If two points are at the same potential, does this meaw s(8s/ld;cjmn that no work is done in moving a test charge 8(/;jcdl swsmfrom one point to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is in,oewd;wq6y *dq/o bx2itially at rest in an electric field, will it move toward a 6,q dd*b;/wo o2ywxeqregion of higher potential 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 elect6i k5zfignl0ml ay8g57/ n,mv ric field, (b) between electric potential and electric potentii/m l iv5g7fmn8al,nkz y56g 0al energy.

An electron is accelerated by a potential difference of, say, 0.10 V. Ho92* yqlu 5q9 oi*wpulaw much greater would its final speed be if it is accelerated with four times as2wil*9a u y95up*oqlq much voltage? Explain.

Is there a point along the line joining two equal posit2ps4x qfi a;x:8 cvrd*ive charges where the electric field is zero? Where the electp2rv* x q4a:cd;fix 8sric potential is zero? Explain.

Can a particle ever move from a region of low elw +1.j9 jizvc)hm8bh tectric potential to one of high potential an1mh8 hbv wc+9t)jzji .d yet have its electric potential energy decrease? Explain.

Compare the kinetic energy gained by a proton,8+he3ar ms mi $(q=+e)$ 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 ysjrf7,1 ) ps)z ljghol d4;. a;tu5dscross? Explain.

Draw in a few equipotential l ymy+6et2 op9 d+xtb/rines in Fig. 16 – 31b.

What can you say about the electric field in a region of space that hasbvl)) 5s;xqc)zl*3a mkz mhj+d 1;evh the same potentiam) eqzk;j;l)h) hxc 531*s+blavdmvz l throughout?

A satellite orbits the Earth along a gravitational equipotential liy.gyy-uc* vp, ne. What shape must the orbit b,. gypyv*y- cue?

When dealing with practixh9hl6n67 81 mffx2,p2 dlbvno;uhkr cal devices, we often take the ground (the Earth) to be 0 V. If, instead, we said the ground was howlhx29p d1 uf7hbx86,;l 2m6nk vfhrno 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 acquire chaon5 1zn,boi68 c,v2njf. vl xkrges of the same magnitude? Will this be true if the two conductors are diffncvn v 15,k 8,2o6nb flxio.jzerent sizes or shapes?

We have seen that thd ia295 f/ yq/8dkuojee capacitance C depends on the size, shape, and position of the two conductors, as well as on the dielectric constant K. What then did we mean when we said that C is a constant in Eq. 17 – 7?y28d/u9jek/ iq fd5ao

  How much work does the elect9w pqypain;z1;q;1wbric field 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 dtigsr9jgmm09k b /q :2o in moving a proton from a point with a potent 20t9rij/s km:mbqg 9gial 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 electkq7e5(wrfsxvx s7 (b+;gy o8mron gain (in joules and eV) if it accelerates th7wr5xeov;q+b x y7g mk8(ss(f rough a potential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires l3o21ydhstx w,b7 .b d$7.45 \times10^{ -16}\,J$ 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 fi;ul.woqk4ij- v )nt6k eld between two parallel plates 5.8 mm apart if the potential kv- 4;nk6j.qw i) luotdifference between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field ofj+r q.wcnua0x7:w91py( iwpy $640V/m$ 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 hy3lt+ -jw:gdy ww r0/to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parale6eoz: u /jd9aot l)k)2lkly 5lel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference k8ayte9 7 rd;*gzgp;7f 6nkvyis 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 power supply, are s -0f)3xcz*t 5o-wjgluqfgxfbwu; 8; ueparated by an air gap. How small can the gap be if the air is not to become conducting by exceeding its breakdown vgg o);f0cfw ub;zw fu83--tjxu5 xq *lalue of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an externa/b z(swoep:m-pc w,xch(ri21 w8bfy) l force to move a $-8.50\mu C$ charge from point a to point b is $15.0 \times10^{ -4}\;J$. If the charge was started from rest and had $ 4.82\times10^{ -4}\;J$ of kinetic energy when it reached point b, what must be the potential difference between a and b?    V

  What is the speed of an ej9f05awagpq/4mp/ q7fdg - 9wcln od/lectron with kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a protonj.j31uvv7 /msf eza4e whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which9fj0 pe( tpdb- 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 poted,k 0i -3j scq1n-ytkential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric 9 ;pyejw x2d(ard7n(c 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 n:(va kjkm: a+ q/ol+w6smmt2regative cha6k a/:s2 jvq kmlo(mtra+m+w:rge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential h3i(039.dzuz ltt kb jt1 z0naa distance of $ 2.5\times10^{-15 }\,m$ away from a proton?    $ \times10^{ 5}\,V$
(b) What is the electric potential energy of a system that consists of two protons $2.5 \times10^{-15 }\,m$ apart — as might occur inside a typical nucleus?    $ \times10^{ -14}\,J$

Three point charges are arranged at the corners of a squarsa zd/en 92zv1p77 4wfvhvm2ge of side L as shown in Fig. 17–25. What is the potential at the fourth corner 9v2f2dzpmg/714ahsz7 e nvwv(point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm z) p)npb;if o06pstq qno26g )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 bring three electrons from a great distance aparg5pw)vw7w heag*7 7jpt tegvapg w5p 77)wjwh 7*o $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a whikh9sprr; mh5 bf3q h(*ch 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 proton (ran:x*k j1)etopdius $1.2 \times10^{-15 }\,m$) 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 s:0 (bttaybsco*l:2o-7xfv:jh buj 9separated by a distance d, as shown in Fig. 17–27. Determineyt ov2j:sl (b bc 9th7u*sx:-f oa:j0b 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 a2khf+x ic pcwms2 r )kn(n.34itom, an electron orbits a proton (the nucleus) in a circul. cnxscm 3pwi4i(rhkfk2 2n+)ar 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 bhy;bm1u 2sw1 are $ 0.53\times10^{ -10}\,m$. apart. What is their dipole moment if they are at rest?    $ \times10^{-30 }\,C\cdot\,m$

  Calculate the electric potential due to a dipole whose dipole momkmv;95v, qa3 3myxr2orxx u-ls +h;y ient 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 negati5p e;tbc3i i 8y4fxn5us0 f 1cv;ewab7ve to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be considered as thwcbi34 ;vec;s 587bt 0fpfn5a i yx1uee 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 capaciu z1vkoa q2)9stor 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 capao,q ,d s-pwhm;pq47vyl dqr3*citor 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 pvj bi ,ump62ki+.rrt9,a5mkzlus 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 para yd pqoc98m h)3i)dri:llel wire in air is 120 V. They carry equd drhip9cm) oy8 )qi3:al and opposite charge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from ea:tyt )h,eku0dbet+uyvs i 2z l; (6a5nch terminal of a 12.0-V battery when it is connected to a(kbvyelshe:; atytnui+0dz)t 2u 56 , $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the pg sw*po /pdu4ch.ppm 9mp.4 2jlates have if they are to be separated .sj/ p dmw2p9 4gom.hpu4pcp*by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor in.dw xc5e-rv(xr+e )nd creases 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 ofm x; wvms5ts-cb(ot6 n xj40t9 $8.5 \times10^{ 5}\,V/m$ 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 opposi 5grcmzw 03:h7k mri8qte $5.2\mu C$ 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 platefx(5*-rjqo e; rjv6rls 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 battev np0/kj 1s fw.lz8kmz e:x6v3ry (Fig. 17–29a) and then is disconnected from the batte0 :6m3wjfvkks pz.vzn xl8 1e/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 capacitanc4 (1dwi axe,vqe of two square parallel plates 5.5 cm on a side that are separated by 1.8 mm of paraff(d xa1qiew,4vin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a radius of 5.0 cxipxkeb wu/4 eph):w b0+e95 km separated by 3.2 mm of me4)k kw: p0b9/eipxwx+he5 ubica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. If a pieczazpqebp, o.xc y4*/ngy6f4i-z )e ih8aa1j8e of mica is placed between the plates, how muchy xe6/1zyqf e8izbgi,o4z- a4)nhp. paa8 cj * charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between ii/n0hv4v9bx 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 2200-pF capacitor. How-4 eb+ gv;hko .e3xmbb.5qexs much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used wbtfczr;*hei)82dd9zj ) 9hyto 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 capacityh)8fji )r 2z9*dd wczhet9;b ance?    $ \times10^{-5 }\,F$

  How much energy is stored by the e/ s x59:teim7toe2j-x4zf igi lectric field between two square plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on the platexos7e-ztg4 29if ixet5m:/ j is are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in. pie pans s7qy5r( : s.fl wq)jwu5 cm apart and connecting them to the opposite terminals of a 9urw(wsq. q lysj:f75)-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 feutr+-m u;i 42 +9ceqg9axqyyixed 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 (sya 4kch9:s5rrhmh(6p, 1urc2nz e a2 a) the potential difference is doubled, and (bh (uerycss,: rh n42mahpc 6z1r2 5a9k) the charge 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 horizontally by 7.0 kV. They.25ve fl :j24oj:iry 0wwpqed 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 d j25 o:iqwvejwf :yel20rp.4center. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a Caq w wqn4t5+(qRT. 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 fin w q(q+q5wt4aeld vary to sweep the beam fully across the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting frr.llv n5co*) (cdo; giom rest acquires 6.3 keV of KE in moving from point A to po5).dcrn(l* ;ovgicl oint 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 24hp8h ccts *nthe 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 surrxjwqc 1, 5ni.face whose magnitude is about $150\,V/m$ How much energy is stored per cubic meter in this field?    $ \times10^{-7 }\,J/m^3$

  In a television picture tube, electrons are accelerated byuahm/ v-va+fkx4k*6 zl;1 vx r 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 b/ fl+kv16a *k -hvxz;vu x4amre 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 h6y (q/.hq(lmlr36(gnsjvko cas enough 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 capacitort,b l aws 8 r;2odcihhg4db7t +c/q7-u 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 as;4d u tq-bg + 7t8lodiwbh7,c2/rchthe voltage between the plates?    V

  Dry air will break down if t3an*p /msr/uhwd3g *,da :n vche 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 coq*sx6vdur7yx 9btn /2; )i dexrners of an equilateral triangle (side L) as shown in Fig. 17–30. Determine the du exvs7)*n 2br;dxxtyq 9/i6potential 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 hx)u3vc nb-3p ld/tgvt3v,;u piece of Pyrex glass is placed between the plates, how much charge w,v3-3 3uhgldnpvbt )/x c v;utill then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelera)+*1 qxhemy :wgfhp6a rrkq .4ted horizontally from rest in a television picture tube by a potential difference of 5500 V. It then passes between two horizontal plates 6.5 cm long and 1.3 cm apart thmy.*1ph gw:64r+afq k )xqrehat 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 capacitanceq:,tfzajlkxe: 1( y, m $C_1$ 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 t87 ;pjo2vuq /p6mndefarad 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 Wh d7mnjp ;qvope8u2 t6/at 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 of ml*msl- y/p;xabout $150\,V/m$ 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 pulsey4c.eb gm 80oi77g3aln ku:lcl5 r:ord 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 differ bd63nsye *73jty5ldm/vy7q rence between the Earth and the bottom of the thunderclouds can be as high as 3*s7/l bd3yjr5tqvd yn m7y6e 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 enough energy y8r.r p bgtfx52p, p:lto 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 at a negative enough potential that the emitted electrons are slowed down and stopped, and return to ttp .lxr2:pgy pb58rf,he 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 pq8 5lrfhf 7h0ilaced 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 coins separated by a 0.1s ku 4el. rlvv,vnk58;5-mm-thick piece of pe ,8v rs.vl4lkn5 kuv;aper $(K=3.7)$ 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 capacitggvf6sgn.a0 hzmk -i vro08g28mu5h0or with plate area $2.0cm^2$ and air-gap separation 0.50 mm is connected to a 12-V battery, and fully charged. The battery is then disconnected.
(a) What is the charge on the capacitor?    $ \times10^{ -11}\,C$
(b) The plates are now pulled to a separation of 0.75 mm. What is the charge on the capacitor now?    $ \times10^{ -11}\,C$
(c) What is the potential difference across the plates now?    V
(d) How much work was required to pull the plates to their new separation?    $ \times10^{-10 }\,J$

  A $2.5-\mu F$ capacitor is fully charged by a 6.0-V battery. The battery is then disconnected. The capacitor is not ideal and the charge slowly leaks out from the plates. The next day, the capacitor has lost half its stored energy. Calculate the amount of charge lost.    $ \times10^{-6 }\,C$

  Two point charges are fixed 4.0 cm apart from each other. Theirgi 0n1a*/k kffjrdet7 s:61zb 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 /b5z8 dmhviq9wj nxc5,on /m6sj9hkk6b /c, m 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$