partial credit. However, answers should be written in
the space provided: if we have to go looking for your answer, you will lose 1 point
off that answer! If you get stuck on any given part, move on, and come back later.
Numerical Answers need only be accurate to two significant figures. "estimates" need
only be within a factor of 2.
1)
True/false 1lPt each)
a.
T
/ff) The voltage across an inductor cannot change instantaneously
b.
(f)
F
At steady state, the CUlTent through a capacitor is zero.
c.
T
/®
Unless there is a voltage or current source in the system, The
voltage across the capacitors in an
RC
circuit will always settle to zero,
~ardless
of initial conditions.
d.
W
F
When applying superposition, you cannot remove dependant
sources, only independent sources.
2)
(2 pts) We stated in class that when applying nodevoltage analysis, for a given
node's equation, the voltage associated with that node should have the same sign
in every instance, and all other voltages should have the opposite sign (the "sign
check") When does this rule not apply? 12 sentences
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3)
(5 pts) You have an LED with the IV curve shown. You want to use a
reasonable amount of current with a 3V battery, so you include a 250 resistor in
series with it. Sketch the IV curve of the LEDresistor series combination on the
same graph, and estimate the power consumed from a 3V supply.
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 Spring '05
 KELLEY/SEYLER
 Vout, node voltage equations, IV curve, absurd RLC circuit

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