If two points are at+s4aiv ru; .jhqh +g +yx5+8y2qwwgwo the same potential, 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 need be exerws+jxgy;4wor5+ a2qwi y hqv.u++8 hg ted? Explain.

If a negative charge is initially at rest in an electric field, will it movelf 5 ls:86myqu5on (,z0b quaf toward a region of higher potential or lower potential? What about a positive charge? How doesb5al(q08 ls f f :,zmun5yo6qu the potential energy of the charge change in each instance?

State clearly the difference (a) be c+zg/w1f9uy ftween electric potential and electric field, (b) between electric potential and electrf/z9g fw c+u1yic potential energy.

An electron is accelerated by a potential difference of, say-c1 i0od(sh o sujw(-t, 0.10 V. How much greater would its final speed be if it is accelerhw0soji-((std c-1 ouated with four times as much voltage? Explain.

Is there a point along the line joining two equal positivggf2+ j),pr trwv6) mje charges where the electric field is zero? Where t2 ,pfr6t)gw jrgv+m)j he electric potential is zero? Explain.

Can a particle ever move from a region of low electric potkm 0thfni 9fmywjoa23;27j nhxz 64u;ential to one of high potenyoij62nf;j4uhtk32awn 0zh m ;7fxm9 tial and yet have its electric potential energy decrease? Explain.

Compare the kinetic energy gained by a pr w gj-2b5(r nc+v:kwzmoton $(q=+e)$ 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 dmus;;o t::ga cross? Explain.

Draw in a few equipotentik/p -)nzue x liowr1,9al lines in Fig. 16 – 31b.

What can you say about the electric field in a region of space that has 6bs0f5co748by k0fe/:uc vfd fqbq4d(d, j ndthe same potb ,84 df60b:fsv5ddb7c0qd(/yq ojcf efun4kential throughout?

A satellite orbits the Earth along a gravitational equipotential line. Whatyv yv :0dv6c+n shape must cvv: nd+yvy60the orbit be?

When dealing with practical devices, we often take the ground (the Earth) toew 0jwmcb.l)1cr,4sp be 0 V. If, instead, we said the ground was how would this affect (a) the potential V, and (b) the elec,cpw b1s)r l0.emw4cjtric field E, at other points?

When a battery is connected to a capacitor, whyj 0s r03pe13y5 n5xv ltjkgl:a do the two plates acquire charges of the same magnitude? Will this be v0yn 5egr l 150a:xlk3tspj3j true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on the size, shape, b nso 1jin a9u5*/hhi/and position of the two conductors, as well as on the dielectric constant K. What then unhjh*o/a1/ b 5iis9n did we mean when we said that C is a constant in Eq. 17 – 7?

  How much work does the electric field do in moving du-zk6 ).8b:gd +hrq7bzlqc xa $-7.7\mu C$ 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 progx 6)nrfp8:tav wst ;w88*ll oton from a point with a potential of ; g8awxn w 88)*ls6lot:ftvrp $+125V$ 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 umrb14nc dvf ff766s3eV) if it accelerates through a potential difference of 23,000 V in a TV pic fmfv463cubsn dr1f 67ture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquirespc3 j6ob9s4 ey $7.45 \times10^{ -16}\,J$ 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 betwee;s1fgrk)b *zi.c: ws-l j(s a0qreey 2n two parallel plates 5.8 mm apart if the potential difference between t qws01;a2ie-fcy.s s:ek(r ljgb*) rzhem is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of n2i wb/z1 - c18pnewkkwz 1t1v$640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two parallel platd3z3cha si 08ib,ff 2ses connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected to a 45-V bafugyuqz (mv6 87d 5kob-.s(o (zego5 dttery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a,yep*6 rw zq)b helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, are separatedmu weuf78/me b8i.i w2 by an air gap. How small can the gap b82 b /f8wue.mium7 weie 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 im jtngu7 d,x6f4jb88external 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 e ,o mn fmlb;;m3r91bc+t+yh;ff h-fk nnergy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whose kinetiubw ng8 vu9b7/c energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which iabt3i gb7c6x .);gvkp7: ip wbl(bz 3ws 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 iz /6zz:ni9g sfrom a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric potential g6v aebtzin,4.-eba* 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 zj+;j-c0r fsij; j/ 3lkyscu32o0 ecvthe shape of a football. This conductor carries a net negative charrckj c+jj;3e y/ u0vo-f;cjs0z 23s ilge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential 8efqc(6hee-;,q,z gs ih8x taa 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 cornerybtx 0j3ekxv0/. ya(l k; *hlhs of a square of side L as shown in Fig. 17–25. What is the potential at the fourth corner (point A)kahtb (3l0h*yvlxx0. ;k/ jey, taking $V\,=\,0$ at a great distance?

  An electron starts from ryq8 ,8nez n:p,gj5arop)pr q :est 32.5 cm from a fixed point charge with $Q\,=\,-0.125\mu C$. How fast will the electron be moving when it is very far away?    $ \times10^{7 }\,m/s$

  Two identical $+9.5\mu C$ point charges are initially 3.5 cm from each other. If they are released at the same instant from rest, how fast will each be moving when they are very far away from each other? Assume they have identical masses of 1.0 mg.    m/s

  Two point charges, $3.0\mu C$ and $-2.0\mu C$ are placed 5.0 cm apart on the x axis. At what points along the x axis is
(a) the electric field zero    cm leftof $q_2$
(b) the potential zero? Let $V\,=\,0$ at $r\,=\,\propto$.

  How much work must be done to bruf2n z9kfyv 2b s-fyasi 49w+/ing three electrons from a great distance apart b -4ynaw9f9ksv2sz+fy f2i u/ to $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 7pah:x6 a(s* ph2 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 accelerate a proton (radiul:iz:l0 nbnsye2of( (tqkm ) 9s $1.2 \times10^{-15 }\,m$) 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;8j iqr-8c fol in Fig. 17–27. Determine a for io-l qc8;jfr8mula 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 8yxm + j,0;+elwumhphuqwt2,atom, an electron orbits a proton (the nucleus) in a circu2eju,ulyt h wm,q p+ wmhx80+;lar 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 prt +* aj)*k(qc1cq vwedoton 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:ch/ eu8rln/b to a dipole whose dipole moment is $ 4.8\times10^{-30 }\,C\cdot m$ at a point $1.1 \times10^{ -9}\,m$ away if this point is
(a) along the axis of the dipole nearer the positive charge;    V
(b) 45° above the axis but nearer the positive charge;    V
(c) $45^{\circ}\,$ above the axis but nearer the negative charge.    V

  The dipole moment, considered as a vector, points from the negative to the ejddt7 e0i1,lrg7s9fw2b d8b positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be considereddlf0sw7te,2 r8bj b1de g9di7 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 capacvv )/sb g)jc.eibv8 )citor 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 cajif tp*am1n a(l2qe/ ,pacitor 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 minus rw 06s +ekfju;iro .5dcharges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference be a c nga9l22w9pw zg+l.gyj14ktween two short sections of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. Whazk 9l4y.l wpncg2agw2j+a1g9t 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 i 8bq.4 u7-j6flmldhzp s connected to4pzh7llbf8- 6m. djqu a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates have if they ari ,5(, pyt1em mqbb xdz:vc,a;e to be separated tpv,myczm;,xa: 1d(bq5,ie b by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increases by .z*zaxp.8k r ))nukno$18\mu C$ 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;xst ,k:lrtj2 2rbp3m $8.5 \times10^{ 5}\,V/m$ 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 op 3k)5qvpz h ylo+hwz99posite $5.2\mu C$ 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 77pp6ct vq:a tydyy*h4q-iz) between the plates of a $0.80-\mu F$ air-gap capacitor if they are 2.0 mm apart and each has a charge of $72\mu C$ ?    $ \times10^{4 }\,V/m$

  A capacitor is charged by a 125-V battery (Fig. 17–29ajls f5 o/p 31xg;4pokdju(o 0fqlvc/6) and then is disconnected from the batte/uo x51dj;63p g/oqo( lljvp 4cksf 0fry. When this capacitor $(C_1)$ is then connected (Fig. 17–29b) to a second (initially uncharged) capacitor, $C_2$, the final voltage on each capacitor is 15 V. What is the value of $C_2$? [Hint: charge is conserved.]    $ \times10^{ -5}\,F$

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

  What is the capacitance of two square parallel plates 5.5 cm on a sidei y p*uy,ukmcx 7xpe(e:q/m1c3rhimj. r,;; d that are separated by 1.8 mm ep3yk.yp;c 7/ji:*mu, ( diue;q mcxx ,h1rmrof paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates wi)ih zk.7noc6 rv;cifbz nv)76 th a radius of 5.0 cm separated by 3.2 mm ok ciifb).z6;6nn) chv o v7z7rf mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is co/mf5q(bf u49y9oi( 2kypy* d scs9ken nnected to a 22-V battery. If a piece of mica is placed between the plates, how much charge will flow fromm *2 9eucbi5sk9f(on4 p/ qysdy (yfk9 the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a ;o0 dp*t- b-gccl-q igtn,9tj 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 md)cm ,f:nr)n wuch energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beating eo .kb,x,a8+kbgxjyzt i43w r5rratically. A capacitor in this dew,a o4rgkx3bt8yjbx5 z,ki +. vice is charged to 5.0 kV and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between two square platu8dzg: zhxg .5es, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on the plates are equal and oppos.x:ghudz 58 zgite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-f elu 0.el2fglyhmj/ fyai, h(5+gd(-in. pie pans 5 cm apart and connecting the uf(gf+ jl(/y.i mgh d5ela,hfy02-lem 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 fit b03o; q+y).ji4;o fxga zrpfxed 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 capacitor change if7 jau3tn1c5uy 5xr67p d 5tqtv0dk6uz (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as the capacitor remains connected tot5 7k7zp n61d va36 ujtuyctr0xq 5u5d 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 ay1q nqofz uep5))kx5n; vv -1nccelerated 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, 1yp1n)unxz)k5q-e;q n 1o 5fvv1 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 ivensh bs2ydtm r;:074a )qjt+s 30 cm wide and is 34 cm from the 2.6-cm-longed; 2by sast7nt 4m:+qh)0jrv deflection 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 4d4xshv 5vh ot aw(;4zvzu +*mfrom rest acquires 6.3 keV of KE in moving from point A to poinhvv 4ts+(wah5;z4vmd 4xz*o ut 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 transfers4u4m u8ttf p9 1tx i*-ub.fnhg 4.0 C of charge and 4.2 MJ of energy to the Earth.
(a) Across what potential difference did it travel?    $ \times10^{ 6}\,V$
(b) How much water could this boil and vaporize, starting from room temperature?    kg

  There is an electric field near2 bv05u5or;5rw onlb z 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 picture5 5ap(kh/.vcqabyl.l tube, electrons are accelerated by thousands of volts through a vacuum. If a television set were laid on its back, would electrons ba/p5 cab lql.k y(5.hve 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 hea lm:f;w9hggdqk30 m tj/ 9ovt.t 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. npj97tssmjvf6v 5 +g40-V battery until it is fully charged, after which it is disconnected from the battery. A slab of paraffin is then inserted between the plates. Wha 5vtf 76pjsgjnv+9 s4mt will now be the voltage between the plates?    V

  Dry air will break down if the el2*0+ wcqtbx dxectric 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 equilat)ky3f tj j./ 0 j/(j/n*dfjitxip,jgjeral triangle (side L) as shown in Fig. 17–30. Determine the potential at the midpoint otj/d(f.tkx)p0* jj/nyj gj3/i ,fji jf 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 battery. I mhdo6/221;g 5wozaw kidjadwq ;3o9 /qf 9zkvf a piece of Pyrex glass is placed between the plates, how much charge will then flow from t61w2wo52dkgq a/ 9;zjzkwodf; /9qm i hov3adhe battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horiz om3*)hvpkpt5, ayn 0rontally from rest 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 differencekhr3om pa) typ,v*05n 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 capacitanclbu7x9* 8dp) gvt(0 slh k1mdnf pk,.qe $C_1$ 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, su6jmwlwn1 58 hpppose you want to make a 1-F air-filled parallel-plate capacitor for a circuit you are building. To make it a reasonable size, suppose you limit the plate area to jlp6n15m wwh8 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 fk.:0gjyn7kn zpus;h8/ct s4v7o y (yl ield 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 nitr pm3q19d8qb lq mm;y6logen 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 Earth and the botn)a0r;q;zw ka81h oym tom of the thunderclouds 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 )hzk1a mn 8;aqory0w;$110km^2$ 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 prov, *lj.y 7p;enstss36aulx dw+ides enough 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 stopped, and return to tu.w7 yj, apss6+ dlt*3nls; xehe 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 placedp irsk2ublug 2.x l.44 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-diameter coins separated by a 0.15-mm-th455 l lo2nb6jc:zbwn wick piece of paper z5bl nljcb625 :w4nwo$(K=3.7)$ 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 wijbdh67/n.5.. tl6a3fsr gph) ocrrg dth 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. Their1fo 8: q6:eyp qbi ilyonbyhuwlq 4+789pvs,5 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. 1 c6m12wdutn 2e7–35 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$