If two points are at the same potential, does this mean that no work is done0f km4euwnc*i;-+ vj o in moving a test charge from one point to the other? Dnij-0fm4 ov; * cukew+oes this imply that no force need be exerted? Explain.

If a negative charge is ifq54 1o egv1qunitially at rest in an electric field, will it move toward a region of higher potential or lower potential? What about a positive charge? How doesofe 51g u4qv1q the potential energy of the charge change in each instance?

State clearly the difwr1qql 4n*d6cn rw(1sference (a) between electric potential and electric field, (b) between electric potential and electric porq1 1sdc6w(l *rqnn4wtential energy.

An electron is accelerated by aqw; g/5 ms mzgwet338y potential difference of, say, 0.10 V. How much greater would itwq wmm3t g3e/gszy;5 8s final speed be if it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining ; ybgf hq 2y-ku73(hiitwo equal positive charges where the electric field (i;u7b2kyqh 3 -figyhis zero? Where the electric potential is zero? Explain.

Can a particle ever move from a region of low electric potential2/ li6wewlhthh.68dd to one of high potential and yet have itslt.ed wh266/8hhidwl electric potential energy decrease? Explain.

Compare the kinetic energy gained by a pzzl cp(q +:k rmzq3m vf0c1:;mroton $(q=+e)$ 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? Explain3p:grpg81*rp2bxv o m.

Draw in a few equipotential lines in Fig. 16 – 31b s7fao9 lg5,x jq)m (qk0 ;6kir5jsjwt.

What can you say about the e kwf x-:-dzp7wm.:v s-lv+ uvqlectric field in a region of space that has the same potential throug p- fvxz.wvvqd-l w-:sk:mu7+hout?

A satellite orbits the Earth along a gravitational equipotentiakr9shv*n3ap,*+sb3p0i kuuzl line. What shape mkurz h3, asusn+*9pkp bv 0*3iust the orbit be?

When dealing with practical devices, we often take the 6+v1 hq5to f7pap5h:peufcr7jq yb-*ground (the Earth) to be 0 V. If, instead7qpvaf +j5e7 q-fb otp*p1:c r6h uy5h, we said the ground was how would this affect (a) the potential V, and (b) the electric field E, at other points?

When a battery is connected to a capacitor, why do the two plates ay0+rhe9ev1 d darts5)cquire charges of the same magnitude? Will this be true if the two conductors are different sized 15 sya)+0tredrveh9 s or shapes?

We have seen that the capacitance C dq4hy humb3. ;h/ (mynpepends on the size, shape, and position of the two conductors, as well as on t hb/4(yh.;h mq 3numpyhe 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 fi d muhs6s)(a9seld 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 eq7 pkhq 5r1,cg(lst)moving a proton from a point with a potential of thl(er5g 7spkq)q,1c$+125V$ 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 joules and eV) ijgv h.j7zgr ;geq.7ffah28 m4f it accelerates through a potential d v.hf.2g zj7r7ggf4j8q m;aehifference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires+kxsb1xy d+p3 qdw8rf ho,s63 $7.45 \times10^{ -16}\,J$ 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 plat,k6c lkgr5+k p i6zp -o2q5hives 5.8 mm apart if the potential differenphiokzpc, l62vkk + gq i-5r56ce between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of ycc/ p,2l,a/qqm2poe$640V/m$ 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 vcva./s q2+r b 7mbt4dconnected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field be)aydlf(0; ou 0lmln3jr:dmt) tween two parallel 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 helium nucleusuza 04 01rpufie.8mm f8poz v( $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power suppujo aow 66) )rm0 zfo:pt(;i/zmric)w ly, are separated by an air gap. How small can the gap be if the air is not to become conducting by exceeding ct wp;o z)f)j:0)m6io/mrz iw6 u(oraits breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force to move a 7g(g.fz zyi-h $-8.50\mu C$ 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 energyc qd3b q2 a.+ ok;fz+b6k3u8r-pocge c
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton ox-pkvc *u+h+ea;s ff) 4zj0kyehu(3 whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (who t-/y*wn2n 7b;ayfi zich is a helium nucleus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric pot791j 6pqpgfoy(93 eg kyrycedxp1.urb6 v/g- ential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creatmkg+j7xpqnh yc*0p* j (h 1tx3es 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 football. This conductor carries a net negf;1 z)u9t cc- dfpd1hgative ch du 9;cpdf)t1gfz-c 1harge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a distance of j;sd/5x clca- $ 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 sq uyhn(f hj:,da 13ahy2uare of side L as shown in Fig. 17–25. What is the potential at th ad 1hny(yu3f:j ha2,he fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed point charge with zwcvx*h sh9* ;$Q\,=\,-0.125\mu C$. 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 grjqe6/peo z 04e7x2fag p*;g t/a0vl jieat distance apart tovx4ejt/0j07glap 2e/zgoa;i6 *q fep $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm north ofqk(5+al ss zv/ 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 1;y-ehyq pra2 to 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 opposite charges are separated by a distanj sbl dfvp g,q5l/;yr, 7,zi5oce d, as shown in Fig. 17–27. Detr jg5lvl/;5,s7 pyi zd, o,bqfermine a formula for $V_{BA}\,=\,V_B-V_A$ for points B and A on the line between the charges.

  In the Bohr model of the hydrogen atom, an electron orbits a proton,x 2jwlotp7qj4m 8kd 6 (the nucleus) in a circular orbit of radlo,xpwjd46 jqk8t7m 2 ius $ 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 ;8k *3yijgw0yxu kr gh8grv/x0jo t 80are $ 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 m *cw1z k*w0uzvoment 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 ;wq, igd .+chgx 7f;xfthe negative to the positive charge. f+x .g;,7wd; gfhqicxThe 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 capacitok0kp/(cjpqw ; r 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 capacitor bj -uwt8*c30t ;jnavq,t;ne l 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 chargg4j;eezl 5 xy;jxr4 :qes of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two-a7p vpf7k,l kb*jf5(y k.eo c short sections of parallel wire in air is 120 V. They carry equaev,kjp7kk7foc p.*af ( -y5lbl 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 bad dde 41,0vtgl (3d/zbqqoza -ttery when it is connected totd e(0dz l-ov/z1,q q3a 4dbdg a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must thew ow2af( ;q8ky plates have if they are to be sepyw8w( 2;ka ofqarated by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacijl:.3hlz8 sm btor increases by $18\mu C$ when the voltage across it increases from 97 V to 121 V. What is the capacitance of the capacitor?    $ \times10^{ -7}\,F$

  An electric field ofbcdite);x86y:g-f ka 2d:gte8 5s jr h $8.5 \times10^{ 5}\,V/m$ 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 oppositef e/f3d. 5ooly $5.2\mu C$ charges on the plates, and an electric field of 2.0 $2.0\,kV/mm$ is desired between the plates, what must each plate’s area be?   $m^2$

  How strong is the electric field between the plates og;o0bkh4b(i2byv- nd f 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 chah9fx;chx3ihu +ob8 q5rged by a 125-V battery (Fig. 17–29a) and then is disconnected from the battery. f9 + cuo;h3qihb8xx5 hWhen 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 ofsh,9i r*p x7 * .ywxki)ntf.sa two square parallel plates 5.5 cm on a side that are separated by raf*9 y,s7.ip txswx.*kih) n1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a radiu euo )8xgkg .m6;vkxp/s of 5.0 cm separaxog k.;6 km g)p/8xuveted by 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. If a pit:f1. ezf, opk 9+7 dg2fs 46dkchtitiece of mica is placed befi p9o+gtitk 6s4.z7f fc2,the d1:kdtween the plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a wh/d maw2f /n;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 capacitor. How much energy is storedtcnx: jwald+:a 8 d.,t?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a he 1wtb-tj5 1r iv qfc(bh ydt+w73l6wl9art that is beating erratically. A capacitor in this device ist1 jwbhwb 1t5d3-+ywiv l9tcr(7fq6l 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 eles65 ek +cgs1lsctric field between two square plates, 8.0 cm on a side, separated by akg+ s6lsse 15c 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-inr;g/sy u (0hix. pie pans 5 cm apart and connecting them to the oppositeu h/ry(gis;0x 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 . jc3xpt m(s8zfixed charges $+Q$ and $-Q$ The separation of the plates is then doubled.
(a) By what factor does the energy stored in the electric field change?
(b) How much work must be done in doubling the plate separation from d to 2d? The area of each plate is A.

How does the energy stored in a capacitor change if (a) the pu2gs 0*nw ggl)otential difference is doubled, and (b) the c*n) 0wlg2gus gharge on each plate is doubled, as the capacitor remains connected to a battery?

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

  In a given CRT, electrons are accelerated horizontallb69cq k8pd ;yxc+sz)yy by 7.0 kV. They then pass through a uniform electric field E for a distance of 2.8 cm, which;x9 +pqs)8zcky 6cbdy 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 e)aw*1r g kuwir(4f:f6.0 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 horizontally deflecting electric fifa*w :( rfuw4)1g eikreld 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 e: 5qymz)dq ka2/vg yo)m07u .p gja)akeV of KE in moving from point A to point Bazv j 7q0)p2maa5y) oqmg /yk:.udg)e.
(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 ofgud ,ay9d45(k vrznuk,3*jl a 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 mnm5:r6t; bnz5 wwmy-p( encc/agnitude 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 accelerqs+ n- ;thvid lv:c73dx4 9kvmated by thousands of volts through a vacuum. If a television set were laid on its back, would electrons be able to move upward against qvvcddvsk:mn;-t9+l3 i 7h4x 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 water tqy,0kw wgfye8k r84 6from 21$^{\circ}\,C$ to 95$^{\circ}\,C$. What is the potential difference across the plates?    V

  An uncharged capacito8,ks)vfu a i1pj.5e8p fmnc*h r is connected to a 24.0-V battery 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 betweensf in 8j 8au.5mvk *1ph,e)cfp the plates?    V

  Dry air will break down z+0a lm i l)bune l71n +y+3v-5;cfmc3jxrivyif the electric field exceeds $3.0 \times10^{6 }\,V/m$. What amount of charge can be placed on a parallel-plate capacitor if the area of each plate is $56cm^2$?    $ \times10^{-7 }\,C$

Three charges are at the corners of an equilateral tzccl l0*nud c* ec;62a: tpv;uriangle (side L) as shown in Fig. 17–30. Delvn p 0z*c ;u2e acctd6cl;:*utermine the 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 p96esg-gofxusl)*r y4*5 o 2 nzny/x qto a 9.0-V battery. If a piece of Pyrex y 6- *e )gxuo ngq /5xpz*frssoy49ln2glass is placed between the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in a telev6)mpr39b ice g8k 7xwjision picture tube by a potential difference of 5500 V. It then passes between two horizontal plwg prm j8) k9x367ebciates 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 capacitan1 -9z wzn 21z)b .vuiytvpf:rnce $C_1$ 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 wantd:qc w 1qx+yo4k)nt3 y to make a 1-F air-filled parallel-plate capacitor for a ciy 3tnc)qxq:w+y 1 dok4rcuit 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 / /.,t yico;e40 3brced)ngylw*f wxt 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 8 eifdyvh- g1/a pulsed nitrogen 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 diemk9.jc* xd )kpojz(4mc6g ,rfference between the Earth and the bottom of the thunderclouds canp.9gj( x)zc4o mk,mjekr d6*c 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 $110km^2$ 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 eno 8;z5 myv6s(pgf esna;ugh 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 of the electrons, another plate above the barium surface is kept 5m(g;6spa fye;vsn8 zat 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 placjudr5ip c83 aizze33snr 9(t .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-cm-diameter coinsk 16a8sq3weknrc4id n;x+0nf separated by a 0.15-mm-thick piece o x;6n4aiks8n 3 nkdf cerq+1w0f 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 platzpq+6:cij:e 5. ogjhj 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 otherzlo u 1roa+y (w8.d47hh ( 9edtpne2wr. 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. 17–3sht/ okd5ej,gp2 9au3 5 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$