If two points are at the same py *tmnc*tj u69,g c)xs y,ft1rotential, does this mean that no work is done in moving a test charge from one point to the other? Does this imply that no force nyg1ymxtn 9ctrs),u cf6,t* *jeed be exerted? Explain.

If a negative charge ih jaj cdyb:3: 5yr2vh3s initially at rest in an electric 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 charge change in each :3: jbyydc 52 rhjh3avinstance?

State clearly the difference (a) between electric potential and electrost frfhh8ygd 3347e*ic field, (b) between electric potential andh 7gh8ry*o esfdf3 43t electric potential energy.

An electron is accelerated by a potential d96f tn tky vq z8)bwwd35h hn7wpa5/2vifference of, say, 0.10 V. How much greater would its final speed be if it is accelerated with four times as much voltage? Explaint zpv623/ 9vyt)qnw7ab5hwfdn k 8h5w.

Is there a point along the line join/sk-h05ivfcc0 obr0ding two equal positive charges where the electric field is zero? Where the electric potf-0ovc r5d00 ibk /shcential is zero? Explain.

Can a particle ever move from a region of low electric potential to ono c(xn-rh uqj k5 qmdo1;d-,i3e of high potential and yet have its electric potential energy decreasxocio-jq51h ;n u,mkdd- (3qre? Explain.

Compare the kinetic energy gained by a prcv/m1agh6zcn - p) alye(,sp94ay gf0oton $(q=+e)$ 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 hkerf60:sc /g cross? Explain.

Draw in a few equipotential likg ja ,v;1lx68g9t ym8fpm .lcnes in Fig. 16 – 31b.

What can you say about the electric field in a region of spacl6o ta;; ,zo hz.ce7oce that has the same p;ze7l ht.ooc;6ac zo, otential throughout?

A satellite orbits the qn2v*uafmw, - Earth along a gravitational equipotential line. What shape must the orbit nvu2a, qw f-*mbe?

When dealing with practical devices 5)e 46tcbcqql, we often take the ground (the Earth) to be 0 V. If, instead, 6)4q c5ce lbtqwe said the ground was how would this affect (a) the potential V, and (b) the electric field E, at other points?

When a battery is connected to a caf* exqmcb(oqobu )9:.pacitor, why do the two plates acquire charges of the same magnitude? Will this be true if m9bo*q )c xf(boq:.euthe two conductors are different sizes or shapes?

We have seen that the capacitance C depends on the size, shape, and positidsmcz7 :/hpu3j gp/sg22 e d+ton of the two conductors, as well as on the dielectric constant K. What then did we mean when we said that C is a constant in Eq. 1 c/2 /g+3szg smet2dup7hp :dj7 – 7?

  How much work does the electric fiel* ewk74 li8 ngn kga)e5n5f8eid 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 from a pointa- u.7b+-q5eeyyf lo b with a q75-ee+ f.ub ayoyb-lpotential 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 jhz:r fh)-i bt oy,nri qq49vu j9qs.,.oules and eV) if it accelerates through a potential difference of 23,r,tq h is.vyz .i)bqonjfq- ,9r4 hu:9000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires *v b,1ltv+egru6d8 +skd etl* 2yf5 md$7.45 \times10^{ -16}\,J$ 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 pkny:i mde/7/t 11y x8yvbkpr0lates 5.8 mm apart if the potential difference b1 8k/deymtn: ri0v yykp1x 7/between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of c(pb:h8ib be( $640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between twk1jajiqt0x l*0hz2p( 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 zo0rf8n 5xi69x (ocqnconnected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential diffe9jm wdqf 42:okrence is needed to give a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V e- wsr4+;atn bpower supply, are separated by an air gap. How small can the gap be if swen ;b+ a4rt-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 :i u3ng joyslq:,k /ljbj2 )a/external 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 ene /vdpb;:fc;u ewg5f/ urgy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whav1i lki/tr /6zm u1a5pwk.j7j-b(,f 3jscp e ose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nucleus, zk6g;5*j6ymjjcu 6 t r$Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric poa3 v,o: rg;rkctential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creawp8tnp yr )gswx*1q8y6,; 8l wzf(j wutes an electric 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 th9ivb x9c:o8tb s9lp:qk)g ;7nw*xv gp e shape of a football. This conductor carries a net negative chakt:v g*n vp9ig :bb;w7 89copl9sxq)xrge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electr0ehr cpa0h(g;ic potential 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 cfd:ljyowc1w 8so .1o *orners of a square of side L as shown in Fig.1*ywsdo. f81jwcl : oo 17–25. What is the potential at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed point chljl -g,t. xhx *nq2ng/tc.cov)jqd2 5arge 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 elect18wvvc0. eao vrons from a great distance apart te 1wo0avvc .8vo $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm1i7-q easm wfkqh9c1,v b 6gi- north of a $-3.8\mu C$ point charge, and point b which is 88 cm west of the charge (Fig. 17–26). Determine
(a) $V_{ba}=V_b-V_a$    V
(b) $\vec{E}_b-\vec{E}_a$ (magnitude and direction).
   V/m
   $^{\circ}\,$

  How much voltage must be used to accelerate a prot+,kcdkrh ) e:dn.4p w emtdf5.on (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 d, as shown in Figxw*z5 eni * h8i/ ywdnxs61s 6rjtg/e1. 17–27. Deter5wi*16hxrwjd1ex n6s y eg/itz n*s/8 mine a formula for $V_{BA}\,=\,V_B-V_A$ for points B and A on the line between the charges.

  In the Bohr model of the hydrogen ag ) )cwx;r ewk74xpoo4tom, an electron orbits a proton (the nucleus) 44poex;w gw)) roc7kxin a circular orbit of radius $ 0.53\times10^{-10 }\,m$.
(a) What is the electric potential at the electron’s orbit due to the proton?    V(Round to the nearest integer)
(b) What is the kinetic energy of the electron?
   $ \times10^{ -18}\,J$
   eV
(c) What is the total energy of the electron in its orbit?    $ \times10^{-18 }\,J$ $\approx$    eV(Round to the nearest integer)
(d) What is the ionization energy — that is, the energy required to remove the electron from the atom and take it to $r\,=\,\propto$, at rest? Express the results of parts b, c and d in joules and eV.   $ \times10^{-18 }\,J$    eV(Round to the nearest integer)

  An electron and a proton +ahp:vhy ( 4 rmkex q 78zsqod,7l3+ohare $ 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 who9) oeqk:8aa hlse 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 fjapx.o vsjow:y/+. *ndz; + srrom the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be considered as oad. or/+xn: wz+s.sy;vpjj*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 ; bptw,f xf:q5hold $+2500\mu C$ 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 0k x(5qf lgys z9exod).cyg1-9*lyfucapacitor 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 minusmnf9-2zqd9 e d charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of parallel wire+zh5e.f8 fy*jazti: c in air is 120 V. They carry equal and opposite charge of magnitudyae5f :fz+zi cj.th*8e 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 battery when it is cj:qu(ys ;.8f mu3hbbs s3hx )connected toxc. 3qs: hs bjuhum;bf3)(s y8 a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. Whatracp6 1ncv +1b area must the plates have if they are to be separapa1c b16crn+vted by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor inb4x ig k1rc3a;creases by $18\mu C$ when the voltage across it increases from 97 V to 121 V. What is the capacitance of the capacitor?    $ \times10^{ -7}\,F$

  An electric field of v51w h2h8-/s4hlinqh/ ktpcs$8.5 \times10^{ 5}\,V/m$ 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 ov;wamts os21k*+4g c *tldw2dpposite $5.2\mu C$ 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 z 5n-t*ecc0wr 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 bat4fp rf lx*qk++tery (Fig. 17–29a) and then is disconnected from the battery. When this capacitor +*qlk fp+x4fr$(C_1)$ 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 than t/cab h; k7 fso1af21df+hy:t are separated by 1.8 mm of paraffc;af1tosh f 7:nfhk+b2y /da 1in?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair o* 5x, x,dpjw(zc,+i3j vr*+ks w wzpaef circular plates with a radius of 5.0 cm separated by 3.2 mm of cv+ *w* xwsjkd+xjw pa ,5,i3,rze z(pmica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connecte1aik: uy-b z)ze29 sbrhn vky)11ejt. ye+ pk2d to a 22-V battery. If a piece of mica is placed between the plates, how much charge will flow from the battery?.2ukb2p9kt1jb-k nayy zi1 s+z1r:e)eyhe) v    $ \times10^{ -7}\,C$

  The electric field bet zm;);bwn4j xyween the plates of a paper-separated $(K=3.75)$ capacitor is $ 8.24\times10^{4 }\,V/m$. The plates are 1.95 mm apart, and the charge on each plate is $0.775\mu C$. Determine the capacitance of this capacitor and the area of each plate.
   $ \times10^{--9 }\,F$
   $m^2$

  650 V is applied to a 2200-pF capacitor. How much energy is stored? urp/- ;w bof8z   $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beating erratically.xqilb0,+(- h/bq9xs t.6dz r- f wkgqi A capacitor in this device is charged to 5.0 kV and tg - b/q90,blfkws6qhr( +-xq zxi.di stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the elect7qahq:;v *fq fhcu) 2wric field between two square plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on the plates are equal and opposite and of:hq2f*cw; q7)fuhva q magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in. pie pans 5 cmdkr i u5t zq,6;auro--jsh9*z apart and connecting them to the oppositr,5z sj-;ro 6ui zk a9h-tq*due 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 charges .-z8hcfxi1 3j3v b* xxj)hxat$+Q$ 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 potjc,1dcvo3kzx(aci(83-u l sh bue7 d3ential difference is doubled, and (b) the charge on each plate is doubled,(h8 ibodc3 , e1l-uj3dva scuc7zxk(3 as the capacitor remains connected to a battery?

  A $2.70-\mu F$ capacitor is charged by a 12.0-V battery. It is disconnected from the battery and then connected to an uncharged $4.00-\mu F$ capacitor (Fig. 17–29). Determine the total stored energy
(a) before the two capacitors are connected,    $ \times10^{-4 }\,J$
(b) after they are connected.    $ \times10^{-5 }\,J$
(c) What is the change in energy?    $ \times10^{-4 }\,J$

  In a given CRT, electroht.f9s:q t3* v8uspcj 3djn)ph4 f .axns are accelerated 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 above vh4 nca8t)xs pt:9dhq.s3pfj3 j *.f uthe 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 wide10h)z pv- gng7qv; pht and is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizontally deflecting electric field vary 0p 7ztv) vq pn-h1;ghgto sweep the beam fully across the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from rest acquir2omrqvs( x9y16 j4py0f:8 mnr3u ;xkv1hgatjes 6.3 keV of KE in moving from point A to 4fn;r9 vskarm y1:2u m 01q(3y8pox vj6gtjxhpoint B.
(a) How much KE would a proton acquire, starting from rest at B and moving to point A?    keV
(b) Determine the ratio of their speeds at the end of their respective trajectories.   

  A lightning flash transfers 4.0 C of charge and 4.2 MJ of energy to t0f8d4hv 9mxye9+tk f()jdp w mhe 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 s 4z+ac*t2wfpfurface 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 thousands of vov 3f4xrwxxp,;w1 fa2 alts through a vacuum. If a telev3 ,w2xafwfxa41v;p rx ision 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? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough stored energy to heat 2.5 kg of water rdxoj*ar1)talb4951tj hp : .x6x rh zfrom 21$^{\circ}\,C$ to 95$^{\circ}\,C$. What is the potential difference across the plates?    V

  An uncharged capacitor is connected to a 24.0-V bat57oz5eyy5zd t , pzbr/tery until it is fully charged, after which it oz r5,tbd ze755y/ pyzis 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 field exc9ursq b/)qn9 beeds $3.0 \times10^{6 }\,V/m$. 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 triangle (side L) as shown 34gm ap7gg5(y.bvmuicb8 ;rl in Fig. 17–30. Determine the pov lrgb(i a.8g5u3pm4 cy;g7b mtential 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 bkh8as(isd04 uattery. If a piece of Pyrex gl(0shu 4ks 8daiass 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 televiuv cpwdb0k dey9xs90p,u9i t3t4)r 2dsion 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 250 V (Fig. 17–31). At v4b 03,k9 t29rxdyuup 9et sdp0)diwcwhat angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capacitab*t e g9 9z1rj /hob0e(;ulhbunce $C_1$ 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 air-filled par70e7ip3lax 6p menp,yallel-plate capacitor for a circuit you are building. To,eei76p30p7 nxml y ap make it a reasonable 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 osefn3-,6h hxg3 yz7-c, di,upi) lg nbf 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 p( t ke9uzisezgct:e *s(j;6 *gulsed nitrogen laser has a $0.050\mu F$ capacitor with a maximum voltage rating of 30 kV.
(a) Estimate how much energy could be stored in this capacitor.    J
(b) If 12% of this stored electrical energy is converted to light energy in a pulse that is 8.0 microseconds long, what is the power of the laser pulse?    $ \times10^{5 }\,W$

  In lightning storms, t;5bw*cf9vsmfnpp odmk-+7mzmo9-* dhe potential 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 typically 1500 m above t5+cv9bp pmm *k- ood7m;df9w zsnf*m- he 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 somh, 84meiw- cil qr3nx6e 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 negativexe w4 8-inril6 q,m3ch 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 ia*( 2m:jz5f1n+nrgpynjy, fjdentical $+33\mu C$ charge. A $-1.5\mu C$ charge is moved from point a to point b in Fig. 17–34. What is the change in potential energy? $\approx$    J (round to one decimal place)

  A capacitor is made from two 1.1-cm-diameter coins separated by a 0.15-mm-t+qzfdhsh)slrg 74 .z1 b;,cg vhick pieqzhfs1+ ;lg .) r 7scvd4zgb,hce 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 with plate area/ql )qrmn x (/lc/lq.ozug0 k4 $2.0cm^2$ 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 n:q0tyzgx q utz6g:o6+9c gdd7nk85y. 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. 17pd3d-xiq12zy34-qac/ 1k umc dmd/ r l–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$