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Unformatted text preview: @ P1.21 The total charge that has entered a circuit element is EE220 CIRCUITSI Chagter #1— Examgles qlil=4(le‘5') whentzﬂandq(t)=0whenr<0. Determine ‘7 "w_____ﬁ_ __ _ _q____ Wat” _ ﬂ ___ _ _ the current in this circuit element for :2 0.
Answer: 1'0) = 202*“ A Cat£3 : M )— 6‘31); P 1.26 An electroplating bath, as shown in Figure P 1—.2—6, ~ :7 — ﬂ —k _ _u # — _
'“ﬁls’Tﬁge to plate silver uniformly onto objects such as kitchen 4. :2 Q; A~ u“ _ _
ware and plates. A current of 600 A ﬂows for 20 minutes, and 2 each coulomb transports 1.118 mg of silver. What is the weight : l of silver deposited in grams? "*" "" :1 :3; :1??? 61/4S Object to
be plated FIGUREP 1.26 Anelectmplating bath. .. _ . ....__,_M . ‘ mm. 419 291er (la  ~ ____., ,, _ _. .,_v,..i.__w. ., Wm. __,,,;.(u.l__ nglbfgwn. ___.
c ; ﬁ @ r 7 P154 An automobile battery is charged with a constant eur— '  . ._ . _ .__. ﬁﬁ A for ﬁve hours. The terminal voltage of the battery is
v=11 + 0.5rV fort > 0, where r is in hours. (3) Find the energy
delivered to the battery during the ﬁve hours. (b) If electric en
ergy costs 10 cents/kWh, ﬁnd the cost of charging the battery for
ﬁve hours.
Answer: (13) 1.23 cents 1:29;. _ mi: beéxeo :Sﬁtﬁéﬁb é. Dr: H +0agt r jlmr 7570 , .. “0x . gee; " )2 “It ~ ' insmg.
U ee e WW W 3 past :3 Wtﬁl’t IJQVL 'Ht' 241? .1 D b sew
D o s...
r  e 2 $233;er _:— (22%: 4— J: j
.. .V. _ .,_ ‘J . D .. .. :vemoé: : 41% KT”. P 1.55 Find the power, p(!), supplied by the element shown
' ' 33—3— . . 7~ sin 3t
in Figure P 1.5—5 when v(!) = 4 cos 31V and 1'0): 12 A. Evaluate p(t) at t=0.SS and also at r: 1 9. Observe that the
power supplied by this element has a positive value at some
times and a negative value at other times. l . . _
Hint: (sin at}(cos bt) = —(sin(n t b)! + sm(a — b)t) FIGURE P 1'5 5
3 An element. Answer: pm = .16. sin 6: w, 13(05): 0.0235 W, pm = —D.0466W " :— 2 ” 'ile;_,&i§52s.£f_;§%  o _W,__ ,
J g  ﬁancee,ng —r:m Cgi+3tjﬂ if — _' ﬂ "81—3—2555? _ W ‘ _ P 1 .58 _ The battery of a ﬂashlight develops 3 V, and the cur—
rent through the bulb is 200 mA. What power is absorbed by the bulb? Find the energy absorbed by the bulb in a ﬁveminute
period. ‘ "Ml? . ﬂue, _'._§_‘r?l€é_.lkbll 4‘9 .2: w: .m Lbbxgxéo _ 1“ A N l85$_ "‘ Section 1.7 How Can We Check. . .? g DEX *# n
P 1.71 Conservation of energy requires that the sum of the I ‘
I“Illoliver absorbed by all of the elements in a circuit be zero. Figure mp5 ‘ V
P 1.7—l shows a circuit. All of the element voltages and currents
are speciﬁed. Are these voltage and currents correct? Justify your (63W (:10; A a I 7
answer. . a! t; l E?
Hint: Calculate the power absorbed by each element. Add up ._ g i \ 3
all of these powers. If the sum is zero, conservation of energy ‘
is satisﬁed and the voltages and currents are probably correct. If .
the sum is not zero, the element voltages and currents cannot be u m _
correct. ‘ A
DDWW P ;: Cozy 2,) + (gxglﬁlxry'
+L§xy HBBQ
. ( _ L
: —Ai>+g«—.2.o+)e Jr) 7 nouns P 1.71 ginoz “ll/era Agom is. r O Whi‘blb 5: “795? Cw? Mrrﬁm". .Me Lea/reci '  A ' “ ' ' ' r ' 'l .S'f 'sth ostim
® «2'11 1 particularcucurtelementis availableinthreegrades. Spcc1fy the grade of this e ement a ety 1 e m Grade A guarantees that the element can safely absorb U2 W portant consideration, but don’t specify an element that is more
continuously. Similarly, Grade B guarantees that 1/4W can be expensive than necessary.
absorbed safely and Grade C guarantees that 1/8 W can be ab sorbed safety. As a rule, elements that can safely absorb more 7 power are also more expensive and bulkier. I ——:'‘:>
The Voltage across an element is expected to be about 20V ' and the current in the element is expected to be about BmA.
Both estimates are accurate to within 25 percent. The voltage g . _.5 —— W
and current reference adhere to the passive convention. __ is? _ C k—4>
V 3‘— 21? V. .3; 1 EA”; 3/1) ,. Maximum: wattage. 1510 x 1.2.: : c233 l/ __.__
l Maximum torrent :— ooogxm: .: 0:01 A _ Sc “lluz :: 523x05]? . Somalng m m. I/l w it. tee, salt/«21L; M 95%ng @ _ h [email protected]__L;t_;_._mﬁ2m_ﬁx.g wme .m‘mr
; ,m.ima;P__ momma!) ___ @ ,, _ @ The manch of a 6 V drycell ﬂashlight battery Assume the drop in voltage is linear with time. How
says that the battery will deliver 15 mA for 6D much energy does the battery deliwariu this 60 hinterval‘?
conﬁnuoua hours. During that time the voltage will drop from 6Vto4V. \ 'JC 7 PLO): é;><2smf3.:4—_spmzs‘3w Jc: éﬂ/‘Yéﬁﬁéb‘: QJEﬂUDB/i '7 lJéDJ‘ZX—‘I
mum) :'_i::;<_):x')6’_3: épxip"3w D ' ' ‘ i  . .J. ,_, 3 " ' All). A 0 gym“g  ‘ @JEMDJKQ
2: .152. m xi, w. ...
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 Spring '09
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