If two points are at the same potential, d: ia8 d3ys5e7mwb cl*does this mean that no work is done in moving a test charge fr5bwmaei* ly dds:3c 78om one point to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at rest in an electric field, will it move tow7d vd,t-4mt )ndzcue 7vzh0i5ard a region of higher potential or lower potential? What about a positive charge? How does the potential energy of the charge change in each int,vzc )zd mnddtu-40 77vhe i5stance?

State clearly the diff of w/5*bwi;cgerence (a) between electric potential and electric field, (b) between electric p5/*wbo;fc wg iotential and electric potential energy.

An electron is acceleratw(pt) +1:vmn4zu vb qsed by a potential difference of, say, 0.10 V. How much greater would its final speed be if it is accelerated with four tvbqz wn1mu ps+: (v4t)imes as much voltage? Explain.

Is there a point along the line joining two equal positive cr4k0gd( cu o+3v1iuban t/5o jharges where the electriu3gb40dno1v +kit c ua/j5o r(c field is zero? Where the electric potential is zero? Explain.

Can a particle ever move fre6/ imxy z()kk k.aus,om a region of low electric potential to one of high potential and yet have its electric potentiamekya xu,kikz/6) (.sl energy decrease? Explain.

Compare the kinetic energy gained , dpop :ui2zmiv:50 qoskut)3by 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 lines cm,qfdkvm (nj*4g98 pgq e gl-)ross? Explain.

Draw in a few equipotential lk xj( fjxlkt/0lr+*;ph6baa1 ines in Fig. 16 – 31b.

What can you say about the electric field in a region of space that has the sa+ 7j5pz(okjyu z0gqg) me potential throughouj+ zg g5j y7kq0ozpu()t?

A satellite orbits the Earth aloj sxu 5*g+tha:ng a gravitational equipotential line. What shape must the orbit begt:*hj ax su+5?

When dealing with practical devices, we often take the n+u :nrvr, v5cground (the Earth) to be 0 V. If, instead, we said the ground was how would this affect (a) the potential V, and (b) the electric field E, at other poiucr, n vnrv+:5nts?

When a battery is connected to a capacitonb0(dnvv(k s4r, why do the two plates acquire chargessnkv bv ((0dn4 of the 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 )g fdn k:dt *uv/p,ta/of the two condug akt:u/ p),*vf/ddntctors, 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 field do kjy09t1r;yh3 ow j.nhqi sa4 2in 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 electt+oaf, vw -j /e atjm6v;63rgfric field do in moving a proton from a point with a potentif, o vttaj-+fa6gj/re;vw 3 m6al 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 a 0 s.8sivduxk poee -m-;ra2a)n electron gain (in joules and eV) if it accelerates thp-s;0s.ad-aie koxr)e m8v2u rough a potential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquiresbep - p2q)gcwif -74lt $7.45 \times10^{ -16}\,J$ 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 mmrab7y,n-eudzp -hb euy5,pc0q : n)l1 apart if the popuyq- bleun 075,hcbpn) re yz: -1ad,tential difference between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of mt;rr 7t*,ejv $640V/m$ 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 batosedaw. 1bz9q, 3ym ogh72s3etery is $1500V/m$ How far apart are the plates?    m

  The electric field b50ly ,l5+n+tqz xyvtzetween two parallel 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 nuc om95 l0 zkbhvawogd(638* uekleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, a(u ihm)w 69uorre separated by an air ga (m u9rwh)i6oup. How small can the gap be 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 exte-j7lkm s.p9pn rnal 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 wit5cw+ ourw,5tj;q6 to; 1htrjm h 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 4lorjs659hqy kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a h6 /nyv/u *pgo0ou f(6nw 4wirxelium 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 simh)nb:h1l 1w2t fy8cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an eledwr9,j 4g5nprctric 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 football. This conductor carries a net neg0ru2,p e p-whwh ley4rh1 r4h:atie1:-p4h04wrph e r ,ur2hlyh wve charge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a distance o:5*.* c ftk1 aujdmag1lm ,epgf $ 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 of3l9yk,/m eozu h 7omd4 side L as shown in Fig. 17–25. What is the potential atzl ,y3dmhm 74k9u/eoo the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed poin(1er,9 et;jpx6 7viq bd5wb het 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 epydc;kt1 8lj/ *htp+ electrons from a great distance apart khj8tp *ly;p+e/t c1dto $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cetf6ud 6nrcjfzj)q71tj 85 y1m 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 bepa 3+nrg pr23l8r.rte used 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 sephpfe jr1.sy)5 arated by a distance d, as shown in Fig. 17–27. Determine a formula s)hp5f.rj1 ye for $V_{BA}\,=\,V_B-V_A$ for points B and A on the line between the charges.

  In the Bohr model of 895szqttu1:cmn/x,lx ly p ;rthe hydrogen atom, an electron orbits a proton (the nucleus) lcl8 ptz;y q9/nrt,s:u 1xmx5 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 proee dhe)v +p,b f98mrx+ton 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 potent(+o(6 o a 6xxts,u2d. 8dtvhoadr/5ql* vvak hial due to a dipole whose dipole moment is $ 4.8\times10^{-30 }\,C\cdot m$ at a point $1.1 \times10^{ -9}\,m$ away if this point is
(a) along the axis of the dipole nearer the positive charge;    V
(b) 45° above the axis but nearer the positive charge;    V
(c) $45^{\circ}\,$ above the axis but nearer the negative charge.    V

  The dipole moment, considered as a vectorpeiz;a1 myz e);xrr *6, points from the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be conside rpzx*em z)rei1 ya6;;red 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 cap,+x. gr */xaghnuv4 xjacitor 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 hmjq9 b+rp2e*qold $+2500\mu C$ 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 plucr7634ec3uh x wd xnc2p:8 ezws and minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of parall(uo; 8 8gjgyneel wire in air is 120 V. They carry equal and oe8 oj(;g8gunypposite charge 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 batg -gf :::krpjwtery when it is connected to akr:w: g-j gfp: $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plab jz jq8c d qi/sv18*:pxy 26:ur2wfjstes have if they are to be separated by a 2.2-mm air d/riw8 2*zjj yx21 p v:ubssq8j:fq6cgap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor incr;(t zc,r/.n h1be jg 8-ozoh;nhzgy*keases 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 r2 p*gv.6z odd$8.5 \times10^{ 5}\,V/m$ 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 jh5vf1m* p-oo s cluzrn5; 93l$5.2\mu C$ 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 el.1 vgj:r-yq;l s(xs wyectric field between the plates of a $0.80-\mu F$ air-gap capacitor if they are 2.0 mm apart and each has a charge of $72\mu C$ ?    $ \times10^{4 }\,V/m$

  A capacitor is charged by a 125-V battery (Fig. 17–29a) and then is disconnectb/t f 5d4gaj-ted fro g4j ftb-tda5/m 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 square parallel plates 5.5 cm on a sid zv.7q1umhy;-by2 teje that are separated by 1.8 mm of parav2 .ymhub je1tzq7;- yffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plateqc9(1mx(ig ; pkxfp3e ;a mpg/s with a radius of 5.0 cm separated bm ep1gp k93f m;; x(gi(/qapcxy 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected tvj jof1. e*7zxo a 22-V battery. If a piece of mica is po.z17e* fjj xvlaced between the plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a paper-se 5(jlri10m*ry nro el2parated $(K=3.75)$ 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 storeev 40v ndtbcu7 /24* zw:syh )d2jybjnd?    $ \times10^{-4 }\,J$

  A cardiac defibrillat/8hza 5 +madzlor 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 energy. What is its capa5 /d8azzam+lh citance?    $ \times10^{-5 }\,F$

  How much energy is stored,eug7. fj/ vs/fq h+rj by the electric field between two square plates, 8.0 cm on a se ug,sh7f/r j/.qf v+jide, separated by a 1.5-mm air gap? The charges on the plates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled m0)k e upanq/)mm;r1t by placing two 9-in. pie pans 5 cm apart and connecting them to the opposite terminals of a 9-V1/ )rq m; m0)epuamtkn 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 fixed chargetop2(7f)y g .otvy0y ts $+Q$ 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 potential differencxjk; o9 +gdr/ze is dx;zkg/r d9o+ joubled, 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 ux)jmxpvx)/l2uj) 7x -gg/s st mv:m 7kV. They then pass through a uniform electric field E for a distance of 2.8 cm, which deflects them upward so they reac ) x/7x-jxtu l2ssg/:mvumg )p 7m)jvxh the screen top 22 cm away, 11 cm above the center. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a wqb 1dl+e31r r6zmor1CRT. The screen is 30 cm wide and is 34 cm 6 l1redrz3+mbr1q o1wfrom the 2.6-cm-long deflection plates. Over what range must the horizontally deflecting electric field vary to sweep the beam fully across the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from rest a:ro lnp-kfdx:ua60i s,w .x re qg9q,c0tnt-3cquires 6.3 keV of KE in moving from point A to point B. q- kte0os,u fx: n39r:,rdi ngt 0p-ac6ql.wx
(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 MJ of ebko n7m 0p+eg;nergy 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 field5vv+/f:iv5b:ry ua73(u z4at q pq npq 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 tubn:bao .o*h+e6z pc.aga .d;lie, electrons are 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 an electron would remain stationary? Assume that the electric ilp *ohb .+a6g.c:.dae; onazfield is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough stored energy to heat 2.5a8 1/q4wmdkjpc iswpqv;;b 9wt/z+ 9b kg of water from 21$^{\circ}\,C$ to 95$^{\circ}\,C$. What is the potential difference across the plates?    V

  An uncharged capacitor is f5i9*3i dta q e9zecux.i:k: mconnected to a 24.0-V battery until it is fully charged,z t3ke .9a9d:c:fqi ui emi5x* after which it is disconnected 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 electriy9apb o b62p+ iihv39yc field exceeds $3.0 \times10^{6 }\,V/m$. What amount of charge can be placed on a parallel-plate capacitor if the area of each plate is $56cm^2$?    $ \times10^{-7 }\,C$

Three charges are at the corners of an equilatera usx8mjpej k7::5vxe /a9gkn)l triangle (side L) as shown in Fig. 17–30. Determine the potential at the midpoint of each of 9nav5 u8:/jxg:pk)7xkmejsethe 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 t+gk8uxjy3dh(.ahgao 1--- dl tr jjj*o a 9.0-V battery. If a piece of Pyrex glass is placed between the plates, how much charge will then flow.h3r(ul j -*g-o khx1ga8djyjdj-t+a from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in a television picturelqyur oq7k65,cg3:wu tube by a potential difference of l q g6y3c:75,k qruwuo5500 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 what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capac3y99 alt6ccpk 0 a1ghritance $C_1$ 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 mq)e0.w4coti40 u5tnsv jd we/ake a 1-F air-filled parallel-plate capacitor for a circuit you are building. To make it a reasonable size, suppose you limit the plate area to What wou 0q)u4 w5ven0t e 4/d.oicjtwsld 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 field of apu5t1 t/*bb9h euujx ejm(c) -bout $150\,V/m$ 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 4g0q6: mb ujqt; +y dsgf6t*jta 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 potential difference n3b*hrdf3 f46 bmtu1 lbetween the Earth and the bottom of the thund6rbf hmfu43b13 *tnlderclouds 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, ultravio :opt9um5:djbh z po)golsx ts;)g8.0let (UV) light provides enough energy to some electrons in barium metal to eject them from a surface at high speed. See Fig. 17–33. To measure the maximum energy of the electrons, another plate above the barium surface is kept at a negative enough potential that the emitted electrons are slowed down and stopped, and return to the barium surface. If the plate voltage is 0)p:d:xu9gjso)o .op8thg t;bmlzs 5$-3.02V$ (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 k/ql-jzvtb;m: e w*z* 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 1.1lq-rw:4rmsm n 8x 1l .oa2,hyq-cm-diameter coins separated by a 0.15-mm-thick piece of po8.4am:1 n 2-rhxsql w,yqlrmaper $(K=3.7)$ 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 witvp ow5pm c4g5q-vza id3 l;bfqr: k727h 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 fis7/5*wg 6vv7brwug9arbgzv j. jw /c)xed 4.0 cm apart from each 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. 17–35 witqom f,o*yrlr4ka 1i:0h $q_1$=$1.5\mu C$ and $q_2$=$-3.3\mu C$ Find the potential difference between points A and B.    $ \times10^{ 5}\,V$