If two points are at the same potential, does this mea ltrhv2a 7 88cqb.,ccnn that no work is done in moving a test charge from one point to the other? Does thic 8,ctcnr.2 8b7 alqvhs imply that no force need be exerted? Explain.

If a negative charge is initially at rest8j 5)/upmqt(kl vmkx( y8 ;i.eb el.tu 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 tl (..ee)(b v8 y8tl/5uxqjti mkpkm;uhe charge change in each instance?

State clearly the difference (a) between electric potential and electric m-a 9fnz/ks/l z1,huk field, (b) between electric po9shz,n1 mz-fuk a/lk/tential and electric potential energy.

An electron is accelerated by a potential difference of, say, 0.10 V. How much ggiqkc z5we6em 4, 1.1xi:evvmreater wou e6 xmvi1ge:wq vcei,.1mk4z5ld its final speed be if it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining twol89hs9f w i5cz equal positive charges where the electric field is zero? Where the electric potential is zero? Explain8l c9zw 95sfhi.

Can a particle ever move from a region of low electr l-v ,bad2s4zpv3pu.hic potential to one of high potential and yet have,43sl-2.hz p bup vvad its electric potential energy decrease? Explain.

Compare the kinetic energy gained by a proc7tupu 1q :;9-qook x .hon,wvton $(q=+e)$ 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 line8ou,e8s. de(p fa*xyeo)pu ) hy2 duc8s cross? Explain.

Draw in a few equipotential ; 3uqx2)nuzctlines in Fig. 16 – 31b.

What can you say about ,0)ks;ik/tc 0vbl 7cu )phhdxthe electric field in a region of space that has the same potenivp/sh,cdhk k)bl t0)7cu x0;tial throughout?

A satellite orbits the Earth along a gravitational equipmx i hgr )hwdevlbt0l)(t nhrb8 64,20otential line. What shape must the orb6hr hw)n,hd tx0e20bvg()r 4lt8lim bit be?

When dealing with practilx l,0::mym mgcal devices, we often take the ground (the Earth) to be 0 V. If, instead, we said the ground was how would this affect (a,ym xm::0gm ll) the potential V, and (b) the electric field E, at other points?

When a battery is connected to a capacitor, why do the two plates 2b26b 6t7tofrpi n)ikacquire charges of the same magnitude? Will thisbo)pir2 t tkibf2676 n be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on ldu1w,stb8/v a* l u6or-cn( rl, (xjwthe size, shape, and position of the tv*1utw ,l/j,orbx l8rd wc6u(- l an(swo conductors, as well as on the dielectric constant K. What then did we mean when we said that C is a constant in Eq. 17 – 7?

  How much work does the (lwlk+6y pqx; 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 from a point with a4p 9m rr9i)i 5bc+znnl potentiazb9l5r+4 nrp)i mi nc9l 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 joules and eV) if it ac/ljn sg 3d; 9qysuf al631yhd:celerates through 3 qaj;hd3gd: fuy9lsy 6/s1 lna potential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquiresmsc950h ; akre $7.45 \times10^{ -16}\,J$ 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 yd gq,2uyw5-t if the potential differeuw, 2y5dqg- ytnce between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of9 pfgz1d;w(cs ic 2us6 $640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field be+)wekn;g oy 3ntween two 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 connected tkhlpizb.eo6p+i yk3lk( )z ,o)p y7 m6o a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a helium nu3ssfaj fu * xjan,ci/+ tg,(0tcleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V 9 j7v+wrr7soz power supply, are separated by an air gap. How small can the gap be if the air is not to become conducting by excsjz w7r9v+7 roeeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an extd cyvra0, isrq*/tov3)p+52dkk sgu* ernal 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 lry3dql:2 : xzkinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whose kin5+ gt 7kp0 8(ybuioamvetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which isi+. v zpn/:yylq3t,ax 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 frol5p1/ a( nc:ucni h2zsm a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an eleci+z30cpe ce1 alkf1 b0tric 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 conducto *2kw +fwsaab dec)5wwq;bi2,r carries a net negative chbbq+w2 ,sw;5w2a*cw )ie fkda arge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potentia q s+)sokw -yt63 2z.bz+nl4mcvk, fgrl 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 r 7l og8:19s,as gyujmat the corners of a square of side L as shown in Fig. 17–25. What is the potential at the fourth corner (point A g r9:um7ja ,gsl1so8y), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a + d mvfvpwjal 116bv1y y/a-(cngr5vccp 3,2jfixed 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 el dq)3kfmi j1b+, jo:c .lbsc-gectrons from a great distance apart ,m1+cs)d3 q b:jlbgi f-jk.octo $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which bysx)ef) g s7i2g.b8l)kvig8 is 72 cm 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 acceleoy4k h xnx0/yc1a6dt:rate a proton (radius $1.2 \times10^{-15 }\,m$) so that it has sufficient energy to just penetrate a silicon nucleus? A silicon nucleus has a charge of $+14e$, and its radius is about $ 3.6\times10^{-15 }\,m$. Assume the potential is that for point charges.    $ \times10^{6 }\,V$

Two equal but opposite charges are separated by a dp rjnz7 qrs/ o.wx,94dgn/s 4 +0jbnrhistance d, as shown in Fig. 1 z /j rwjd 0ogphq.b4nss /,9n4xnr7+r7–27. Determine 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 atom, an electron o q 5adshubu61lz(x3*p rbits a proton (the nucleus) in a circular orb1sz(h 5xb*6ulup3a dqit 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 protonx98)i+vyii)x 5 l*co o yuxsx( 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 wh k*y gux6du,*aose 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,eim/b5 g* d.mady;1 si points from the negative to the positive charge. The water molecule, Fig. 17–28, has a bmme1g* is;/da5.yi ddipole 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 ck3 rj whxi)q*-apacitor 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 c-k ttf p3c0sh8apacitor 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 aahx0l a ))bm6jnd minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections ol-+ i2tj hj7gmf parallel wire in air is 120j+m jgh7-2lti V. They carry equal and opposite charge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each termiryavwahd0 vte 1)trv29 j 2-4onal of a 12.0-V battery when it is connected tojr4o 0v-e )tytvdwr9h22 v 1aa a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What51hvu 78c r;qaghw e c7g*al6g area must the plates have if they are to be lg8va6qhcr1 c *7 egg7uaw;h5separated by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increas)sz 7)rftfpxq; *s(6 /qwn nmzes 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 rqpn6t z6r;b.o lu1 ins:sw56ixux f))6g mq;$8.5 \times10^{ 5}\,V/m$ 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 oppozmcmt 2ui 6q-px//:l bsite $5.2\mu C$ 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 plat o(pjemsp0, 8wr/8byfswtc/ 2es 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-6x;5a0err1 u t7 ipyu irnvwo:x(+ vl. 17–29a) and then is disconnected from the battery. When this ca r;5rxv-ywpatr 6 n+70x1lu (oi uvi:epacitor $(C_1)$ 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 tmo.n11 wl*mgo hat are separated by 1.8 mm 1moonwm*1l g .of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair offeph+ wcb+je/7.3mrc1 vnz 0sg z3fa 6 circular plates with a radius of 5.0 cm separated by 3.2 mc3je fz srbvwan 637p0/.1+egzf+cmhm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. Iv .n887omos3gn;n o f8lntq: bf a piece of mica is placed between the plates, hg 8s 7m.n 8; boqofnlnvot:n83ow much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plat5et syr3(.b+gjr8v gshym :w,es 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 muzxis dt3u 0:9 5vz bj+2rg27eie( pulfch energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is -3y6;y4zec lfvajn(-yha gn5 used to shock a heart that is beating erratically. A capacitor in this device is charged (5yn4lah-a -j;gvc zf6 ny3eyto 5.0 kV and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by thee- :3p xd gbizocq6t5 p5u9ra* electric field between two square plates, 8.0 cm on a side, * te5:xag5pqurz9po6i bdc3- 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 o -n,tsy,k2 pk,.ditxpans 5 cm apart and connectik. 2n x,tio,,kys-tdpng them to the opposite terminals of a 9-V battery. Estimate
(a) the capacitance,    $ \times10^{-12 }\,F$
(b) the charge on each plate,    $ \times10^{-11 }\,C$
(c) the electric field halfway between the plates,    V/m
(d) the work done by the battery to charge the plates.    $ \times10^{ -10}\,J$
(e) Which of the above values change if a dielectric is inserted?

A parallel-plate capacitor has fixed char:si5lle1ht7bde.p7 zdhj /1 i*)bth lges $+Q$ 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 potential dif4yn m xin*+g(fference is doubled, and (b) the charge on each plate is doubled, as the capacitor remx* fyimng (n4+ains connected to a battery?

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

  In a given CRT, electrons are accelerated horizontally by 7.0 kV. -lx tz kp87rh0ge)3mwThey 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 t 7xm)08l 3kgepr ztwh-he 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 fd(pfwpim w56: ok5+ v34 cm from the 2.6-cm-long deflection(pkmw d f+o:iwpf65v5 plates. Over what range must 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 fromg+g3..vt9yf ifld) rwqyld sj3+ lg- , rest acquires 6.3 keV of KE in moving from point A to point B.fgygl-wqvdl3lf )r3ji9g.t ++sy d.,
(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*g- ihn2j i2t:+ nqqdm 4.2 MJ of energy to the Earth.
(a) Across what potential difference did it travel?    $ \times10^{ 6}\,V$
(b) How much water could this boil and vaporize, starting from room temperature?    kg

  There is an electric field near the Eartz9/3tv7thvu rofuot. on9 *f (h’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, electokab+ lpbd 0c d7d 0+l:+md/skrons are accelerated by thousands of volts through a vacuum. If a television set were laid on its back, would electrons be able to move upward against the force of gravity? What potential difference, acting over a distance of 3.0 cm, would be needed to balance the downward force of gravity so that an electron would remain stationary? Assume t:dd0ll0a+pkcsm /dk 7+odbb+ hat the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enoughg s0j,dodxfl/ y a.7h1b4* 9qz+bkxjl 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 a 24.0-V battery until it is fu6idu p/ 21yvyklly charged, after which it is disconnected from the battery. A slab of paraffin is then inserted between the plates. What16ky up/yv2id will now be the voltage between the plates?    V

  Dry air will break down if the electric fi l qsv).5uyi7beld 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 (siln*i (axde6uw992rqcg,t6b s de L) as shown in Fig. 17–30. Determine the potential at the midpou6e, r*xtn q(cig29as6l 9wdbint 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 batun uyk+1vhxu(*q o .p8tery. If a piece of Pyrex glass is placed between the plates, ho( 1x8q*u u.npkyh+vu ow much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest9 zdcg6h0 jz* )fflwd3edj6:j in a television picture tube by a potential difference of 5500 V. It then passes between two horizontal plates 6.5 cm long and 1.3 cm apart that have a potential difference of 250 V (3 gfd9 fdzjc* ej6h)0j:z6ldwFig. 17–31). At what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capacxlye2 - z b0t0g*;zzgsitance $C_1$ 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 5oqo6 iy0x l hjrugrti5pk9p-ts +/ 56parallel-plate capacitor for a circuit you are building. To make it auyh6pos0ij+5 toprl/- 6 i955x r gtkq 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 ele8pmco:4ogy ps (po76j87ko j jctric 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 nitrogen laser ha1t k.-ewg3m qjs 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 differencm sbs4x7 dn)97yy4 wv+;xuan ne between the Earth and the bottom of the thunderclouds can be as high as 35,0n7m7)b; 4uyxny sand sx9 w4v+00,000 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 energy to some ze7rh r2ls*v wrwzj,1j-25 vnelectrons in barium metal to eject them from a surface at high speed. See Fig. 17–33. To measure th7v 5,wzr- vzenr 2rhj*2slj1 we 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 identicv :c2q0ws acpz)0wm*d2g +u;ibmsx w,al $+33\mu C$ 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-diamez,h /7gsj+8)9 lndwu,t*p jlos:b tgw ,eepj,ter coins separated by a 0.15-mm-thick piece oztowe , ),w* phljs,gsjgeb,8/l9+u7: jd n tpf 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;+nc ev/rx5jz 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 chqj1 l+s y m.2vsl1n,foarges 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 showni n)l-fae5o tjx-3fn*+6 *ix0qbs nl p 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$