If two points are at the same potential, does this mean that no work is d;;pw 7vlsb 0npf9a4adone in moving a test charge from one point to the other? Does this imply that no fop9wdbp 7;la 0s;4 fnavrce need be exerted? Explain.

If a negative charge is initiall)15a3(kgvllc4e of am8 xnrku(jz 5y.y at rest in an electric field, will it move toward a region of higher potent31fn(mcl 4(j zke5. okv 8yalx5)uarg ial 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 pm5bwp1ur4s b ;otential and electric field, (b) betwr4ws ;m 5bupb1een electric potential and electric potential energy.

An electron is accelerated by a potential di/w sk.vqco2m- vfmiq-, -n e(ifference of, say, 0.10 V. How much greater would its final speed be if it is accelevminw-c,f . si2e k-qvm/o-q (rated with four times as much voltage? Explain.

Is there a point alongytal(, zi8 m/(uczx c5 the line joining two equal positive charges where the electr(i( m8,cxz y ucazl/t5ic field is zero? Where the electric potential is zero? Explain.

Can a particle ever move from a region of low ek;6q37ztsyd plz3d 1*q* lhb1och b6plectric potential to one of high potential and yet have its electric potential energy decrease? Exp**37dyb;3tl zhq6dsh q 11bozlc6p kp lain.

Compare the kinetic energy gain :1kux1o omx0ued 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 cr10xl- psdon70q ;u7fw ebaps9oss? Explain.

Draw in a few equipotential lines in Fika 1qr7,lojvln9: mjclw eg1n4r7 /y+g. 16 – 31b.

What can you say about the electric field in a9cln8n31a t ve 9)8cagw m-uqq region of space that has the same potetau9-qnnl9e)cc883w a g 1 vqmntial throughout?

A satellite orbits the Earth along a gravitational equipotentir9xybmdq gs nu.t(u3jez2lr/8(6 - yaal line. What shape mu rqx3l8n 6s2/gdbum(zeya(.t9-ruy jst the orbit be?

When dealing with practical devices, we often take the ground . wkb,fsuwl).(d:uw u(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, at other poi.ul wu kb):(wfdu,ws.nts?

When a battery is connected to a capacitor, why do the two plates b5fv8 zk.xvc5acquire charges of tcxbz. vf5k 58vhe same magnitude? Will this be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on the size, shape, and position o7h7u. cjfporsx3m p/0 f the two conductors, as well as on the dielectric constant K. What then did we mean when we said 70ux m7 /jo.fpcrp3hs that C is a constant in Eq. 17 – 7?

  How much work does the electric field do in moving a v vuqphz y;k6tctz4u;qrm+uz4 w,)(*$-7.7\mu C$ charge from ground to a point whose potential is $+55V$ higher?    $ \times10^{-4 }\,J$

  How much work does the ele5w ;+xc *sbb oioe(-lyctric field do in moving a proton from a point with a potwy*e +si b;(xboo5l-cential 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 joules ar+84x5 rwy0usxcl cy4nd eV) if it accelerates through a potential difference of 23,000 Vw450 ly+4x yxuc8rcrs in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires lcvc+zjs:1 s(yqm2tv17 aw(y $7.45 \times10^{ -16}\,J$ 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 twoy7(7t y sd rp58lzw,ho parallel plates 5.8 mm apart if the potential difference between the,zo7 ryps75wd 8tl y(hm is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of l j538(*-b uxxgwz/ukk n6i58e n kvy 0vbz1wj$640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two parallel plad0v; fc7 5 axhpvd.u.ttes 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 a /saelh 8 o/( rb zlni2 +xjqtw:7o;9r:ie;ya u45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is nee+og uf45wyq7 un0e3 laded to give a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connew :5h9 m4jgxskcted to a 200-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 breakdown value ok: 9mhx5jsgw 4f $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force to nsshrk4 cz 2 *u6os7z5move 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 wit1m8w (a(zkbag zj2 m2mh kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whose kinetic energy y(kp ):hi+t ofis 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium 09x4air pb,.zuk;xrv 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 potential 15.0 cm from ac7f1y:j3ctjbp 6s7 hkegn3z ( $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creatlssg fh a1xu6/(xb; .xlun+7fes 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 s-y bav9 a6z7fa/neq+p(6 mum0by c +enegative ( cqyb+7z feaay /ma6-+ 0vbm9enp6su charge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potentia /)6t mzhf gd1k e)t7:b*iqxiul 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 ou 59y4 tyd1g/htbr 0uqf a square of side L as shown in F0r/ht 145t qyuygb ud9ig. 17–25. What is the potential at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 3sa)pilh;t 5x: 2.5 cm from a fixed point charge with $Q\,=\,-0.125\mu C$. How fast will the electron be moving when it is very far away?    $ \times10^{7 }\,m/s$

  Two identical $+9.5\mu C$ point charges are initially 3.5 cm from each other. If they are released at the same instant from rest, how fast will each be moving when they are very far away from each other? Assume they have identical masses of 1.0 mg.    m/s

  Two point charges, $3.0\mu C$ and $-2.0\mu C$ are placed 5.0 cm apart on the x axis. At what points along the x axis is
(a) the electric field zero    cm leftof $q_2$
(b) the potential zero? Let $V\,=\,0$ at $r\,=\,\propto$.

  How much work must be done to brind99kl5 rh sq9v.wfgw)g three electrons from a great distance apart twgd w.9qvr9 lhs fk59)o $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a whit:10mk ri o7wnc3w fd1mn//m gch is 72 cm north of a $-3.8\mu C$ point charge, and point b which is 88 cm west of the charge (Fig. 17–26). Determine
(a) $V_{ba}=V_b-V_a$    V
(b) $\vec{E}_b-\vec{E}_a$ (magnitude and direction).
   V/m
   $^{\circ}\,$

  How much voltage must be used to accelerate a prot 9vm, ow3 /q n* oabon:1*ycmkuy;3 ed.nhd6mlon (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 cha ewprf.+6czu v,p0ho 4a ,ul1nrges are separated by a distance d, as shown in Fig. 17–27. Determi+1awprvh6,fp ,o04e cuzl. unne 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 a22;k nyer3 2aty)rt satom, an electron orbits a proton (the nucleus) in a crkaytn 3y22a;s) 2 ertircular 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 :+i6pn)ict2 iralj n6$ 0.53\times10^{ -10}\,m$. apart. What is their dipole moment if they are at rest?    $ \times10^{-30 }\,C\cdot\,m$

  Calculate the electric potentv x)kam6yal- b gn:(o1ial due to a dipole whose dipole moment is $ 4.8\times10^{-30 }\,C\cdot m$ at a point $1.1 \times10^{ -9}\,m$ away if this point is
(a) along the axis of the dipole nearer the positive charge;    V
(b) 45° above the axis but nearer the positive charge;    V
(c) $45^{\circ}\,$ above the axis but nearer the negative charge.    V

  The dipole moment, considered amvqy(gq l7 -a-1 e,lz :rb1emxss 7ts(s a vector, points from the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be considered as the vector sum of the two dipole q: 7gel zsv-a-,(x1m smbl yt1sqr7(emoments, $\vec{P}_1$ 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 capacitorz9f p(8woovk6 2o-ohh 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 c(vh vxs- 0bkx-apacitor 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 char rcwkor+:55kn ges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference b ab0ho3io6c* /c sm/cb96k m/kdyw2gjetween two short sections of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is the capacit6 gw6/kjos bmcc0 dmob/cak9y*i/2h 3ance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each teghv0 w)n x+n:grminal of a 12.0-V battery when it is connected t0gnxv+g :wh) no a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desi6f0( ef6hi lah yuk/cbfcnk+) m ;h)w4red. What area must the plates have if they are to be separated by a / 6khnclwif0u(efmc6b+)a;h)y 4hfk 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor7:4awjq-j ec;o o+ zbi 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 of v:5i - /a0 ns*wustdkx$8.5 \times10^{ 5}\,V/m$ 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 opposite ,9v)l +phcczb49k2jh3 ee yv f$5.2\mu C$ 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 betonb jj)h,6fs/ ween 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 ir mk q9 zff-+68rv+fcos disconnected from the batte+96fcqfo zrrmkf v+8 -ry. 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 5.5 cm on a side that ak yfw/ gf*,ohf.nis1 jv32ts.5os6d d re sepas w5*t fdfkd3yfh.6o.1gv2i,/ ssnojrated by 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of1xul x 1y o+rw/x,mej38hy+ye a pair of circular plates with a radius of 5.0 cm separated by 3.2 mm of mica? j/1xyx1x3ew yue l mh8o+ y+,r   $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V peqwmce3-+ 7rcjxj;g1+xhre7).ii hbattery. If a piece of mica is placed between the c hx g7i j1r-r.ee;x+hm7q)c3 w+pije plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a paper-separa wej+(ep ,t(z6qealo,ted $(K=3.75)$ 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 stored? h1vv)z nmca-i kr co2 qt2ewm7*mv .8+   $ \times10^{-4 }\,J$

  A cardiac defibrillator is used tzf+,upsds;r*vi/j / ko shock a heart that is beating erratically. A capacitor in this device is charged to 5.0 kV and stores 1200 J of energy. What is its ;/j/ ikfz* uprvsd,+s capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between two s5(zh;qx18utw y r0whhpa b:h7 quare plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on the plates aret hz;wbqhhhyr(70: a8pux 51w equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in. pie pans 5 cm apart and+ s2 r/lum xs4ei +c9owi/7ycqm9e 0kg connecting them to the opposite teqi yugs4mk+mxce/09rc2+7e 9 ol/ wi srminals 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 chqhubu27xwloh ;y b370 arges $+Q$ 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 iv9gg.9r q aaj+f (a) the potential difference is doubled, and (b) the charge on a.+rvqga9j9 g 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 hou8bq*ete4 k- rrizontally 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 thrt uqek-8e* b4ey reach the screen top 22 cm away, 11 cm above the center. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in6 k fg ughj/pv7-wfx5p /,(-n8z wopkyo5ll7h a CRT. The screen is 30 cm wide and is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizontally deflecting electric field vary to sweep the beam fully acjpwkfg 5-8l n/ o/7plzw-(hv7u,yk x5p og6 fhross the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from rest acquires 6.3 keV of KE y rxkclx1n/od4;; y et d),y6din moving from point A to poind6;x,ryk dn/ )dy leoc4tx;y1t B.
(a) How much KE would a proton acquire, starting from rest at B and moving to point A?    keV
(b) Determine the ratio of their speeds at the end of their respective trajectories.   

  A lightning flash transfers 4.0 C of charge and 4.2 MJ of energy to the Earth. l y0 tp1ju1rhhctjv - wf/,,j(
(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 surf ;+mr3il,d0c;qe(g;ij 4a 4upoyyuhmor6p5d ace 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, 080o l xmidsx+electrons 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 nis0 xlo8md+ 0xeeded 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 5nyi0ptk2r/p2n,(mj6hsv t b 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 fu0 tbhs ex71un,lly charged, after which it is die,1 7st0ubnxh sconnected from the battery. A slab of paraffin is then inserted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down if the electrbb t,jhj x)d27ic 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 equilatera9c d7g9ma.el-tkd/w ft* b sw;v7efu 5l triangle (side L) as shown in Fig. 17–30. Determine the potential at the midpoint of eacf.t/sba td 5-u7l m7wdgew*f9v 9ek;c h 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 batte0ldurk:x cj9 j33 :)js9uzdsm;tp ya 2ej,o /sry. If a piece of Pyrex glass is placed between the plates, how much charged,3ao;m2kcu:s3 tu rd0xjsl 9 pj9e)ys:jj/z will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally2+b 7si9a 4twv fxg-lg from rest in a television picture tube by a potential difference of 5500 V. gstvw9ax2+- bl7g i4fIt 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 capaci(dmevetdafcn44q,y(-ln07t/ ncp /j tance $C_1$ 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 uyf dn,okzbfp+f7i 285i .4mhyou want to make a 1-F air-filled parallel-plate capacitor for a circuit you are building. To make it a reasonabl24zf8+ h.b7fn5i yof,i mdukpe 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 electrigq-/icus ) yk cx.)s,u sgf)7uc field of about $150\,V/m$ which points downward. Two identical balls with mass $m\,=\,0.540kg$ are dropped from a height of 2.00 m, but one of the balls is positively charged with $q_1$ = $650\mu C$ ,and the second is negatively charged with $q_2$ = $-650\mu C$. Use conservation of energy to determine the difference in the speed of the two balls when they hit the ground. (Neglect air resistance.)    m/s

  The power supply for a pulsed nitrogeh 5qcws 89thnve2 1gzsre4h+,ju9u9 jn 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 potentiabu3tttbu em/1( kp83bws5f9 vl difference between the Earth and the bottom of the thunderclouds can be as high as tkb ts(t9 b33fu /1p8 emvw5ub35,000,000 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 electia z,2k gkbt,)rons 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 pla zb ,igk2k)t,ate above the barium surface is kept at a negative enough potential that the emitted electrons are slowed down and stopped, and return to the barium surface. If the plate voltage is $-3.02V$ (compared to the barium) when the fastest electrons are stopped, what was the speed of these electrons when they were emitted?    $ \times10^{6 }\,m/s$

  A point charge is placed 36 juj: gav pk,t*/)l;l ;eq,shev(6c ma cm from an identical $+33\mu C$ charge. A $-1.5\mu C$ charge is moved from point a to point b in Fig. 17–34. What is the change in potential energy? $\approx$    J (round to one decimal place)

  A capacitor is made from two 1.1-cm-diameter coins separated by a 0.15-mm-thick-awdytfso: a 85g41kw y(o4x k piece of pap 1( kf awk5s:xaog48wyo-4 dtyer $(K=3.7)$ 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 area n,v) ozgs61fcl sa/2ubc a9 z)$2.0cm^2$ 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 other. Their chargesw( s.j,lh wvn7s2x v1z are $Q_1$=$Q_2$=$5.0\mu C$, and their masses are $m_1=1.5mg$ and $m_2=2.5mg$
(a) If $Q_1$ is released from rest, what will be its speed after a very long time?    m/s
(b) If both charges are released from rest at the same time, what will be the speed of $Q_1$ after a very long time?    m/s

  Two charges are placed as shown in Fig. 17–35 withh8hs o/ j95whx $q_1$=$1.5\mu C$ and $q_2$=$-3.3\mu C$ Find the potential difference between points A and B.    $ \times10^{ 5}\,V$