If two points are at the same potential, does this mean that no w50zxy *com9ae s+g t-sork is done in moving a test charge from one point to the other? Does this imply that no force need bec gtyz90*xo-s+mes5 a exerted? Explain.

If a negative charge jjc x/;+uq lp+0l j+boes2(+ni4otwl is initially at rest in an electric field, will it move toward a region of higher potential or lower potential? What abo ++wje2ijuq;sl obl4+ oxj(lt/pc+0nut a positive charge? How does the potential energy of the charge change in each instance?

State clearly the difference (a) between electric potential andzucl9wkf ,a5tju0byo,8k9 /lew-b 1y electric field, (b) betl9-8u1k 5lc9a,zb kf0w,o e/ytjuyb wween electric potential and electric potential energy.

An electron is accelerated by a potential difference ofmtyvxi+r ,goh v f 9zr3* b.(ikzqh731, say, 0.10 V. How much greater would its final speed be if it is accelefxg+*hivkr. (3yb v1rzm, 3q z9tio7hrated with four times as much voltage? Explain.

Is there a point along the line jmyy uvcpi;mg2u 2 +:l7d,agpx j 5)jp8oining two equal positive charges where the electric field ism8,mpl 2y2auc jjgvigy 7pdxp)+:u 5 ; zero? Where the electric potential is zero? Explain.

Can a particle ever move from a red(m:d-eh ,k9 f msc5imgion of low electric potential to one of high potential and yet have its electric potential hm: 5 -9sce md(fdkim,energy decrease? Explain.

Compare the kinetic energy gained by a yvw f7zx9d9b93b pk1cproton $(q=+e)$ 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? Ex vm)ga zts05m6kss8k 9plain.

Draw in a few equipotential lines in Fig. 16 – 31b.dxm) y :vmpdi,lud)) 3

What can you say about the electric field in a region of space that has ttvgs;l7: fox)he samefgt; slx:o7) v potential throughout?

A satellite orbits the Earth along a gravitational equipotential line. Wha7yu8mto .5t lnt shape78ly.nt tmu5o must the orbit be?

When dealing with pryb7hp (:1gc5tqs ;u lnh ga).factical devices, we often take the ground (the Earth) to be 0 V. If, instead, we sagb(p ts:c lq)1uf7y . ahng;h5id 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 capacitor, why do4ok5yje4 5ks s the two plates acquire charges of the same magnitude? Will thoey k sjk454s5is be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depen(z7 i/td0ty eads on the size, shape, and position of the two conductors, as well as on the dielectric constantiyetd0/z a7 (t 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 movinrkv; a mu/g9.cg a $-7.7\mu C$ charge from ground to a point whose potential is $+55V$ higher?    $ \times10^{-4 }\,J$

  How much work does the2idbis2b7t,zgg* ci c1)z p n8 electric field do in moving a proton from a point with a pntgic *2 7bp2s1z)i,di8zcb gotential 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 el kpm c r2p/:fjd10yr2 xdf+,xbectron gain (in joules and eV) if it accelerates through a potential difference of 23,000 V in a TV picture tube?mjyrfpdd/pk+r1 c2 x2xb,0f:
   $ \times10^{-15 }\,J$
   eV

  An electron acquires.mb8 qbkavi; bss/7o z6,*qlx $7.45 \times10^{ -16}\,J$ 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 mm apart qd y- yy, 7.obb,dfpx+if the potential difference between odbxyb p,y-,7 qy+df. them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field ofulu( ni*sw+jp8 1(opafmzl54 $640V/m$ 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 connectedx.w-8w h95lf (otpuewotvd; lk:pd :7 pfg/b( to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected tw46qa bm2zn +mo a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give:vl(k.wuv 9pkn0y9r g 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 sm: bg5g sven4(eparated by an air gap. How small can thevs5 :gm4nb( eg 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 et di-qr:)/1 g6e5an gzjr t:dqxternal 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 ).teubva84jfc ,b6e a an 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 proton whose kin0;hq/ szwun5*b g8vonetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nu.cphgdo , xc4+)5c ybhcleus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) 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 frtdrone.hs u3b *rn :y8;;2lizom a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric po7x6 g48nbdcmze /e3kntential 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 shapa.0+ d ta3/9oxhqqyml(hw ts*e of a football. This conductor carries a net negative a0(y+h*q3q9tswdt /mxh ola .charge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potdr xjudvn.) o:1hu.p1 ential 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 sidedc1p8 lvxx3d. L as shown in Fig. 17–25. What is the potential at the fourth corner (point A), taki1. xxddpv83clng $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed point charge wit5bg jx.+a2irb5dd 4 l5dxb+r bh $Q\,=\,-0.125\mu C$. 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 threzc zgd2z w0/i5;7prxx4 h.pi le electrons from a great distance apart tlhz5g07xz .id 4zr2p/ xpi;cwo $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm north of a 8y(sh ri7f)9l13qh zs*p0d ifg-b tsl$-3.8\mu C$ 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 fz5 hi671rhola bc(:c(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, asay g-3w3q 8qqt-x- qwzv/9fzw shown in Fig. 17–27. Determine aqfqqa3 wqt w3g--zzvy9 8/- wx 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 at hp/t;c r9d/s 50svxuzom, an electron orbits a proton (the nucleus) in a circular orbit oz/rvx 9stu/ h;c5spd0f 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 protoned v/rm/el ,z .5f9- elpef6 m3id8led 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 whose d2llw :,g: + g2-je7* ilpz0r acgcukxdipole 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, coh; +g3kp)kt (;rszw: jgibxk+nsidered as a vector, points from the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which ca;3gkh+ (bkkt jx wzg :s)rp;i+n 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 capacitorec:45f( lgy;wy rqfoa;vk2h2 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 capacitoaw1oumv:hnl bos;+ /8 r 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 anha zf m+k-w ebg/n2c413ces6sjc o5b;d minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference ;r)*phtc2mocbetween two short sections of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is the) m;c*pr t2cho capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal otz( wnr5+s(ac o : snn3rc6ah:f a 12.0-V battery when it is connected :a(cw5 6trznh 3rcnsa (:+ osnto a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates have if they are to be rn4 6x p76qyporys8 f(0g0u weseparated by 0spo6 w yuxry4(r q06gp8fe7na 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor inca0qq,jhmu 7on 0 lp4ry4z:oop7(n 7pcreases 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 ofd(k hdi;6evt, qrp-0j $8.5 \times10^{ 5}\,V/m$ 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 oppositoc-,7jccpqc: e $5.2\mu C$ 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 bxk3 /ab :bw2ogetween 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 (Fi,pldt7pk edh* 4abk (/n0sm (agtyw0:g. 17–29a) and then is disconnected from t kdsmbal/pt( d a*ky:hw0n7 e0, t4(gphe battery. 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 s3;wd .( fq)xqe fmixtn*)b4gdquare parallel plates 5.5 cm on a side that are separated by 1.8 mm offim.)bg e(dtnqxdf) * wx;34 q paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circula4lbhbl4.*g6h.gw3i :9w 70e fo2xqljl uqlp jr plates with a radius of 5.0 cm separaww2fx0 lpbeg : 4jhhqbi.q loj l*lg9.u7l634 ted by 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V b+6h58wfr d-n u oldcpgj0yj76attery. If a piece of mica is placed between the plates, how much charge will flow from the 0g8jdj +h-nprl6c wo f6yd5 7ubattery?    $ \times10^{ -7}\,C$

  The electric field between the plates of ao,)ft*,(euy9foq ym ;ai r w/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 st bdbmt*z*;4 : xmrso/pored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beating erratically. fd/2fx1+9sabq iyy-1m )i qz6y* qt goA capacitor in this device is charged to 5.0 kV and stores 11qqftoiby*y-yxi+g/sa ) z m129f 6qd200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electyifbz +t9,n2d ric field between two square plates, 8.0 cmfnz9, d2t yib+ on a side, separated by a 1.5-mm air gap? The charges on the plates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in. pie pans 5 cm apart an*bo8ka j wx,*pd connecting them to the opposite terminals of a 9-Vp* x*wo bj8ak, 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 fixedsrvvl(u bsj2v n;36 2p 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 capacfu3rz(tke2xh2 ggl4: i;;n vcitor change if (a) the potential difference is doubled, and (b) the 4g:nxkhi; flvrtug2(e c2z;3 charge on each plate is doubled, 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, electrons am v7j0r zesj:8uodh/ .re 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 t j ujh oezmv/sd7:.80rhey 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 screen is 30 cm wide aq+9p- 6 vlwju4nxlhu 9nd is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizontally deflecting electric field vary to sweepu9p9 jvwxll6qnu+ h -4 the beam fully across the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from rest acquires 6.3 keV ofk1b8 +2bi5 p sh8vrisq KE in moving from point A to point B. si82s +5phv kbq8rb1 i
(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 Mqaj4ko 8osamt-e;u85u ft-6e J 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 whot;pk1vh;em .t se 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, electr7:gimb zyp,4b4 veadj )wt-(rons 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 need e(-:tbwbmp,gr44)y v az7ijded 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 fromqvufus6io:t1 /x5 t 9se/2zup 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 batterywga*r sukt . li8xrr6p 22 g0(yxml,:k until it is fully charged, after which it is disconnected from the battery. A slab of paraffin is then insy6tlxs2gukg2:rxrr * ,pa 8. wikl( m0erted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down if the electr lquab3c n2t)nym*-7*j7ay rsic field exceeds $3.0 \times10^{6 }\,V/m$. What amount of charge can be placed on a parallel-plate capacitor if the area of each plate is $56cm^2$?    $ \times10^{-7 }\,C$

Three charges are at the corners of an equilateral triangle (side L) as shown inqgfy b7+;zqf-) pfxc3u d97qn Fig. 17–30. Detecqqfgfxb7un9z;y )3 d-+q7fp rmine 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 batterd 3,.jhw 5nvvly. If a piece of Pyrex glass is placed between djnhlv,.v5w3 the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in a televi,; ki uslmxri5,u unbtzqrj.;k -;;. ksion picture tube by a potential difference of 5500 V. It then pasxk l rs.iu;ku jrq5, i;z-mubtkn;,. ;ses 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 capacitancsi 0mp*mhid jf;-8 +ole $C_1$ 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 aipaln5l2b2 apy6 r,xf-r-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? Is this practica22xappa5 6ylbl,n f -rlly achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of k *di+,hvps f:the Earth there is an electric field of about $150\,V/m$ which points downward. Two identical balls with mass $m\,=\,0.540kg$ are dropped from a height of 2.00 m, but one of the balls is positively charged with $q_1$ = $650\mu C$ ,and the second is negatively charged with $q_2$ = $-650\mu C$. Use conservation of energy to determine the difference in the speed of the two balls when they hit the ground. (Neglect air resistance.)    m/s

  The power supply for a pulsed n44/i0qt98yvtiqy+zmb bbryx/ pk90n itrogen 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 potential difference between the Eartp+gw 4 nw64p* y:eb twq3g;jxrh and the bottom of the thundercloudsw3wnrqg:b4yget p; +4xj*6 wp can be as high as 35,000,000 V. The bottoms of the thunderclouds are typically 1500 m above the Earth, and can have an area of $110km^2$ Modeling the Earth–cloud system as a huge capacitor, calculate
(a) the capacitance of the Earth–cloud system,    $ \times10^{-7 }\,F$
(b) the charge stored in the “capacitor,”    C(Round to the nearest integer)
(c) the energy stored in the “capacitor.”    $ \times10^{8 }\,J$

  In a photocell, ultraviolet (UV) light provides enough f.24fuw9zoyapf* t e gl2.fu9energy to some electrons in barium metal to e2wfp9ftzu .og2 .4lfea9 f *uyject 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 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 3x+wf0,lg13 x olp . xh1ubu5pf6 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 coins separ, cl gevxv)*;i p 1xjrk.v13krated by a 0.15-mm-thick piece of ji3rek*kvlr 1 v1p). ;,vgcxxpaper $(K=3.7)$ 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(apms/wmkqivl 9+ +,x sbs9y6 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 ei(cr agz*vy-(ach 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 placed9d-xgg p;ui:e as shown in Fig. 17–35 with $q_1$=$1.5\mu C$ and $q_2$=$-3.3\mu C$ Find the potential difference between points A and B.    $ \times10^{ 5}\,V$