If two points are at the same potential, doexf ot4m p/n)/ax4heh2 s this mean that no work is done in moving a test charge from onhfh x/4t) nmox2/pa4e e point to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at resuh qadcq-t 236t in an electric field, will it move toward a region of higher potential or lower potentia2t6h c3 aqduq-l? What about a positive charge? How does the potential energy of the charge change in each instance?

State clearly the difference (a) between elecxu16tm*qw1im vzfs8;xch1z)p 07 lq jtric potential and electric field, (b) between electric potential w h*u8ip zf0txq 1lz6s7j)c vm;q 1xm1and electric potential energy.

An electron is accelerated by a potential difference of, say, 0.10 V. How much *duxrm/d;j6 kref,)tfip: 0zgreater would its final speed be if it is accelerated with ff :p xm0;tue,6*zf)/idk rdjr our times as much voltage? Explain.

Is there a point along the line joining two equal positive chargxvl-mkrfk0rd ar92urv c .44 +es where the eler9uld 4x r am.rfc 42k0v+vk-rctric field is zero? Where the electric potential is zero? Explain.

Can a particle ever move from a region of low g-impx1wxs; 0bp g0 z8electric potential to one of high potential and yet have its electric potential energy decrease? Explaig0pb 01;xwm8-zgpi s xn.

Compare the kinetic s af2ng7,e 1aoo rfjc.o97tx8energy 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 xtbyl..x1v iyto3w 0)c j:e-l lines cross? Explain.

Draw in a few equipotent.m xv r bo/ymlh/(3*djial lines in Fig. 16 – 31b.

What can you say abou2syhil9j. l8r * ghws:t the electric field in a region of space that has the same .hhl 2lsr *i8wjyg:9s potential throughout?

A satellite orbits the Earth a gq/bz0th /o.sr l58f+ ldqcl3long a gravitational equipotential line. What shape musl3tfc 0q hr8dblzq+ 5 l/g.s/ot the orbit be?

When dealing with practical devicv 6egf0 um+j+ qdeyf:)es, we often take the ground (the Earth) to be 0 V. If, instead, we said the ground was how would t 0ve: u)yjd+g6eqffm+his affect (a) the potential V, and (b) the electric field E, at other points?

When a battery is connected toryf3l 0qfl 7t: a capacitor, why do the two plates acquire charges of the same magnitude? Will this be true if the two conductors are different sizes or shapes?07:l qfytl3fr

We have seen that the capacitance C depends on the s:pw rkxd(dv) xon7)nrg *;gz :zok+h)ize, shape, and position of the two k)rkn (zrwg)v):n*z + 7oodxh; gpdx: 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?

  How much work does the electric field dog6u3yu9 aj3i6hpr6aep d*is6 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 moving a proton from ))qm d3 4ampdtqj4jdi .l7-tla point with a potenp 3tqqj4.djl- )l diadtm 7)m4tial 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 and eV) if ith)kdn2ibnc 3fzd m2ee.: 4d *j accelerates 4 fbd 2m2:zdh3c.e n*nkji )edthrough a potential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires 3qx8l 8t; zlj4zyjqn)$7.45 \times10^{ -16}\,J$ 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 electrptpm* cw45k zons )l3b0k6j8 oic field between two parallel plates 5.8 mm apart if the potential difference betweomk4o)lc3 05pjs*8 pt nkzb6wen them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of kir(t ea6:b uu6n( :*ja ql9dh$640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between twa4m9+q 1v. a9up+cy*mdrzsy s o parallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected to a 453:h9bmp r ual0-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a helz*wnxpb1)bg.tx-q (z ium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, ar;ohvuw15.tu tz*dw p:e separated by an air gap. How small can the gap be if the air is not to become conducting wh otvt5puw 1uz;:.d*by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an exte 1dk3u vky)drp4h 1ptkbn40z4rnal 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 electron with kinetic energy zhle.q3c5 t(d
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton wh6 ;;jryqcop6 mose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which i)wi.gnpu e6q9ora e8 p4:grp +s 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 potential 15.0 cm fro: r/0o pv;epnc37jkafcn u d*2m a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric lubi6+r3 uh 25 pxni1spotential 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. Tg(v i4gen(9 msvu (*3ztpctf4his conductor carries a net negative charge,e(cp* g 9g4nvi mvt4usz(3f( t $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a ;dp7rx0mu w q7distance 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 )trd.llkm)8x2a temjb5:jj n0,vo 4 g corners of a square of side L as shown in Fig. 17–25. What is the potential at the fourth corner (poimdjen)m ajgk0r:8bo t l l.4t5jx2,v )nt A), taking $V\,=\,0$ at a great distance?

  An electron starts from resg3r7 (ayz 0o8ssqd+d b7 rfms2t 32.5 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 bring three electrons from a greatapag j-u.n wjq20t yz69lh3*l )hjl 8u distance apart toaulgh6uln-jw8 .lj)q0z 32a*yh j pt9 $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 7x31 l:,uxljo tyj*e4v,/g svv2 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 q 3.e17ls1*lw *oa a;veszb usaccelerate 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 ay *:eqywa 7ag;:72x fc jyor;yre separated by a distance d, as shown in Fig. 17–27. Determine a y *7 q:wy :geaj;yacfry2xo7 ;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 3vl1.v7f8g0x7 m: lkjvzg kyv hydrogen atom, an electron orbits a proton (the nucleus) in a circular orbit g7vz.0v xjymk v:7fk13vlg8 lof 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 prd6/pd x,zx o+ td0 zn-xwh9d/voton 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 whosefg,(e iv-w8fyplz 4*j 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, c n1qmt vcuf8s,f*ugz. f+8/lsi+i1zw onsidered as 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 momentssuz1w+.u z m*8f8ng/si tlf+vi q, cf1, $\vec{P}_1$ 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 capam ,z*l0ghm .bmcitor 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 holdvjy-)w k2co)k $+2500\mu C$ 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 an rj3pn: ukijl,5pa8xprj7 33qd minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference betjy g;svr 5s+0ls0 d3llween two short sections of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is the capacitance of the twojds;g50s lyl30 +l vrs wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of a 12.0-V batb5qpe057;yxl4z iz+r6 x p vvptery when it is connected t4b5vzxpe7r6 pq 0pz;x v+ yl5io a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What areatdpf x (w:ue9az4k l7yb 9f4v, must the plates have if they are to be se:4wk4pbe,xl f y(t fuv7a99 zdparated by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increase icp*a ban14i qjl,7;i+6chips 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, sypt ( nkec7-)ybzyyu-s.,- 0ij mku $8.5 \times10^{ 5}\,V/m$ 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 opncat(axzc- vf yh af-x+4tf48gs97w/posite $5.2\mu C$ 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 pldugs:5*pa+ jj3zh w*p3,pdegates 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 th 4l/js r.v.oh j.*rsifen is disconnected from the battery. When thiss*/. rh.l s4 fjovr.ji 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 0uwf5+ ustf /othat are se5t+wo0suu f/f parated by 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of aa8s6 ;afkky nvdmup64s8 o* 2a pair of circular plates with a radius of 5.0 cm sepaad p8un;kas8m*6f 4k26oy svarated by 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacito1xd,qdf4az2s q2edt )+ wgs 8or is connected to a 22-V battery. If a piece of mica is placed between the plates, how much charge will flox8w d2go z, qas)e+fsq21 tdd4w from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a paper-sx6 sz3 siwlvz: xaj+w*w 23q3ej m,bl1eparated $(K=3.75)$ 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.t 5,epdrq 4xe/ How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beating erratieig ad7krjl3 m+2,e)zcally. A capacitor in this device is charged to 5.0 kV and stores 1200 J of energy. What is its capace+23dge m,rakl ) 7zjiitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electro d06cy2f8pa.o ou(hc ic field between two square plates, 8.0 cm on ad8.ca (ho0fp uo2 y6co side, separated 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. pie pans 5 c3n7r s (lmy4gcm apart and connecting them to the sy4gml(7 3nrc opposite 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 capaciev 34x4t g1vvgtor has fixed 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 potensss 266l zelh )9f,ofyq*x.cttial difference is doubled, and (b) the charge on each plate is doubled, as the . oq,fht6 fc)zlsx*6ys29sel 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 0dkl77o9w unxjjz1m0 accelerated horizontally by 7.0 kV. They then pass through a uniform electric field E for a dist7mlj1 oxdu00wj97k znance of 2.8 cm, which 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 6.0 kV in a CRT.yxqg+g o8z/ zr fu+j)af3bh 15 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 acrossz1rz) ++u5hxq og8af gjfb3 /y the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from rest acquires 6.3 keV of KE in moving fro ,mof2qv jppax1x:55zk2:tca m point A to point B.ov1 5xm 2a zp 2kfa5qp:jx:t,c
(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 transfere5 q3:mey-h ufx.zc*ta)l o;ys 4.0 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 surfacxe3 4kfx . hq(f m,gnzw.a;q3v+iq3gfe 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,8h8 a l/s6f/ y;yozzcl 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 needed to balance the downward force of gravity so that an electron would remain stationary?ys o 8l/f;68/zyalz ch Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough stored energy to he c gl*o*i0g oxq*k3mf1/drj 1qat 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 cobfxyyr yo ii6.ag+ 8)6nnected 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 plat6 rb6yyogy+ .f iix8a)es. What will now be the voltage between the plates?    V

  Dry air will break d/ df, :-igfanu g-y4axkt(v9g m gp9-uv b/b1yown if 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 t00iaantk1 i/ yriangle (side L) as shown in Fig. 17–30. Determine the potential at the midpoint y akia/001intof 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 isikhkq .+9a6mj connected to a 9.0-V battery. If a piece of Pyrex glassi. 6akkj9+mq h 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 television pictureg45vvf 7f/ur 3 wq3autx5yl :l5hp(to tube by a potential 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 (t /r hw(3up5a7o5: vfu 53vq4lflgytx Fig. 17–31). At what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capacz 6 ehtw/8wnxirem.9,itance $C_1$ 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 want to make a 1-F yfnud4ud) a/(air-filled parallel-plate capacitor for a circuit you are building. To make it a reasonable size, suppose you limit the platnf/a4ddu (u)y e 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 electrj31j od3p+ ouhic 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 nitrogen laser ha6sf1 x6l d:jog gt5fo*s 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 Earx o986cw(hb sqth and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of b 9x c(68oqshwthe 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, ultraviolzv8b rc4v93k 8/zz ezset (UV) light provides enough 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 at a negative en vc98rzz83ksb z4vz/ eough 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 placpudguq9-8, bd 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-dnq.vn2r.rp zpm 4cm51iameter coins separated by a 0.15-mm-thick piece o .mr1z n.pmr5c2qpv4n f 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 capacitor1 gzb e+odh24t 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. Their charges are aebyp/x6 (jw 2mvx:n/ezoy -/ k5w8d)gd xec( $Q_1$=$Q_2$=$5.0\mu C$, 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 iv1x:ck fxs*)x6x:g tg n 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$