If two points are at the same potential, does thisp i/flck r491 q30hz6 9dptifl mean that no work is done in moving a test charge from one point 4f3phi rl0 fpq/961ztli dc9k to the other? Does this imply that no force need be exerted? Explain.

If a negative chargez ;n3xax.f; n vw-owr8:1ddzu is initially at rest in an electric field, will it move toward a region of higher potential or lower potential? What a8:rwnzw .zu1ndvf a ;xo3-dx; bout a positive charge? How does the potential energy of the charge change in each instance?

State clearly the difference (a) between elect 5dd 7rl2kvr94)l001 dwzbbnd phrt5s ric potential and electric field, (b) between electric potential and electric potential en d drw07br94sd lh)b201 k55dnlvrpz tergy.

An electron is accelerated by a potential difference of (dtwtnmf m,8+ a ,01q+rgqviq, say, 0.10 V. How much greater would its final speed be if it is accelerated with four times as much voltage? Explaifm(wv rg ,n1m8,+a+qt d0iqtq n.

Is there a point along the lindukwgduztv y kd/1j60 6 :fqd1v- +p(we joining two equal positive charges where the electric field is zero? Where the electric pote1udwtu j0p1 d/k-dd k+ zwyg(fv6: vq6ntial is zero? Explain.

Can a particle ever move from a region of low electric potential to of2ku q5 ykg()wne of high potential and yet have its electric potential energy decrea2 k5(kfq guwy)se? Explain.

Compare the kinetic energy gained by a profca3jfncgi -)g d/tbnq-e2 0 n4b.n*hton $(q=+e)$ 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 9 esu x+bu8/omlines cross? Explain.

Draw in a few equipotential lines in F q;3nriw;+ pjxig. 16 – 31b.

What can you say about the electric fieldbgvzu;n znm**.uf(n d 5cl-:d in a region of space that has the same potential throughoudn uu-dcl.zb *:(znf*gmn5 ; vt?

A satellite orbits the Earth along a graq-pedm/ bl 1qzm )l-o9vitational equipotential line. What shape must thm /lm -q1- )blz9oepqde orbit be?

When dealing with prvaakbl; dcxqs3 s 05( xg46c .zb/:jetactical 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 potential V, and (b) the electric field E, at :5.t6db b0s/lca( 34j gxzcv;aek sq xother points?

When a battery is connected to a capacitor, why do the two platey v5z0w79 pwsss acquire charges of the same magnitude? Will this be true if the two conductor59p wywvzss 70s are different sizes or shapes?

We have seen that the capacitance C dependskxsx gg0rh0ul9 q t;,pceyf(u 55pp8* on the size, shape, and position of the two conductors, as well as on the dielectric constant K. What then did we*stgc,h pk gle uyp9x; p5r08(5xf0uq mean when we said that C is a constant in Eq. 17 – 7?

  How much work does the electric field do ivdfv- 4m e;49dob hpw0yn/2swn 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 froie 4ux*6 /+;*sgz0gi3h) joc:xvf d wp y:cvhem a point with a potential of ixg;dvy j *g4f6zc::vw*+hph/03xc) esuioe$+125V$ 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 gaq6 dhpql 5v g0g;pau-f)y0f3ain (in joules and eV) if it accelerates through a potential diffdg-ap lu ;h5g3q0qf0fy p v6)aerence of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquiresdo t8x4qdn7 a uug6)g7 $7.45 \times10^{ -16}\,J$ 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 5.8 mm2-2 7l,vfo xstyp8l tn5/cjxwig1i1m apart if the potential dif/glf18t 2x x-octvmp2i7 j5sy1n il,wference between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of dcpe8q s;1*d,2ai guu$640V/m$ 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 sdfwh 2z us..,+3 -0*rkvaosr z-odqv45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected th:wg x3+buw qan6m c1p(6j 4tfo a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a heliqj.fu mq;ykndfx-rm hlra-4:h -y076um nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-gar 0sv:pf75bm, ygh)V power supply, are separated by an air gap. How small can bhf,r:sy7 gm5a0g) pvthe 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 external foi)i+uidwdkzn/4j77mh 5 wk9g rce 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 enermz+a7u;s* 4a;gclk9hu-bjcje ut k )+gy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whose kineticeo,ntxp 3*vp7 energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which*wqsjp4mg 8ruy 9(f-l 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 potential 15.0 cm from as0 rjkmv9.eizjmu0b3 gnjmb-:22lr;4 fxt -s $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an elehw- uz*svahq7.nh0i 1ctric 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 negatc /l b 675 lc;lplgo72tdas3bvived;aglo cl5c s 277/v l3blb6pt charge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potentia 9n.b ,gzwok(g/8oa( fe,lowtl a distance of $ 2.5\times10^{-15 }\,m$ away from a proton?    $ \times10^{ 5}\,V$
(b) What is the electric potential energy of a system that consists of two protons $2.5 \times10^{-15 }\,m$ apart — as might occur inside a typical nucleus?    $ \times10^{ -14}\,J$

Three point charges are arranged at the corners of a square of s;czp 0 nfevs4fc* 6;ioide L as shown in Fig. 17–25. What is the potential pncvo0z4f; s*6e;ci fat the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 334du+ fokc+)vlw4 b(h tip )r:f*flk y2.5 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 8a h2zss zo(p 59h;fowelectrons from a great distance apart to592 zz sfhh(a;p8 owso $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 (ngwp2z,u,rgcr) a2 fcm 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 acceleran t au* h-re113lrf2tmte 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 bogb(.p1 1 *xkrvjm k7wy a distance d, as shown in Fig. 17–27. Determine a formwvm*p.b x(g1kj 7ro k1ula 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 atom, an electron o z8skz0htfo mlk9xo krr3(iog/99g2; rbits a proton (the nucleus) in a circular orb k 8 /(hgog 93o;9osrzm2kzi9lkt0xrf it 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 protrjc,gjb p dn4d88k 64r8dw2cbw w.tg( on 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 dipolb becl 9oar-x6 z/5:lbe whose dipole moment is $ 4.8\times10^{-30 }\,C\cdot m$ at a point $1.1 \times10^{ -9}\,m$ away if this point is
(a) along the axis of the dipole nearer the positive charge;    V
(b) 45° above the axis but nearer the positive charge;    V
(c) $45^{\circ}\,$ above the axis but nearer the negative charge.    V

  The dipole moment, considered as a vector, points q0cu lgq2di2 5vh;bk+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 moments, hv2q5 0u ;2lcd+gqikb $\vec{P}_1$ 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 c 4 nlc)gi7we.capacitor 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 hold *+ j;js;knho, b uc,ep$+2500\mu C$ 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 chargei*5mrsim .ls9 s 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 aa iuzy bd fk*0zm lun,92uy)3 )u77qlgir is 120 V. They carry equal and oppos)yy ug23uudf* lu,0laibmnkz 7)z7q 9ite charge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of a 12.0-V )dlzny0w0 re *battery when it is connected to0ey) wl zdrn0* a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plata(hfu 7v:d(gmfkl -/ges have if they are to be separated by a 2.2-mm air gap? :df(- m/khvlua7gf(g    $ \times10^{ 7}\,m^2$

  The charge on a capacitor inc-sp(cp3xw3 ;rikbg.sbfts 9q9jy+g, 7occ 8kreases 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 6s orpcm:u+w ;3xpzf fhd5)l )$8.5 \times10^{ 5}\,V/m$ 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 opposita z2z7gmq j61s7p-h gbe $5.2\mu C$ 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 fiefv p 8:2:hefxcld 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 is dij-oaxls :e; 5vsconnected from the batteo5sl; :xvj-e ary. When this capacitor $(C_1)$ is then connected (Fig. 17–29b) to a second (initially uncharged) capacitor, $C_2$, the final voltage on each capacitor is 15 V. What is the value of $C_2$? [Hint: charge is conserved.]    $ \times10^{ -5}\,F$

  A $2.50-\mu F$ capacitor is charged to 857 V and a $6.8-\mu F$ capacitor is charged to 652 V. These capacitors are then disconnected from their batteries. Next the positive plates are connected to each other and the negative plates are connected to each other. What will be the potential difference across each and the charge on each? [Hint: charge is conserved.]
$V_{final}$ $\approx$   V(Round to the nearest integer)
$\begin{array}{l}
Q_{1}\\
\text { initial }
\end{array}$   $ \times10^{-3 }\,C$
$\begin{array}{l}
Q_{2}\\
\text { initial }
\end{array}$   $ \times10^{-3 }\,C$

  What is the capacitance of two square p0 hxu:h1h f-e r j5k,9nuzzwg*arallel plates 5.5 cm on a side that are separ*zwfuh10:n ukhgr e hjz59- ,xated by 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pai09wn rxvw49 rfmz/2 sv+pghk. r of circular plates with a radius of 5.0 cm separated by 3.2 mm of mica?w9 /xrr v2 pg0w4hv.nzfmk+s 9    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capa .qbt;ih;dr k7citor is connected to a 22-V battery. If a piece of mica is placed betwer7dq; b.hkit;en the plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a paper-separatedcj cu((z1ie8z $(K=3.75)$ capacitor is $ 8.24\times10^{4 }\,V/m$. The plates are 1.95 mm apart, and the charge on each plate is $0.775\mu C$. Determine the capacitance of this capacitor and the area of each plate.
   $ \times10^{--9 }\,F$
   $m^2$

  650 V is applied to a 2200-pF capacitor. How much energy is stored; 8ojow,gnj1v52bv i95ox.t6yv bjf y?    $ \times10^{-4 }\,J$

  A cardiac defibrillatmz7+i 0;umb+8jim-ff se4 bomor is used to shock a heart that is beating erratically. A capacitor in this device is charged to mueioz8m4 s i ;fm0jfb+m7- +b5.0 kV and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stox ; wsiauo5dtfrs rm8 m:j91mp 4i;4.nred by the electric field between two square plates, 8.0 cm on a side, separated by a 1.5-mm ai sd8rm oj5m94im4s1;;niu rtxpw.:afr gap? The charges on the plates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is asseuayaadd. vwz7 2rg+):mbled by placing two 9-in. pie pans 5 cm apart and connecting them to the opposite terminals of+vra u7a y:d ga.d)wz2 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 chargexj,8wevw d (x/s $+Q$ 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) tm u*boc li*na)d hxf,l(jf,9xa1 -w- xhe potential difference is doubled, and (b) the charge on each plate is doubled, as the capacitor remains connected to a batt,ab*,xf1w-x)ojdumfh *n lx9 l ci-a(ery?

  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 then pass 83ix )b1ap4hvxxeps9 through a uniform electric field E for a distance of 2.8 cm, which defl3xs b94e) h81xippaxvects 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. The scrw*4fibr0ra9zwii/o g ; df2 c3een is 30 cm wide and is 34 cm from the 2.6-cm-long deflection plates. Over what range robifzfarw wc *g9/2d3i 04;imust the horizontally 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/ wrdd:q8p8ji1/ ra ie keV of KE in moving from point A to irepqra8j8/ : 1di/dwpoint 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 traq1w+8cga+uw x,(1f -cn( 2 zwsqezzdmnsfers 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 nea-0tjp. e 0ljw3lvn .1 snsbk,or the Earth’s surface 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 by thouort s,e6h9,wysands of volts through a vacuum. If a television set were laid on its back, would electrons be able to move upward against the, wh, s69tryoe 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? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor ha lbtj a-g6xuryl u-w+g1u0 *5ws 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 capacitor is connected to iw1g2(hucr ( ba 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 the gur b2i(ch w1(voltage between the plates?    V

  Dry air will break down if t-yppd (4 l0ki kf,e2wghe 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 equilahov)16 t h5 zn0mh1vfz:fh4o rteral triangle (side L) as shown in Fig. 17–30. Determine the prmho :5 vt1n46hoh1fv 0) zhfzotential 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 aqviu5v sxbnu :--6fe96a,xkb 9.0-V battery. If a piece of Pyrex glass is placed betwe,a: ix -uebvv6- kbf nxqs9u65en the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally fro25ht ,,mh9 c 0mqqadjlm rest in a television picture tube byl2tm a0mchhdj,q9, 5q 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 (Fig. 17–31). At what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capacitance 7/ p2o67rvd0x ap;co k up5lsu$C_1$ 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 1y-. u*6. wvpgg)nuj ao-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 What would the gap have to be between the plates? -uo6)gynug.p vja. *wIs this practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there is an electric field of about-ez7:qy tnl;1sl7vc f $150\,V/m$ 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 ha1bz9 aks k*eq/9,ku bss 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 Eart-ktib lh1yu) :8c. kqqh and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are typically 1500 m above tuk hq.8-cbk) lyi1 :qthe 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, ultr 9 1:rud),zb f0xxaeigiu)bt/ aviolet (UV) light provides enough energy to some electrons in barium metal to eject them from a surface at hidigaf )/zb,e i:)uutr9x x 01bgh 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 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 identical enzu+t/yk/ oea;+(k l $+33\mu C$ 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 t8 c) evy8o6jdx4ve qb-wo 1.1-cm-diameter coins separated by a 0.15-mm-thick pi 8ceeqbj8dvv6)x4-yo ece 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 capacitor wgif j4mx24k:q ith 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 arx2w e .7rkl3wze fixed 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. 17l t5z.k /8(ovxwaso t-–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$