If two points are at the same potential, dou/yml( me)i: h pay(3zes this mean that no work is done in moving a test charge from one point to the other? Does this imply that no force need be exerted? Expl(ye(a l/3h)mi ump:zyain.

If a negative charge is initially at rest is0,fn*d(zh ij n 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 thesni,hz*( 0fjd charge change in each instance?

State clearly the difference (a) between electric potentia5iah/6yb -r+af ve9je0ex 9gul and electric field, (b) between ee vh9jx /iar -a6y059buee+ fglectric potential and electric potential energy.

An electron is accelerated *+jq ab/ 9ga;xo8ju,kb ht/ ubby a potential difference of, say, 0.10 V. How much greater would its final speed be if it is accelerated with four times abhxa8 gubqt,/ kjuba9o+ /*;js much voltage? Explain.

Is there a point along the line joining two equal positive chaa+a,wk4epn-z+ adz )bz:8c;pg(e akq rges where the electric field is zero? Where the e:wzbzkanpca,zae p qak d-g +8()+4e; lectric potential is zero? Explain.

Can a particle ever move from a region of low electric potential to one of h 6;lr +.tkkroyigh potential and yet ha.lkryo ;rkt6+ ve its electric potential energy decrease? Explain.

Compare the kinetic energy ga fp(q6a-yay ns3qgu8)z.e5p ivs,2 mwined by a proton $(q=+e)$ to the energy gained by an alpha particle $(q=+2e)$ accelerated by the same voltage $V$.

If $V\,=\,0$ at a point in space, must $\vec{E}\,=0$ there? If $\vec{E}\,=0$ at some point, must $V\,=\,0$ at that point? Explain. Give examples for each.

Can two equipotential lines cr9j m )*5ab n)ypvv:daqoss? Explain.

Draw in a few equipotential lines in Fig. 16 – 31b v kh)+jqnd gi(x(uumb:95qh;v i*)yp.

What can you say about the electric field in a region of spa6yj+rxi*5rr23gxfb ngz:n + nce that has the same pot *r 6j xrgng+frn n3zby5i2x+:ential throughout?

A satellite orbits the Earth along a gravitat ug wva46*ft rgw9dnymt;j+,. ional equipotential line. What shape must ttjn*wg4,v.gu+f6 myar 9;w dthe orbit be?

When dealing with practical devices, we often take the ground (the Earth) lfti 9lh3b l,ys: s/3kto be 0 V. If, instead, we said the ground was how would this affect ksy/llfs 3ibh,l9t:3 (a) the potential V, and (b) the electric field E, at other points?

When a battery is connected to a capacitor, why do the c m3+c vglbp)b30v ox-two plates acquire charges of the sameg c0)c3 mbo3xvvplb-+ magnitude? Will this be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on the size,99e*lc ttq df 2djc9ox: (n1mw shape, and position of t c1w lx2fo*(d9e 9djncttmq 9:he 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. 17 – 7?

  How much work does the electrbb8m5uuf )r8:n r le:sic 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 r;o bh0i2gsw-fe 5t 4tfrom a point with a potentia 4w;e -hfgibt sr052otl 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 gampm )je(t kol.++st dn8,)moxin (in joules and eV) if it accelerat+todl)kx.jso +,nmm)e m p( t8es through a potential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquiresvsdxs ,o *za hn48fein. 5-y,t $7.45 \times10^{ -16}\,J$ 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 if thec(c:fvlh.lg) ft d3m: potential differt:ghcl(:d)f3vf.mlc ence between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of sil61e0k2q ndp9qs35 t rop(l $640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between ksae4utln7bb2s u)-x* -zt*-abg/ hl 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 plad9fonf; 7fwk1;8owfpsbk9 8 wtes connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a helium nuclee s0f,hi* -3ywxix)i7 zc*nheus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 2003 zr2383bx//os/ qo bvwstjz*up y6u v-V power supply, are separated by an air gap. How small can the gap be if the air is not to become conducting by exceeding its bre*s3 zyb/ 3oz 8oj/ts/urp36xv 2wbvquakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an exe.8/d2kbzbo mternal 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 elec d 17 5lg.no8vufm5ptoq3wxvns , ci)2tron with kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of) f).rb:y hxqg a proton whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nucleus, wj95rsj-jn5b 3,yu fc$Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) 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 fz2r i-crebv7,rom a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric potentia 3c)j zl3zl qzfrw.*lq5kw8n,l 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 jo(o6vo)k :st. This conductor carries a net negative charj oso:vk6o )(tge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a distance oort-y/2a9 g,qn bf,j. xiyjv9 f $ 2.5\times10^{-15 }\,m$ away from a proton?    $ \times10^{ 5}\,V$
(b) What is the electric potential energy of a system that consists of two protons $2.5 \times10^{-15 }\,m$ apart — as might occur inside a typical nucleus?    $ \times10^{ -14}\,J$

Three point charges are arranged at the corners of a square of side9gznn*q i5ix1i ):mn7my thg8 L as shown in Fig. 17–25. What is the potential at the fourth corner (p97nz miy:tin* 5)8hqggn xim1oint A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cmilekvpu,yc4xl(a: x (r j5pjy. 2 c+-q 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 electrons from a g ;j.ky ;yib4v9fp*m,m4kqo uqreat distance apart m*p ok fqy4iym;4ju9,.qbk; vto $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm north b8/ w*rocw 7saeic22wof 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 acceled6q u vn9.r*yh6dlsr6rate 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 distance d, lkxu5;b luj97 as shown in Fig. 17–27. Determine a formula follj75u;xb9 k ur $V_{BA}\,=\,V_B-V_A$ for points B and A on the line between the charges.

  In the Bohr model of the hydrogen atkeh/) 0: ztnaf1,lu gfom, an electron orbits a proton (the nucleus) in a circular orbit of radius)fkl01th: nfa uze ,g/ $ 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 pr eufw yncy2q (:nq n)8f8tmobiu7vf.*/x 4p:hoton 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 diph*jre.b 1qgw 2ole 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 from the negat5x kg(a4l k*sq9h;xj sive to the positive charge. The water molecule, Fig. 17–28, has a jsl4xxasq g95hk;k*( dipole moment which can be considered as the vector sum of the two dipole moments, $\vec{P}_1$ and $\vec{P}_2$as shown. The distance between each H and the O is about $ 0.96\times10^{ -10}\,m$. The lines joining the center of the O atom with each H atom make an angle of $104^{\circ}\,$, as shown, and the net dipole moment has been measured to be $p\,=\,6.1 \times10^{-30 }\,C\cdot m$ Determine the charge q on each H atom.    $ \times10^{ -20}\,C$

  The two plates of a capacitor hoita z,fq3q jb3bee ah4/8 0*x/07nuq)vtnq ijld $+2500\mu C$ 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 holdvu gyc p5o:s10vv uplx;+/c/t) ff3qv $+2500\mu C$ 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 charg*lzhixe7 j)d 8es of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference betbfjv(lxiyyz n /im ,m 091,g)gween two short sections of parallel wire in air is 1gy ,(/zmb mij10l9i,x) nvf yg20 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 termin ypurw/ r u;8k-za/ 7nebb -w5c0tjxe.al of a 12.0-V battery when it is connected tok5x.tec/z -8rru/n;jb a yb-w0wuep 7 a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor ib;b, kv 6qku0vs desired. What area must the plates have if they are to be separated by a 2bq,k vkub06v; .2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitfztie o695n+ ior increases by $18\mu C$ when the voltage across it increases from 97 V to 121 V. What is the capacitance of the capacitor?    $ \times10^{ -7}\,F$

  An electric field of 7e w,y4ozknnf(z 4f j2$8.5 \times10^{ 5}\,V/m$ 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 opposiz h+(eu,g8 ig kf2-vocte $5.2\mu C$ 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 platesp9ail kk0++vt/ga l63/upbk-u ,hxdl 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 bvm )d riz+a*(lattery (Fig. 17–29a) and then is disconnected from l( m+i*adz r)vthe 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 squlfzhc2(.( qfnare parallel plates 5.5 cm on a side that are separated by 1.8 mm of pcfn((lzfh 2q.araffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair o-t5 ,hzrc1fx-z /tqr)bh d wr9f circular plates with a radius of 5.0 cm separa5-rdb hr w/,1) xc 9zt-zfhtqrted by 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery.aq0mc,p .zv,je( (x.h c9:ss :vyj .lfqh0xts If a piece of mica is placed between( vc:s xzqjm 0 hqfsyh0jc:lsae p.9v,.,.x (t the plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the paetw3a eum*+/ ezweqc1u8 kgks(. 5z8lates 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 d9i:g8hrf* das goe 28stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is0zuo 00a u2f+ut0lrxxx f;cu4 c+ps;x beating erratically. A capacitor in this device is charged to 5.0 kV and stores 1200 J of energyxucu0x04r tz+;u a0xf+o 0ulp ;2cfxs. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field bdgrm ibbz.px 19 7i/1between two square plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges i /gmx.rb191b 7b pzidon the plates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9o a9xd29(sc7:w e jyqx-in. pie pans 5 cm apart and connecting them to the oppos9deys 9:qxoj(cw7xa 2ite 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 chal9( eb:medet2 ;lpa c6rges $+Q$ 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 differen(n+,gt(p0 cq4p . ipol mo;xfjce is doubled, and (b) the charge on each plate is doubled, f(cng xt.0+lpj (po;qop im4, 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, electrkr+ :cf +vm )kalt(yq39xfg*mons are accelerated horizontally by 7.0 kV. They then pass through a uniformf + kmvrtc+:y9*a3gf kl x)(mq 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 the center. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a CRT. The screen is 30 cm wide and is 34vrlyl;eor* mv2rr3 mhc)q,7 x tu.7-l cm from the 2.6-cm-long deflection plates. Over what range must the horizontally deflecting electric field vary to swee7ro *mtuhl qvr)lmr2;.lc,r- 3 7exyvp the beam fully across the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from rest acquires 6.3 keV ,l j-)aohes6g.p)gtu c nut3 9of KE in moving from point A to poigt,a6guun9htl e) j)sc p.o-3 nt 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 d1i(;u,uh q ,u1 fgvdqto 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 neartnn*lr l9p)w; 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 accelerad)4 oc 0 vydt:mwu :(2ligscg1q3r0un ted by thousands of volts through a vacuum. If a television set were laid on id:rcgtm2 i 4 oqv y:dcw1)ugsu0n03l (ts 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 enouiwy) .pf)c3q72gac h wgh 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 z.; (*e/d7+rwevmk/dvgzx.u 7bvj -jzs kz+k it is fully charged, after which it is disconnected from the battery. A slab of paraffin is then inserted between thejzwv+dvr7k7 /em.bzk+ u; svz-z* /kxd.ge j( plates. What will now be the voltage between the plates?    V

  Dry air will break down if the electric field exceu9c *m; nx2vr2va)rj keds $3.0 \times10^{6 }\,V/m$. 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 corner+hhxr)f68e( poc () q)8vux chdex 5zhs of an equilateral triangle (side L) as shown in Fig. 17–30. Determi cvuhho)ec) h fdqzxp (5)8x+hx86er(ne 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 tmoxhm+n3( ( tbattery. If a piece of Pyrex glass is placed between the plates, how much charge w((o x3hm+ttnm ill then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in a televy9d0 hzk p*v 08q29+o tneaxdkision picture tube by a potential difference of 5500 V. It then passes between two horizontal plates 6.5 cm long and 1ov 9+dhn0* z8xtdkp2 09kyaeq.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 capacital crnl(nqa365q(nec e1z x/2ince $C_1$ 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 wadvse6bypi nq*+ wcur,95+hw+ nt to make a 1-F air-filled parallel-plate capacitor for a circuit you are ew+ 9y,uv+q s +*56chrndbpiw 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 practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there is an s35jorwv* bvd 7p ,bk((npa4cq) kis9electric 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 pulsed3)g-nungpy 9b 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, the potential difh2r m kj*,-srgxe:i9 uference between the Earth and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are2u: k*,-m rxsjgrh9e i 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 e8 juy:62gjbb 0 qgnai,nough energy to some electrons in barium metal to eject them from a surface at high speed. See Fig. 17–33. To measure the maximum energy of the electrons, another plate above the barium surface is kept at a negative enough potential that the emitted electrons are slowed down and stopp, 82 yj:gqi0auj bngb6ed, 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 plazdli;e w3e d5jy,;gbn3g49 suced 36 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-c31o f/:f7 ;4 sibnw/agl3ukin a 0dekdiameter coins separated by a 0.15-mm-thick piauk:ws nk7ila 0n 3;fdb1c 4i/f/e3ogece 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 capa+u+w1ge: xp rtb:5*kooblrt 1 g6fns 3citor 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 apalezwa; iyofv -1a19o ,rt 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 a rr.1s ,avu,fss 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$