If two points are at the same ,osw:xrh6 ik 6* cky5,d2rzpo potential, does this mean that no work is done in moving a test charge from one pow,,pdc s2 x yi*k6:ok5hro z6rint to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at rest in an eom72q( (dgl3co- +s sdvbs w9olectric field, will it move toward a region of higher potential or lower potential? What about a positive charge? How does the potential energy of the chargo9s(v o-d(gb7l 2 sqmws cd3o+e change in each instance?

State clearly the difference (a) between electric potygh z)0iv/h 0tvk: td5ential and electric field, (b) between electric potential and electric p0dthhvtivk: 0yg/)z 5otential energy.

An electron is accelerated by a potential difference of, say, 0.10 V. How o xkc;huqm v9:0v)-,kb nw u2w;bu0exmuch greater would its final speed be if it is accelerated with four times as much voltage? Expe0;m)bk9bv,u cx -0ouv w;xk2quwhn:lain.

Is there a point along the4g j3d i8+cdtd line joining two equal positive charges where the electric field is zero? Where the electric potential is zero? Expla jid d+g3d8ct4in.

Can a particle ever move from a region of low electrip 4i:gvb gbkq23bvwj6agfnz(5u+i04 c potential to one of high potential and yet hav:(np3kiua 0gbz6jwv5bq 4i vfg4 bg 2+e its electric potential energy decrease? Explain.

Compare the kinetic energyfi rw l(n +c*ut*e0y/f gained by a proton $(q=+e)$ to the energy gained by an alpha particle $(q=+2e)$ accelerated by the same voltage $V$.

If $V\,=\,0$ at a point in space, must $\vec{E}\,=0$ there? If $\vec{E}\,=0$ at some point, must $V\,=\,0$ at that point? Explain. Give examples for each.

Can two equipotential lines cross? Exm3k *w14 ws al2zey7m8ci6ftt plain.

Draw in a few equipogq7q /4grxa7y)ogz tdhga 2f) (uz 5i:tential lines in Fig. 16 – 31b.

What can you say aboutkop;*u8o(xz 9erb x8t the electric field in a region of space that has the same potential(8*o;u x8 xpero kzbt9 throughout?

A satellite orbits the Earth along a gravitational e9) swoijw4 vq7zys8n1quipotential line. What shape must the 7v9oni 84qj1s)wszyworbit be?

When dealing with pra/ctli;pdvc5z3y/sae juxk v *z7q ++ 6ctical devices, we often take the ground (the Earth) to be 0 V. If, instead, we said the ground was how would this affect (a) the potentiaacp; /z6/k s u3d+yi * c5jztvvqex+l7l V, and (b) the electric field E, at other points?

When a battery is connected to a capacitor, why do the two platesltkxef0.(jr zy t ,77u acquire charges of the same magnitude? Will this be true if the two conductors are different sizes.7y ,ltej70z(ruk f xt or shapes?

We have seen that the capacitance C depends on the size, shape, and positio8-7cxbecf.7 vxzw2s , ysg4s on of the two conductors, as well as onexbc g27.z8o 4,-7w xvsscy fs 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 do in movinesk1p4a)c.ji)r sao / g 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 a point with a fq(ckj*tw0ocx x)rudnm -lb5-4w(o f5h s0q3 potenxc(3 - 5n4xocfkl o)hw tumd q( 0b*qf50sjw-rtial 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 joulesgt ;a76y96ydu- dw uujz1des+ and eV) if it accelerates+ ydwg71 zeu jdat6duusy6-9; through a potential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquiresx tn78h.vx +.ma8 u) ytlznze) $7.45 \times10^{ -16}\,J$ of kinetic energy when it is accelerated by an electric field from plate A to plate B. What is the potential difference between the plates, and which plate is at the higher potential?
   V
plate ----待选择----AB 

  How strong is the electric field between two parallel plates 5.tf. j7dbtp,ar1fw74 piedm7- 8 mm apart if the potential differencepdj77wed f1 tpf4rma-, 7. ibt between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of 6+sbrbyu27p,+bn)*oiif wp n $640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two parallel plates connected to a (cz y/ rg:qj5bvh.fl245-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two aqa1 oxo odd4m(+if1e s (z+1hparallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is 5:cya2 gd o;8mc n(se6as s6soneeded 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 separated by a+cuok :qzx/ p2n air gap. How small can the gap be if the air is not to become conducting by exceedingzucop q/x+2:k its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force to move ah1 wfv 0 4edivp-0,ci)3bhjqi $-8.50\mu C$ 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 a yb-2z 5xmoh.kp*xswnn 59;p xn electron with kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a.q s kap*e .be y x/oah(het8(8w:(asu proton whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helzdv; a: fe;7ycium 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 fnnn5* lm6( cqbt+a vg+rom a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric potential ofaj899zn q8yskl f4ub6 $+125V$ 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 i18 3e :bzylyicarries a net negative charge1e3yl:iyb i8 z, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a/mft*(a6 s/ck8zr dnrq)0t le 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 are1q)4 3gfd0b vvsdqcqq6.ffu. arranged at the corners of a square of side L as shown in Fig. 17–25. What is the potential at the fou s4.fqfvdq)uqbf. qc160 d3v grth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed point charg aiw,*ua 1.4gxu4ubyne 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 elt i(ac* vf oc/gq n/1:bj5q1xlectrons from a great distance apart to :1 cxq/ ( qvc 5*jin/alt1gofb$1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 3-)dnbswp/a ncm 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 acceler/e 5jv.sh 1jidate 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 distance/yshf gd83*ues yd,5r d, as shown in Fig. 17–27. Determine a formula for 83 / dshyd*ersyg5f,u $V_{BA}\,=\,V_B-V_A$ for points B and A on the line between the charges.

  In the Bohr model of the hydrogen atom, ywu)vwcw7.4cei)b b;an electron orbits a proton (the nucleus) in a wvb7cuw4) y; .e cwb)icircular 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 pr3)bc5me, nai9k1ikz9u gtim :7jj90eozoc m/oton 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 2 a (j/ee h;zs4zdjyiqx;ug d8*u( r5jwhose dipole moment is $ 4.8\times10^{-30 }\,C\cdot m$ at a point $1.1 \times10^{ -9}\,m$ away if this point is
(a) along the axis of the dipole nearer the positive charge;    V
(b) 45° above the axis but nearer the positive charge;    V
(c) $45^{\circ}\,$ above the axis but nearer the negative charge.    V

  The dipole moment, considered as a vector, points from the ch4r3 ox5 ;odw3kgr6hnegative to the positive char5 ;rhoh3kg rcd64 o3xwge. The 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 w0bo :ras3 s+zcapacitor 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 cavai1ojm+h s)s9aw tp0-joh yrw)d xg,a :4a9+pacitor 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 charges of,r2oap8j tc6+kijy- b $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of parallel wire iq tbdh;h k1:;v1z /giin air is 120 V. They carry equal and opposite chabq/k 1:ht vi1;zd gih;rge 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.ze 0g lc15jya -dxo8 5zfzm27uyf zi/:0-V battery when it is connected toi :xm81z20-y7y j l5egocz/f afz5uzd a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates have if the ru+dim wu;+x ob(0ze+y are to be separated by a 2.2-mm air gap? (irmb u d+u+ wx+o0ez;   $ \times10^{ 7}\,m^2$

  The charge on a capacitor increasesl ai r511.a+ fqqa/*fa ;lg-vadu0rob 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 ofc.39ma ufre. /;8wki1mjotnp $8.5 \times10^{ 5}\,V/m$ 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 o*faj7-tshr n6 6,ntgc pposite $5.2\mu C$ 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 betwe(2 2y5vljc x .iu)z 6s/pyqnsten 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 char6 pjjit 8)+a7vdzewh/ vwy 1f9ged by a 125-V battery (Fig. 17–29a) and then is disconnected from the battery. When this capacity d 81ehvt7jpi9 /aj )wv6zfw+or $(C_1)$ 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 cfd i(:yc7 6mm7vpk,u em on a side that are separ vkui 76dpy me(mf:c,7ated by 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circul;i 8x k*kzdrk9m jtqa(;n)1h/y+z szo ar plates with a radius of 5.0 cm separated t/y;*k;qkx a8zdim(sn)jz zo hr +k19by 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacibwg35 *mp- 6oqfr zb:ctor is connected to a 22-V battery. If a piece of mica is placed between the plates, how much charge wiwr*mcq fb b3:z5o6p- gll flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a/ ugxg0,**ge tpndo g25x5yuv azg0/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 c ma:jq 3s5k*r2200-pF capacitor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that4rdw w kz9pm4sye95* h is beating erratically. A capacitor in this device is charged to 5.0 kV and sto95h zkwe49prs*d4 y wmres 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between two squarb 64mk ll93 3 dofuystplxn3u:1u(bt0e plates, 8.0 cm on a side, separated by a 1.5-mm air gap?l6uy3uf9tkt3b n ldo4us:p 3m 1b0(x l The charges on the plates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing tpg: m q35w nt)w9hcgy)wo 9-in. pie pans 5 cm apart and connecting mn93wqyw :5 )t)chgg pthem to the 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 capacitor has fixed umyf5s*p //,odnvu tu;;lx ,j 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 +9 kk2f25yysr 7zdcfb1yl( j h)r3 wkjcapacitor change if (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as the capacidy1f(2hrwjy7 zjkrly k 3 sf5bc2) k9+tor 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-z8gv g4q;rvdu)l fj0 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 thedzu gg-)j0 ;vrvf4 ql8 center. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.c9kbba31ec w6l9 wry1 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 horizontall369lck w1bwr 9bacy1ey deflecting electric field vary to sweep the beam fully across the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from rest acquires 6.3 keV of KE in moving from poz x8pfs r.*(d31agdnnint A to poin(1pds 3.xng az8 dn*frt 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 transfer1u,iis ;ggqumz-n9fs ;9*oz ws 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 surface whose magnitude is k5uac7 icu.x:+c7 rj qabout $150\,V/m$ How much energy is stored per cubic meter in this field?    $ \times10^{-7 }\,J/m^3$

  In a television picturessll7t ks *z8*k)j : ;g(uorhb3g 0fwr tube, 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 woulfbwl :s r7r8)*j3l;kgustoh*(ks z0gd remain stationary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough stored energy t ndg:.y z;pwu*o 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 connecnzksv3 7f2jv j8 :ep6rted to a 24.0-V battery until it is fully charged, after which ipzv:8fj k63sne7v j r2t is disconnected 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 electric vc(n5)l qq al)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 o*k+:6oifs1)gr zud z corners of an equilateral triangle (side L) as shown in Fig. 17–30. Determine the potential at6+ki dour:ozszf*)g1 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 capa q wh 83y(iokn2f),5jw4xgf2dhwnfb, citor is connected to a 9.0-V battery. If a piece of Pyrex glass is placed between the platesqb2whng, n,jfwo32w5 d4 y(8ifxfh k ), how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizbk:pl:+.j yza4 ) ;wmml;b:esx7wl i vontally 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 that have a potential difference of 250kb;jabsi l:l47z mw.)lw:em v +;x: py V (Fig. 17–31). At what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capacil38ap-m je s2 2 -kboks(-qwhjtance $C_1$ 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 yoq)sdfkjt*ig- :a:t -z u want to make a 1-F air-filled parallel-plate capacitor for a circuit you are building. To make it a rezjg- qa* t::kdfi-t)s asonable 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 electric field es1 lhd7 ajvdl-2qgq6q :ajws) 30 u.rof 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 n+/88es/n0 ztwqk2 i9r axhvsoitrogen 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 potentim(nojo8 l 1c2t ce7d(z6due348h ubxval difference between the Earth and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are typict uee z3nmhoj 68dc du(l( 472v81xcboally 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 electro olo*1/+ axzuhns 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 u ax1/h zo+*loslowed 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 pl-dzg-q +0hsrk;8hko saced 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 cow mj4 j . eod9z4r9qs5s07r+c, wuw-rvc9wbakins separated by a 0.15-mm-thick p,ud5qrws-wrw.j4waczoem r0skc9v +749 b j9iece of paper $(K=3.7)$ A 12-V battery is connected to the capacitor. How much charge is on each coin?    $ \times10^{-10 }\,C$

  A $+4.5\mu C$ charge is 23 cm to the right of a $-8.2\mu C$ charge. At the midpoint between the two charges,
(a) what are the potential    $ \times10^{ 5}\,V$
(b) the electric field?    $ \times10^{6 }\,V/m$  ----待选择----leftright 

  A parallel-plate capacitory 1ony5nf2d)w 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 fixed1oe(r: w+9il;u m;t;usuoi n i 4.0 cm apart from each other. Their charges are $Q_1$=$Q_2$=$5.0\mu C$, and their masses are $m_1=1.5mg$ and $m_2=2.5mg$
(a) If $Q_1$ is released from rest, what will be its speed after a very long time?    m/s
(b) If both charges are released from rest at the same time, what will be the speed of $Q_1$ after a very long time?    m/s

  Two charges are placed as shown in Fig. 17 f54cz,peo2f3,s dqp x–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$