If two points are at the same potential, 2t.tjjr9 0/0: pxuiyb ks)cyb does this mean that no work is done in moving a test charge from one point to the other? Does j:y/)xik cp 2r0yu9t0sjbb t.this imply that no force need be exerted? Explain.

If a negative charge is initially at rest in an electa*+xa c4h/pd qric field, will it move toward a region of higher potential or lower potential? What about a positive charge? How does the q +*phaxd4c/apotential energy of the charge change in each instance?

State clearly the difference (a) between electric potential and -fki.qqp a6ji;(4sfuelectric field, (b) between electric pot; -upi6(f4. qajkifsqential and electric potential energy.

An electron is accelerated by a potential difference of, say, 0.10 V. How mucyome 0)a of)q8wjbm 15h greater would its final speed be if it is accelerated with four times as much voltage? Explain m5mj81oeay ofwb 0q)).

Is there a point along the line joining two equal positive charges where rok cp3; q*d0cthe electric field is zero? Where the elp0;ocrd*k q3 cectric potential is zero? Explain.

Can a particle ever move frv-agijsh,:) g iop7h4om a region of low electric potential to one of high potential sa7viph-,h i:4 gjog)and yet have its electric potential energy decrease? Explain.

Compare the kinetic enala*by:twlm.l/jw k09r 8pj 1ergy 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 line6e-g6aef gz1yb.pys(s cross? Explain.

Draw in a few equipotential lines in Fig. 1628+g rmovkv+br;srp1 1b1 fe x – 31b.

What can you say about the electric field in a regic cnv;)chk* 1oon of space that has the same potential thrhcc1nk)vo* ;coughout?

A satellite orbits the Earth along a gravitational equipotential linqlfogmma 24) (m5b o:be. What shape must :)2fomba m5bq o4m( lgthe orbit be?

When dealing with pracn*yys (v* m4p2cbbm k:l(-ygb tical devices, we often take the ground (the Earth) to be 0 V-bbbl(n (vcm pysy4k *2 *mgy:. If, instead, we said the ground was how would this affect (a) the potential V, and (b) the electric field E, at other points?

When a battery is connected to a capacitex 2wx5ncz( 7 2 88trrjpc*jbe92y1mro7omwyor, why do the two plates acquire charges of the same magn ntjx1 2wr*9xbrje2m mcpr7z52(o8oey7ycw 8itude? Will this be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on the size, shape, and position ofxjp b(v :*s7 +cl5mtkf the two conductors,ft*cxl(m p j75ks+bv: 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 electric f7v1eo,w 3*e wvl9y seaield do in moving a $-7.7\mu C$ charge from ground to a point whose potential is $+55V$ higher?    $ \times10^{-4 }\,J$

  How much work does the electric field do in moving a proton from a pu x62*.ace,hev e,xoyoint with a potential o.eoe 2xcx,h ya,e 6v*uf $+125V$ to a point where it is $-55V$ Express your answer both in joules and electron volts.
   $ \times10^{-17 }\,J$
   eV

  How much kinetic energy w.mv/8jmk+f3/iru gm5hqlj+ hy3 s g1vill an electron gain (in joules and eV) if it accelerates through a piq+5.gjm/sg u y3j38lm fvhhrk+m 1/votential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires +lmflmf6 h7, h$7.45 \times10^{ -16}\,J$ 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 i7y0it1;lnq j bf the potential difference between themn0y1qlib 7 j;t is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field ofa4c s9u)mto: y $640V/m$ 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 connected to a 45-V battery iz z67)tlhxgi+ s $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected xzxyo , 25nfmonr:9i(to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a helium nucljqco*-4*kyi;9kswv,quv4o i eus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, are separated by an ain( w:;mxfhazao 9y53mr gap. How small can the gap be if the air is not to become conduct3xmmwfa95 h yz; (a:noing by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an 7i- 64u;69w caahl bsu.byaciexternal 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 ,vlehac fx,*loh 59qy*-4ehni 1e9akwith kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a protolh w 1:o9f6k;sshgj chx-p8.g4n .yp rn whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nucleus, :y9g,k(q9bkd )d nnpoxjl:w5 $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric potew /r4;c(8b.cc+2 moveyj horantial 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric potentim fewx*iel- q) pl05*nal 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 thvi/- 8hu3 hhd,l rnnyp-*itj/e shape of a football. This conductor carries a net negative rh,/v/ji l8 h i nnhy-*pt3d-ucharge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potenq1h1o . u9yxvti(s0sw tial a distance of $ 2.5\times10^{-15 }\,m$ away from a proton?    $ \times10^{ 5}\,V$
(b) What is the electric potential energy of a system that consists of two protons $2.5 \times10^{-15 }\,m$ apart — as might occur inside a typical nucleus?    $ \times10^{ -14}\,J$

Three point charges are arranged at the corners of a square of side L as shown ign hje9 bsz); olp3v29n Fig. 17–25. What is the potential at the fourth corner (point;j92e sb3pzghnlov 9) A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a 5 od)cu;.it;0rp3g k. yrrrchfixed 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 electry hc/. :rtwl.9hgoe:c7a a1qyons from a great distance apart to:a7og/ e9l.c.w1hhyq c y:rat $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm nort, mjugwz y-8u:x.xo1l(d - prkh 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 (radius,i5f nn4 1gtxx6u;era $1.2 \times10^{-15 }\,m$) 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 disqpv p-3: rrnr -1yu:.i1-iqbdnf cb5mpo:3 dztance d, as shown in Fig. 17–27. Determine a formula fqn u1p n-ob.5v -: i: -3cqdrpprr:yi1mz d3bfor $V_{BA}\,=\,V_B-V_A$ for points B and A on the line between the charges.

  In the Bohr model of the hydrogen atom, an electron orbits a prokg d7qm1 t:;h zu*y/veton (the nucleus) in a circular /dtzmgh u7:q1e ;vyk*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 4uil-)dxagd u.(o8kowc+l7mare $ 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 yr/ybi*dmr 0, 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 ask*8 2axo5bc+ h3ktj8mf g6i vo a vector, points from the negative to the positive charge. The water molecule, Fig. 17–28, has a dipch ogoi3fx 8ja6 mk5b*+v8k2tole 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 tek9 cn14na c7capacitor 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 capacqf pq:9 uu h0y1 mbmifl-79n5ditor 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 charges of ayl7 r/fm7,bo )jqqg1$ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short secgy+mk94. etbov+c;j9ag yn2m tions of parallel wire in air is 120 V. They carry equal and opp;y4y29t+avme9ncgm k . gb +joosite charge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each termine.r/8yead ) cek*8 yanal of a 12.0-V battery when it is connected ye/ayn*88ee dcak .) rto a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What are8ypsjcd y.( :1.21x boysr4ymeb jxq +a must the plates have if they are to be separated by a 2.2-mm air y.1ys2y(b s jq.b cyxoxp8ed+rm 4 j1:gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor incf ;tmy fx6qh6 pp:m3)4q6w)czgs p*aureases 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*ev ,m ia1jp7y $8.5 \times10^{ 5}\,V/m$ 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 opposite/t wuu2h/v o.z $5.2\mu C$ 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 betwaw/my79 x(hx6xcw m4r4w* q bbeen 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. 17–29a) and then as:o m56ll(psc66o en is disconnected from the battery. Wo s(6ep ml o5s6ca:6nlhen 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 twte +w4/n 2g27bc:w knvd: zmxao square parallel plates 5.5 cm on a side that are separated by 1.8 mm of w7 v +g:4z:bk /2nae2mnxw cdtparaffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a radius odka,94rfmv1sp2 d cvmjq o )/7f 5.0 cm sepjv d/)qmdcsf 2ko4 p,1a m97vrarated by 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battjn yk1xu,9)zw :7ds(vt g/oxlery. If a piece of mica is placed between the plates, how much charge will flow u(k:ols /7x gvzj)dxy9n 1t,wfrom the battery?    $ \times10^{ -7}\,C$

  The electric field between th vdish :5 :f78pof mv):s d8hyvr4g*zne 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. h ;2kc) 1hf8tb6ikne4;- f oze*kiyotHow much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator05m7tf1l tg8jcv1 w co is used to shock a heart that is beating erratically. A capacitor in this device is charged to 5.0 kV and stores 1200 J of eg 15 1cvo7 0fct8mjtwlnergy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric fie)maw; fqf+k y+uhy4me+ 8r w:lld 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 anul+mywe+q84akm)y ff : wr ;h+d of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by pl)sm n1 kzy2d:lqjvx** acing two 9-in. pie pans 5 cm apart and coksdxy q: n*mz12vj l*)nnecting them to the opposite terminals of a 9-V battery. Estimate
(a) the capacitance,    $ \times10^{-12 }\,F$
(b) the charge on each plate,    $ \times10^{-11 }\,C$
(c) the electric field halfway between the plates,    V/m
(d) the work done by the battery to charge the plates.    $ \times10^{ -10}\,J$
(e) Which of the above values change if a dielectric is inserted?

A parallel-plate capq,41o q7zdtq 8 vx ztub/js1y/acitor 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 potefbescoxl+ d0(p(;-ew ntial difference is doubled, and (b) the charge on each plate is doubled, as the capacitor remains connected to+ d wel(boe(pfc x0s;- 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.gcz 7r5qz1d5s, q rxy00 kV. They then pass through a uniform electric field E for a distance of 2.8 cm, which defrq5z5 ,y0s 7z qgc1xrdlects 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 accele :e /faj(ae b1bbq-m)zrated by 6.0 kV in a CRT. The screen is 30 cm wide and is 34 cm from the 2.6-cm-long deflection plates. Over whaej:)m /1( bzbeafb-aq t 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 froa bk ;axbb)ueves- 9a t7nf-+-m rest acquires 6.3 keV of KE in moving from point A to point Bb7a-bna-kv 9;bf)s et+ uaxe-.
(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 trantfr,t ):.wxls is 54yok :jy0xsfers 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 near the Ea sfy -7l sp8ge z8c*rc-bq,j9irth’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 aree dfho/ -d7aw9 accelerated by thousands of volts through a vacuum. If a television set were laid on its back, would electrons be able to move upward against the force of gravity? What potential difference, acting over a distance of 3.0 cm, would be needed to balance the downward force of gravity so that -wadf9e/h 7 doan electron would remain stationary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough store ppjf,9q.llwa5 l t:8td energy to heat 2.5 kg of water from 21$^{\circ}\,C$ to 95$^{\circ}\,C$. What is the potential difference across the plates?    V

  An uncharged capacitor is connected to a 24.0-V battery until it icj/* l0iu1 gbgs fully charged, after which it is disconnected from the battery. A cj*ib / 1uglg0slab of paraffin 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 exu /k.ms+2h uvvceeds $3.0 \times10^{6 }\,V/m$. 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 coo/lo7d ;u0jn+y: f psjrners of an equilateral triangle (side L) as shown in Fig. 17–30. Determine the potential0n/: ;jj+o fy upd7los 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- x d09 2b3glrp /qb)ck(azl1zhf2, ylbqc(zz9V battery. If a piece of Pyrex glass is placed between the 3bhbk92 /f(zzlx,d) q yzgccl br( 1lqa0 z2p9plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated hxg+0t.qdc8 qyrv2 n)wpj t14jorizontally 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 ap 4 .)d j0v+x 1cq8j2ttpqywrgnart 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 capacitanyj.scf;,5y z )he1oha 5ui/rs 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-filled pahe nq3pfram2() / n4ftrallel-plate capacitor 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 achie4n3te2f/)fqhmr npa (vable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there is an electric field k w986uy ylh/v8ux)ytof 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 pulse.lbau+ zl )3o i,3;nbxcw /vmmd 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 difference bc*n+;1mxqau q etween the Earth and the bottom of the thundercloudnq ;+*mua1qc xs 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 $110km^2$ 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 e1o,rw2y7o4x sgm *ej-7 axpghoo q0h) nough energy to some electrons in barium metal to ej)omo12- a* s407g 7ohwqxypjhox ,greect 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 the barium surface. If the plate voltage is $-3.02V$ (compared to the barium) when the fastest electrons are stopped, what was the speed of these electrons when they were emitted?    $ \times10^{6 }\,m/s$

  A point charge is placed 36 cm from an idlb: 0i5mpwkesz9m tgi z.4 y98entical $+33\mu C$ 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-mc b,vv(m8vc1r m-thick piece of paper cvb mv1v, (cr8$(K=3.7)$ 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 +iwm;5z4mjbea-bgf 4xs3ph: plate area $2.0cm^2$ and air-gap separation 0.50 mm is connected to a 12-V battery, and fully charged. The battery is then disconnected.
(a) What is the charge on the capacitor?    $ \times10^{ -11}\,C$
(b) The plates are now pulled to a separation of 0.75 mm. What is the charge on the capacitor now?    $ \times10^{ -11}\,C$
(c) What is the potential difference across the plates now?    V
(d) How much work was required to pull the plates to their new separation?    $ \times10^{-10 }\,J$

  A $2.5-\mu F$ capacitor is fully charged by a 6.0-V battery. The battery is then disconnected. The capacitor is not ideal and the charge slowly leaks out from the plates. The next day, the capacitor has lost half its stored energy. Calculate the amount of charge lost.    $ \times10^{-6 }\,C$

  Two point charges are fixed 4.0 cm apart from each other. Their cjm ,xp-ugc*zi5b) 9 frharges 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)v8(i mm0h)hck (smhlfqgcokz*b421 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$