If two points are at the same pu409 kyohw(h yotential, does this mean that no work is done in moving a test charge from one point to the other? Does this imp4 (k0 wyh9uyohly that no force need be exerted? Explain.

If a negative charge is initiallb s, r4lif tk7aaw;-a.y at rest in an electric field, will it move toward a region of higher potential or lower potential? What about a positive charge? How does the potential energy of the sbrf4a ;-ali,a7tk. w charge change in each instance?

State clearly the difference (a) between elec/,gm, volu3 +vb xaob4tric potential and electric field, (b) between electric potentou/ 4lgbv+,x,ov3ma bial and electric potential energy.

An electron is accelerated by a potential di sw.izy;4e.k gfference of, say, 0.10 V. How much greater s. eiy w4zk;g.would its final speed be if it is accelerated with four times as much voltage? Explain.

Is there a point alonpmf1 *--n8ihio.h aje n)kis 3g the line joining two equal positive charges where the electric field is zero? Where the electric potential -.1kpii ha)j-ne*n8i o3fshm is zero? Explain.

Can a particle ever move from ar wvib88osfm8yq/c qk-kn :(1 region of low electric potential to one of high potential and yet have its electric potential energy decrease? Explain. 88/( oqnf vs8krc1wiy-:bkmq

Compare the kinetic energy gained b6;pd z-hhz281pbsvp2qag ig t8p9s l2 y 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 equipotentialws/ (ffswo- ;cuf )v;e(0 aioc lines cross? Explain.

Draw in a few equipotential lines(ij 3p ;7loh7f zcu,6sfcl u;f in Fig. 16 – 31b.

What can you say abo(5v go y:tc. b .o)twhhncg (k4m7/fjfut the electric field in a region of space that has the same potential c(5oyc wfgtf.mjv 7 thkbn.hg( : /)o4throughout?

A satellite orbits the Earth along a gravq keafvp(w*o,co ncb,3 29sq9itational equipotential line. What shape must theo pqq9bcnofkc, 9 (e*3 2vs,aw orbit be?

When dealing with pracsaqowv0d- 1 w.j8)guq tical devices, we often take the ground (the Earth) to be 0 V. If, instead, we said the ground was how qdsg)vw-8w1 u aq.oj0 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 do the two platen q+h-uzha*+cyt 6-g5j:a h kas acquire charges of the san5uyt-hzaa:qc6h *- h + g+jkame 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, shapegq )pyx;(+a dydhto0dydu n2,n(85bz, and position of the two conductors, as well as on the dielectric constant K. What then did we mean when we 0)yy n zhu8 d(p2 gddxd y5q,+nto;b(asaid that C is a constant in Eq. 17 – 7?

  How much work does the electric field do in movt 3ld/l3y53b nj o2mnving 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 protopdb e9if)r: .+yfl ,ann from a point with a pot9ei,: ) fn bfpaly.+rdential 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 ir:gmv( i2. h)q xji*imi;c1 opt acceleratesi;)iq1i.r* h :m ovx c(m2gjip through a potential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquiresbd q )17vaf,)cdq m,ir $7.45 \times10^{ -16}\,J$ 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 if8 +2zdhte4 :p(qeu mkufo+ e 9iqc5.cq the potenti2 + dutck:m5c+(p f4hi.euo qe 9qzqe8al difference between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of :t 2hnjyvh(tqj f5-1dcu 7z+s $640V/m$ 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 connec9nb, yff w 4a+:. fzjvqx,dn5nted 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 battery jd,m9vk7qrdqdnh.4n gj9y8q/ug+3h is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to givj4 s jp40)mr y0u xp9i)iohy8ze a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connecte4b . 9judf 8ehl,h.k,+ bni9oucxsohr3 w:r)ad to a 200-V power supply, are separated by an air gap. How small can the gap be if the air is not to become cahw99rr)lohf uokj e:u3 i.cdb 8,hn.bs+x4, onducting by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external fowo eyi2f35 t4orce 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 enj,rffmy3u (5 m-k)/m cdljdz3ergy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whose kinetic energy isx:; ,gk-dwud:agq n85, xwh5uuy e7yy 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a .q * 3eizqoeh*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 cma :9wcv s.x;;g(fo 5cwais,e7+eag gc from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an e,wb6jt,* jcj jf;+7qxuzbt 1clectric 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 footo el/bk9qb4-rzb6- leball. This conductor carries a net negative chlbkq9e oe-b -z/r4 6lbarge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential aui,my:x uhxkgxa4n ;lb)n+y5lndoi 5 3/b8 /q 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 *1smp vhux.lji/:zy :yx*t/o corners of a square of side L as shown in Fig. 17–25. What is the potential at the f:j:pil/hx o.u*tv*m z/ yys1 xourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed 71(ctk mu xc8/mptrap6- :wf,ajr2xd 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 thre+(qsbc 9swm :le electrons from a great distance apart tob9q:(+lc mw ss $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a whicheq2-5kl m6il h 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 accelerate a pas4/u 9qcld p5)0x mbsroton (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 zja+)0 nbelvtemn:l+, 6i 1 uuby a distance d, as shown in Fig. 17–27. eu1blv l6n) j,m t0:+z+a iuenDetermine 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 orbits a proton (th3mnpot/v- 4wxe nucleus) w4 xovt mp3n-/in a circular orbit of radius $ 0.53\times10^{-10 }\,m$.
(a) What is the electric potential at the electron’s orbit due to the proton?    V(Round to the nearest integer)
(b) What is the kinetic energy of the electron?
   $ \times10^{ -18}\,J$
   eV
(c) What is the total energy of the electron in its orbit?    $ \times10^{-18 }\,J$ $\approx$    eV(Round to the nearest integer)
(d) What is the ionization energy — that is, the energy required to remove the electron from the atom and take it to $r\,=\,\propto$, at rest? Express the results of parts b, c and d in joules and eV.   $ \times10^{-18 }\,J$    eV(Round to the nearest integer)

  An electron and a proton ao7q ovm+ mp:c lz5;a6gre $ 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 dipole mo i-)wggowvq5 /ik2 29a x6uhitment 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 vectok3 a(old 42rfn r*d.0jy medd*r, points from the negative to the positive charge. The water molec 3o4r(d*d.l2fey* ma k jndd0rule, Fig. 17–28, has a 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 ca++fxrfqw;5i .ub zf )zpacitor 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 capacitor ht5s fok v.*fc0d( wx:1g aa3 ht+by7rrold $+2500\mu C$ 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 hol6l; eab2 +nbgs :fykh4ds plus and minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference betwee+ qrzoihe:6f8 n two short sections of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is the capacitance of the + 86irh qoefz:two wires?    $ \times10^{13 }\,F$

  How much charge flows froem 0pr -68qwt 5vyrr)n5y0cqf m each terminal of a 12.0-V battery when it is connected to ar tfnw68-mrec) q0vry0 5yp5q $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What 2tf- ;dm0t eowarea must the plates have if they are to be sepa;wt02odmf t-e rated by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitorgk1mu 9: i9;vgkfhmo 2 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 s6 5zc oviy*f8pgs9g od /s.dveu;.;p$8.5 \times10^{ 5}\,V/m$ 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 oppom6ca1cul2)p.ao8*k;a pmrct site $5.2\mu C$ 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 betweendauk34kxh;hu0 9v/z)q imts 3 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 bna.ly g 9;l5z e shg7ehh4u+0sy a 125-V battery (Fig. 17–29a) and then is disconnected from the battery. When a7 l s;hhy4.eg0zg un lsh5+9ethis 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 side that 0xn4xvnku l-5,.t9gfhe *cte sy( gd-are separated by 1.8 mm of paraffin? dyg5-9sfh* lc4 .t vn,-eketu(gx0 n x   $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plf;1 rbr( hao.xates with a radius of 5.0 cm separated by 3.2 mm of mica rh1fx(;o .bra?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. Iw85:fy wij(d;)hmyce f a piece of mica is placed between the plates, how much charge will flf()w8w: jc d5mei h;yyow from the battery?    $ \times10^{ -7}\,C$

  The electric field bv la;s6 qyy -w0/,.c1yuatq iretween the plates of a paper-separated $(K=3.75)$ capacitor is $ 8.24\times10^{4 }\,V/m$. The plates are 1.95 mm apart, and the charge on each plate is $0.775\mu C$. Determine the capacitance of this capacitor and the area of each plate.
   $ \times10^{--9 }\,F$
   $m^2$

  650 V is applied to a 2200-pF capacitor. How much energy is stord8x 1k.e4j 1oqjytqk 4ed?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to sym xv.k)1e vt(hock a heart that is beating erratically. A capacitor in this device is charged to 5.0 kV and st)tvkv. 1yxm(eores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between twoi/xut, +huw )f square plates, 8.0 cm on a side, separated by a 1.5-mm air gap? Theu,x+wi)fh / ut charges on the plates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing :2n g:jj: kszwtwo 9-in. pie pans 5 cm apart and connecting them to the opposite terminals of a 9-Vz:: j2k:gnwjs 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 capaci.j 3-x/yc8ih* we ko mm4ni9oetor has fixed 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 if (a) the potentia,g - 5r2volaie.c gt(cl difference is doubled, an2r-ie,otg ac (l.g vc5d (b) the 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 are accelerated horizontally by 7.0 kV. They then yotb+y,- /wc7 c n* jcxb3.u2 gdakbt.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 the ctcj+d3 t.w*/ oucn -.bbbac2kyx7gy,enter. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a CRT. Thrj/inhv 0 :egqq:ruv,1+*hgwmiw 3n- e screen is 30 cm wide and is 34 cm from the 2.6-cm-long deflection plates. Over what range must t:-h0 n ue1*/+gq qrhgwiinjrv3, wv m:he 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 from rest acquires 6.3 kemk qsih) ;uvr5t ies;3u/e0;aV of KE in moving from point A to poin;si 3)u/eikmh0q a;; ev u5rtst 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. 53tyzsw bb9j 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 near the E,i(lg0+n9rw f woi9qs arth’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 accelerate9rdn ;wcxr 4qqty1 c/9gy .v-jd 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 sw9-x. c1trrdyy qg n;9qv/4jc o 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 kgs5(0 )tn-k+qmz hg gmy of water from 21$^{\circ}\,C$ to 95$^{\circ}\,C$. What is the potential difference across the plates?    V

  An uncharged capacitor is+:ra i o : 4)gdwxpyt5m.5hgbi connected to a 24.0-V battery until it is fully charged, after which it is disconnected from the battery. A slab of pgmdbr wi.g:t5a4+ )p:5oix yharaffin is then inserted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down if the electric field exceeds vx: p.;yi,lpfc3 csie a40(yu$3.0 \times10^{6 }\,V/m$. 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 shown35 gx2s*o/aks94bs p7 cnbgzz in Fig. 17–30. Determine th as3c2gszxgpo 9s *bb7 k/n45ze 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 batterrk ga3x:y) bn1y. If a piece of Pyrex glass is placed between the platgn)xyb 1k r3:aes, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally fro*:+7jhvcb.o 1w +uh,hl3g qpx4blie tm 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 difference of 250 V (Fig. 17–31). At w+,4 c*:jlxlbpt +3 ebwvoh1h uq ih7.ghat angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capacitance : 3ysp7zw6og:4cnve t a/3xw q$C_1$ 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 b flu,f 6t f8q 9ef7uqse;g9d9nig a farad is, suppose you want to make a 1-F air-filled parallel-plate ca9 6f7e, u8qg; n9lsftefuf9 qdpacitor 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 practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of 5iv h2if, d/s ym s*gld5mmj38the 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 nitrogxsj ra1.dfn1.q1/p.zqk 3 svwen 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 h e(-ju-br2 7i+hr92 vzgs kfjand the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds ar v bf+-r jg2k2i( ezjrsh9-uh7e 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 ene-pm., pu() hma wmzbs7rgy 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 slowepam,-)hpm.(u szm 7bwd 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 placag6uzt 1 am;zr;bx.k7ed 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 tw( ns8qt my+ufk;6w4.nz (obuno 1.1-cm-diameter coins separated by a 0.15-mm-thick piece of pqy6 mnu(+ft 8nobs;wn4u(kz .aper $(K=3.7)$ A 12-V battery is connected to the capacitor. How much charge is on each coin?    $ \times10^{-10 }\,C$

  A $+4.5\mu C$ charge is 23 cm to the right of a $-8.2\mu C$ charge. At the midpoint between the two charges,
(a) what are the potential    $ \times10^{ 5}\,V$
(b) the electric field?    $ \times10^{6 }\,V/m$  ----待选择----leftright 

  A parallel-plate capacitor with plate area c:b7o cg dic3tsvo;z,1/sm c 3$2.0cm^2$ 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. Th+ oy )ptftft+-eir 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,j x5xna3dka 97–35 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$