If two points are at the same potential, does this mean that no a./k9hedoaoto9 +lhg sj :+8jwork is done in moving a test charge from one point to the other? Does this imply that no force need be exerted? Explao+e s.jgha olko8d9+ j9h t:/ain.

If a negative charge is initially at k w52of,; ui9 4onafo1yzkt(crest in an electric field, will it move toward a region of higher potential or lower potential? What about a positive charge? How does the potential energy of the charge change in eaao1 f9o4ykz5intc(ok2, ; w fuch instance?

State clearly the difference (a) betweennas9f.q -o qm: electric potential and electric field, (b) between electric potential and .f n-:qq o9asmelectric potential energy.

An electron is accelerated by a potential difference of, say, 0.1r )muf- */ris(ktcuj(5hj(cu 0 V. How much greater would its final speed be if it is accsc-*i5h(fuckm (t)jj (rr /uuelerated with four times as much voltage? Explain.

Is there a point along the line joining two equwpub9 *2htqr9/*omw-f. gib gal positive charges where the electric field is zero? Where tq fribwbgt/p.g9- u *hmo9* w2he electric potential is zero? Explain.

Can a particle ever move from v 72cxm)b q4jc s1ik)z(g ae)ja region of low electric potential to one of high potential and yet have its electric potential energy decre7cvke1i) b)s jcgaqz(4 mx2)jase? Explain.

Compare the kinetic energy gained by a proto1glak m6 i-w1an $(q=+e)$ 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? Explain.y0,;,wmb8 ra na76d4gxzf oce

Draw in a few equipotentia o. -nqoswc,b7pl5i b, ghh7p6l lines in Fig. 16 – 31b.

What can you say about the electric field in a region of space that has thewqa .k8cpw9 y( same potential throq.kww c9(py8 aughout?

A satellite orbits the Earth along a gravitational equipotential l4gl v nbup/p 9(ko3ag 06a25 mspugyc/ine. What shape must gbkyulp5ap ( 2 3/u o0mg/pcv9ag64snthe orbit be?

When dealing with prac)t 5wh; t2rtwx1n.ksi , mr-dttical devices, we often take the ground (the Earth) to be 0 V. If, instead, we said the ground was how would this affect (a) the potential V, and (b) the electric field E, atthkrs5wxt.w ,;2i -)nrm td1t other points?

When a battery is connected to a capacitof 1 / te7wd swcs-d0:pif32nzor, why do the two plates acquire charges of the same magnitude? Will this be true if the two conduccs : zfts2newp o0 d71idw-f/3tors are different sizes or shapes?

We have seen that the capacitance C depends on the size, shapes c k6r tt69ia6olq6s89dt/uy , and position of the two conductors, as well as on the dielectric constant K. What then did we mean when we said that t9 tt66/u9 6kcrs8dl yioaq6sC is a constant in Eq. 17 – 7?

  How much work does the electric fiedq7 ; h1e1 hm mc622axzlogn,fld 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 electric field do in moving a proton fv:2 umuk.j . 8i:ifg25 ehtrmv76yq bwnp dc*1rom a point with a potential oqhbv7*vr:w5u6 n k i8g muct21e .ym2j:.fpidf $+125V$ to a point where it is $-55V$ Express your answer both in joules and electron volts.
   $ \times10^{-17 }\,J$
   eV

  How much kinetic energy will an electron gai: s5*ztlz4ubmn (in joules and eV) if it accelerates through a potential difference of 23,000 V in a TV:ubzl* smzt54 picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires wh5/w0 ri w);bphrpm2i.p8tg f /;rne$7.45 \times10^{ -16}\,J$ 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 twi )cog5n:j()avx3 mo he potential difference between them is 220 V mav5j()iox )gw3 :ocn?    $ \times10^{ 4}\,V/m$

  An electric field ofhvee;(i e9i2c $640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two parallel plates connxvh6jy me9m8 (ected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parall ze/pq l6kmgz6r//zfgbx9q;1 el plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a h )l o/.qkqju 5l0w5 omv*fye*yelium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, are separ1r4 5e3snur*v-/hmsijn rqom :- 6jbkated by an air gap. Hoj u v/rn5nk jqmb6rh3irm :1-seo-*4sw small can the gap be if the air is not to become conducting by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an externalkduwm, 4 +9uxc force 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* 1.k 0g hlxeup 4hia*1ldu(jj an electron 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 kinetic energy is 3.2 ke q/ ezxuj*tv +.(waev3V?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nucleus,- bcv(y0 z-gzm k7j)revu7di3 $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric potential 15.0 c s))dma- sipg4m from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric pot1colwfwaxcp:q 5b16 ;ential 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 a football. Th 0vdcs kv7u/ k*(tqm:gis conductor carries a net negative charge,/tu(s 0:7mdgvvc*kq k $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electtuwxox40 n d1;ric potential a 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 1 8/nm+seceozthe corners of a square of side L as shown in Fig. 17–25. What is the potential at the fourth corner (point cnsm1ze /e8+ oA), taking $V\,=\,0$ at a great distance?

  An electron starts frobttb hajq- rv6 :az 0wy(;t-s(m rest 32.5 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 dis m fxq:wv9h:w6tance apart tw6 q :wmfv9hx:o $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a whic7 u6wa(ocmht)0)* b;bz i yteoh is 72 cm 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 accelerate a proton82oo) u (ocmep (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 d, as shown in Fio1ijvxc **se+ dg-zd 5g. 17–27.vo+c5*dz-sgje 1d i*x Determine 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 tb6 k r28piy ko4n7gx/vhe hydrogen atom, an electron orbits a proton (the nucleus)ok8kx6 r47/2gbpynvi in a circular 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 aq71wp3)hxxwcuofr m;.u8b q8q8 azr( 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 potkdh2qgs +sms/xm1nil2 + 5wd ; -lmg)gential due to a dipole whose dipole moment 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, pointsniji( n,(rjq / from the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can nr, /(nqjii(j be considered as the vector 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 capacitor9kq t56ajufz n6-l(nk 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 kj/l1tth1*yxz :pw-m capacitor 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 minus charges ofl 7-dbsy:wul7 $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential differ iw-453r v iy/sceed6tence between two short sections of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is the capacitan 5-3/4se6yi rwdcvit ece of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of a 12.0-V battery when it is3v1;ty7ebyq rr.fs g; connected tos;bt7y g rfvr1;3 q.ey a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates a6gs,7xd i(ht-updzjr 25 8 kehave if they are to be separap,6iagerd 2h ukdt8j-75s( xzted by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor incred66p8mnegl* lg rb 56sases 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 sdl2u2 t/do6y tc/68 gzy8mhc$8.5 \times10^{ 5}\,V/m$ 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 oppositwk.6 s(9 kpygte $5.2\mu C$ 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 betwe,z+9z gb/ *qsqjzr(i 88 hxzseen the plates of 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 by2t 2a (aaq0+q oar/ijr;e b2rl a 125-V battery (Fig. 17–29a) and then is disconnected from the battery. When this capaca (aa2rto+er 2q2a0r/j ; iqlbitor $(C_1)$ 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 parallb kdi8 t9 elc89kjxs.)el plates 5.5 cm on a side that are secils8kdx8jt 9 )b. e9kparated by 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a radius of 5.0rf6qni +dxv9xl2wn q71*z qg+ cm separated by 3.2 mmvig7 r 2q6xdn1fqxzw +9*+nlq of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery*1u9bs.:z0n h estlku. If a piece of mica is placed between the plates, how much charge will flow fro e1lhus.90n:k uzst*b m the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a paper-s:,spf9 -x5d)sh2w 1e mpgspsw eparated $(K=3.75)$ 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 2200-pF ce46-hq2jkxt wm0;ny 68 pzc xdapacitor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beating err6d0h./ jnj1p a pjh873ubvt qpatically. A capacitor in this device is charged to 5.0 k u0 hp8vhp71/3jtn.jp6ad qbjV and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between two square plates, nd39c cj hk:p-8.0 cm on a side, separatednpjch9:d- c3k by a 1.5-mm air gap? The charges on the plates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembxe9 30m7ttnc re cb,ye98z:dcled by placing two 9-in. pie pans 5 cm apart and connecting them to the op,e90 ecr3 c9nc:myd8 xz bt7teposite terminals of 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 capyd5 si,epu29:r-vd y uacitor has fixed 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 changej)funs bsc/m. dg- .jles*.)lezp m24 if (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as the capacitor remainscj s)nfs m*2 usbzdg/e.l4e.p)l-.jm 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 accelerated horizontally by 7.0 kV. They 48rzhr*/jwkvthen pass through a uniform electric fiel8jkh/rr4z *wvd E for a distance of 2.8 cm, which deflects them upward 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 by 6.0 kV ijuphm4aol ,10n a CRT. The screen is 30 cm wide and is 34 cm 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 scr jo0mp 1lh,ua4een?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from restnewopouy -(n1 1f7o5 a acquires 6.3 keV of KE in moving from point A to pn 5(pnu1-7faooow 1yeoint 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 energ0 h cdq/6-v hq3.gkw.+aapn4e uhgi u7y to the Earth.
(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 t* euao8kkw*i6bs fj 6+he Earth’s surface 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, electrons are accelerat vky1b3i2 rz/n+ reub6ed by thousands of volts through a vacuum. If a television set were+rveb ibzy k1 2u/63nr laid on its back, would electrons be able to move upward against the force 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 stored energy to heat 2.5 kg of watere7oejgfejggpe9 2 o4t)my*98 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 fu;) e1hxpus+gedn x*3clly charged, after which it is diecu3 h xpe gd*xn1;+)ssconnected from the battery. A slab of paraffin is then inserted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down if the eleci0jhjxn13oudmkw)91e-.1 u taui q6lxx* oz*tric 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 any-dl aap h0+widz82p 2 equilateral triangle (side L) as shown in Fig. 17–30. Determine the potential at the midpoint of each of thhw-dz82+ 2ypp da0 liae 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 9.0-V battery. If a piece of ed9p qnnlx/u) d4c.d-i*nh-f Pyrex glass is placed between the plates, how muc-pd-x*9.in q 4c /nhfe)dlndu h charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in a televi yte ggv957an2sion picture tube by a potential difference of 5500 V. It then passes between two horizontal plates 6.5 cm long and 1.3 cm apart that have a potential differt a e5y9g7nv2gence 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 capacitance :v 3v-6 d o;onzsrdaw:$C_1$ 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 a farad is, suwrx 3;n (.no savld2+xppose you want to make a 1-F air-filled parallel-plate capacitor for a circuit you ar.n x a x2n;+rosvd3l(we building. 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 Earw ibnvm/dnqy+ +v5-e5th there is an 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 nitrogu ef: 2i 8z8+ecvxm8cjen 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, the potenozr2m, yo.)l hq(5kuosmg-1itial difference between the Earth and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are tysl2-gr)io, 1om h.qk(u5ymzopically 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) lig t ao v*0w5b a.bp)-:cyhmbzy2ht provides enough energy to some electrons in barium metal to eject them from a surface at high speed. See Fig. 17–33. To measure the maximum energy oftpa.2:5ycbwa b-h)ybv*0 zom 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 3;ud qs74,z;g zvwq3ff 6 cm from an identical $+33\mu C$ 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-k( b;4x/l mh l2j9lojvmm-thick piece o;lj2/bl4j (vox9mk lh f paper $(K=3.7)$ 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 plat.ez- b,u63p qq io(28x sm-s(fosce;yb e;sko e 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 each ot5- faj xcuxi00d n jis;r23;q(g3 pqrnher. 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. 17–35 l p9,km8nt8(hw aw ha/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$