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Unformatted text preview: Illtwolk Recording Player  znlnnsjmsnlsiwkis Eile view !nlu ﬂelp Meeung Number 719 739 558 Date: Tuesday. May 15, 2mm mg 6 58 PM, Lucamme (GMT 05 an) a .1 Pa rticipams :3 Ex
Name Julnlnﬂ “WE /LEaWIE DmE
Curl Lvrldl D5 53 PM ID7 D} PM Daniel Hale us as w m 52 w J Table of Contenu E ' mu m 24
nu ‘ 12‘ 14 DeVry University Online Physics 216 Live Lecture Week 5
Professor Daniel Hale network Recording: Plaver r 2n1nn5jllv521s,wx,5 Eile view lnla help Meeung Number 719 73a ssa Date: Tuesday, May 15, mm me 6 5a m, LucalTlme (em as an) E a
.l Participant: Ex
Name Joining lime Hem/VIE lame
CurlLyndl use; w yum: w
I DEI’llEl HElE D5153 PM ID7159 PM Adade’Dlln D7DIPM/D759PM
_ ' This week we cover the connection between
electricity and magnetism. ' This will also conclude our study of
electromagnetism for this course. mal duraan m m uz l' shew all
Tull: nu ma Du Ll B EMF an M 40
m MnnanalEMFI DD‘JD‘M
D MnnnnalEMFU DD112114 re mumsl m: “was ° We will also look at circuits a bit more and
even include some AC current into them. ° Any questions before I start? ‘ I Network kemdmg . '3 DatumenuMltm. < villi 339 PM Metwork lemming Player  2n1nns_vmsns_wu_s ﬁle Elem !nlu ﬂtlp Meeung Number: 719 739 ass Date: Tuesday. May 25, mm ma: 6: as PM, Lmlnme (GMT mm) a J Participants :s; Ex Name mining m Hem/mg ume
DENEI HEIE 06:53 PM [07:59 PM
Adam MEPDIin D7 D1 PM [D7 59 PM E M F CurlLVndi umwM/umg PM ' Our ﬁrst topic this week is induction and an EMF Jrﬂg‘aﬁmiﬂf u
' So what is an EMF? l— Shn Activity “me L Recording Start uuzuozuu Ll
' Right is sounds funny since the original term for an
EMF as Electro — Motive Force, but an EMF is really a 35:35:13; 3:33: rs mm;in m: Emmi: VOItage‘ ' They dropped the whole Electro — Motive Force thing
and nowjust call it an EMF.  Before we saw that a potential difference comes from a
distribution of charges. ' How does the EMF differ from this? ' Right, we are creating this from just the changing flux
from a magnetic ﬁeld, no charges involved! Egan 0— E 1 E]. Dacumenu ial Physicswltm network Recording Plaver r zulunsjilvszlLWKJ Eile view iniu Help Meeung Number 71; 73; 655 Date: Tuesday, May 15, zum Time s as PM, Lucal'l'inie (em as on) E
.1 Participants m Ex
Name Joining lime /LEEVll’IQ time
DEI’ilEI Hale D5 58 PM [D7 59 PM Adam Muialin D7iD1PM ID7159 PM Motional EMF l J Table of Cornell: El
Ynlal duraan D1 D1 uz ' With this now in mind let’s look at our ﬁrst way we can create
an EMF. l— 5m 5
Activitv “Me : REmrding siart an an an Ll
 With these think of a square wire with a moveable section. SESSWW“ ESE: E1 lrlmiorial EMF 1 an in 24 ' This is then placed in and perpendicular to a magnetic ﬁeld B, ETTHBIEZZI ‘ 2:13: 7
like this: A 6 i5 i EJEPM t Nam/Dr e E] Dmumenu , J ral Phyiiriwlt Mztwork Recording Player  2n1nns_Pmsns_wu_s ﬁle gm 1m ﬂtlp Meeung Number: 719 739 ass Date: Tuesday. May 25, mm ‘ﬁme: s: as PM, anmme (GMT mum) Motional EMF  ' Now what we do is move the metal rod to the right in this
case. ' So from last week we see that the force here is given as
(with q = e in this case):
F3: ev x B ' Now this must be the same as the force the electron feels,
which is FE=eE, so then they two must be equal and
opposite like this: eE= ev x B now we cancel the e to get
' E = v x B so this is the induced electric field. ' Now finally we remember that AV = EL in this case, so we
get: AV = vBL ' Questions? J Pa rticipams :s; Ex
Name Joining lime /Leavlng ume
DanielHale D6153 PM tum; PM Adam Manlln n7 n1 PM 1D7 59 PM cun Lvnm uquM tum PM —
J Table of (lolltellu B
mal duraunn: D11D11DZ Activity Recording Elan: uuzuozuu U
B Elethnmagnebsm an oz 35
m EMF mum B Mammal EMFI E549 0— ": [I [a ” ,ﬁlienevaanyslcswuc... “a r :H l EDacumenurl‘yﬁcm... network Recording] PlaVEI‘ r 2llll1I157PllV52167WK75
Eile Elew lniu Help Meeung Number 71; 73g 655 Date: Tuesday, May 15, zum Tm s as PM, Lucal'l'lme (cm as on) Motional EMF Example ' Okay now let’s do one from the Practice quiz. This time
#1 A metal rod of length 2.0 m is moved at 6.0 m/s in a
direction perpendicular to its length. A 5.0mT
magnetic ﬁeld is perpendicular to both the rod and its
velocity. If the resistance of the rod is 15 mg what is
the current in the rod? ' So what do we do?  Right, ﬁrst we need to ﬁnd AV, since I = AV/R. ' So we see that AV = vBL so we get:
AV = (6.0 m/s)(5.0 x103T)(2.Om) = 6 x 102 v
Finally: I = AV/R = 6.0 x lOZV/15 x1030: 4.0A .1 Participants m Ex
Name JDll’lll’lg lime Hem/mg lame
DEI’HEI Hale D5 58 PM [D7 59 PM Adam Mﬁalln D71D1 PM ID7159 PM Curt Lvndl D7 04PM ID7 59 PM —‘
.1 Table of Contenu El
Mal duraan n1 n1 n2 M:th
B MnﬁnnalEMFﬂ
b Motional EMF E ample B Quashans’ nunms
B Elethi: Generamrs an 19 27
B PawerPlams amuse m chum/u. s... E] ” ﬂ Genevalphyilriwlt I New :wdlng . El Dazumenurmrm lietmrk lemming Player  2n1nns_Pmsns_wu_s ﬁle Elem !nlu ﬂtlp Meeung Number: 719 739 558 Date: Tuesday. May 25, Zn)“ me: 5: as PM, meme (GMT mm) B a
J Pa rticipams :s; Eix
Name Jolnlng nme /Leavlng ume
DanlelHale uses PM tum; PM Adam McPuIln n7 n1 PM 1m 59 PM Electric Generators ' Now we can start to look at how this principle can be used to J “seamen: is
created electricity. melauramnlmmz  The main thing to remember is that it is the CHANGING ﬂux that
creates the electric ﬁeld. ' In our previous example we changed the size of the "hole" that the
ﬂux was going through. ' But you can also change this by rotating a wire (or coil of wires)
inside a large coil of wire this is creating a magnetic ﬁeld. Activity nme e
D MononalEMFU umz: 14 7
B Moﬁonal EMF Example an 15 as * E549 0— E ” ,ﬁ General Physicswuc... E]. Documenu e Micrer < LEW 3:55 PM Elli] network Recording Plaver e zumnsjmszlLWKJ Eile grew lnlu Help Meeumg Number 71; 73g 655 Date: Tuesday, May 15, znm Time s 55 PM, Lucal'l'lme (cm as on) E g
.1 Pa nicioan ts m 5*
Name Jolnlrlg nme Meal/mg lame
oemel Hale as 53 PM {D7 59 PM Adam Moialln D71D1PM/D7159 PM Power Plants ' So how many types of power plants can you
all think of? B Faraday'slaw muons m
B PamerPlamis nugsaz 7 ' Good, lots of examples (Coal, hydro — electric, 322:3;1'2" 33.2.3: m “A...” Mn 1: as gas burning, nuclear, wind power) and all of
these (solar is the only exception) use this
principle. They mechanically turn a large
turbine inside and electromagnetic and create
an EMF! Ely 4» 0— e
W. t Men :lrdlng . @Daeumenuemm. < ii?" 357 PM {a ” ﬂ Generalphyslrswlt network lemming Player  2n1nns_Pmsns_wx_s Eile grew !nfu ﬂtlp Meeung Number: 719 739 559 Dace: Tuesday. May 25, mm Wile: E: 59 PM, anl‘ﬁmE (EMT mm) B a
J Pa rticipams :r; Eix
Name Jelnlng ume /Leavlng ume
Danlel Hale uses PM tu7rs9 PM
Adam Mdelrn d7 d1 PM {B7 59 PM Fa raday’s Law ' This will help us understand the relationship between the
induced EMF and the magnetic ﬁeld. ' Just like we had with electricity there is a magnetic flux:
(qu = BA cos 6
B Quesudnew  where 9 is the angle from the perpendicular that B is with respect to the surface. J Table of (lolltellu B
rural duraudn: mzmznz l— Shaw all
Activity Tulle ‘ D PdwerPlanls 99:21:59 B Faraday‘slaw an 13 29 m m PauerPlams T ' So remember before we talked about the changingflux, so we
see that the induced EMF is given as: EMF = {MM/(At)
Or for a Coil: EMF = N(ACI)B)/(At) E549 0— e General Physrcswrc... 1 Men E]. Ddcumenu a Mum.“ < IS 9: 9:00 PM network Recording Plaver a zumnsjllvszLLWLS Eile view lnlu Help Meeurrg Number 719 739 655 Date: Tuesday, May 15, znm TIME s 55 PM, Lucal'l'lme (em as on) E g
.1 Participants m Ex
Name Jnlnlrlg lime Hem/mg lame
DEI’HEI Hale D5 58 PM [D7 59 PM
Adam Mﬁalln D71D1 PM ID7159 PM
M CurtLvndI D7D4PM/D7 59PM
—
—‘ ' These are basically the opposite of a generator: J TahleofContenIs 9 rural durahnn n1 n1 n2 ' This time we use a changing current (AC) to produce a
force of rotation on a shaft.
' Then this rotating force is where we get the motor aCtion _ ' Where are some examples of where you all can ﬁnd
electric motors? B Transfurmersl
B Transrarmerslr dug9.31 ﬂ
B Transformers Examples an 33 41
B Transformers Examples (ca... aura3:49 ' Good example, heck what about the computer you are
on right now? ' Right the CD drive and Hard Drive are examples right
there! Also all the different fans! t < ii?" 902 PM {a ” ﬂ Generalphyslriwlt E] Datumenu a g . network lemming Player  2D1ﬂns_PllV5116_WK_5 file giew !nlu ﬂtlp Meeang Numaei: 719 739 see Date: Tuesday. May 25, zinn ‘ﬁme: a: 58 PM, anl‘ﬁmE (GMT {15:00) E a
1 Pa rticipams :s; §:x
Name Joining nme Hem/mg ume
Daniel Hale D6158 PM tum; PM Adam MaPaIm n7 D1PM/D7 59 PM Transformers  ' This is a nice piece of electrical equipment that is used to stepup or _
stepdown the current or voltage in an AC system. Jﬂmwcmem B  This is basically and electrical system where a soft core piece or iron
"loop". Then you wrap wire around the different sides Total auiaunn: mzmznz [— Shu Time e W126134 ' The key is that you wrap a different number of turns around the g 31:32::mm 22:: D
primary and secondary coils. a rammeeeﬁmaee nmqw
l'h Vlﬁiiﬂnvr mmmqu V
_
anaiy Secnndary
winding winding
' NSWMS 5mm“ < :31" 9:03 PM network Recording Plaver e zumnsjilvszLLWLS Elle view Info help Meehng Number 71s 739 655 Date: Tuesday, May 15, zinc Time s 55 PM, Lual'l'inie (Gm 415 on) E g
l Participants in Eix
Name Jaimng hme nearing hmE
Daniel Hale as as PM 157 59 PM Adam Muialin D71D1PM/D7159 PM Transformers  ' So even though the changing flux can change the
current and voltage, their product is the same. ' Remember that P = IV
D TransfurmersExamples ' So since you must conserve energy (remember power isjust the energy expended per unit time) then this MUST stay constant. ' So with the primary and secondary coils we see that:
Ipr = ISVS
‘ which if we remember that V1 = N1(A<I)B)/(At) we get:
Vs/VP = Ns/NP and ls/IP = NP/Ns
' Any questions? J Table of Canteen: Ea
Tnial duraimn n1 n1 n2 I— Show a
Activity ﬁne A B Mninrs an 15 34 B rransiurmersi B Transmrmersii pas1.31 an 33 41 < 6.1!) 905 PM natumk handing Player  2n1nns_Pmsns_wu_s ﬁle Elem !nlu ﬂtlp Meeung Number: 719 739 558 Date: Tuesday. May 25, mm Wile: E: 58 PM, Lmlnme (GMT mum) Transformers Examples: ' Here are two quick examples about transformers
from the practice quiz: A transformer has 200 turns on its primary and 12 x J Participants Name Joining m /Leaving ume
Daniel HEIE 06:53 PM [07:59 PM
Adam Md’alin D7 Di PM [D7 59 PM
Curl LVl'idI DYIDQPM [07:59 PM J Table of (lolltellu B EX
mal uurauan: mzmznz l— Shaw all Activity B Transformers Examp as (:a an 39 4a
m Indutmrs aama turns on its secondary. If the input voltage is 2000 V, what is the output voltage?  Where do we start?  Right, we remember that V5/Vp = N5/NP. ' So this gives: V5 = Vp(N5/Np) = (2000V)(12/200) =
120V ' Questions? E549 0— General Physicswltm 1 Men E]. Dacumenu r Mum... network Recording Plaver r zumnsjmszlLWLS < ﬁlm 9:13 PM Eile view Info Help Maeung Number 71; 73; 655 Date: Tuesday, May 15, zum Time s 55 PM, Lucal'l'ime (am as on) Transformers Examples (cont): ' Here is another one: An ideal transformer has an input voltage of 20,000 V and an
output voltage of 260 V. If the input current is 26 A, what is the output current? .1 Participants m Ex
Name Joining lime naming lame
Damal Hala as 53 PM {D7 59 PM
Adam Mazalm Wm PM tum PM
Curt Lyman u7 mPM m7 59 PM — —‘ J Table of Contenu El
ralal durauan n1 n1 n2 Activitv B Transformers Examples B Indutmrs
B AC Circuits! an 47 1a  Where do we start? ' Right we use these equations: V5/Vp = NS/Np and Id“: = NP/NS
' So ﬁrst we need to solve for the ratio Ns/Np via the voltage
equation. 50 we see that VS/Vp = Nde gives:
(20,000V)/(260V) = 76.9 = Nsle.
' Now we use l5/IP = Np/Ns to get: IS = lple/Ns) = 26A(76.9) =2000A
E my an 0— ' E] Datumenu r {a ” ﬂ GeneralPhysiriwlt g . < 6.1!) 917 PM lietmrk neeonling Player  2n1nns_Pmsns_wu_s Eile Elem !nlu ﬂtlp Meeung Number: 719 739 558 Dace: Tuesday. May 25, am me: s: 58 PM, immme (EMT mm) B a
J Pa rticipan is i—iii x
Name JDlnlrlg ma /Leavlng ume
Darllel Hale uses PM tu7l5a PM Adam Manllrl n7 n1 PM {D7 59 PM Inductors ' Okay one more little circuit idea for this term. Total durahnn: DIIDJIDZ
' We see that in an AC circuit, there is a item called self—
inductance. ' An inductor is basically a little coil of wire. Activity
DD133142
[a an 39 40 D Transformers Examples: an .47. ID ' So the deﬁnition of the inductance (L) is: W?“ v
NED: Ll or: L=NCI)/
' For a regular coil this is given as:
L: ponZTtrZE and since N = nf, this is also:
L = (lioN2nr2)/f
' What this then means is that in an AC circuit there is a
voltage drop/gain across an inductor: EMF =  L(Al)/(At) E 5 4D 0— a E]. Dacumenu a Micrer < E m 9:20 PM ” .ﬁ lasnelaanyslcswm... 1 New, Elli] network Recording Plaver a zulunsjmszlLWLS Eile Elew lniu Help Meeting Number 719 739 555 Date: Tuesday, May 15, zum TIME s 55 PM, Lucal'l'lnie (cm as on) E g
.1 Participants in Ex
Name Julnlrlg time neaan lame
Danlel Hale as 53 PM {D7 59 PM
I _ Adam Mu7allrl U71U1 PM tum PM
AC I CunLynm u7mPM/u75aPM ° This now brings us to our next topic, AC taftttiiitfzf t
circuits. ° The main difference here is that the current W U
and the voltage sinusoidally cycle from a positive value (+\/, H) so the same negative
values (V, ). ° 50 in addition to voltage, resistance and current, now amplitude and frequency (0))
are main factors in the AC circuit. B AC Clrmlis in M5139
B AC Examples: an 57 35 , < l3" 921w netmrk Recording Player  2n1nns_Pmsns_wu_s file Elem !nlu ﬂtlp Meeung Number: 719 739 558 Date: Tuesday. May 25, am Wile: E: 58 PM, anmme (GMT mum) J Pa rticipan Is :s;
Name JDlnlng nme neaan ume
Daniel Hale D6153PM/D7159 PM
Adam Manlin n7 n1 PM {D7 59 PM AC Circuits   So this means the voltage and current are given mar duraunn: mzmznz [— Shaw all i(t) =  sin (cat) and v(t) = (an sin(oat) where l and €me and the maximum values of the current and 2332i:
voltage.  The power is then given by:
p(t) = i(t)v(t) = IV sin2((ot)
 But the average power dissipated is given as:
Pa“, = 1/2(V) = 1/2(2R)
 Make sense? Egan 0— a El Dacumenu e r < ﬁlm 9:23 PM network Recording Plaver e zulunsjmszlLWLS Eile view lnlu Help Meeting Number 71; 73; 655 Date: Tuesday, May 15, 2mm TIME s 55 PM, Lucal'l'lme (am as on) .1 Pa rticipan ts m Name Joining nme Meal/mg lame
Daniel Hale as 53 PM 1m 59 PM
Adam Muialin Wm PM tuna PM AC Circuits   Next we can see how capacitors and inductors come into play in AC J madman: a
circuits. mammaan n1 n1 n2 l— Shaw all . . . , , MEN“ Tulle ‘
' So what we see Is that the voltage drop across a capaCItor In an AC crrcurt B “mm mm
is VC = IXC where XC is called the capacitive reactance and is measured in o warmmu Ol'l ms. B AC mm
B AC Examples: an 57 35 7
' AlSO we see that Xc= 9— B QM vv159117 l—l  It is important to note that in an AC capacitor the voltage and current are M m m
out of phase by 71/2 or 900. It is said that the current leads the voltage in
this system. ' There is a similar quantity for inductance called XL where we get:  VL = XLIL and this is called the inductive reactance.  Also we see that XL = (0L ' Also again in an AC inductor the voltage and current are out of phase by
11/2 or 900. It is said that the current lags behind the voltage in this system. ' Questions? < 6.1!) 929 PM Metwork haunting Player  2n1nns_pmsns_wu_s Eng Maw wu ﬁeip Meeung Number: 719 739 ass Date: Tuesday. May 25, 20]“ ‘ﬁme: a: 58 PM, meme (GMT {15:00) E a
l Pa rticipams n; Eix
Name Juining time (Leaving time
nameIHaIe 06:53 PM tuna PM
Adam Manlin n7 n1 PM {D7 59 PM AC Examples: ' So here is an example from the Practice Quiz: ma uraunnzmzmznz [— s nwa
What is the inductive reactance of a ZOO—mH inductor Jim “L n '
attached to a 120V rms 60.0Hz source? D AC Circunsi Unii715?
3 Ac omen DD4354
' So what do we do? B ' Right we remember that XL = (0L.
 So XL: (211*60 Hz)(200 x10—3 H) = 75.4 9
' Here is another one: What is the capacitive reactance of an 8.00—pF capacitor
attached to 120V rms at 60.0 Hz? ' So what do we do?
' Right we remember that XC = 1/(0)C) so:
' xC = 1/[(2n*60 Hz)(8.0 x106 F) = 332 Q E549 0— E I Nah Dldmgm Elm manneriiumi.‘ ' < '51!) 9:30PM ai Physicswltm ...
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This note was uploaded on 03/09/2011 for the course PHYS 270 taught by Professor Danielhale during the Spring '11 term at DeVry Chicago.
 Spring '11
 DanielHale
 Physics

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