If two points are at the s;*gvmn 4u,g9e2yb9gdn z 4jsjame potential, does this mean that no work is done in moving a test charge from one point to the other? Does this imply tjgm vg *nsj,ne ;yg249 94zudbhat no force need be exerted? Explain.

If a negative charge is initially at rest in an electric field, will j. e8 qeie-mo qd:vqe0sz:rw w)px 088it move toward a regioi wqz8e0dwrjm. )es:qqe :vp8o0 - e8xn of higher potential or lower potential? What about a positive charge? How does the potential energy of the charge change in each instance?

State clearly the differen .tn*5v4e4uyy*a a aecce (a) between electric potential and electric field, (b) between electrit4yc.y5e*n4aav au*e c potential and electric potential energy.

An electron is accelerated by a potential difference of, say, 0.1:9v+vimh5kbk 0l (qhz0 V. How much greater would its final speed be if it is accelerated with four times as much voltage? Ex (9l zqmkv50ihbhk: +vplain.

Is there a point along the line joining tw5r;i6g pqoke4 *af3aco equal positive charges where the electric field is zero? Whe6; oe3qafg*r4 c ik5apre the electric potential is zero? Explain.

Can a particle ever move from a region of low el 37c ;kva4wrb-usr 1jl0v hf7vectric potential to one of high potenlfcvsj bvr- rv13ka0 7hu47;w tial and yet have its electric potential energy decrease? Explain.

Compare the kinetic energy gained by a i :9 ovgq kpo7k.e1l(fvc798z3yaiykproton $(q=+e)$ 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 ld5drq .m8nzg - ex-.plines cross? Explain.

Draw in a few equipotential lines in Fig.hfucd(vd iqwdyb31 xl 0 )/a0, 16 – 31b.

What can you say about the electric field in a 8xt4s2:gso x2irg k;sregion of space that has the same potential throughout?4gki xt sss2;og8:2 xr

A satellite orbits the Earth along a gravitational equipo:w5bz kbf2ft-vxdv ( 3tential line. What shape must the or: vff5vwz- 2b dktb(3xbit be?

When dealing with practical deh5/8b x5gg2yu seah9tvices, we often take the ground (the Earth) to be 0 V. If, instead, we said the ground was /9xtha2u gey 5gb8 hs5how would this affect (a) the potential V, and (b) the electric field E, at other points?

When a battery is conneguwyn eeyn78z x;*tc*u o 23k9cted to a capacitor, why do the two plates acquire charges of theun93wz et8x*ckn2 y ;7 yo*eug same 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, shape, and position o k1wjx s3/v:daf the two conductors, as well as on the dielectric constant K. What then did we mean aj3ws v /k1d:xwhen we said that C is a constant in Eq. 17 – 7?

  How much work does the electric fiezm6 t*b+zo,kn ld 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 2hf9,gkfp f z1field do in moving a proton from a point with a potgz pfkf,21h 9fential 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 jou;tv8lz 5u 3jmdles and eV) if it accelerates through a potential difference of 23,00;8mj vlz u53dt0 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires i)7+d m;enk q,s ysrajtn9b-iia a3h,34 ii5z$7.45 \times10^{ -16}\,J$ 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 pa wfgiocu 4th)kuw/k8,kt1 ( *.sadn5wrallel plates 5.8 mm apart if the 1wchw/ )dant5i wk8 ,ustufk. k4 (o*gpotential difference between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field oflatyqe pn-; l40 *ui5e $640V/m$ 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 connear4m y2p 69rqlcted to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parbxaby .;-rq ;nallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a helium nucl,oauj kdx5 -6weus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, are separated by an airkvb1/i e7miyciag+5qc8nk:z i4g. t 8 gap. How small can the gap gtva4iicy.8: /7eqzk i 1kg 5+mni8cbbe 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 y7.tlxts 2oa*6o5 btf*1 gytrexternal 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 +engr8qa/: tqenergy
(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 5+c )hv f6 ze9oqy)nzjc 2v fc87h1arxis 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (whvi -)t(rb )pyb- yjqy5abte6c at,d.7ich is 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 potehu k2;dm q8:ldntial 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creayfys+q1jqw *)tes an electric 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 footballf*z*gc) w5 qct. This conductor carries a net negative charge,*cqtw gcf5 )z* $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential hd8 7tr08pnc, ,esuew 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 zq 9;hs;uyl )aarranged at the corners of a square of side L as shown in Fig. 17–25. What is the poten z;;a qy9sh)ultial at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from 3 x6mk54t q0jij 2jedja fixed point charge with $Q\,=\,-0.125\mu C$. How fast will the electron be moving when it is very far away?    $ \times10^{7 }\,m/s$

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

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

  How much work must be done to bring three electrons from a great distance amy;c gy(t 131oy3znivlhq* h t/(b,vr part ttc/o1t* yhl,z1(gryvbhnm;iy3(v q 3o $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm north of acg *b v: n(q :0cyqf)wls)kkm*vw. myhj.l6*f $-3.8\mu C$ 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 (ra -25ms r2a kel *ow9m4nnhmowc3(u8o ddius $1.2 \times10^{-15 }\,m$) 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 sho5)4dh*)blo hgqg rbl9 wn in Fig. 17–27. Determine a for5ql bb4grhlo9 *g))dhmula 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 pr ;g7dh 2/gyxjroton (the nucleus) in a circular orbit of radd y/xrghj ;72gius $ 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 proto/e z,vog wl3s/n 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 d8a i 9u.mvy:dtipole 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 0h f:8skf (g f :hsty7:zin-yathe positive charge. The water molecule, Fig. 17–y 0ntf-8gassikf:z (yh:fh7 :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 capacitor hold t ;6:uzch4cfi $+2500\mu C$ 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 ik13xda56v8dsg.yjblktqx: 0kb 6a d(+3 ttccapacitor 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 eyih8:d; f,bg minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential differeo9 sdu+ej,m z6nce between two short sections of parallel wire in air is 120 V. They carry equal and opposite chj,s9d6e+u omz arge of magnitude 95 pC. What 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 is connec7il nlha12y2chi;b;mdxx2:s ted t xhbl1h;:y2dln ci;2sa m 7ix2o a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates have if they are rs a1e7oqj- dp9,+w ol9a3w(hcr l1v dto be separated oj9rdpdal o1,q9 l3a veh s+(-c ww1r7by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increawvy wp2xm4l8 n vion714w-ti7j,o2 sb ses 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 ehmrx yl+df/8)v 5rnu dx.:fkbjx 58($8.5 \times10^{ 5}\,V/m$ 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 oppx mxj:9mud4 6q2(clzbo aa+ogs 6tc)*osite $5.2\mu C$ 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 bepuqeh r7z 9pgl:xnt93r/ (2q ztween 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 charguk+dz uqhad( 3v0y r)dg- txv67l :uo8ed by a 125-V battery (Fig. 17–29a) and then is disconnected from the battery. Wheua ug:+) 7-(u8xtvkrd v0d36ylz odqhn 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 side that arek-/7e3mnw g1:iflh cl separated by 1.8 mm of paraffinlnc gwfiek 3/7l-m:1h ?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circularptuki3p5bm j;b0by- xo9 m 44q plates with a radius of 5.0 cm separated by 3.2 mmo yiu043tp4b;bq 5kmx-bm9pj of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is csdyf,95f vo 6qmd -3awonnected to a 22-V battery. If a piece of mica is placed mf6d9q3 w va -y5ds,fobetween the plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plr.o w),tm bqy4ates 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.*. r)kg5kmeua s m7f,k How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used d,rg0p4rlau-b9-a nl:bi 4-w ponf f5 to shock a heart that is beating erratically. A capacitor in this device is charged to 5.0b9-alba50forp lud - :,fnrniwp 4-4g kV and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electri4dat hj(93sf ou:b 1zlc field 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 aao4zdfshu(39:1b l jtnd of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9b3w ;m u.)aabh-in. pie pans 5 cm apart and connecting them ;m ahab)wb3u.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 fi.wmjw xr;7vj;xed 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 qus+a3v(2e i rcapacitor change if (a) the potential difference is dou3+ sv2 uraeiq(bled, and (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 t-: o/ile;*w tpepk9pqhen 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 cent/p qipet:9 ep-lk* ;ower. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV ind6*a ,i.yal vnk;1sun a CRT. The screen is 30 cm wide and is 34 cm from the 2.6-cm-long deflection plates. Oksidnlv,n.y1 a6 a*; uver 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 from res47 (jtrc5a4mjnm sz o6t acquires 6.3 keV of KE in moving from point A to 64 4s( zc57 nartojjmmpoint B.
(a) How much KE would a proton acquire, starting from rest at B and moving to point A?    keV
(b) Determine the ratio of their speeds at the end of their respective trajectories.   

  A lightning flash transfers 4.0 C of charg6sgg/o+hywx/ c , jd0re 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 Earth’s surface whose magnitude is abouynl+cp 9 yh yv04t4 39t-;pralsmtf t+t $150\,V/m$ 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 vz+ lgdcwa+6 :jolts 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 wl +6gd+j a:zcgravity 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 wq3nc58 iq ke: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 is fully chakw az4t gzm269rged, after which it is dikgw 6z492ma tzsconnected from the battery. A slab 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 exceeds 9svwa( t09p5 z5 ylzkh$3.0 \times10^{6 }\,V/m$. 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) wgl9y98v5cd -q5n vr eas shown in Fig. 17–30. Determine the potential at the l9erdn9q-y5vwc8 5gvmidpoint 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 conis:s*4p9c x ftnected to a 9.0-V battery. If a piece of Pyrex glass is placed between the plates, how much charge will then flow from the ba:piss xc9 tf*4ttery?    $ \times10^{-8 }\,C$

  An electron is accelerat kd 8thb(xp0r0ed horizontally from rest in a television picture tube by a potential difference of 5500 V. It tth d 0(brpk8x0hen 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 what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capacitan5qd*vt;un ye:/w ) aeece $C_1$ 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 faunbh7lls, g9- +o ,+ lz)jddglmyu+:brad is, suppose you want to make a 1-F air-filled parallel-plate capaci,d+m:9ubj-+ ,7o+ hylng z) sgllbuldtor 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 the Earth there c 0ag287 uxy1v5o(mq dy r/ulx w72iisis 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,rr e3afxfu(6 a pulsed 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 potent)slh*/zvi7b 47 u :brxmbb:mfial difference between the Earth and the bottom of the thunderclouds can be as high as 35,000,000 V. The ubfsv/rx:mblmz b4 :7ih)b7 *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 en*fd:-w xzb,ff2l* bak ,awh3w ough 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 powf ,zhf* ,*fa 2:-lbdaxbkww3tential 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 place dx9dw 89lt0v f0wss 0hs-kww5d 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 8;gdxp+op:v j.1-cm-diameter coins separated by a 0.15-mm-thick piece of jogvd+;p:x8p 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 w dad4kv ,-j 7+lcszz easf54av fv53/fith 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 eacmo( drzq:d3u1h other. Their charges are $Q_1$=$Q_2$=$5.0\mu C$, and their masses are $m_1=1.5mg$ and $m_2=2.5mg$
(a) If $Q_1$ is released from rest, what will be its speed after a very long time?    m/s
(b) If both charges are released from rest at the same time, what will be the speed of $Q_1$ after a very long time?    m/s

  Two charges are placed as shown in Fig. 17uhl10 t 6wt*yi–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$