physics exam
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RE: physics exam - 4/3/2008 11:54:10 AM
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Nauree
Posts: 2909
Joined: 6/16/2007
From: Ponchatoula, LA
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What is your physics 222?
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RE: physics exam - 4/3/2008 12:34:43 PM
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jakemc
Posts: 58
Joined: 2/14/2008
From: Houghton, MI
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I love physics 2
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RE: physics exam - 4/3/2008 1:13:07 PM
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cyber00677
Posts: 316
Joined: 6/9/2007
Status: offline
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well congrats on the B. i use to like physics but then it got boring fast
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RE: physics exam - 4/3/2008 1:45:11 PM
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specializedfuji
Posts: 168
Joined: 2/27/2007
Status: online
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physics 222 is magnetic fields, heat transfer, optics and such.
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RE: physics exam - 4/3/2008 2:07:58 PM
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Nauree
Posts: 2909
Joined: 6/16/2007
From: Ponchatoula, LA
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OO I'm taking that one next semester.
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RE: physics exam - 4/3/2008 3:29:44 PM
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DFour
Posts: 434
Joined: 6/14/2007
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B and E is next semester for me too.. along with atomic and nuclear. everything up to 214 in physics has been good for me so far. i dont really feel like taking calc 3 this summer but oh well.
what are your fields of interest? I like electrical and optical, mechanics gets BORRRING with tha quickness.
you done research or internship yet?
oh yeah, check out the march issue of Physics Education, i got an article in there 
http://www.iop.org/EJ/abstract/0031-9120/43/2/F02
< Message edited by DFour -- 4/3/2008 3:39:42 PM >
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RE: physics exam - 4/3/2008 3:32:02 PM
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vpsophmore
Posts: 4716
Joined: 8/10/2006
From: ATL
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Great job! LoL I remember getting 20s and 30s on Chemistry exams and having the highest grade in the class... I ended up getting a minor in Chemistry a few years back on total accident. the thing about science professors is that they think you know what they know.
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RE: physics exam - 4/3/2008 3:38:01 PM
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Nauree
Posts: 2909
Joined: 6/16/2007
From: Ponchatoula, LA
Status: offline
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quote:
ORIGINAL: DFour
B and E is next semester for me too.. along with atomic and nuclear. everything up to 214 in physics has been good for me so far. i dont really feel like taking calc 3 this summer but oh well.
what are your fields of interest? I like electrical and optical, mechanics gets BORRRING with tha quickness.
you done research or internship yet?
oh yeah, check out the march issue of Physics Education, i got an article in there
http://www.iop.org/EJ/abstract/0031-9120/43/2/F02
Quote your shit up here. I an't buying it.
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RE: physics exam - 4/3/2008 3:49:37 PM
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DFour
Posts: 434
Joined: 6/14/2007
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lol aight buyin what? im not sellin anything..
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RE: physics exam - 4/3/2008 3:51:57 PM
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Nauree
Posts: 2909
Joined: 6/16/2007
From: Ponchatoula, LA
Status: offline
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Gota buy a subscription to Physics Edu to see the article.
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RE: physics exam - 4/3/2008 3:53:32 PM
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DFour
Posts: 434
Joined: 6/14/2007
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F r o n t l i n e
Lighting accounts for a relatively large fraction of
annual energy consumption in many industrialized
nations. One way to reduce this consumption is to
replace traditional lighting with alternative sources,
such as LEDs. Since the use of such alternatives is
sure to increase in the future, an understanding of
how these devices conserve energy is important for
students of physics.
This article presents two circuits to show how
traditional and LED lighting compare. The supplies
required for these demonstrations include a
spring-loaded circuit board with sockets (or another
means of connecting the circuit elements), three
0.9 W incandescent bulbs, three green LEDs, wire
leads and a 9 V battery (or DC power supply).
In the first circuit three incandescent bulbs are
connected in series with a 9 V source. In the second
circuit the three LEDs and three bulbs are wired
alternately in series (figure 1). The LEDs must be
forward biased for the demonstration to work. The
circuits should be connected before the beginning
of the class, except for a final lead that serves as a
switch. During class, images of these circuits can
be projected onto a screen, or students can connect
the circuits themselves and make observations and
measurements.
As the first circuit is shown, students should be
asked the following questions:
What do you observe when the three bulbs are
connected in series with the 9 V source?
What are the measured current and calculated
power for this series circuit?
Measured values for voltage and current are shown
in table 1 for our set-up.
Students can then observe the second circuit and
answer three additional questions:
What differences do you see when the three
LEDs are added to the circuit?
What is the measured current in the second
circuit?
How do the power requirements compare for
the two circuits?
Once students have responded to these questions,
we usually discuss their answers in a large group
setting. There are helpful ways to direct these discussions,
an analysis of which is given below.
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In the first circuit the three bulbs are brightly
illuminated when connected in series. While in
operation, a potential drop of approximately 3 V
is present across each bulb. The series current is
measured at approximately 0.31 A, so the power
required for each bulb is 0.93 W (from P = VI).
Thus the total power supplied by the battery is
2.8 W (9 V × 0.31 A, or three bulbs × 0.93 W).
In the second circuit, the LEDs are brightly illuminated,
whereas the bulbs show no illumination.
This drastic change clearly indicates a decrease in
the power required to operate the circuit. The reasoning
here is that the battery serves as a constant
voltage source so that the power delivered by the
source is the product of the constant voltage multiplied
by the current supplied. From a measured
current of approximately 62 mA, the total power
delivered by the source is 0.56 W, compared with
2.8 W for the incandescent bulbs.
The power requirements for the second circuit
can be reduced further by decreasing the applied
voltage with a variable voltage source (as shown in
figure 1), since LEDs typically require only a few
milliamps for nominal illumination. However, the
L i g h t i n g
LEDs provide ‘green’ energy
Figure 1. Circuit board with three bulbs and three
LEDs wired alternately in series to a 9 V power
source. The LEDs are brightly illuminated while
the bulbs show no illumination. The multimeter
indicates a series current of 0.062 A.
F r o n t l i n e
goal here is to use readily available supplies, so a
9 V battery is best for general classroom use.
Further discussion may focus on why the two
devices require such vastly different currents for
operation. To handle these questions, instructors
should focus on how light is generate
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