If two points are at the same potential, does this mean that no work ()hvq/afgkazlhvx, 46u .gq2is done in moving a test charge from ga (avq/6k2lh qh gx.z)vfu, 4one point to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at restv/a:m4w,e; tgmikrs0 xa4e j9 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 eachexa;s/mw, 4tm iearj0:g9vk 4 instance?

State clearly the difference iqkr c5l zau9y ;d(;mfq7 *hz*(a) between electric potential and electric field, (b) between electric pr;iym hcd;z(lfa q7**z9q k5uotential and electric potential energy.

An electron is accelerated jkoj5(l ;p- u 5qv b9)4uidfxzby a potential difference of, say, 0.10 V. How much gj lzk- i;uqd4)xfuv5j9p(o 5 breater would its final speed be if it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining two equal positive charge,)a;qwfglogyp 7zpq u 4/o0( as where the electric field is zero? Wheoqp0 (oal; ggy4w),qazup/ f7 re the electric potential is zero? Explain.

Can a particle ever move from a region of low46,ak uk,o 8nlc6cu ; js:fjmn electric potential to one of high potential and yet have its elect a;m, ukoccl6:j,uf4n s6jkn8ric potential energy decrease? Explain.

Compare the kinetic energy gained byki 0p :zi2m2wt 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 lm1lsqvku7ls*. 6d .t5k) btyr ines cross? Explain.

Draw in a few equipotential lines in Fig. m;mhkldfq*y v h .78yht5.)skg ;uv+d16 – 31b.

What can you say about the electric field in a region of spauw2v+kbh, 1d zce that has the same potentiad+ hkb1 ,v2zwul throughout?

A satellite orbits the Earth along a gravitational equipotentia8g3l,ydkw;q0 ki; tj hl line. What shape must th ;tkw8qh 30yj lg,d;kie orbit be?

When dealing with practical devices, we often take the ground (the Earth) to bzt kh)7,*o gft(f:td pe 0 V. If, instead, we said the ground was how would this affect (a) the potential V, and (b) the electric field E, at other poftt: t*o(d,)p7h fgzk ints?

When a battery is connected to a capacitor, why do the two plates acquirebt,vma: t): lfnypt.5 u8h2 zg charges of the same magnitude? Will this b.u:)t2fvl t, athb 5:mgypz8ne true if the two conductors are different sizes or shapes?

We have seen that the capacitance C dep6* kf7. 1mw3 v )bx-nsoroffefends on the size, shape, and position of the two conductors, as well as on the dielectric constant K. What thow b f6o-f ff)*mevr1 kx3ns7.en did we mean when we said that C is a constant in Eq. 17 – 7?

  How much work does the electric field do inaivu 0h /bh v851jv6po 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 9ykj:1 pn a3yfelectric field do in moving a proton from a point with a poyj :y31 kfpna9tential 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 energy7 j0i dvminb:u cb7e.5 will an electron gain (in joules and eV) if it accelerates through a potential difference of 23,000 V 0dc 5vb7ubi.m7 ni :jein a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires lksl6wofv5l9 mf7ugua-f 3 44 $7.45 \times10^{ -16}\,J$ 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 f1e tem4a( vekjn8db 1/4 h.otjield between two parallel plates 5.8 mm apart if the potential difference between th bh td81o/tm(jv4eje.k a1 n4eem is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of mnoy )o/y-db6 $640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two parallel platesmv7wuf:;t(*xfettq:, : dzyh connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates chgjnb:15h f.9fa1 h+w aizzj(onnected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed te4ph-ve fr/alr9p z b--/4kzbo give a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 20 h;b: sc4-cyqy0-V power supply, are separated by an air gap. How small can the gap be if the air is not to become conducting by exceeding its breakqcch :y-b4 ;ysdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an externa+c*b2 h6pg mcoaax:3z l 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 an electron with kinexc:qpfq5 139yh6 l: 1hak roeztic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whose kim9g:6ky q anx3netic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nucleuyax 0u:*tk 5a-)ko-k xirwn x,s, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric potmfzx :he432otraz)yb47j k+ wential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates anejn28v1qqi 4 k 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 a football. This cog24.cuc1hu7zck n5 wonductor carries a net negative char7 co1uu2z 54 chcn.kgwge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric p8: i5ke h:hkxfotential 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 the corners of a squareg.sg+st+hc knk8u+v: of side L as shown in Fig. 17–25. What is the povnku+h k:s+s8 .+cgtgtential at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from ) lxv(iqma6b:d ,uy3 ui .v2xxa 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 zrtg 8:bn4r9mfrom a great distance apart to 8 r4g:nmt9 rbz$1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 6s jlp r(w,-ytcm 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 t; 6 ctb9dxjgu fc50bs)o accelerate 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 oppositxqqw 891 a(olui;*ntp5aqx9fe charges are separated by a distance d, as shown in Fig. 17–27. Determa1 l p*q(noaq9if; x58wx9 qtuine 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 atomfr (:c k1tqvb1, an electron orbits a proton (the nucleus) in a circular orbit of radiuv(bt:k 1 qc1frs $ 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 hlx 2)w rsi+e(are $ 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 mome(cnq2 *uuzmn l7 o/wile1wl9-nt 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, points from the negative to the pdufr n( rr6j33ositive charge. The water molecule, Fig. 17–28, has a dipole moment which can be consi3j rrn (frd6u3dered 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 capaci*ya+q,/8.5ik cy j brlzu .zfdtor 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 capacyn qc(:ze7j)c k7e+n*3)mbbb m r+idritor 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 cu6rujm(l8 q,m zgg9g ;harges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two wgo9ejj 3lc57 short sections of parallel wire in air is 120 V. They carry equal and opposo39 wj7g5e lcjite charge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of a 12.0-V battery when it is conn0u +wqz -w0werected -0eu w0+wzrqw to a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the ef5b+g-epp p( plates have if they are to be sepa p-gf5 (bepe+prated by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor im f6m467gu akf:atj hb/)dx-qncreases 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 - 9vc9);e bhx6vj jje3 si1 rnn3jmo)t$8.5 \times10^{ 5}\,V/m$ 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 opi5y, ,j ra2;1ar hkqeuposite $5.2\mu C$ 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 fie:btw9/os ihq7 ld between 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 by a 125-V battery (Fig. 17–29a) and then is discou los9i3m+h0brh ozwtg9n29;8hw t,snnected from the battery. When th st32ng s9 tw9bholo;w8h0 ,+m9uzrihis 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 plates 4h(f x(cx) jbi5.5 cm on a side that are separatedh (x (xcb)fji4 by 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with euhqk( w+ ,c(ca radius of 5.0 cm separatu(e(whqckc, +ed by 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. If a piece/x3hc1x hu0 c)8.k-k b wpdb ji:uj8hm of mica is placed3kj x)c8ihwdmk-j cb0:x1 up/ h.hu8b between the plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a paper-sepyzv8 +timb;. z/j;urharated $(K=3.75)$ 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 capacitor. How much emh11v;fafjbc, n 9aq 4nergy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator izp7 ss ia2ezz0-2 ox+xs used to shock a heart that is beating erratically. A c22z7szxx0-p+as z ie oapacitor in this device 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 electric field between two square prp 2 c*h7hin +hj0)1 vkfqrsc)lates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on the plates are equahcjk)sc*nr )0hp 17rqv fhi +2l and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in. pie pans 5 cm apart ncv -:i.q a -8pbb63m ngtd:teand connecting them to the-bntt: . -m6 qbda:p8cnev3ig opposite 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 capacitor has fi p xph4i0hp0+)x8 bv*e wwjms-xed 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 (9:tck2ubi9b s c.qzd rdo6 +n7a) the potential difference is doubled, and (b) the charge on each plate is doubled, as the capacitor remain nqs kt2c 6zb.+r:o 79c9buddis 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 then sbo,bb; 9fnq ihb0 5ou24 bor4pass through a uniform electric field 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. Esubq ro;f0n ,9bh bbbo52si4o4timate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a CRT. The screen is 30 c(w;n:g:-q94qrjf pef j1b l bxm wide and is 34 cm from the 2.6-cm-long deflection plates. Over what range must thlgw;f 41bf qpreq-xj(9:j n b:e 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 rest acquires 6.3 keV of KEwh s *1 f-p. sg7cnhxmkq5+0nj in moving from point A to point B. jc71 gn*fs+s-nwhmhpk5x.0 q
(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 Ek73av:caj+s,6x oce8h v4a tzo:4g t larth.
(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 sua7q0w7t*j2qn) dl dbd zcs)k;rface 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 accelerated by tajm+ z:8ypm7 khousands of volts through a vacuum. If a television set were laid on its back, would electrons be able to move upward against the force of mpkj :+z 8m7aygravity? 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 en .t ,;xx1t mvli 5ukt)2eieq7cough stored 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 battelfk uu- g53 gfuz)gb9-ry until it is fully charged, after which it is disconnected from the battery. A slab of paraffin is then inserted between the plates. What will now be the voltage beug53 lz)guuff9 - g-kbtween the plates?    V

  Dry air will break down if thes 5fq )tzw;i0 n*ooq,3jyy:f d 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 opcslva;tq (*b5b +.8u 6/nfyvamq:qan equilateral triangle (side L) as shown in Fig. 17–30. Determine the potential at the midpoint of eachvm+8bv .5a*bfu(c:l ;/ qqospq6 naty 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 7 rvvg:pz -t:9pwxjw b+oy4d09.0-V battery. If a piece of Pyrex glass is placed between the plates, how much charge wid0y :j oxpvwp7w z: brv-+4gt9ll then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in ti) /mm s1k/f;aiea ;ea television 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 difference of 250 at1ke m/ af i)ie/;m;sV (Fig. 17–31). At what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capacitano wv9m3szq68l ce $C_1$ 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, suppose you want to make a 1-F/gkjofwl78b aw ,9tk 9 air-filled parfj9ba/ ogtkw7k9,8 lwallel-plate capacitor for a circuit you are 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 Earth there is an electric field o t,hf2kpsel:eiw)0 ej33zg e6 f 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 nitrogen le,unb jf9(,r*qiyr g7 c.e hz8aser 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 potential difference betweebp4l ui:7 aeu/n the Earth and the bottom of the thunderclouds can be as high as uupae47b: /i l35,000,000 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 provides enough energy to some electron*d :fsn7zauu*+qdbb 9s in barium metal to eject them from a 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 enoughn: qfub*+7db du*9asz 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 placb gi0f thcqgi7 o 3l9 h3q3t(f4nbp6x,ed 36 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-cl;4dty s* ;m w6- hcv 8cqhbjs7zhb37om-diameter coins separated by a 0.15-mm-thick piece of papecd6q- v3lso7mht;74z8cw* bs y jh;hbr $(K=3.7)$ 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 capaci ac ktkh6xgu zm699of(z s+d/8;sa2n vtor with plate 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 frogic8qt/ju(l/csag5 / m each 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 Figk-j 9;ixevi-he3 zu 1c5v 0rr htiq*b6. 17–35 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$