What quantity is measured by a battery ratingbcn9c66ps c8e given in ampere-hours $(A\cdot H)$ ?

When an electric cell is connected to a circuit, e1l;p;elpekrm 0 wwp:2 lectrons flow away from the negative terminal in the ;mkwrep welp0pl1 2 ;:circuit. But within the cell, electrons flow to the negative terminal. Explain.

When a flashlight is operated, what is being used up: battery curren ylb:n m56 dxynjzd- q.7jk()st, battery voltage, battery energy, battery power, or battery r(n6 7dnm) xz.5bykd :qjjsly -esistance? Explain.

One terminal of a car battery is said to be connected to “ground.” S9krvl0u b/ qbky:mop-v2 bi/-.sya b,ince it is not really connected to the ground, what is meant by thiypk/v ,qm/yb2-ar-v9bik b : uls b0o.s expression?

When you turn on a wafrgpp h2x0; h:ter faucet, the water usually flows immediately. You don’t have to wait for water to flow from the faucet valve to the spout. Whhp0p 2fhgr;:x y not? Is the same thing true when you connect a wire to the terminals of a battery?

Can a copper wire anin b+ho-md+cuc12uu ,d an aluminum wire of the same length have the same resistance?+i1dmh,+uco -2nucub Explain.

If the resistance of a small immersion heater (to heat1trkufb2 b4t 0 water for tea or soup, Fig. 18–32) was increased, wk2b 40tftbu1r ould it speed up or slow down the heating process? Explain.

If a rectangular solid made of carbon has sides of lengths a, 2rfk lfx))uucj0196vd5 ;bw,zpu web 4a, and 3a, how would you connect the wires from a bfb5ux 0 v k91z4p;uwb)ljr6)deuw c,fattery so as to obtain (a) the least resistance, (b) the greatest resistance?

The equation $P\,=\,V^2/R$ indicates that the power dissipated in a resistor decreases if the resistance is increased, whereas the equation $P\,=\,I^2/R$ implies the opposite. Is there a contradiction here? Explain.

What happens when a li qa/.u*m v7p+yamj7ww ghtbulb burns out?

Explain why lightbulbs almost always burn out just as they are turned on asg+ leqdra;b94 +iij+:d ay t28zhrd 8nd not after they have been on forrdq:a+t z+glr j;ha 9+ib8dd8i4ys2 e some time.

Which draws more current, a 100-W lightbulb or a 75-W bulb? Which sc qb 36ng7ng(has the higher resistancenbq(s76cng g 3?

Electric power is transferred over large distances at very high voltages. Expla813gp rhm kjektf.ca /0cvv20in how the high voltage reduces power lossesvkkm c0chtg2p. j1 8rv 30a/ef in the transmission lines.

A 15-A fuse blows repeatedlu7gb 2)vk kwee t-*ho(g )ote)y. Why is it dangerous to replace this fuse with a 25-A fuse?v)g (et g)ot 7 2ew*kh)oub-ek

When electric lights are operated on low-frequency ac (say, 5 yre (r423o 2q u2op9cfcwcbz/ Hz), they flicker noticea23c2/2wrzy fcce oq urp4b(o9 bly. Why?

Driven by ac power, the same electrons pass bacl.+xjx1 90bk ) zaucq zsw;-cz *qyt/fk and forth through your reading lamp over and over again. Explain why the light stays lit instead of going out after the first pass of electrons.)1*kwc ja zqql;xf+z.-/y9u0tsxb cz

The heating element in a toaster is made of Nichrome 9f-(dulzo-)f- i80i rmyp j eywire. Immediately after the toaster isu-iomr i(d 9 pelf fz80j-y-)y turned on, is the current $(I_{rms})$ in the wire increasing, decreasing, or staying constant? Explain.

Is current used up in ogq2tr. v 3 2qgvrdy.3a resistor? Explain.

Different lamps might have batteries connected in eittc a0iy14ga tx 8x+h+sher of the two arrangements shown 0tga t+ yx84chx1a+ isin
Fig. 18–33. What would be the advantages of each scheme?

  A current of 1.30 A flows in a wire. How many electrons arej7kt1g hc0myyd2;( /eel uys 3 flowing past any point in the ;eh u/gketc( 2m0yy7sjly 3 1dwire per second?    $ \times10^{18 }\;electrons/s$

  A service station charges a battery uk. jk+zd-1 p,c8aelot sing a current of 6.7 A for 5.0 h. How much charge ppc-dj ,8ekal kz1.+o tasses through the battery?    $ \times10^{ 5}\;C$

  What is the current in amperes qzyp5hu8i+k * if $1200\,Na^+$ ions flow across a cell membrane in $3.5\mu s$? The charge on the sodium is the same as on an electron, but positive.    $ \times10^{-11 }\;A$

  What is the resistance of a toaster if 120 V produces a current of 4.2 A? 04+mj5 vqg lejyhm.nqmb 6h)(    $\Omega$

  What voltage will produce 0.25 A of current tsgi vvm-38:jy : l8zo7wgs1 wkhrough a $3800-\Omega$ resistor?    V

  A hair dryer draws 7.5 A when plugged into a 120-V line.vj(/ *sm mgu:+df-vc n
(a) What is its resistance?    $\Omega$
(b) How much charge passes through it in 15 min? (Assume direct current.)    $ \times10^{ 3}\;C$

  An electric clothes dryer has a heating element witp+k:nk 3vjs - 3mxlz3eh a resistance of $9.6-\Omega$.
(a) What is the current in the element when it is connected to 240 V?    A
(b) How much charge passes through the element in 50 min?    $ \times10^{ 4}\;C$

  A 9.0-V battery is coaa:n,-wdgn-nf e )f 5rnnected to a bulb whose resistance is $1.6\Omega$. How many electrons leave the battery per minute?    $ \times10^{21 }\;electrons/min$

  A bird stands on a dc electric transmission line carrying 2800 A (Fig.b(*+:n ga3rhxzfb p7huioyy *ai8: l) 18–34). The line ha*+( i7fhxyl b3u:biag)rhp yaz8:*no s $2.5\times10^{ -5}\;\Omega$ resistance per meter, and the bird’s feet are 4.0 cm apart. What is the potential difference between the bird’s feet?    $ \times10^{-3 }\;V$

  An electric device drall.sznv+4hyz.si 5q s-5* ephws 6.50 A at 240 V.
(a) If the voltage drops by 15%, what will be the current, assuming nothing else changes? $\approx$    A (retain one decimal places)
(b) If the resistance of the device were reduced by 15%, what current would be drawn at 240 V? $\approx$    A (retain one decimal places)

  A 12-V battery causes a current of 0.60 A through a resistor.r-j(jh:nxrnw-m e fw.fh 83u+
(a) What is its resistance, $\approx$    $\Omega$
(b) how many joules of energy does the battery lose in a minute?    J

  What is the diameter of a 1.00-m lengtn3(7iubaq op2fy1 i9b h of tungsten wire whose resistance is $0.32\Omega$?    $ \times10^{-4 }\;m$

  What is the resistance of a 3.5-m length of copper wir( lp-p gm;xm5ue 1.5 mm in diameter?    $ \times10^{ -2}\;\Omega$

  Calculate the ratio of the resistance of 10.0 m of aluminum wire 2.0 mm in diame,vj ; g50etqjuter, to 20.0 m of copper wire 2.5 0,qe v;jjgt u5mm in diameter.   

  Can a 2.5-mm-diameter/ u1n c xt5.h:lqe5 7kiwa0cnr copper wire have the same resistance as a tungsten wire of tr ne 5u/hc 1k7.ic 50x:laqwnthe same length? Give numerical details.    mm

  A certain copper wirc bz3 l/uh*6x9tzlgr 7e has a resistance of $10.0\Omega$ At what point along its length must the wire be cut so that the resistance of one piece is 4.0 times the resistance of the other? What is the resistance of each piece?
$R_{short }$   $\Omega$
$R_{long }$    $\Omega$

  How much would you have to raise the temperature of a copper wire (origipx91py7w:/ ;jugqi ;rqg9bh +vf6p y anally at9: i fybu+pq 1rygjqa;97pgvx 6/hp;w $20^{\circ}\,C$) to increase its resistance by 15%?    $C^{\circ}\,$

  Estimate at what temperature copper will have thewmux96hh6u )n u/ mu.b same resistivity as tungsten doe66/) h mubuu hxm.un9ws at $20^{\circ}\,C$.$\approx$    $^{\circ}\,C$ (Round to the nearest integer)

  A 100-W lightbulb has a resistanx-w7bk /x2l+uh;,yz - wpn22kuq jcu lce of about $12\Omega$ when cold ($20^{\circ}\,C$) and $140\Omega$ when on (hot). Estimate the temperature of the filament when hot assuming an average temperature coefficient of resistivity $\alpha\,=\,0.0060(C?)^{-1}$ .    $^{\circ}\,C$

  Compute the voltage drop along a yuq 7,o 13,mk6pr;, spih jylx26-m length of household no. 14 copper wire (used ioik,q 1 pu;mj,6yrplsxh73 , yn 15-A circuits). The wire has diameter 1.628 mm and carries a 12-A current.    V

  A rectangular solid made of carbon has sides of lengths 1.0 cm, 2.06je i q3)dk ozzjw,9e;2bka ,ylwt+1a cm, and 4.0 cm, lying along the x, y, and z axes, respectively (Fig. 18–35). Determine the resistance for current that passes through ;dyb eqz6+,z,jae2lkwwoi3 )a j91 kt the solid in
(a) the x direction,    $ \times10^{ -4}\;\Omega$
(b) the y direction,    $ \times10^{ -3}\;\Omega$
(c) the z direction. Assume the resistivity is $\rho\,=\,3.0\times10^{ -5}\;\Omega\cdot m$.
   $ \times10^{ -3}\;\Omega$

  Two aluminum wires have the same resoqq 9;wy7,2ki0 q,.ta pyymocb4h6td istance. If one has twice the length of the other, what is the2y o6;imak9y7th bd.wc,qt0 y4p qqo, ratio of the diameter of the longer wire to the diameter of the shorter wire? $\approx$    (retain three decimal places)

  A length of aluminum wire is connected to a precision 10.00-V power supply, and 3 9amw4ndhlj)a current of 0.4212 A is prec)3dwjl9hma 4nisely measured at 20.0$^{\circ}\,C$. The wire is placed in a new environment of unknown temperature where the measured current is 0.3618 A. What is the unknown temperature?    $^{\circ}\,C$

  A 10.0-m length of wire consists of 5.0 m of1g1 s:yqke4bln* 1tqz copper followed by 5.0 m of aluminum, both of diameter 1.0 mm. A voltage difference of 85 mV is placed across the lzk:1*4qe 1tq y1nbgs composite wire.
(a) What is the total resistance (sum) of the two wires? $\approx$    $\Omega$(retain two decimal places)
(b) What is the current through the wire?    A(retain two decimal places)
(c) What are the voltages across the aluminum part and across the copper part?
$V_{Cu}$    V(retain three decimal places)
$V_{Al}$    V(retain three decimal places)

  For some applications, it is important that t. 9, ,*wypo u7rizcd3qk2vpsdhe value of a resistance not change wp,ycd2 zv7or . dqw si9k3*,puith temperature. For example, suppose you made a $4.70-k\Omega$ resistor from a carbon resistor and a Nichrome wire-wound resistor connected together so the total resistance is the sum of their separate resistances. What value should each of these resistors have (at 0$^{\circ}\,C$) so that the combination is temperature independent?
$R_{0C}$   $\Omega$
$R_{0N}$   $\Omega$

  The heating element of an electric wu.km l/6j to6fqi0b +-*qdmhoven is designed to produce 3.3 kW of heat when connected to a 2hm -q/ .wf6kiljd* omq06+but 40-V source. What must be the resistance of the element?    $\Omega$

  What is the maximum power consumption of a 3.;b*9oqd5 c m8 gmzglj)0-V portable CD player that draws a maximum ogqb 5g)d*l8;zcmm j o9f 320 mA of current?    W

  What is the maximum voltage that can be applied acrosssuph/q 32pf- s a $2.70-k\Omega$ resistor rated at $\frac{1}{4}$ watt?    V

  (a) Determine the resistanc+uhziu 5h.2spe of, and current through, a 75-W lightbulb connected to its proper source voltage of 120 V. ihu2sh .zup+5
   $\Omega$
   A
(b) Repeat for a 440-W bulb.
   $\Omega$
$\approx$    A(retain one decimal places)

  A 115-V fish-tank heater is rated at 110 Wnu210ggte xbs : *msr8. Calculate
(a) the current through the heater when it is operating,    A
(b) its resistance?    $\Omega$(Round to the nearest integer)

  A 120-V hair dryer has two settings: 850 s mgu572vonm(e iu xt4 a7s)-yW and 1250 W.
(a) At which setting do you expect the resistance to be higher? After making a guess, determine the resistance at
(b) the lower setting;    $\Omega$
(c) the higher setting.    $\Omega$

  You buy a 75-W lightbulb in Ekxi/)v/ jam3turope, where electricity is delivered to homes at 240 V. If you use the lightbulb in the United States at 120 V (assume its resistance does not change), how bright will it be relative to 75-W 120-V bulbs? [Hint: assume roughly that brightnesstim)vx/ kj3 a/ is proportional to power consumed.]    as bright

  How many kWh of energy does a 550-W toaste)+k9hc,:wt3 jfhx hh fr use in the morning if it is in operation for a total of 15 min? At a costk:3ch )wf+hh hj,x9tf of $9.0\,cents/kWh$, estimate how much this would add to your monthly electric energy bill if you made toast four mornings per week.
energy $\approx$    kWh
cost $\approx$    cents/mouth

  At 0.095 dollars per kWh, what :ml ,bg pl+g2em4o1jadoes it cost to leave a 25-W porch light on day and m:,gj el +alo4m 1bpg2night for a year? $\approx$    dollars

  An ordinary flashlight uses two D-cell 1.5-V batteries connected in series as inp2a sed. kpk6q(s74cy Fig. 18–4b (Fig. 18–36)eca(yq pp.7k 4 sks6d2. The bulb draws 450 mA when turned on.
(a) Calculate the resistance of the bulb and the power dissipated.
$\approx$    $\Omega$(retain one decimal places)
   W
(b) By what factor would the power increase if four D-cells in series were used with the same bulb? (Neglect heating effects of the filament.) Why shouldn’t you try this?   

  What is the total amount of eneil w3jn)wx ywu5(lbow 9vh x*9i(2/hi rgy stored in a 12-V, $85-A\cdot h$ car battery when it is fully charged?    $ \times10^{6 }\;J$

  How many 100-W lightbulbs, connected to 120 Vx(v2p(.n y vql as in Fig. 18–20, can be used without blowiv(l2 xvp(q y.nng a 15-A fuse?    bulbs

  An extension cord made of two wik aa,3f2 * df,rpzzglo;a2 p0lres of diameter 0.129 cm (no. 16 copper wire) and of length 2.7 m (9 ft) is connected to an electric heater which draws 15.0 A rl laoz, 2a,*0kgf;dpfz32a p on a 120-V line. How much power is dissipated in the cord?    W

  A power station delivers 620 kW of power at 12,000 V to a factory tm7i: k5wne(wbf k2w3k) fk h;ihrough wires with tw)(2nbeii7 wkmh 3:kk fk; fw5otal resistance $3.0\Omega$ How much less power is wasted if the electricity is delivered at 50,000 V rather than 12,000 V?    $ \times10^{ 3}\;W$

  The current in an electromagnet connected to a 240-V*vm+ s*kq8m8 z; oahlq line is 17.5 A. At what rate must cooling water pass over the coils if the wat*;ha8zvm*lk m+oq qs8 er temperature is to rise by no more than 7.50 $C^{\circ}\,$?    kg/s

  A small immersion heater can be used in a car to heat a cup of w *kbn);-u dg 1cvvdor)ater for coffee or tea. If the);udvo -kb1gdrv c*)n heater can heat 120 mL of water from 25$^{\circ}\,C$ to 95$^{\circ}\,C$ in 8.0 min,
(a) approximately how much current does it draw from the car’s 12-V battery, $\approx$    A(Round to the nearest integer)
(b) what is its resistance? Assume the manufacturer’s claim of 60% efficiency.    $\Omega$

  Calculate the peak currx3rzlof-96it oj2wi . ent in a $2.2-k\Omega$ resistor connected to a 220-V rms ac source.    A

  An ac voltage, whose peak value is k-. 7:z qo: 38.brrdrafkttm/u *a djm180 V, is across a $330-\Omega$ resistor. What are the rms and peak currents in the resistor?
$I_{peak}$$\approx$    A(retain two decimal places)
$I_{rms}$ =    A

  Estimate the resista sc 1o1q2tt5ownce of the $120-V_{rms}$ circuits in your house as seen by the power company, when
(a) everything electrical is unplugged,
(b) there is a lone 75-W lightbulb burning.    $\Omega$

  The peak value of an alternating current in a 1500-W d/i/wn r7y)06fv0ss mgm amw3 hevice is 5.4 A. What is the rms voltage across it? /m0m)i 0wgv/w sr6n73 mfyash   V (Round to the nearest integer)

  An 1800-W arc welder is connege* pbr5i ey vu-j+,ozpdb,ybe(-1-pcted to a $660-V_{rms}$ ac line. Calculate
(a) the peak voltage$\approx$    V(retain one decimal places)
(b) the peak current.    A

  (a) What is the maximum instantaneous power dissipat ml 0w+gy4z(xuxz.m:9xc 4wthed by a 3.0-hp pump connected m4y9wmx:(xz0. + ctw zl4h xguto a $240-V_{rms}$ ac power source?    W
(b) What is the maximum current passing through the pump?    A

  A heater coil connec:s :77pc ny,afhervru7w1i3vd c. ,jnted to a $240-V_{rms}$ ac line has a resistance of $34\Omega$.
(a) What is the average power used?    W
(b) What are the maximum and minimum values of the instantaneous power?
$P_{max}$    W
$P_{min}$    W

  A 0.65-mm-diameter copper wire carries a tiny currentggw ; zk2mb;oqwspn/gz4- m 97 of $2.3\mu A$. What is the electron drift speed in the wire?    $ \times10^{-10 }\;m/s$

  A 5.80-m length of 2.0-mm-diameter wireqvmp yoqgtkp/01eez 3(x 94b+ carries a 750-mA current when 22.0 mV is appli9/qp obx+ m43gp 0(vz1eqte yked to its ends. If the drift speed is $ 1.7\times10^{-5 }\;m/s$, determine
(a) the resistance R of the wire, $\approx$    $\Omega$(retain three decimal places)
(b) the resistivity $\rho$.    $ \times10^{-8 }\;\Omega\cdot m$
(c) the number n of free electrons per unit volume.    $ \times10^{28 }\;e^-/m^3$

  At a point high in the Earth’s atmosphereb z9 .cvyno7y3, $He^{2+}$ ions in a concentration of $ 2.8\times10^{12 }\;/m^3$ are moving due north at a speed of $ 2.0\times10^{6 }\;m/s$. Also, a $ 7.0\times10^{11 }\;/m^3$ concentration of ${O_2}^-$ ions is moving due south at a speed of $ 7.2\times10^{6 }\;m/s$. Determine the magnitude and direction of the net current passing through unit area $(A/m^2)$.    $A/m^2$  ----待选择----NorthSouth 

  At a point high in the Earth’s atmosphelq-/mtlg) v- r js uj)sgya3,.re, $He^{2+}$ ions in a concentration of $ 2.8\times10^{12 }\;/m^3$ are moving due north at a speed of $ 2.0\times10^{6 }\;m/s$. Also, a $ 7.0\times10^{11 }\;/m^3$ concentration of ${O_2}^-$ ions is moving due south at a speed of $ 7.2\times10^{6 }\;m/s$. Determine the magnitude and direction of the net current passing through unit area $(A/m^2)$.    $A/m^2$  ----待选择----NorthSouth 

  What is the magnitude of the electric field across an z3ncqk57p :u kj*r ke6/el:xr axon membrane $ 1.0\times10^{ -8}\;$. thick if the resting potential is $-70 Mv$   $ \times10^{6 }\;V/m$

  A neuron is stimulated with an electr3wwnw5,.p1b5hrp s8ufrq ms (ic pulse. The action potential is detected at a point 3.40 cm down the axon 0.0052 s later. When the action potential is detected 7.20 cm from the point of stimulaw5 8sqru, nm5wbf3s ph r.p(w1tion, the time required is 0.0063 s. What is the speed of the electric pulse along the axon? (Why are two measurements needed instead of only one?)    m/s

  Estimate how much energy is required to transmit one action potelv+ 19ccd o5dqntial along the axon of Example 18–15. [Hint: the energy to transmit one pulse is equivalent to the energy stored by charging the axon capacitanceccd vdl+9 5q1o; see Section 17–9]. What minimum average power is required for $10^4$ neurons each transmitting 100 pulses per second?
E =    $ \times10^{-11 }\;J$
P =    $ \times10^{-5 }\;W$

  During an action potential,b.ldiyyw*x tn09ktdsg.- 5/ v $Na^+$ ions move into the cell at a rate of about $3 \times10^{-7 }\;mol/m^2\cdot s$. How much power must be produced by the “active $Na^+$ pumping” system to produce this flow against a $+30-Mv$ potential difference? Assume that the axon is 10 cm long and $20\mu m$ in diameter.    $ \times10^{-9 }\;W$

  How many coulombs are the;hml/ )hg nbmwz0;)ol re in 1.00 ampere-hour?    C

  What is the average currente0;uk( 0a1qybc xc2y/ izz :ep drawn by a 1.0-hp 120-V motor? $(1 hp\,=\,746\,W.)$    A

  A person accidentally leaves a car with the lights on. If ea, mse*do v,*jt dsivko 5*53ntch of the two headlights uses 40 W and each of the two taillights 6 W, for a total of 92 W, how long will a fr5ij,*s kne d,tsvo5*m*v o3dt esh 12-V battery last if it is rated at $95A\cdot h$? Assume the full 12 V appears across each bulb.    h

  The heating element of ;wb/1okz;,u9l b a ym x2ppxtu27bjf6a 110-V, 1500-W heater is 5.4 m long. If it is made of iron, what must its x b,2;x7pjz/kapuf62b wy uto l9;b1mdiameter be?    $ \times10^{ -4}\;m$

  The conductance G of an object is defined as the reciprocal of z w-n 4oejgyvhf2n)s3d(:lf t p0d* +ithe resistance R;jd0h4f(p:ng zt -w)yesiold*v3+f2 n that is, $G\,=\,1/R$. The unit of conductance is a mho $(=ohm^{-1})$, which is also called the siemens (S). What is the conductance (in siemens) of an object that draws 730 mA of current at 3.0 V?    S

  A small city requires about opktzi .,3/tpe3s -w oft qfv8yk*.w:10 MW of power. Suppose that instead of using high-voltage lines to supply the power, the power is delivered at 120 V. Assuming a two-wire line of 0.50-cm-diameter copper wi- iq/o3okwspt*zttyew: fvp3 8k, .f.re, estimate the cost of the energy lost to heat per hour per meter. Assume the cost of electricity is about 10 cents per kWh.    dollars per hour per meter

  (a) A particular household uses a 1.8-kW hexw//hgqy t,y51k p+cg/+r hapater $3.0 h/day$ (“on” time), four 100-W lightbulbs $6.0 h/day$, a 3.0-kW electric stove element for a total of $1.4 h/day$ and miscellaneous power amounting to $2.0 kWh/day$. If electricity costs $0.105 per kWh, what will be their monthly bill (30 d)?    dollars per month
(b) How much coal (which produces $7000 kcal/kg$) must be burned by a 35%-efficient power plant to provide the yearly needs of this household?    kg of coal

A length of wire is cut in half and the two lengths are wrapped 9ylog; g8l x.0tcf +setogether side by side to make a thicker wire. How does the resistance of this new combination compare tog efl.+tg 0l;8 yscxo9 the resistance of the original wire?

  A 1200-W hair dryer is designed3k ltf7d6a6 :szhgwi: for 117 V.
(a) What will be the percentage change in power output if the voltage drops to 105 V? Assume no change in resistance.    % decrease
(b) How would the actual change in resistivity with temperature affect your answer?

  The wiring in a house must be thick enough so it does not become so hot as to stshr+4xp3+ eepart a fire. What diameter must a copper wire be if it is to carry a maximum current of 35 A and produce no more than 1.8 W of hep srx+4pe3+ heat per meter of length?    $ \times10^{ -3}\;m$

  Suppose a current is d4ct 6ov+lyk ncn50 80*gtoki a:4b lygiven by the equation $I\,=\,1.80sin210t$, where I is in amperes and t in seconds.
(a) What is the frequency?    Hz
(b) What is the rms value of the current?    A
(c) If this is the current through a $42-\Omega$ resistor, write the equation that describes the voltage as a function of time. (  sin 210 t)V

  A microwave oven running at 65% efficiency delivers 950 W of energy pel*um3 2lw7stk1y+lyfr second to the interior. Fin lsyuklw7mt32yf+*l 1 d
(a) the power drawn from the source,    W
(b) the current drawn. Assume a source voltage of 120 V.    A

  A $1.00-\Omega$ wire is stretched uniformly to 3.00 times its original length. What is its resistance now?    $\Omega$

  220 V is applied to two different conductors made7z k8vne;2tmxbii x(.dy) 6yg of the same material. One conductor is twice as long and twice thee b;zymvgid2 x6kx i 8ty)n7.( diameter of the second. What is the ratio of the power transformed in the first relative to the second? $P_1$ : $P_2$ =    : 1

  An electric heater is used to hea xav 9ok9,7klft a room of volume $62\,m^3$ Air is brought into the room at 5$^{\circ}\,C$ and is completely replaced twice per hour. Heat loss through the walls amounts to approximately $850 kcal/h$. If the air is to be maintained at 20$^{\circ}\,C$, what minimum wattage must the heater have? (The specific heat of air is about $0.17 kcal/kg\cdot C?$)    W

  A 2200-W oven is hooked to a 240-V souro(o07l*ny x: n:i gnycce.
(a) What is the resistance of the oven?    $\Omega$
(b) How long will it take to bring 120 mL of 15$^{\circ}\,C$ water to 100$^{\circ}\,C$ assuming 75% efficiency?    s
(c) How much will this cost at $11 cents/kWh?$    cents

  A projected electric vehicle makes use of a9 p)on07ew-tvep 0d kstorage batteries as its source of energy. Its- 0dnpo7kav90te) pe w mass is 1560 kg and it is powered by 24 batteries, each 12 V, $95A\cdot h$. Assume that the car is driven on level roads at an average speed of $45 km/h$ and the average friction force is 240 N. Assume 100% efficiency and neglect energy used for acceleration. No energy is consumed when the vehicle is stopped, since the engine doesn’t need to idle.
(a) Determine the horsepower required.    hp
(b) After approximately how many kilometers must the batteries be recharged?    km

  A $12.5-\Omega$ resistor is made from a coil of copper wire whose total mass is 18.0 g. What is the diameter of the wire, and how long is it?
L =    m
A =    $ \times10^{-4 }\;m$

  A 100-W, 120-V lightbulb has a resib0bae xog)/r5(2pseistance of $12\Omega$ when cold (20$^{\circ}\,C$) and $140\Omega$ when on (hot). Calculate its power consumption at
(a) the instant it is turned on,    W
(b) after a few moments when it is hot.    W

  The Tevatron accelerator at Fermilab ze- qc*se,mscde 30m9(Illinois) is designed to carry an 11-mA beam of protons traveli3qee*9d,ss emzm 0-ccng at very nearly the speed of light ($ 3.0\times10^{8 }\;m/s$) around a ring 6300 m in circumference. How many protons are stored in the beam?    $ \times10^{12 }\;protons$

  An air conditioner draws 12 A at 220-V ac. The connecting cord is copper wire wy0 np 6ijt qbo)fn,h;/ithf0qoyt;p,hjn/ i 6 n)b a diameter of 1.628 mm.
(a) How much power does the air conditioner draw?    W
(b) If the total length of wire is 15 m, how much power is dissipated in the wiring? $\approx$   W(Round to the nearest integer)
(c) If no. 12 wire, with a diameter of 2.053 mm, was used instead, how much power would be dissipated? $\approx$   W(Round to the nearest integer)
(d) Assuming that the air conditioner is run 12 h per day, how much money per month (30 days) would be saved by using no. 12 wire? Assume that the cost of electricity is 12 cents per kWh. $\approx$   cents per month (Round to the nearest integer)

  A fish-tank heater is rated at 95 W when connected to 120 V. Tho-rr ,8qb wq8hcam 7r8e heating element is a coil of Nichrome wire. When uncoiled, the wire has a total length of 3.8 m. What crrbom h7q8r, q-w88a is the diameter of the wire?    $ \times10^{ -4}\;m$

  In an automobile, the system voltage varies/k21.qvn noi- +hnyw m from about 12 V when the car is off to about 13.8 V when the car is on and the charging system is in+vyokn2 .nwnh/ 1iqm- operation, a difference of 15%. By what percentage does the power delivered to the headlights vary as the voltage changes from 12 V to 13.8 V? Assume the headlight resistance remains constant.    % increase

  Lightbulb A is rated /.nrp 5v xawz1at 120 V and 40 W for household applications. Lightbulb B is rated at /v.z5 p 1nxarw12 V and 40 W for automotive applications.
(a) What is the current through each bulb? $I_A$ =    A $I_B$ =    A
(b) What is the resistance of each bulb? $R_A$ =  $\Omega$ $R_B$ =  $\Omega$
(c) In one hour, how much charge passes through each bulb? $Q_A$ =    C$Q_B$ =    C
(d) In one hour, how much energy does each bulb use?    $ \times10^{5 }\;J$
(e) Which bulb requires larger diameter wires to connect its power source and the bulb?  ----待选择----Bulb BBulb A 

  Copper wire of diameter 0.259 cm is used to m. rxv5)hoiq c(lgz-+connect a set of appliances at 120 V, which draw 2.)vqcorl zh- 5+ixg( m250 W of power total.
(a) What power is wasted in 25.0 m of this wire?    W
(b) What is your answer if wire of diameter 0.412 cm is used?    W

  A copper pipe has an izdrfi 6u522-4l sho.wo/ uny fnside diameter of 3.00 cm and an outside diameter of 5.00 cm (Fig. 18–37). What is the resistance of 10.0 m of this piuf-uol.drno6s4f /z 2whi2y5pe?    $ \times10^{-4 }\;\Omega$

If a wire of resistance R is stretched uniformly so that its length doubles, ov3;d.mp8i 4zd on1z nby what factor does the power dissipated in the z znmooni4d 18;p.d3v wire change, assuming it remains hooked up to the same voltage source?

  A tungsten filament used in a flashlighhihlzme7oe25wur-)x c2 60wq t bulb operates at 0.20 A and 3.2 V. If itshx6rem)chl -07w2woqe z 5ui2 resistance at 20$^{\circ}\,C$ is $1.5\Omega$ what is the temperature of the filament when the flashlight is on?    $^{\circ}\,C$