If two points are at the same potential, does tho10j5i rr4lrp is mean that no work is done in moving a test charge from one point to the other? Does this imply that no force need be exerted? Explal5ro1r4i0 pr jin.

If a negative charge is initially at resifd: (l -mo rgtr9yq:qz- z*pt 3hd1(st in an electric field, will it move toward a region of higher potential or lower potential? What about a p-3t 1:o pzmfddq9(r *yz: (qlhstgri-ositive charge? How does the potential energy of the charge change in each instance?

State clearly the difference (a) between electric potential and49wlre k/uo j1vg98zn electric field, (b) between electric potential and electric potential en9j4v rzg19/k8ew ul onergy.

An electron is accelerated by a potential difference of, say, qo v3snx)l3f-0.10 V. How much greater would its final speed be -3x)s3l vno qfif it is accelerated with four times as much voltage? Explain.

Is there a point along th62e rynkoo-i+ dx 8jv3e line joining two equal positive charges where the electric field is zero? Where the electric potential i6vjdy3+o ik 8n2ox -res zero? Explain.

Can a particle ever move from a region of low electric k2zxah1hel37 potential to one of high potential and yet 72a3hekz 1lhx have its electric potential energy decrease? Explain.

Compare the kinetic energy gainew5-i5vab xm org +b;t.d by a proton $(q=+e)$ to the energy gained by an alpha particle $(q=+2e)$ accelerated by the same voltage $V$.

If $V\,=\,0$ at a point in space, must $\vec{E}\,=0$ there? If $\vec{E}\,=0$ at some point, must $V\,=\,0$ at that point? Explain. Give examples for each.

Can two equipotential lines cross? Explaip(ze err0a i3aw9v6 04 rmvm;wn.

Draw in a few equipotential lines in Fig. 16 – 31b.qeouiy,axp0l:m2 h5(

What can you say about the electric field in 7 t0yd2o q(yrcki. tw3;yqq*j a region of space that has the same potential thqywcy* t3y qd2jqir o0k 7(t;.roughout?

A satellite orbits the Earth along a gravitational exnv +3wm6scz0 quipotential line. What shape must tscz+ wn 36mx0vhe orbit be?

When dealing with practic- *)a 0rprjgm*;vfyqg al devices, we often take the ground (the Earth) to be 0qr ym* 0-agr*vj;g)fp V. If, instead, we said the ground was how would this affect (a) the potential V, and (b) the electric field E, at other points?

When a battery is connected to a capacitor, why do the two plates acqiyj -aev/i75f uire charges of the same magnitu5yj/ ifva -7eide? Will this be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on the size, sh : lzkn fd;.cdc+sq28pape, and position of the two conductors, as+ c.dnc :dp zkqs8;2lf well as on the dielectric constant K. What then did we mean when we said that C is a constant in Eq. 17 – 7?

  How much work does the el7sfm ) -no1( kkrx,9yab7guj eectric field do in moving a $-7.7\mu C$ charge from ground to a point whose potential is $+55V$ higher?    $ \times10^{-4 }\,J$

  How much work does the electrinvq-b6p*zs cf 5 d7ak.c field do in moving a proton from a point with a ponbvd q65. 7askz-*f cptential of $+125V$ to a point where it is $-55V$ Express your answer both in joules and electron volts.
   $ \times10^{-17 }\,J$
   eV

  How much kinetic energh* 4hb .lyd:l*vzwmw 5y will an electron gain (in joules and eV) if it accelerates through a potential difference of 23:l.whwbd m5h l*z4yv*,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires evdl 5q fw b)cf)c723 b/p+tsi$7.45 \times10^{ -16}\,J$ of kinetic energy when it is accelerated by an electric field from plate A to plate B. What is the potential difference between the plates, and which plate is at the higher potential?
   V
plate ----待选择----AB 

  How strong is the electric field between two parallel plates 5.8 mm apart if yer5m h;hdropego bv n*4 7892the 4ore*; 59r 27bhedg pnoyhm8 vpotential difference between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of j/bi1. iuh5rf $640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two pilks -)x: m()ra lk i0i.nz. t,gbdx(parallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plambr:p u 6ij0:-w,wpz ktes connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a w9.k qm19tc khv ,z/jghelium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V powth, .9 aghyxqyeno+2 -er supply, are separated by an air gap. How small can the gap be if the air q,2 h-ayho.x+y ngt e9is not to become conducting by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force1i q1a; * xzc 5j*le*trmirw7p to move a $-8.50\mu C$ charge from point a to point b is $15.0 \times10^{ -4}\;J$. If the charge was started from rest and had $ 4.82\times10^{ -4}\;J$ of kinetic energy when it reached point b, what must be the potential difference between a and b?    V

  What is the speed of an e v 7vp5qf7gpm;lectron with kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whose kin p(v7:s4ycgw hetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which , qwi/sdxb/ wbpe d95:is a helium nucleus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric poe j+p5 soej3uqtc:* ue9ah+j*zkg 9k5 tential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q crenr t 5k*g *yld)ar xz+a*3jy4,z+nijbates an electric potential of $+125V$ at a distance of 15 cm. What is Q?    $ \times10^{-9 }\,C$

  A $+35\mu C$ point charge is placed 32 cm from an identical $+35\mu C$ charge. How much work would be required to move a $+0.50\mu C$ test charge from a point midway between them to a point 12 cm closer to either of the charges?    J

Draw a conductor in the shape of 6*jwvme96 kay40a whk)n h:ypa football. This conductor carries a net negative 6 9 yyahm*w6kah)4vw kpje n0:charge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential avwsbz: ) 0mu s8yhb)v40x5q)nz(mz(uh o; dxs distance of $ 2.5\times10^{-15 }\,m$ away from a proton?    $ \times10^{ 5}\,V$
(b) What is the electric potential energy of a system that consists of two protons $2.5 \times10^{-15 }\,m$ apart — as might occur inside a typical nucleus?    $ \times10^{ -14}\,J$

Three point charges are arranged at the corners of a square of side L as showng/zz.htze5rpk en3 ) ) in Fig. 17–25. What is the potential at the rp.h3z/t)g nee5z kz)fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.(c5hx;,jf xz 4 zlxhe.5 cm from a fixed point charge with $Q\,=\,-0.125\mu C$. How fast will the electron be moving when it is very far away?    $ \times10^{7 }\,m/s$

  Two identical $+9.5\mu C$ point charges are initially 3.5 cm from each other. If they are released at the same instant from rest, how fast will each be moving when they are very far away from each other? Assume they have identical masses of 1.0 mg.    m/s

  Two point charges, $3.0\mu C$ and $-2.0\mu C$ are placed 5.0 cm apart on the x axis. At what points along the x axis is
(a) the electric field zero    cm leftof $q_2$
(b) the potential zero? Let $V\,=\,0$ at $r\,=\,\propto$.

  How much work must be done to bring three electrons from a great dkv9,oj ov8h+ listance apart to9vo+ o l,vh8kj $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cmt4:f;xhie gjyg2q)0j north of a $-3.8\mu C$ point charge, and point b which is 88 cm west of the charge (Fig. 17–26). Determine
(a) $V_{ba}=V_b-V_a$    V
(b) $\vec{E}_b-\vec{E}_a$ (magnitude and direction).
   V/m
   $^{\circ}\,$

  How much voltage must be used to acc rny/.ktt8c:w elerate a proton (radius $1.2 \times10^{-15 }\,m$) so that it has sufficient energy to just penetrate a silicon nucleus? A silicon nucleus has a charge of $+14e$, and its radius is about $ 3.6\times10^{-15 }\,m$. Assume the potential is that for point charges.    $ \times10^{6 }\,V$

Two equal but opposite charges are separated by a distance gwcb2 622ya,ll/m h5-jx fjrsd, as shown in Fig. 17–27. Determine 2a2lcw/ ,jfbr j 2gh6y5m-xls a formula for $V_{BA}\,=\,V_B-V_A$ for points B and A on the line between the charges.

  In the Bohr model of the hydrogen atom, an electron orbits a protl sl46 xi 7l 0dhj2kix3ch75tmon (the nucleus) in a circum idlj2x i3cl70sl5xhk 47 h6tlar orbit of radius $ 0.53\times10^{-10 }\,m$.
(a) What is the electric potential at the electron’s orbit due to the proton?    V(Round to the nearest integer)
(b) What is the kinetic energy of the electron?
   $ \times10^{ -18}\,J$
   eV
(c) What is the total energy of the electron in its orbit?    $ \times10^{-18 }\,J$ $\approx$    eV(Round to the nearest integer)
(d) What is the ionization energy — that is, the energy required to remove the electron from the atom and take it to $r\,=\,\propto$, at rest? Express the results of parts b, c and d in joules and eV.   $ \times10^{-18 }\,J$    eV(Round to the nearest integer)

  An electron and a proton avsjc 9xq7km/ i3gs89yx nugb p xe73/:re $ 0.53\times10^{ -10}\,m$. apart. What is their dipole moment if they are at rest?    $ \times10^{-30 }\,C\cdot\,m$

  Calculate the electric potential due to a dipole whose dipole moment 8t-x1 gxjlu0c is $ 4.8\times10^{-30 }\,C\cdot m$ at a point $1.1 \times10^{ -9}\,m$ away if this point is
(a) along the axis of the dipole nearer the positive charge;    V
(b) 45° above the axis but nearer the positive charge;    V
(c) $45^{\circ}\,$ above the axis but nearer the negative charge.    V

  The dipole moment, considered as a vector,ubl 1esmoo.) yh 2t/dm *3oc.t points from the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be considered as the ve)yu1 e3tot2s.l mm/ d.cobh*octor sum of the two dipole moments, $\vec{P}_1$ and $\vec{P}_2$as shown. The distance between each H and the O is about $ 0.96\times10^{ -10}\,m$. The lines joining the center of the O atom with each H atom make an angle of $104^{\circ}\,$, as shown, and the net dipole moment has been measured to be $p\,=\,6.1 \times10^{-30 }\,C\cdot m$ Determine the charge q on each H atom.    $ \times10^{ -20}\,C$

  The two plates of a capacitj, dzq wvvm8(;or hold $+2500\mu C$ and $-2500\mu C$ of charge, respectively, when the potential difference is 850 V. What is the capacitance?    $ \times10^{-6 }\,F$

  The two plates of a cz:ffs3h ;q 5zwapacitor hold $+2500\mu C$ and $-2500\mu C$ of charge, respectively, when the potential difference is 850 V. What is the capacitance?    $ \times10^{-6 }\,F$

  A 9500-pF capacitor holds plus and mi /pdgb lp-e ay47e344 ygnshmc+9 6ioqnus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of parallel wire in ani9 1mg9uulz3ir is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is the capu9 9 1ulg3mnziacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows fp+byfi8v49rj x gxz2vj+oh1.rom each terminal of a 12.0-V battery when it is connected +x x8yjbzv2 i1ovfrpj 4+h.9g to a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates have if theyf583qmhc( mx5.fa x zp are to be separat f f(zh5mam3q5cx.x8p ed by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capamn9xaq* +cjqr2:h ) w/ca f9jfcitor increases by $18\mu C$ when the voltage across it increases from 97 V to 121 V. What is the capacitance of the capacitor?    $ \times10^{ -7}\,F$

  An electric field of l l fe0 ua3+v2cw)nnm:$8.5 \times10^{ 5}\,V/m$ is desired between two parallel plates, each of area $35\,cm^2$ and separated by 2.45 mm of air. What charge must be on each plate?    $ \times10^{ -8}\,C$

  If a capacitor has oppositeqiki lz6o-n7: $5.2\mu C$ charges on the plates, and an electric field of 2.0 $2.0\,kV/mm$ is desired between the plates, what must each plate’s area be?   $m^2$

  How strong is the electric field between the plates of7*3:5txbj 2bynka50 xm xfi0-kgzwp l a $0.80-\mu F$ air-gap capacitor if they are 2.0 mm apart and each has a charge of $72\mu C$ ?    $ \times10^{4 }\,V/m$

  A capacitor is charged by a 125-V battery (Fig. 17–29a) and then is discou3icz8q /coy:nnected from the battery.8q o3z/yc uc:i When this capacitor $(C_1)$ is then connected (Fig. 17–29b) to a second (initially uncharged) capacitor, $C_2$, the final voltage on each capacitor is 15 V. What is the value of $C_2$? [Hint: charge is conserved.]    $ \times10^{ -5}\,F$

  A $2.50-\mu F$ capacitor is charged to 857 V and a $6.8-\mu F$ capacitor is charged to 652 V. These capacitors are then disconnected from their batteries. Next the positive plates are connected to each other and the negative plates are connected to each other. What will be the potential difference across each and the charge on each? [Hint: charge is conserved.]
$V_{final}$ $\approx$   V(Round to the nearest integer)
$\begin{array}{l}
Q_{1}\\
\text { initial }
\end{array}$   $ \times10^{-3 }\,C$
$\begin{array}{l}
Q_{2}\\
\text { initial }
\end{array}$   $ \times10^{-3 }\,C$

  What is the capacitance of two square parallel p ei +be7k;4svplates 5.5 cm on a side that are separated by 1.8 mse+4 pi7; bekvm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a radius of 5.0 cm s4gi0l mxgl 8y)un8jl3fkpc17 bhj.0i eparateiif4p3m. culh)08lxg01 7k g8 lynjjbd by 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacia-ceyh / (2taktor is connected to a 22-V battery. If a piece of mica is placed between the plates, how much charge will flow ch -ayk/(2ae tfrom the battery?    $ \times10^{ -7}\,C$

  The electric field between the plat:6l tscju7* xm/ d:zv gjg-u3onr p8/aounl2;es of a paper-separated $(K=3.75)$ capacitor is $ 8.24\times10^{4 }\,V/m$. The plates are 1.95 mm apart, and the charge on each plate is $0.775\mu C$. Determine the capacitance of this capacitor and the area of each plate.
   $ \times10^{--9 }\,F$
   $m^2$

  650 V is applied to a 22r y flczi.h s)8 tgc8.nd;.+7xenop9n00-pF capacitor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is zbb+ mh-m22b/3s ( ruatpdrm2 used to shock a heart that is beating erratically. A capacitor in this devic2 bs-t+d2 z2/3pmruhb(mma r be is charged to 5.0 kV and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electricwq ws7 r (uxuro 8xg),)/-z+dupsa. ss field between two square plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on the plates are equal anduar -7 uw+qsx )8s . /,ow(guzrdxs)ps opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placinggl ba0 hp(83mb two 9-in. pie pans 5 cm apart and connecting them to the opposite terminals oa8 hlbp0mg( 3bf a 9-V battery. Estimate
(a) the capacitance,    $ \times10^{-12 }\,F$
(b) the charge on each plate,    $ \times10^{-11 }\,C$
(c) the electric field halfway between the plates,    V/m
(d) the work done by the battery to charge the plates.    $ \times10^{ -10}\,J$
(e) Which of the above values change if a dielectric is inserted?

A parallel-plate capacitor has fix 1vv4usqi z sfib155;c8nh a.zed charges $+Q$ and $-Q$ The separation of the plates is then doubled.
(a) By what factor does the energy stored in the electric field change?
(b) How much work must be done in doubling the plate separation from d to 2d? The area of each plate is A.

How does the energy stored in a capacitor change if (a) the potential diffequ/diaph x*9ut+9 p3u rence is doubled, and (b) thei9* qhu9 tupduap3+x/ charge on each plate is doubled, as the capacitor remains connected to a battery?

  A $2.70-\mu F$ capacitor is charged by a 12.0-V battery. It is disconnected from the battery and then connected to an uncharged $4.00-\mu F$ capacitor (Fig. 17–29). Determine the total stored energy
(a) before the two capacitors are connected,    $ \times10^{-4 }\,J$
(b) after they are connected.    $ \times10^{-5 }\,J$
(c) What is the change in energy?    $ \times10^{-4 }\,J$

  In a given CRT, electrons are acceleran *y/cqrz )th8ted horizontally by 7.0 kV. They then pass through a uniform electric field E for a distance of 2.8 cm, which deflects them 8ch )/rn zt*qyupward so they reach the screen top 22 cm away, 11 cm above the center. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated r s w3k:emmx3;/zmyp 3 31htqyby 6.0 kV in a CRT. The screen is 30 cm wide and is 34 3 :yxtr mz3ekhqym3s p1;3/mwcm from the 2.6-cm-long deflection plates. Over what range must the horizontally deflecting electric field vary to sweep the beam fully across the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from zvb3 1tv xwon rcrk3(a77*b1brest acquires 6.3 keV of KE in moving from point A to point 1r3a*1x73(n tv vzbr7wk bcob B.
(a) How much KE would a proton acquire, starting from rest at B and moving to point A?    keV
(b) Determine the ratio of their speeds at the end of their respective trajectories.   

  A lightning flash transfers 4.0 C of charge and 4.2 MJ of energy to the Earthq /rakcw.73u b9 gfzo(.
(a) Across what potential difference did it travel?    $ \times10^{ 6}\,V$
(b) How much water could this boil and vaporize, starting from room temperature?    kg

  There is an electric field near the Earth’s surfacer y*r k3yxig 5:)5akgorrn,1- /xphvs whose magnitude is about $150\,V/m$ How much energy is stored per cubic meter in this field?    $ \times10^{-7 }\,J/m^3$

  In a television picture tube, electrons2((h. n4tnebop4yq kg are accelerated by thousands of volts through a vacuum. If a television set were laid on its back, would electrons be able to move upward against the forcen pbyn(h.tqk44 ge(2o of gravity? What potential difference, acting over a distance of 3.0 cm, would be needed to balance the downward force of gravity so that an electron would remain stationary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough storedd ja2zuhe m+ .l9,cf-1dcpjg; energy to heat 2.5 kg of water from 21$^{\circ}\,C$ to 95$^{\circ}\,C$. What is the potential difference across the plates?    V

  An uncharged capacitor is connected to a 24.0-V battery until it is fully g:k2h/e/m i qrcharged, after which it is disconnected from the battery. A slab of paraffin is then inserted between the plhimqerk/ :/g 2ates. What will now be the voltage between the plates?    V

  Dry air will break down ision9mr0 6+h8ihi :ujf the electric field exceeds $3.0 \times10^{6 }\,V/m$. What amount of charge can be placed on a parallel-plate capacitor if the area of each plate is $56cm^2$?    $ \times10^{-7 }\,C$

Three charges are at the corners of an equilateral triangle (side L) as shobxe ;s r*.gx1 bbkz/,jwn in Fig. 17–30. Determine the potential at the midpoint ob1xx*; s zk/gbrb,.e jf each of the sides.

  A $3.4\mu C$ and a $-2.6\mu C$ charge are placed 1.6 cm apart. At what points along the line joining them is
(a) the electric field zero,    cm left of $q_2$
(b) the electric potential zero?

  A 2600-pF air-gap capacitor is connected to a 9.0tc*m:pt.2iuzv,e:+)od;u* nj anau h-V battery. If a piece of Pyrex glass is placed between the plates, how much charge will then flow from the batterttdo::* .2c p hu muzvanu)aej+i*;,ny?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally -vrhx rf0odawh 8, t7/zgxlt67b )dy *from rest in a television picture tube by a potential difference of 5500 V. It then passes between two horizontal plates 6.5 cm long and/06xzawol,hy xtbg hddrf7* t)v - 87r 1.3 cm apart that have a potential difference of 250 V (Fig. 17–31). At what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capaci)ten0 ximwg gff:*k:(tance $C_1$ carries a charge $Q_0$. It is then connected directly to a second, uncharged, capacitor of capacitance $C_2$, as shown in Fig. 17–32. What charge will each carry now? What will be the potential difference across each?

  To get an idea how big.ns8n)qyr 9dtppd z 93 a farad is, suppose you want to make a 1-F air-filled parallel-plate capacitor for a circuit you are 899p3rd zn.)t npdqysbuilding. To make it a reasonable size, suppose you limit the plate area to What would the gap have to be between the plates? Is this practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there is l*/t8 6 -tb 3o,a(knroan)f p9pv bjjgan electric field of about $150\,V/m$ which points downward. Two identical balls with mass $m\,=\,0.540kg$ are dropped from a height of 2.00 m, but one of the balls is positively charged with $q_1$ = $650\mu C$ ,and the second is negatively charged with $q_2$ = $-650\mu C$. Use conservation of energy to determine the difference in the speed of the two balls when they hit the ground. (Neglect air resistance.)    m/s

  The power supply for a pulsed nitroge r8b:n )kn8noan laser has a $0.050\mu F$ capacitor with a maximum voltage rating of 30 kV.
(a) Estimate how much energy could be stored in this capacitor.    J
(b) If 12% of this stored electrical energy is converted to light energy in a pulse that is 8.0 microseconds long, what is the power of the laser pulse?    $ \times10^{5 }\,W$

  In lightning storms,6 a)z ltf35 gnc0gpji*,t nn dz(+jhc6 the potential difference between the Earth and the bottom of the thunderclouds can be as high as 35,000,00a6hf n*j,zzjc 5 pln+3 (cndg6ti)tg00 V. The bottoms of the thunderclouds are typically 1500 m above the Earth, and can have an area of $110km^2$ Modeling the Earth–cloud system as a huge capacitor, calculate
(a) the capacitance of the Earth–cloud system,    $ \times10^{-7 }\,F$
(b) the charge stored in the “capacitor,”    C(Round to the nearest integer)
(c) the energy stored in the “capacitor.”    $ \times10^{8 }\,J$

  In a photocell, ultraviolet (UV) light provid ykmfe28swj 0sd .5x/ses enough energy to some electrons in barium metal to eject them from k/2ysw .s8e sfdx j5m0a surface at high speed. See Fig. 17–33. To measure the maximum energy of the electrons, another plate above the barium surface is kept at a negative enough potential that the emitted electrons are slowed down and stopped, and return to the barium surface. If the plate voltage is $-3.02V$ (compared to the barium) when the fastest electrons are stopped, what was the speed of these electrons when they were emitted?    $ \times10^{6 }\,m/s$

  A point charge is placed 36 cm from an identical9*mwanes(l;h7yi:3jq(rp j o $+33\mu C$ charge. A $-1.5\mu C$ charge is moved from point a to point b in Fig. 17–34. What is the change in potential energy? $\approx$    J (round to one decimal place)

  A capacitor is made from two 1.1-cm-diameter coins separated by a 0.15-mfc mlh)xbr 5/l1p92hw m-thick piece of pallf2 91h5rmw)cbp /h xper $(K=3.7)$ A 12-V battery is connected to the capacitor. How much charge is on each coin?    $ \times10^{-10 }\,C$

  A $+4.5\mu C$ charge is 23 cm to the right of a $-8.2\mu C$ charge. At the midpoint between the two charges,
(a) what are the potential    $ \times10^{ 5}\,V$
(b) the electric field?    $ \times10^{6 }\,V/m$  ----待选择----leftright 

  A parallel-plate capacitor with plat0l 4qn+wj5g4 qtpu0xd 22 opele area $2.0cm^2$ and air-gap separation 0.50 mm is connected to a 12-V battery, and fully charged. The battery is then disconnected.
(a) What is the charge on the capacitor?    $ \times10^{ -11}\,C$
(b) The plates are now pulled to a separation of 0.75 mm. What is the charge on the capacitor now?    $ \times10^{ -11}\,C$
(c) What is the potential difference across the plates now?    V
(d) How much work was required to pull the plates to their new separation?    $ \times10^{-10 }\,J$

  A $2.5-\mu F$ capacitor is fully charged by a 6.0-V battery. The battery is then disconnected. The capacitor is not ideal and the charge slowly leaks out from the plates. The next day, the capacitor has lost half its stored energy. Calculate the amount of charge lost.    $ \times10^{-6 }\,C$

  Two point charges are fixed 4.0 cm apart from eachs5ih7tf 4zt43 v uc:tm other. Their charges are $Q_1$=$Q_2$=$5.0\mu C$, and their masses are $m_1=1.5mg$ and $m_2=2.5mg$
(a) If $Q_1$ is released from rest, what will be its speed after a very long time?    m/s
(b) If both charges are released from rest at the same time, what will be the speed of $Q_1$ after a very long time?    m/s

  Two charges are placed as shown in Fig. 17–wvgp,7is *1+0cvbw on 35 with $q_1$=$1.5\mu C$ and $q_2$=$-3.3\mu C$ Find the potential difference between points A and B.    $ \times10^{ 5}\,V$