If two points are at the same potential, does this mean that no work i:rsurc0 j 5(sas done in moving a test chas(js r5uc0r:arge from one point to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at -x/ /w ajfvk.te5ko2vvhzsov9 sg0+0 rest in an electric field, will it move toward a region of higher potential or lower potential? What about a positive charge? 9sho+/ksgex vj2v av o0.z-/t 50kwf vHow does the potential energy of the charge change in each instance?

State clearly the dipk vtj *x4dn4x8jy0 tzwjh8w6q/-f ,l fference (a) between electric potential and electric field, (b) between electric potential anwd q8 8wn -f4j/yv6l zjth4tpx0 *,kxjd electric potential energy.

An electron is accelef8w*jz9e-y ic zxn uzj ky-:u457m;c urated by a potential difference of, say, 0.10 V. How much greater would its final speed be icc *uwk-y x:zyzne9f4- ; 8j5jiuu 7mzf it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining two equal positive charges where the elel7no2ww r(gkre.n6:e ctric field is zero? Where the el:eewr kn.ng 7 ro2w6(lectric potential is zero? Explain.

Can a particle ever move from a region of cuwq t b817wk.kp ue3)low electric potential to one of high potential and yet have its e bue3 pkuc1)8qww7.ktlectric potential energy decrease? Explain.

Compare the kinetic energkkl d8xem yu ,-;c2t1u3)i pdwy gained 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 / *djfad/dui;lines cross? Explain.

Draw in a few equipoti3;frue nyi4r1x9d 4rsb ,6teential lines in Fig. 16 – 31b.

What can you say about the electric field in a region of space that hak/pai. ),e3: mn whpqp*oknh:s the same po: np ,i w*q:epopk m.hnha)/k3tential throughout?

A satellite orbits the Earth along a gravitat kosq )m +jk r4o,ctdaagp);19fse8a9 ional equipotential line. What shape must the orbpkm)r1kfa d8g,s9 +as)o; o94e cqjtait be?

When dealing with practical devices, we often t7+-4t,1ehx iojmu wazk39k4v ezi) rqake the ground (the Earth) to be 0 V. If, instead, we said the ground was how would this affect (a) the pote m 3 zwj9r1 ivx)7k+ik44-eetzhuq oa,ntial V, and (b) the electric field E, at other points?

When a battery is connected to a capacitor, why do the two plates acquire ch 8ef)ae4mgb nrw:f d+(;aya1 harges of the famhweag yr)db; 8a:1 (4fen+same magnitude? Will this be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on theu6-7v0b0tvu zk 27zfae xxmdg) 0ta6e size, shape, and position of the two conductors, asku-m fa72 ) vzuvx0tbtdege 06x6z70a 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 electe 0x/iq4 vd:kxjes, -nric 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 mwwy *qesz4x2w2,zfe 8f7 4elt oving a proton from a point with a poten4zw2yws,q*82xe fe7z4fe w tltial 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 uuuxa5h*7n7b o*iu+hand eV) if it accelerates through a potential difu h7huno7bu5xui**a +ference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquiresf45fi 9outduu ,hk* v. $7.45 \times10^{ -16}\,J$ 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 aparj(cim 3 +.mtmrh/tra/w(y6ef t if the pote(/ratim +c j(6wt3 hmm/.rfeyntial difference between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of (:7son eikppx 6( e-zv, v)kkn$640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two paralleu:hdmw x 5aj7+l 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 to a 45-V bae9m,6z mt)ddd2 ) kgtpttery is $1500V/m$ How far apart are the plates?    m

  What potential difference isq p eex*rxi frgzr3: yn(q9w47x; *m,s needed to give a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V pa /c7hmzr4ts75;lzzdwtm9w8w0gnf s d2- q/ kower supply, are separated by an air gap. How small can the gap be if the air is not to become conducting by excee qzd7d/tzw0an2r4c/t97 kglw5f ;hwzm m-s8 s ding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an e3qtu48 vj 6x)vzfypx- xternal 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 wi08kyfrptkh ;. /3e;hrtk* xrjopt1e q;/ f;gdth kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whose kinetic e: dn5rwr ,amonyj*r2 ,.c jt3vnergy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nuclemdiwxf cx 6 *g oy0,-6/k,ktnyus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric pot0fb.pugwyd s+gh x4v; 3j:x rit-oy 08ential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an efjpp:j9 p+b ;yj k +1 poq7ctxhs/7ss)lectric 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 : 1sacd. rya hfn* kg/78b8ers5pgu/dof a football. This conductor carries a net negativp*sra 8.7gusarn/1 g/8eyhfk 5dd cb:e charge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a disvhj ti4+8m76ax-*o am yobca2tance 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 r4z5rjcc sf) ,oz n+d0at the corners of a square of side L as shown in Fig. 170dr)zzrc ,5ocs4jf +n –25. What is the potential at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed point charge with v3t7qbtd l 0sisp).*s $Q\,=\,-0.125\mu C$. 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 l :xx(q7ff7nnfrom a great distance apart to nnxq 7f fl:7x($1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm noai.vifa6jrn;h 0 6 di+rth 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 ;m1elj . ifd7.bho.h cused to accelerate 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,)i d)piu+mua ; as shown in Fig. 17+ m)uau)i;di p–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 electrons8lkl l 9,mp0m orbits a proton (the nucleus) in a circular orbi ,kls 8l9mml0pt 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 provsq*ipmj5e7 ixqug 9w(s0n -i:m:pv7ton 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 d 4b6pei40wwfd rsi1ozil* f+ ;ipole 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,s9f +e6it5gbhiuz0 o from the negative to the positive charge. The water molecule, Fi0otiz i9+fg6hb 5s,eug. 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 6soj hk:0p:0 jasytg s 6uz0z*capacitor 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 capacit m sbnfgr ss9e0y1;9/a p 0rhct3-tdw3or 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 cha2ena+ )4 yqm cdm*7aoxrges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short / bn 87qrjgt;usections of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is the capacitance of the two wires? j;8 r7bgqt/ nu   $ \times10^{13 }\,F$

  How much charge flows from9rg20,dspud(s h okb) each terminal of a 12.0-V battery when it is connected toobd0 r u)g9 (,hspsdk2 a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area mu4bq( 1gcsef1p st the plates have if they are to be separated by a 2.2-mm ag f (b4sq1c1epir gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacito 4- l7oqb+)clbum/bslr 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 ) ltf-s p5u1h(qd* wnp (a9eiq0yr/hm$8.5 \times10^{ 5}\,V/m$ 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 oppo ;t8q -vo)h3mbajgna*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 between the plates of am7jgxl/w 0py+ $0.80-\mu F$ 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 jxo;zfe15xca 0 *2+ey b3 aqada 125-V battery (Fig. 17–29a) and then is disconnected fe0 y*f;2 aejbzaq1a+3 xxdc5orom the 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 74ts k /drfozvr 4xs8n8*rnx(square parallel plates 5.5 cm on a side that are separat8r st 4kn o/d( x*874snrxvzrfed by 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a paig x 1:3vq2ec u:tc cs*trpg1b .c.snx6r of circular plates with a radius of 5.0 cm separated by 3.2 mm of m*gc2: t:rxp116 bg. unc.etscvsqcx3ica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor i*ngh-ajxu5d ,fn :9p bs connected to a 22-V battery. If a piece of mica is placed between the plates, how muchdnb:hx9 f,uga*5jnp - charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between/m:nokqdap-.m8u n- h 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 storec,b4r ;wfvtk;0 6 jtzzd?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beating erratically.,hbtd5li-4; gq nn9do A capacitor in this device is5b-hl d4 n ,gidn9otq; 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 fi n88u i+xhaj1zd.pz:3yt3 ctbeld between two square plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on the plates are equal and opposite and of m c.3 j:zzdtpyt8i13u+a bhn x8agnitude $420\mu C$.    J

  A homemade capacitor is assembled bylalx;5g:0 wgaz 3lh+q placing two 9-in. pie pans 5 cm apart and connecting them to the opposite termin :aqxal 3lhz5wgl 0g+;als 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 fe/8gtp+f. j clixed 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 storesq oa 20uhew1cihhazy(fm.8:d +/qq 4d in a capacitor change if (a) the potential difference is doubled, and (su e. +ay2mhzfh8oa/hqd0cqq( w14 i: 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 horizontallr(9f/k xk+cpcwfa s 8v6z,b /iy 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, 11 cm abovfk( c + a6xwir/9fcp,ksv 8zb/e 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 anxt1 b.haj*c bwda -,r15dlya9 d is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizlwddrhtb axb*a, 59y- 1j .a1contally 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 0+n0 ewass5c.g tehcn8l aa4(acquires 6.3 keV of KE in moving from point A to point B.n0at+0esa 8eg5 wa(4h nc. slc
(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 c nq5qlg 3s6d ) uxvvnsa3d* (sgi/2w-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 fielt((fy2a.nji zd near 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 accelerated by thousands of volfhm- dew(5bs kef8n,,ds 6fq2ts 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 po fdsnfqe 2(bwhmd6-5 ,fk,es8tential 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 heat 2.5 kg of water from nb drls n:hf0i 9kz)z3x/ v09k21$^{\circ}\,C$ to 95$^{\circ}\,C$. What is the potential difference across the plates?    V

  An uncharged capacitor is connected to a 24.0-V battecy yjnr70h * lnhn:*f9ry until it is fully charged, after which it is disconnected from the battery. A slab of paraffin :7yn *flh9rjc*n yn 0his then inserted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down if the electric f rj isrcoh.19:1moh5 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 fnc:m2tut7w/ corners of an equilateral triangle (side L) as shown in Fig. 17–30. Deter27/ttnm:u f cwmine 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 capacitp*be g 2hwwf5,or is connected to a 9.0-V battery. If a piece of Pyrex glass is placed between the plates, 5ewphwg2 f, b*how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is acceleratie ds0b3 myqwbc1 -s9ytdwg 3jv x4ic2+-z;d/ed horizontally from rest in a television picture tube by a potential difference of 5500 V. It then passes between two horizontal pzc ts9/4isie-yddwy3 xqb j;g+ wbv -m03d1 2clates 6.5 cm long and 1.3 cm apart that have a potential difference of 250 V (Fig. 17–31). At what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capacitann (k )u7w(b1m aeev ynar)cdb,dr, 4s)ce $C_1$ 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-f8sngi2-j tg: filled parallel-plate capacitor for a circuit you are building. To make it a reasonable size, suppose you 2n-gstjf8:i g 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 electric s uw)svk** 02e og:enxz3u8dxfield 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 has a*w, w0uxqyi5z $0.050\mu F$ 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 bottom o0:gjbkdq/be4 w:ug y/f the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are typically 1500 m above thebeukj:0 4:/dqwgg b /y 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 /fsh u8lb1jdb gc(c2 8energy to some electrons in barium metal to eject them from a surface at high speed. Sb (b j2hsuccl8/ d1fg8ee Fig. 17–33. To measure the maximum energy of the electrons, another plate above the barium surface is kept at a negative enough potential that the emitted electrons are slowed down and stopped, and return to the barium surface. If the plate voltage is $-3.02V$ (compared to the barium) when the fastest electrons are stopped, what was the speed of these electrons when they were emitted?    $ \times10^{6 }\,m/s$

  A point charge is pwuyy6s39:5 pvxrfhm 6 laced 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-cm2xgp4d d 7m;oqgp0cfl;e 5il+-diameter coins separated by a 0.15-mm-thick piece og; e2; 4lfdxdim c5pp7qg o0+lf 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 with plate are h2fmx9hrlh +bnn/8:oa $2.0cm^2$ 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 charges argm8rm+ jssm(yqvf- e.(5 n)l re $Q_1$=$Q_2$=$5.0\mu C$, 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 showb )vq +xos(wze1 3f3xtg ,y9ton 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$