If two points are at the same potential, does this mean that no work is done in 0t-ozwfed 1(7 dovvg8 -dw gs)moving a test charge from one point to the other? Does this ims zg doefd(1dt)o0vg w87vw --ply that no force need be exerted? Explain.

If a negative charge is initial 2pd/tcn03abgly at rest in an electric field, will it move toward a region of higher potentiaapn dg/ct20 3bl 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 3a)ht-c 8nomyx rdg92potential and electric field, (b) between electric poten -dy)3htxg 8armnc92 otial and electric potential energy.

An electron is accelerated by a potential difference26xfr g i)ma: uy5vq,- twand/ of, say, 0.10 V. How much greater would its final speed be if it is accelerated with four times as much voltage? Expla65 -xu/ry,im wfavtg n:2)qadin.

Is there a point along the line joining two equal positive charges where thz95dzldcb h . krn5p+lr;k-/ye electric field is zero? Where-/;k d 5rnl.yp9zhb 5rlzkcd+ the electric potential is zero? Explain.

Can a particle ever mek-3 dut) +7tpn7. iwka-nnalove from a region of low electric potential to one of high potential and yet have its electric potential energy den73w d-ptnal7kauk )eitn.-+crease? Explain.

Compare the kinetic 2( 5axxda6d+kwx7q tugoi yj )d9u 6j/energy gained 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 cr 5uobepk n8)1ooss? Explain.

Draw in a few equipotential lines i( zl2yffv1xae 601 hdbn Fig. 16 – 31b.

What can you say about the electric field in a rhky;wyt.b4 2 segion of space that has the same potential tt;4 whs y.k2byhroughout?

A satellite orbits thee2;f70ok ;tgr;kx ksd Earth along a gravitational equipotential line. What shape must sgkxk;f;t e2rk;od 07 the orbit be?

When dealing with practical devices, we often take tg0*zfpyk) jze3(-; /o jdqkyd(tml n-he 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 elect jm(nyoktg0 --f3)(z kl/p ;qj*yddze ric field E, at other points?

When a battery is connected to a capacitor, why d.qrtl2u;mc 93pu./ r*-7sspvz k dkdvo the two plates acquire charges of the same magnitude?*/vk2.c;qd79s t d.l rz-ukv 3srmpup Will this be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on the size, shr1.ztvhk f1*.o+k fjyape, and position of the two conductors, as well as on the dielectric constant K. What then did r.vo*1fk1 + k.jf tyzhwe mean when we said that C is a constant in Eq. 17 – 7?

  How much work does the electric field do in dp+qssd9 -n. imoving 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 movcy+giyisp3y+ggyx +a /*2 1p rcc (/tcing a proton from a point with a pote rg3yx2 *yg/yc1gc/+y c+i i(spcp +atntial 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 energy will an electron gain (in jostx; 9o x*vo6 hy9pr9oules and eV) if it accelerates through a povo69roohtp* ; 9x sx9ytential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires-y)ovux fwj93d77vg3 j pql6x $7.45 \times10^{ -16}\,J$ 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 npoq ) 5se6d:rj.z1wxv,hm wni3u1c( 5.8 mm apart if the potential difference between them is 220 V?: w.)3h1jz(5,1rq inscvpwn 6m exdou    $ \times10^{ 4}\,V/m$

  An electric field ofo)d5q7j +h3dwlpje(gsmh) 5m( eb ij1 $640V/m$ 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 connected to a 2.sx x)g/.qla u31jnk:bhobk 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected to a 45-V hnce vb8v3vw*;ve 13q battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a heliumg r1 3.mpc(wgr nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V r2wuk8q d.j0 a:)ciz tpower supply, are separated by an air gap. How small can the gap be if the ai :aut0cw8)kqr2.dzji r 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 external fo+et/h 2-fz h-;l+qtqwdyawi7 uan/b 1rce 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 u-/xdt,gn,,av zxzm 1ty q,s: energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a prof4f +;-u5qzsfg ubcbxm x :d+7ton whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nucle .fz,favbyh e5(4k7x eus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) 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 cm 6n56 45rvl5 n9km wkm ;xjolk:uw vdc3;mt,iz from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q crezj0hy1w5v t.qates 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 a forp m7e4)gk ei4otball. This conductor carries a net negative charge, pm7 keri)e4 4g$-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a distance cy41r6-mfjpewgw) 0tof $ 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 rvn((.g e -kcupx7sgf3r a+.zof side L as shown ikz(an+7gf -3cur. rpegs .x(vn Fig. 17–25. What is the potential at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a(;hvqng6a rt .tu;a,y 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 elekuqtd wqkah49y5 lrsy6 96tg;+m:v/gctrons from a great distance apart /6 5:w kgk4qd;6tvqyst9r yhm 9gal+uto $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which i8vp1k r r:iao1 ve8c7ns 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 proton (r d2bwchg qkku1+ )3t1qadius $1.2 \times10^{-15 }\,m$) 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,k 3(d5ht zna4b as shown in Fig. 17–27. Determine 4da5( ktn3hbza formula for $V_{BA}\,=\,V_B-V_A$ for points B and A on the line between the charges.

  In the Bohr model of;nw 6yjv1v9kd the hydrogen atom, an electron orbits a proton (the nucleus) in a circula;nd 1wvv6kj9 yr 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 - d0apdf1t7dnvkw8o- 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 tym.c;4b zpau7o 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, points from the gprp* y :wxw5mc*qp54negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment 4yx* qw5wgmprp p5*:c 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 holkkae2z)e /czty3:e0 c d $+2500\mu C$ 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 2ws p,d3o2nkx,h b r(ccapacitor 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 hold9goeuhw0: w-ss plus and minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference q,itx .r iia 5v,+btad409qwibetween two short sections of parallel wire in air is 120 V. They carry equa.xbvq90d54t+r iit aq, wiai ,l and opposite charge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each te)v rsu*cka d :jb28fy +.hpdx;rminal of a 12.0-V battery when it is connected to;p : dysjf+uacbh.2 r*8vkd)x a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates have if thet5 +h38enhal ygd -14jgs0w hgy are to be separated by a 2.2-mmt ys -egwag40 nd3h5hh+l18gj air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increasesjq,ef2 a np)6b 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 afbgl.n u1w(t5t)(v j j6 xd4b$8.5 \times10^{ 5}\,V/m$ 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 opp(vgpbh b04*m vwy2(wgosite $5.2\mu C$ 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 bep;kpbuaw/v; le45:l(ah3x g btween 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. 17–2a kfp4 t x3)1rfua7l:b9a) and then is disconnected from thk ) f34b a7rt1pfx:laue battery. 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 plates 92 vfk9b ht 82goz9duffkve7 /5.5 cm on a side that are separated by 1.8 mm of paraffibz9ovt29 ehv7f fd9 /uk2kfg8n?    $ \times10^{-11 }\,F$

  What is the capacitan.2sd um qaln/9+civf.ce of a pair of circular plates with a radius of 5.0 cm separated by 3.2 mm onqf2di l+s9u. v.mac/ f mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V b n 20*icwrukcc4z,*i(gpr) zj5bdgk8attery. If a piece of mica is placed betwe2*i84g(g bizd0*rk)cw zjr ckcp,nu 5en the plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between tq dl:tdi uasz 7f.7)x;he 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 2200-pF capasq. 2vceim/ ,wcitor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beating erri8/xtsh x2vsv79i 4uhatically. A capacitor in this device is charged to 5.u8xv v/h94xs 27siith0 kV and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the eldj.q5) ngx7(ib xtf-f ectric field between two square plates, 8.0 cm on a side, separai-. q bdf7gn f()x5txjted 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 assembled by placing two 9-in. ppl05ew 9y)vn*+) ffijenqt vj-b9:xmie pans 5 cm apart and connecting them to the opposite terminals of a 9-V battery. Estima9+mf j9i nqypn*)v0fb)l-et5evwx j :te
(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 fixedw*ew;p gog/lu ea ,w6+xy;1 (pz3dtcf* ms1ad 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 capars. e3;q04r djlhysh9 citor change if (a) the potential difference is doubled, and (b) the charge os0q. shy9 d3r;l4jre hn 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 accel +6fv(sw2pol4twk k,as k. a5 -rc(vdzerated 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 cents w(sc45ov d2+rw6 zv .(klf-k,aka pter. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a CRT. The screen is 30 cm wide and 1myv/ lr39tyx-qwrl1 ix cs2(s)wiz:is 34 cm from the 2.6-cm-long deflection plates. Over wh( i1)tlcrxrxsw2/s9- 1mvq zl:y3 wyiat 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 rest acquires 6.3 keV of KE in moving from point A to 4462/obvmavtdab1( iqln3a w pointo6/ab lv34wv (a a4imt1qbd2 n 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. 0n; mit2pxaktb d/od00gb(t50 C of charge and 4.2 MJ of energy 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 the Earth’s surface whose magnitude is about,e/g 4 ywvx.pcx qhg-9 $150\,V/m$ How much energy is stored per cubic meter in this field?    $ \times10^{-7 }\,J/m^3$

  In a television picture tube, elec0yxf iz12)oha trons 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 force of gravity? What potential difference, acting over a distance of 3.0 cm, would be needed to balance the downward f)z0xah2iy1 o 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 enou(7fl 8t3v 4lfgdo7yu)og *l41qtkavpgh 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 battery until it is fully jtxn *.f8tok a. jq6oh91fc4wcharged, after which it is disconnected from the batte1on9wk.f8a6 fj*o. thtj q c4xry. 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 electric fielf+6-,l.z*rkv mqp/b y1u sev u/1 iqmld 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 meh x/7jc4g .ltriangle (side L) as shown in Fig. 17–30. Determine the poten /lmc4xe7j.hg tial 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 battery. If a piej)4qt(k zml9: bb 42i kvhh0cece of Pyrex glass is placed between the plates, how much charge will thenh bzh9e0k 4 mib:2qcltj4kv() flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontdcgqe*7 xp ax:+nlt6 *ally from rest in a television picture tube by a padxtlxq7c: + gn pe6**otential 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 V (Fig. 17–31). At what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capac.z hj+- u:iwzc7mvl x(,w2m thitance $C_1$ 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 farfbf,kl +a wk9i5 v1l9pad is, suppose you want to make a 1-F air-filled parallel-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 , +5fl9kpkbva9w1l fi practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there is an electric field o4weyi20mx lv )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 laser has; +yi;kl 9s6az dnszy; 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 Earth and bfl* 5an/*2 ; uodljhythe bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are typically 1500 m above the Earth, and can have an area of;5 udbl j/*f*2nol ahy $110km^2$ 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 cu6 tiqjiwzj m y42na6b0t+x.r;h9 0osome 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 surface. If ix t0yu.0c62wbmr+ n;4joatq9i j z6hthe 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 99r h(jioqx3sfrom 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 sep,iw+3cka 2p+sx:m xpf vz6aflvm5(a 9arated by a 0.15-mm-thick s3 f, m+av 9li65p+wfvp2:x m(k aaxczpiece 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 u(jh5 4*tn.bykb0aq kplate 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 0(fw hu bv2pk )ccie6,apart from 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 shong0qsi 58p0 3jjs4k d 8qdrek.wn 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$