If two points are at the same potentiaxhd h5 /wggw 99y-8ayrl, does this mean that no work is done in moving a test charge from one point to tghya9d h-5g/9 xw8w yrhe other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at rest in an electric field, will iivy7 :j bo(g7qsmp: ,it move toward a region of higher potentiajqg b7vsmo: ipi(,7 :yl or lower potential? What about a positive charge? How does the potential energy of the charge change in each instance?

State clearly the difference (a) between electric potential and electfg k* x2,ca-fnric field, (b) between electric potential and electric potential energy.affn-,*2gxkc

An electron is accelerated by q52 0u9uq jupva potential difference of, say, 0.10 V. How much greater would its final speed be if it is accelerated with four timespu52ju9q0q u v as much voltage? Explain.

Is there a point along thi6s,3ttz gg8fz3j p2 qe line joining two equal positive charges where the electric field 6,q itgzpszj83ft g23is zero? Where the electric potential is zero? Explain.

Can a particle ever move from a,lan t,h5xg0k region of low electric potential to one of high potential and yet have its electric potential energy decreast, l 5xha0,gnke? Explain.

Compare the kinetic energy gained by a pr-dco+ofo lg- 0;nx-uooton $(q=+e)$ 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 l,xe,mm*7gg) jk2x( s.b y qkdrines cross? Explain.

Draw in a few equipotential lif f:03nz) 1 a qd2sv,mxh+xpxhnes in Fig. 16 – 31b.

What can you say about the electric field indafj h r/6nu66 a region of space that has the same potentia/ duan fj666hrl throughout?

A satellite orbits the Earth along a gravitational equipotential line. What sha(xjyk4 /q( 8i lxjw3d1 zxx6mfpejxiq8jl1 f(w3 myk6xx/4( xzd must the orbit be?

When dealing with practical devices, we oftenuiib-p (k6 ac5 o9xru1 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,c-abopi6 (5iu1xr9 ku at other points?

When a battery is connected to a capacitor, why do th- l0+tj.8yrc;c z soave two plates acquire charges of the same magnitude? Will thiscc8.+oj- sy r;0a lvzt be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on the size, shape, andr/h *1: sk:domp)znak position of the two conductors, as well as o:ohm:z) *kprsna/ d k1n 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 electric field t t*fskhx8 y03c,qy: vdo 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 d r9e8ra/iacuyx4 x99m;y ie2ko in moving a proton from a point with a potential of e;4/9y9i eycx2ruk9m8i aa x r$+125V$ 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 electro(cwugm 04m0p) 9q :gkb-iaaoq: t 1rpdn gain (in joules and eV) if it accelerates throughp-:(:doi0q0pa1t49m w ug bka )mg crq a potential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires x8;r 4-o e1tm .s5qeqc/e nxdv$7.45 \times10^{ -16}\,J$ 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 paralm lt c+z*.d7 y0l+lhnmlel plates 5.8 mm apart if the potentialnl+ dy+0ml7t* .z chml difference between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field ofsf0a+s-v up0vco ( e-a $640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between tz+mmgw7j4(mo6rt rjj (- t,fkwo parallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected to e2(,nvd apxc3 a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential differbly ub:bs2ei* vsi 68cg t.j 6dm15h6nence is needed to give a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V pow vv*ptiv(7xu /er supply, are separated by an air gap. How small can the gap be if the air is not to become conducting by exceeding ivtp*/uxvvi( 7 ts breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external fabk -ncf*w8f/ orce 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 kinetic eniz)bky su// b2ergy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whose kinetics5-jz-tltm;o energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a heliuqsy(y l;bh * . r2slj8(xbhk0u6pts q:m 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 poteco3s cjop /)xcmv1j t/fw*) (so/aip: ntial 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electr 70(9k4 g,ybmdjkotk yic 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 shtu:9w4wyy(ukg:8 1gqj5 wxpy ape of a football. This conductor carries a net negative charge, j:pw 9qyu4 8ux1( ygwtyk g5w:$-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electo.qn+a 1s,zl- k+s0f-toepz lric 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 the c0 zqu4tft 11f*hjn, se(a seq.orners of a square of side L as shown in Fig. 17–25. What is the pn ftess*10(u h,tq a.j14qz efotential at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed p3w4vnlpf )d) 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 electronuu1gbl,d 8aos c4wy blp /c;+hkz6w+3s from a great distance apart to ; 1 +cdp4k 8/3yous6zgblbc, uwhwal+$1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm north of a dx-qyj,d k9qp*3kub5l7 s e0g-ru m,j$-3.8\mu C$ 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 acczlua-jbw -9mtx ;3ui7elerate 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 chw e d-i1w- gllgfvx v:g/0e7skb-v,5narges are separated by a distance d, as shown in Fig. 17–25vgg 7dle-vnsvw--1 0b x: w/lkgi,ef 7. 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 tht 08m6 k.skufoqp/74qudbli 4 e hydrogen atom, an electron orbits a proton (the nucleus) in a circu4kf84.s6qpk /q mulbu o0dit7lar 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 are )ivfyfhaw5t0 k0f7kt m.e;u4 u/rd 2q$ 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 5c q5cs qx yt3e+rd0 k.v ek+phh867vmis $ 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, point:w (st3pf/i jus from the negative to the positive charge. Ti/pt3j (f swu:he water molecule, Fig. 17–28, has a dipole moment which can 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 capacitor hold k 9 8gc +ru.zu2sfjz(f$+2500\mu C$ 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 capacitor holbfnbwxe3q- ,wj 44-cxd $+2500\mu C$ 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 hold:/ 5z k:sf gxnmlf-s(vs plus and minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of parallel :qhlucu:2t* l enp hds:no26+wire in air is 120 V. The n6n2d:hhpo 2uq:slu+ce*lt: y carry equal and opposite 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 )w1l6sdp, 7im9; g,p 8scy uhz(f 8to/ifactgbattery when it is connected t,7wti 9a zl/pdgf16sf;i8 ,c pugct)o8(y shmo a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates have if they are to bzzt*sne+by+e3) 7cm/h w:h2+ apb 3 oll:a fthe separated bywnl+b seh+zt:h2fe3+czbp)h:m o7 a t*/a3l y a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increases by m *axqf+pls vrz3n942 $18\mu C$ 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 n-a hfken27-h/ jf- qs$8.5 \times10^{ 5}\,V/m$ 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 opn4 q1cz;0 yhbgposite $5.2\mu C$ 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 be82vb /wd;x p j6q5mzmztween 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--;bs .ah 3v8rpk- wxfn1oq8spV battery (Fig. 17–29a) and then is disconnected from the battery. When t8bsxpo; r3anf-qskw8p.-v 1hhis 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 platd 1m4yio-ucka8z q.)n es 5.5 cm on a side that are separated by 1.8 mm of 4a-1z8q m icy).nd kuoparaffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a p 3*1ib4vn fjspswgo xm0c;g1: air of circular plates with a radius of 5.0 cm separated by 3.2 mm of miw :vg1fs1b oxs4c * gjn3pm0;ica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V bat8b7anvt00 nl /tnbx9:nzr fq0 tery. If a piece of mica is placed between the plates, how much chn98nz tbbfv0tx:0qln/rn 07 aarge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field betq/p jod8 ,od9 tvt/m8lafyo31ween the plates 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 220*uw3 ye gq5bnaytg6u3 d h;s+00-pF capacitor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beating erraticawiwqs +5fs4t8 rjl8h7 8jt, iplly. A capacitor in this device is charged to 5.0 kV and stores 1200 J of energys 8irjqsi4t78h,j+ f 85wwptl. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric fiel/g zio ,gow:*gd 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 and opposite and of magnitudezi*wogg :/, go $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in. tfvjar+,sj+ l)nr 15/sbmm j- pie pans 5 cm apart and connecting them to the oppo +nms1tvj)r+ -r5m jlb/fa ,sjsite 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 fixed charges 0s xglr g92ll9;pb4sud( - tav$+Q$ 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/ 0afht+fl9 n6e fn2jpssu4s. difference is doubled, and (b) the charge on each plate is doubled, ash6 9 plaf+fe2./4 tjn sss0nuf 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 acceq 8hj41c dpg0olerated horizontally by 7.0 kV. They then pass 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. Estimate thjcq h48 01dgpoe value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by kol 3 9kf:ekgqtoc4 ;*6.0 kV in 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 horlk:t qeo3 4cg9kf; *okizontally 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 az n)sw3ncw+ 8mwp7f+ycquires 6.3 keV of KE in moving from point A to point B.w+nfc8)3my7wz+sp w n
(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 Earth. e:j hgl(t. /t*sq w+loey/+kl
(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’s3sxld jt:1t-z 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 acceleraf2q e*.sbjwk -ted by thousands of volts through a vacuum. If ekj2*b.-qwfs a television set were 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 enoub ca b80eko,6o5w(/aw my ht:rgh 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 24.0dh7v4xpb ow1mpk. z7 m0y2p) b-V battery until it is fully charged, aftepbmb.0wm k7dxp 7z2o1y)v h4pr which it is disconnected 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 trsyfwhui )f a 42:b*z3he 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 .pg6dfbyy8nn1io* 5etriangle (side L) as shown in Fig. 17–30. Determine top e1yfd g.5y8innb* 6he potential at the midpoint of 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 9.0-V battl6 s :sfghot29ery. If a piece of Pyrex glass6:gs h92lo stf is placed between the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally f 3 dm3wuyxsv+lg8v(3 from rest in a television picture tube by a potential difference of 5500 V. It then 3ldyvx(v swufm+38g3passes between two horizontal plates 6.5 cm long and 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 capacit gedn4zlb*;g ,ance $C_1$ 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, supposenu2lxd 1 2*opyoyd(42mu;qn n you want to make a 1-F air-filled parallel-plate capacitorlnnpoyu m(2uy; d2 qx 1d*42no 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 obkg31l.cz f:3hnf 1 wuf 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 mwnacaw w*e jm.pp0-m sp-c( 66kt-+znitrogen 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 potential difference between the Eart4h rk*cl3h gowe/e4k;h and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclo l;ekoh*3c /kwe rh44guds 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 j33vg d wdvfzf36o)gqrqr 4.4some electrons 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 enough potential that the emitted electrons are slowed down and stopped, and return to the barium surfarj vo)4 vzwdfqq 3 3fgd.g634rce. 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 plac :o-ur(tf hu18hh f9hzed 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 1.1b .9+6s m mdg/y4lyizm-cm-diameter coins separated by a 0.15-mm-thick piebg iys4d/ml m6m .9yz+ce of 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 plate arech:hd5;gpftvwl 4 tr22jar9 0a $2.0cm^2$ 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 e7+g* v b)ohct9t;s8vgptm ;pcach 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 bzw98ht. 3mu+z9cefr shown in Fig. 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$