Download Quick Quizzes

Quick Quizzes
Dave Shattuck
ECE 1100
Quick Quiz 2 (TuTh F2001)
• Take out a sheet of paper. Print your name on it. Imagine that
Texas and California are connected by a transmission line.
Sketch this. (Labeled boxes will do.)
• Define a voltage variable which is the voltage at California, with
respect to Texas.
• Define a current variable which is the current flowing from
Texas to California.
• If the voltage in Texas is 100[kV] higher than in California, find
the value of your voltage variable.
•
If the current flowing from California to Texas is 5[kA],
find the value of your current variable.
Quick Quiz 1 – MW 9AM Fall 2001
• Take out a sheet of paper. Print
your name on it.
• Sketch a rough diagram of a
cockroach. Define a voltage
variable which is the voltage at the
head, with respect to the tail.
• Define a current variable which is
the current flowing from the tail to
the head.
• If the voltage at the tail is 50[V]
higher at the tail than at the head,
find the value of your voltage
variable.
• If the current flowing from the tail to
the head is 5[A], find the value of
your current variable.
Desk of Power Quiz
Fall 2001 (MW 9AM)
During the preparation for the mayoral debate, it
was found that the desk for one of the candidates had
a voltage across it, and a current through it. The
voltage and current that existed for the desk are
shown in the figure below.
Write an expression for the power being absorbed by
the desk. Find the power absorbed by the desk.
3[A]
desk
+
180[V]
-
Desk of Power Quiz
During the preparation for the upcoming presidential
debate, it was found that the desk for one of the candidates
has a voltage across it, and a current through it. The
voltage and current that exist for the desk are shown in the
figure below.
• a) Is the desk absorbing power?
• b) Write an expression for the power being absorbed by
the desk.
3[A]
desk
+
180[V]
-
Desk of Power Quiz
a) Is the desk absorbing power?
b) Write an expression for the power being absorbed by the desk.
Solution:
a) In the first part of this problem, there is an assumption being made.
The question “Is the desk absorbing power?” is assumed to really
mean, “Is the desk absorbing positive power?”
To answer this, we need to find
the power associated with the
desk, which is part b). So, let’s
find it.
Let’s start by determining which
sign convention is being used.
desk
Just for clarity, I am going to
define a couple of variables.
+
180[V]
3[A]
-
Desk of Power Quiz
We have defined a couple of variables. 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
pabs,desk  vDiD .
iD = 3[A]
desk
+
vD = 180[V]
-
Desk of Power Quiz
Notice that we use a subscript to make it clear that
we are writing an expression for the power being
absorbed by the desk. We can now plug in the
values for voltage and current, and get
pabs,desk  vDiD .
iD = 3[A]
desk
pabs ,desk   180[V] 3[A]  540[W].
+
vD = 180[V]
-
Desk of Power Quiz
Using this answer, we can answer part a). The answer is no, the desk
is not absorbing positive power. It is delivering positive power. It is
absorbing negative power. This is another way of saying that the desk
is acting like a source, in that it is delivering power to the electrical
circuit that it is connected to.
pabs,desk  vDiD .
iD = 3[A]
desk
pabs ,desk   180[V] 3[A]  540[W].
+
vD = 180[V]
-
Quick Quiz 3 Tu-Th 4:30PM Section
• Take out a sheet of paper. Print your name on it.
• Imagine that Dr. Dave has a voltage across him,
and a current through him. Sketch a picture of Dr.
Dave, labeling his right and left hand. (A stick
figure will do.)
• Define a voltage variable which is the voltage at
his right hand, with respect to his left hand.
• Define a current variable which is the current
flowing from his left hand, through his body, to his
right hand.
• Write an expression for the power absorbed by
Dr. Dave using your variables.
• If the voltage is 3[V] higher at his right hand than
at his left hand, and the current flowing from his
right hand to his left hand is 6[mA], find the power
absorbed by Dr. Dave.
Electric Candidates Quiz
Let’s do another quiz. Get out a sheet of paper.
-3[V] 4[mA]
+
-
-6[V]
+
+
6[V]
Gore
Buchanan
-2[mA]
Nader
2[mA]
4[mA]
3[V]
+
-
Bush
Electric Candidates Quiz
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
Quick Quiz 3 MW 9AM
• Take out a sheet of paper. Print your name on it.
• Draw the schematic symbol for an independent
voltage source. The value for this source is 15[V].
• Label the terminal of the voltage source that is
nearest the + sign, with the letter A. Label the
terminal of the voltage source that is nearest
the - sign, with the letter B.
• Define a current variable which is the current from
terminal B to terminal A, through the voltage
source.
• Write an expression for the power delivered by this
voltage source, in terms of the this current variable.
• If a current equal to 2[mA] is flowing from terminal
A to terminal B through the voltage source, find the
power delivered by the voltage source.
Quick Quiz 4 TuTh 4:30PM
Find a numerical expression for the power delivered
by each of the batteries.
+
Battery 3
3[V]
-
6[V]
+
4[mA]
- 6[V]
Battery 4
Battery 2
3[V]
Battery 1
-4[mA]
-2[mA]
2[mA]
Quick Quiz 1 (Spring 2002)
1. Take out a sheet of paper. Print your name on it. Sketch a
picture of Sarah Hughes. (Artistry does not matter. A stick
figure will do.)
2. Define a voltage variable which is the voltage at her left hand,
with respect to her right hand.
3. Define a current variable which is the current flowing through
her, from her right hand to her left hand.
4. If the voltage at her right hand is 100[mV] higher than at her
left hand, find the value of your voltage variable defined in 2.
5. If the current flowing from her left hand to her right hand is
5[mA], find the value of your current variable defined in 3.
Baseball Facts
The World Series, which includes teams from only
two countries, begins this weekend. In the
baseball bat shown below, the end that you hold
onto, is called the handle.
The end which hits the ball is called the barrel.
See the diagram below.
barrel
handle
Quick Quiz 1 (Fall 2002)
1. Take a 3x5 card. Print your name on it. Sketch a baseball bat,
and label the barrel and the handle.
2. Define a voltage variable which is the voltage at the barrel,
with respect to the handle.
3. Define a current variable which is the current flowing through
the bat, from the handle to the barrel.
4. If the voltage at the barrel is 30[V] higher than at the handle,
find the value of your voltage variable defined in 2.
5. If the current flowing from the barrel to the handle is 5[mA], find
the value of your current variable defined in 3.
Electric Companies Quiz
Let’s do another quiz. Get out a sheet of paper.
+
+
Enron
-800[A]
Reliant
220[V]
-
80[V]
300[A]
Dynegy
500[A]
-80[V]
-
+
Williams
Dr. Dave
470[V]
+
-
330[V]
-300[A]
+
Electric Companies Quiz
Find a numerical expression for the power
delivered by each of the electric companies.
+
+
Enron
-800[A]
Reliant
220[V]
-
80[V]
300[A]
Dynegy
500[A]
-80[V]
-
+
Williams
Dr. Dave
470[V]
+
-
330[V]
-300[A]
+