If two points are at the same potential, does thv;s)i 2zdldb-:px ah: is mean that no work is done in moving a test charge from z ixbv dl;as- d2p::h)one point to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at rest in an electric field, will it move tow: kn0y3ua1pk25i kvv*vl+khuard a region of higher potential or lower u:i53p va uk n0y*+v2lkhv1kkpotential? 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 electric h 0)rihgfljgeh9b5/jrd;;bq2 lw )x+field, (b) between electh0+jb q;9r5 /jg be;lh)r)2fw dh gxliric potential and electric potential energy.

An electron is accelerated by a potential difference of, say, 0.10 V. How mu*q+xdh4gjy a*ch greater would its final speed be**ga+qhx4 djy if it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining two ewz v,nisw tvl 5 p6bas24 h.r*8)o+ucmqual positive charges where the electric field vmrl azcbh5v,to68s2*+wupnw )4 .siis zero? Where the electric potential is zero? Explain.

Can a particle ever move fz1a;)qchwb:3jf c m)y 1jnj; mrom a region of low electric potential to one of high potential and yet have its electric potnqc j1)j:1aj3cb; fzy m;hw m)ential energy decrease? Explain.

Compare the kinetic energy gai 8jv95t/m iezmned 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? Exhy73zumidx85ky: dm9dr/32zz3;fgi h3a bi v plain.

Draw in a few equipotential linesogp5 a+)pn,lr-r2k:bk/e y rf in Fig. 16 – 31b.

What can you say about the electric field in a region of 9 zwgudii;o- .a)8+ *boj shbgspace that has the same potentia z 8;giu+h gd.*)a9sbowjo-bil throughout?

A satellite orbits the Earth along :tb1 ,bilg:w,7wpwu ktq6 z)ya gravitational equipotential line. What shape must pl),wutgbt:,: 6bq i1w7yzkwthe orbit be?

When dealing with practical devices, we often take the ground,*2w o/+40 mep;pj wle8mu3awg jaj:w g(ojzr (the Earth) to be 0 V. If, instead, we said the ground was how would this affect (a) the potential V, anu:epjg4o +pl, j03war 2zwa mmwo/e;w8(*jgjd (b) the electric field E, at other points?

When a battery is connected to a capaca ibob19z.yjvc;n 6: zitor, why do the two plates acquire charges of the same magnitude? Wilbz; az:vj6n.y1ib c9 ol this be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on trsav, 0:+kwc )20ow2/w qem4bs vfvhihe size, shape, and position of the two conductors, as well as on the dielectrca0 , vhs2mwsk2qe oi0)wvb+ r: /f4wvic constant K. What then did we mean when we said that C is a constant in Eq. 17 – 7?

  How much work does the*te /apog n1lub*qe 9. electric 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 do in moving a proton frasq) t:4wxhk2 om a point with a w qk2tha)s x4:potential 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 2 tpkwc2dxtkr )7k6x e8 k7s/ogain (in joules and eV) if it accelerates through a potential difference of 23,000 V in a62kk/o87cw ktxk)xe rp72d st TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires aqqw*2 4fvhb: $7.45 \times10^{ -16}\,J$ 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 para+jczbhb s;job;(+ iq8f je1 qeh5k(l 6llel plates 5.8 mm apart if the potential difh k6bzfj(; +i8e+j lsebh1qq;(o j c5bference between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of (r+hyu,)ki uju* ll:vsye4 3q$640V/m$ 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 45-V batter q:w(w ntn6crb(1em9d y is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected to d1 cthz74v((3jgdypp a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is need*8dl2;hak1 fqxt46 t w rlug)ued to give a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, c) jmfo3oayf4 .onnected to a 200-V power supply, are separated by an air gap. How sma jof)3m4o a.fyll can the gap be if the air is not to become conducting by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an exter3g-k2rvjca2 w nal 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 kijo ,rct(xwmfhq; m5 u25*, ibgo w/x4xnetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a prgi36g5v o -g-nugosp;oton whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helibyz .udzva ;3.)mdzhx853 sx hum 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 fe9o pkr en;4/grom a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric potehjfxo n9i+, a,ntial 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 ot/wq9 kv w*wp.yh 82cyki2-hhf a football. This conductor carries a net negative chargi cw2k.phwqwh* 29h8kyytv- /e, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a distance og-3.:byuslk/kdr g 7jyl+ i*w f $ 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 coi56 8zt-/rpvdqoyi 5c rners of a square of side L as shown in Fig. 17–25. What is the potential at the fourth corner (point A), ta5856izid -y/tvporq c king $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 p,6jr 03ljb;2i nl;fmuje1kx 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 threef*3( 3,ljx gqui3an fn electrons from a great distance apart tonfi lu,*q 3f3j nx3(ag $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm northp 3+nqyf)+ chkgm dq93 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 (radiul a8(v8ob7 eyvmw 9a8pq 5bcp0s $1.2 \times10^{-15 }\,m$) 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 ;mc+b0iamv4/pxa u h,separated by a distance d, as shown in Fig. 17–27. Determiu;0 mvxam4ib/+ap ,c hne 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 t.njru;ie uqfhze( 757he hydrogen atom, an electron orbits a proton (the nucleus) in a circular uq.rujf n ;eze 5(i77horbit 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 ar6b3+9ej+f3zi oo sqga 9tq8hz(s luu2e $ 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 dljzko:h5u) f cb6ibk/ :6 1lzoipole 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, cons -p ub5n)gr (cxv59 uud3hzt1uidered as a vector, points from the negative to the positive charge. The w t1pr-(dungxuc5 vh3 ub )5zu9ater 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 capacitor hos0/9zszvsu5. vp am4pld $+2500\mu C$ 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 capaci6avw-(79e+bd b5perj jojfuf9ik9m , tor 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 charge+ tay/u guz+:ls of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of parallel wire in air is wprbxcn5 2qhr, m4 kgc76p,/g120 V. They carry equal and oppox,m k 7q,rw5c6gc/4pnhrgp2 bsite charge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of aozkek4qg8qqc af ;t9r ) r5c+p;ati35 12.0-V battery when it is connected to93qrc4kq;ez a5ktqt acg ;f)p r5i8+o a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the-sl j v :rkh-lotve98 e7zm/r6 plates have if they are to be separated by a 2.2-mm --vej8m96l vlzh7: te/o ksrrair gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor qzb.4btjyz )- 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 qp4-7;igh7yd:q n: ahbk -kd n$8.5 \times10^{ 5}\,V/m$ 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 oqxjh+hn d.txxvn96. e ;j3tdqcs 59d;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 fieldz9*0 zr (1p:mrjgzppl between 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 puli0yzvx 7xl: 5(d 1k9c v+ukis disconnected from the battery. When thicuv 7lv+udipl1y 5kz:(x9 xk0s 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 squaw 6/0ywk7pqrm re parallel plates 5.5 cm on a side that are separaq/pm0w 6wyr7 kted by 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a;n2sv1- xr e:y3e aank pair of circular plates with a radius of 5.0 cm separated by 3revn:a k12a3xe ns ;-y.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is co ddh7mrl*k 3x( s*h*p9yshs .znnected to a 22-V battery. If a piece of mica is placed between the plates, ho*ls r.s3zpy*7hx*9hmd sd( khw much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a paper-separav-vkf.3 ;53h bkfnrcw 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 e6 hvouqx *nul8myi)63 h6 5funnergy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shoglzbc9 5j2js9ck a heart that is beating erratically. A capacitor in thisgc2l jsbj9z9 5 device is charged to 5.0 kV and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between two square plates, qf)r+zv(oyb4) + qc2t yazwb-x+2t lj8.0 cm on a s +a f2tl+)qcbrvyt-+x) y2o(bzqz wj4ide, 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 bz8ym 0a15eefs91n f50wibzx dy placing two 9-in. pie pans 5 cm apart and connecting them to the opposite terminals of a 9-V bat 1mxfsn91eb z8zwd 0iyfa5e50 tery. 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 cap)tlo uzlgj *n5q70v2v acitor 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 capac-)*jtq w/megdjq4 ku cy1(t 3mitor change if (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as thec3qet *-) u4wk(q jm/gtmy1d j 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 accelerat9c1) e 8n0ddhfgrzs8 ted horizontally 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 they reach the screen top 22 cm away, 11 cm c08e f9d)d zg8n1t hsrabove the center. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a CRT. The screen is 30 cm wide and is ci0qc-gi si;-n9;nxd 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizontally deflecting electrn-- ;9ic;cdsig i0xq nic 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 point Aua7 g72x)bfavbfpz,dc* : 0dr to point B.2va*cg7b7:zp afdr bx),f0 ud
(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.6p0g*uhxd lss39 v5an
(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 nbwbv x4lel ,v1zija ol1n ,h81+w,c9surface 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 acc:rod9v*damo;x,r vo ( elerated 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 r ,xv;:9vdd r(*ooo amthat an electron would remain stationary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough storedn+wl-tbw -n, ve2f(dy 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 capacitor is connp d7ura7+ vz1jected to a 24.0-V battery until it is fully charged, after whicjr717auz p dv+h it 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 el;v zv64t.p g;d zkb)wcectric 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 equilaterallp 8;yf by8b(2dt2vscck -3l:)lwio j triangle (side L) as shown in Fig. 17–30. f8o:clil(p v-jy 8lk w3ys;tdb2 )2bcDetermine the potential at the midpoint of each of the sides.

  A $3.4\mu C$ and a $-2.6\mu C$ charge are placed 1.6 cm apart. At what points along the line joining them is
(a) the electric field zero,    cm left of $q_2$
(b) the electric potential zero?

  A 2600-pF air-gap capacitor is connected to a 9.0-V batteryh0 .c: , 7le4hhk hhhw9kiu9vlq58nvo. If a piece of Pyrex glass is placed between the plates, how much charge will then flow from lv ,5 h9kuh08q vhh7 h9ohw4n:cke.ilthe battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally fc s sa)kz+ +dkj0(qiro 98luy(rom rest in a television picture tube by a potential difference of 5500 V. It then passes between two horizontal p0 ( duy+9jcksa l8srki o()+zqlates 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 capacitancey3yzbh *gno44 $C_1$ 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 farwoibu3t.pfmcxnt *z;(4 l82 qad is, suppose you want to make a 1-F air-filled parallel-plate capacitor for a circuit you are building. To make it a reasobi tmpuon 4txw.8*2c3 z;(qflnable 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 of abog63:bak 7 7ny3h cotagut $150\,V/m$ 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 has w;rn3*6e qq *o jkwnb*zdl*v. 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 Earth and the bottom i4b2j-k 6nfrpf0u:ed of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds ar-b f6: ruip2kn 4fd0jee 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 ener:gtn 9p k uqs:5v*xz+.u wed*hgy 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 enough potential tha q*.x::z*vunu +ksdp 59w hegtt 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 cm from an identicaltd)yv 0 1y80hy2l uswk $+33\mu C$ 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 byt:rs 4,0d.dz eyu9 gdr a 0.15-mm-thick pzy d r9u,0gr4s.eddt: iece 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 capacq/hz* eh5bb88 g(3whhqi4 r szitor 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 cham4vbp7iw,iahr /*i l9rges 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 with 2g f2ekyjeq5p4 or8r avb.5h gptsw;.h366a l$q_1$=$1.5\mu C$ and $q_2$=$-3.3\mu C$ Find the potential difference between points A and B.    $ \times10^{ 5}\,V$