Download Electric_Candidates_Quiz_Fall2000

ECE 1100 – Fall 2000
Electric Candidates Quiz
Shattuck Section
October 12, 2000
Find a numerical expression for the power delivered by each of the
candidates.
-3[V] 4[mA]
+
-
-6[V]
+
+
6[V]
Gore
Buchanan
-2[mA]
Nader
2[mA]
4[mA]
3[V]
+
-
Bush
Solution:
In this problem, we have four power expressions to write. Let’s start by determining
which sign convention is being used for each candidate, and then write the expression for that
candidate.
For Buchanan, the reference polarity of the current, is in the direction of the reference
voltage drop. This is what we call the passive sign convention. From our rules, then, we can
write
pdel , Buchanan    6[V] 2[ m A]  12[ m W].
Notice that we use a subscript to make it clear that we are writing an expression for the power
being delivered by Buchanan.
For Nader, the reference polarity of the current, is in the direction of the reference voltage
drop. This is what we call the passive sign convention. From our rules, then, we can write
pdel , Nader    6[V] 2[ m A]  12[ m W].
Notice that we use a subscript to make it clear that we are writing an expression for the power
being delivered by Nader.
For Gore, the reference polarity of the current, is in the direction of the reference voltage
drop. This is what we call the passive sign convention. From our rules, then, we can write
pdel ,Gore    3[V] 4[ m A]  12[ m W].
Notice that we use a subscript to make it clear that we are writing an expression for the power
being delivered by Gore.
For Bush, the reference polarity of the current, is in the direction of the reference voltage
rise. This is what we call the active sign convention. From our rules, then, we can write
pdel , Bush   3[V] 4[ m A]  12[ m W].
Notice that we use a subscript to make it clear that we are writing an expression for the power
being delivered by Bush.
Please note some things.
 This time, we chose not to define new variable names. However, if we did use
the variables in our equations, the variables need to be defined. We do this by
labeling them in the diagram.
 Always show units. Your answer can be given in [W] or in [mW]. That choice is
up to you.
If you have any questions about any of this, now is the time to ask someone, and get it
cleared up. We will grade this quiz, but it will be a small part of your ECE 1100 course grade.
However, understanding this may end up being a large part of your ECE 2300 grade.
Thanks,
Dr. Dave
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