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Unformatted text preview: es, equations, d raw ings, and / or graphs, m ake a clear and concise pred iction
that solves the task. (H int: H ow can you m ake a qualitative prediction w ith as m uch
d etail as possible?) EXPLORATION
System atically construct an electric field m ap using EM Field program . For instructions
o n how to use this program see the Exploration section of the “Electric Field Vectors”
lab problem . Save your result to pd f.
N ext, construct a physical m od el of a d ipole using the battery, rod s, and cond uctive
paper. Make sure to read the suggested append ix m aterials for d etails on how to use the
D MM and the cond uctive paper setup. Follow the instructions given there to set up the
cond uctive paper. 16 ELECTRIC FIELD FROM A DIPOLE – 1302Lab1Prob2
O nce the rod s are connected to the battery, set the d igital m ultimeter (DMM) to DC
volts and turn it on . Place the tip s of the probe on the cond uctive paper m id w ay
betw een the tips of th e tw o rod s. Ad just the units on the DMM until you obtain
reasonable read ings. Recall the field m aps you generated in the w arm up questions and
w ith EM Field . Rotate the probe so that the center of the probe stays in the sam e spot.
D o the values change (pay attention to the sign)? Is there a m inim um or m axim um
value as you rotate the probe? Are there any apparent sym m etries as you rotate the
probe? If there are large fluctuations in the read ings, d eterm ine how you w ill m easure
consistently. Determ ine how you w ill use the probe to d eterm ine the electric field
direction a t other points.
N ow place the field probe near, but not touching, one of the rod s and rotate the probe
as you d id before. Record your d ata. Determ ine the d irection of the electric field .
Com pare the m axim um DMM read ing at this point to the one you found at the m id w ay
point. Com pare your m easurem ents to your pred iction; d oes the value d isplayed on the
DMM becom e larger or sm aller w hen the electric field becom es stronger? Consid er how
you w ill use the probe to d eterm ine the electric field s trength a t other points.
Test a few m ore key points on the cond uctive paper. Where on the cond uctive paper is
the electric field strongest? Weakest? Consid er w hether your observations m atch your
Discuss in your group how you w ill use the probe to d eterm ine the field s trength a nd
d irection a t an arbitrary point on the cond uctive paper and how you w ill record the
results on the w hite copy of the cond uctive paper. Discu ss how you could construct a
system atic m ap (hint: think grid ) of the d ipole’s electric field . M EASUREMEN T
C om plete your m easurem ent plan for m apping the electric field on the cond uctive
paper. Select a point on the cond u ctive paper w here you w ish to d eterm ine the electric
field and d eterm ine its m agnitude a nd d irection . Repeat the m easurem ent to gain an
estim ate of the m easurem ent uncertainty. Record the result on the w hite copy of the
cond uctive paper. Repeat for as m any points as need ed to system atically create a field
m ap that can be used to check your pred iction.
IMPORTAN T: Dissem inate electronic copies of your results from this and exploration
section to each m em ber of your group. Your TA can provid e you w ith scans of your
hand -constructed d ipole m ap, or you m ay scan it on your ow n tim e after lab. A N ALYSIS AN D CON CLUSION
H ow d oes your m ap com pare to your pred iction? H ow d oes it com pare to the
sim ulation program ? Where is the field strongest? H ow d o you show this in your 17 ELECTRIC FIELD FROM A DIPOLE – 1302Lab1Prob2
m ap? Where is the field w eakest? H ow d o you show this in your m ap? Do your
answ ers som ehow d ep end on the axis of sym m etry und er consid eration?
Overall, w as your pred iction successful? Why or w hy not? 18 PROBLEM #3: GRAVITATION AL FORCE
ON THE ELECTRON
You w ork in a research laboratory that is attem pting to m ake a better electron
m icroscope. The project requires precise control of a beam of electrons. To stud y your
ability to m anipulate electron m otion, you d ecid e to use a Cathod e Ray Tube (CRT) (the
sam e d evice that is the basis of old er, box-style TV sets. In the CRT, electrons are
em itted at one end of an evacuated glass tube (called the cathod e) and are d etected by
their interaction w ith a phosphorous screen on the other end (called the anod e). Every
object near the Earth's surface is subject to the gravitational force. Your team -m ates are
w orried that the gravitational force w ill d eflect the electron from the d esired path, and
that this d eflection w ill d epend on w hether the beam is vertical or ho rizontal (or at
som e general angle of inclination). From your physics experience you also know that
th e acceleration of all objects in free fall d ue to gravity is the sam e, ind epend ent of their
m ass. You d ecid e to com pute how far the beam d eviates from a straight-line trajectory
at d ifferent angles of inclinatio...
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This document was uploaded on 02/23/2014 for the course MANAGMENT 2201 at University of Michigan.
- Spring '14