If two points are at the same potential, does this mean tr2 ;0 h1cqqcxjhat no work is done in moving a test charge from one point to the other? Does this imply that no force need be ex qcj;x 01r2hcqerted? Explain.

If a negative charge is initially at rest in an electric field, will it movdk+03dnjjgj7(0h0i +evogj f e toward a region of higher potential or lower potential? What aboutijkd vd0o7 nj0(3ghe +jj fg+0 a positive charge? How does the potential energy of the charge change in each instance?

State clearly the differenc:m6)92q+noi3nt;hpl idjkus e (a) between electric potential and electric field, (b) between electric potential anst i39 n6jouhlmqp+dn2 ik):;d electric potential energy.

An electron is accelerated by a potential difference of, say, 0.10 V. How muc1e,bj1 fufbw;f:0(;qe0 xmi zzwc ;alh gre,zz;0aceje0f wm(:w ;f;b1x1 bufqliater would its final speed be if it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining two equal positive charges b ;jud)6etdh .where the electric field is zero? Where the electric potential is zero? Et )jhd6d e.u;bxplain.

Can a particle ever move from a region of low electric 7mj e-msr.:)ka1 kvxc3cbzs6potential to one of high potential and yet have 3 )mm:bas. kzv -je6r1cs7ckxits electric potential energy decrease? Explain.

Compare the kinetic energy ga;xo7ribo o1 i7ined 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 lines cross? Explafq6e)i.h /fnhin.

Draw in a few equipotential lines in Fig. fk m0z 9j239 rp8ylu;y3slz yk16 – 31b.

What can you say about the electric field in a region of space that n m+6k0 6eohvphas the same potentiav eo+p6h6k0nm l throughout?

A satellite orbits the Earth along a gravitationbf( (bk-3 )+n ctreosial equipotential line. What shape must the or rtbs+cb()e-(3 o fkinbit be?

When dealing with practical devices, we often take the ground (the Earth) to * /: 2qkll8yvyc qp-pgbe 0 V. If, instead, we lvqygk8qpp -c/y l2:*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 capacitor, why do the two plates acquire charo5/du))qw cnt6g0pvo oo8 v;f ges of the same ma/ cup)8wnoft)0qdo ;6 vovgo5gnitude? 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 4nvz dnuuo2;ak 8;hm4 of the two conductors, as well as on the dielectric constant K. What then did we mean when we said that C is a constant in Ehun 2mkon;z d;48 uva4q. 17 – 7?

  How much work does the elhiapo:p a-k;2 ectric 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 i7c* 4tuaq+a )bgryy6gn moving a proton from a point with a po qcr6y+ a4g7)y*ugb tatential of $+125V$ to a point where it is $-55V$ Express your answer both in joules and electron volts.
   $ \times10^{-17 }\,J$
   eV

  How much kinetic energy will an electron gain (in joules and eV) if it accelera/mk6s i:1/ hrmokr -mites through a potential di iri1s-mmrhk/6k: /mo fference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires f:rkr7s7qk wa)dv4u( $7.45 \times10^{ -16}\,J$ 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 fielwgraj-irqene m)t-r s.c)(+ 5 d between two parallel plates 5.8 mm apart if the potential difference bqract-(5r -jse.n))m ier+gw etween them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of im(eo:))8 fanmhdt j. $640V/m$ 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 is1y63z(qrerrvmr 6t,q qv-zt0 $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel pf 9t7nszkw t;( 9evgo2lates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to git(hd28:fem g bve a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, p7m 3wlnfhva8*j9csox 7myx8or bg(a -75;baare separated by an air gap. How small can the gap be if t9x m7sa 7g8 v; apfbr-y7 ho5mx(*jawln3o cb8he 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 exter9b2ayd xi.;a gfu*fcx:7tzo -nal 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 kine7q.55; zuetwdx geli3 tic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton )+ak;pa cyayu4 1me5 cwhose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (whicsa4g1jk5 aunp4 r l*4xh 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 p7h0 lm xq1zk7potential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an evodgk 99s. ;s jf,h.a bp:zz:flectric 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 neg+ j :me,dwbl0t negative cha g :m+b0dlejw,rge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric poten-bfc;xb)x(l g 3z:apqtial 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 sideud0 6,w1dakon L as shown in Fig. 17–25. What is the potential ,a udk0nw61d oat the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from chkz4zg*i x o,z-6, 9*,viu xzdrp5rkrest 32.5 cm from a 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 fromp m0w83:jjkoy,oesy le- 1gd4 a great distance apart to , ed y-0o:4 jplj8ok wey31sgm$1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm nx7z.;fu6kvh e1aw2 ex orth 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 accelera s9mkz +w-sy)jifsi ,97xc8r+t:hugo te 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 d qz49p9nu i)bigylr:9istance d, as shown in Fig. 17–27. Determine a formulryibzgn9lu:9i4 ) 9pqa for $V_{BA}\,=\,V_B-V_A$ for points B and A on the line between the charges.

  In the Bohr model of the hydrogen atom, an electron orbits a proton (the nrnvrd ;zb. lcc2uu*)zw .xl58 ucleus) in a circular orbit of radiu*rl2ccvr5w .u);zz n8d.u xbls $ 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 protc0h8( vs4j*mdyi/xm jon 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 dipole moment xr2+52c m;/,c6 hrollvl2unzx rz ll(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 veo j5o:cl ; z,tlb4ffoufa; p,,ctor, points from the negative to the positive charge. The water moleculcj lo, ,f,4zopoaf:;u5tl;bf e, Fig. 17–28, has a dipole moment which can be considered as the vector sum of the two dipole moments, $\vec{P}_1$ and $\vec{P}_2$as shown. The distance between each H and the O is about $ 0.96\times10^{ -10}\,m$. The lines joining the center of the O atom with each H atom make an angle of $104^{\circ}\,$, as shown, and the net dipole moment has been measured to be $p\,=\,6.1 \times10^{-30 }\,C\cdot m$ Determine the charge q on each H atom.    $ \times10^{ -20}\,C$

  The two plates of a cawqxe, aef s+d5*8nh3io y7,axpacitor 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 holwdtz a 2203ewhd $+2500\mu C$ 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 hrf, i+*+iz,dhyo3 sxv wu0u8m5o z- eoolds plus and minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between t 9jxx i*22dujg1xci1 *aojdm0wo short sections of parallel wire in air is 120 V. Thg* uo d*jicxxi19dmj1220a j xey carry equal and opposite 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 battery when c*j j5e7inpcm7 b)0ab)3h huz it is connected to)p5*ajmz n) hcu 0 bh377cjbie a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates havey -g5zc q4j8* (pn7mive.vfym if they are to be separated by a 2g8* (.mc4yqzj5npem-v 7viyf.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increay-py-hn3brdytx a;13vk g96r5xo xmj yl0:4kses 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 6px-0q7xjd qz$8.5 \times10^{ 5}\,V/m$ 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 qzydmw 5*6tn,$5.2\mu C$ 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 betwee;e;+ef)t wov zn 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 the2 aqu7fij 2qa(n is disconnected from the iaf2(uqj7q a2 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 squ l89rcrzil9;sixa dx 71;9mhxare parallel plates 5.5 cm on a side that are separatez9icrr 9hil9 s xx;d;1 a8lmx7d by 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular platedbmf13)y 1hkcs with a radius of 5.0 cm separated by 3.ck h fdy1b1m3)2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V n +.3/*q bgqzskpltt7 battery. If a piece of mica is placed between the plates, howqt *n/pq3b.+ gtksz 7l much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a paper-sep/i 7hd7q4no1.e gazu0gjoz h/0xhk2y arated $(K=3.75)$ 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 capacito )zi(oyp,lxds ka27 3sr. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator isyj azodbwabn+6g.x upv 6/x5 5;cy x.rerf)2 : 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 capacitance? vcx;26 g y/xj5wban y+u6.pexrr.df 5)b:ao z   $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between two sq fl/+4v0 :o0fx)rfd9bap hlgxuare plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on thlbhxgad f 0f0frvpx/):9l+o4e plates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in. pie pans 5 cm ag +pz9b0 sk b.zq/f,vbmvvl06part and connecting them to the oppoz fzmbq/l b.+0s0kpvbv g ,v69site 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 capac0hl5p0 upfynp6ca-w1d s v)u,itor 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 iywnty*((xh :wh3ua5 mn a capacitor change if (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as the capacitor 5yw3 wyxnm(h:h(t*ua 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 accelerab 0f1/pg2:9d cyiqs mdwa+:k pted horizontally 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 rewd :2 pf/d19si0pby+k c g:aqmach 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 CRT. The screen i:idl.k)/nc hhs 30 cm wide and is 34 cm from 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?h ikh:l)/n cd.    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from rest acquires 6.3 keV of KE in moving frod,yk;ra e1e(o m point A to point o(d,e y; aekr1B.
(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 4uwj/2a6n5 0:ojl stup .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*5xh*z5pt(qz x sci,9kkh7sr k , dt9s 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 qc 8ddy2)-a0 isr.bhtvolts through a vacuum. If a television set were laid on its .bdi8-) s q0hctyrd2a 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 field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough stored energy to heat 2.5 kg /b- e03fsxad gd t(.brm/r)wo 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 ;:n/ ko;w 7jwgdg ei57j6mbiogx rt/0battery until it is fully charged, after which it is disconnected from the battery. A slab of paraffin is then inserted between thi:oedb57n7mk x/or;/ij0; ggww tgj6 e plates. What will now be the voltage between the plates?    V

  Dry air will break down if the electric field excl:kn-.2f go exrls a9+eeds $3.0 \times10^{6 }\,V/m$. 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 equilggccw j( o-wro9 y199iateral triangle (side L) as shown in Fig. 17–30. Dggi9 wr91 c-(wjyoco 9etermine 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 capacitor is connected to9 c7 or**b0epgng sz+e a 9.0-V battery. If a piece of Pyrex glass is placed between the platee+rp0e*g7 og nb9szc* s, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated q;0faw xq;xn;horizontally from rest in a television picture tube by a potential difference of 5500 V. It then passes between two horizontaq;; ax nw;xf0ql 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 capaci+kp qa7nr+anz6t m9g4*7x fqptance $C_1$ 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*brx0dy: z)w*wkung8v 2j 5pl -filled parallel-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 achievu p5* 8)gybxnz0wkjw :vld2*rable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there is an electric fieldnk g03 ea9 aowe2hk k o2m;5js5;kunn: 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 nitrogg n t5190obtc a z:+dhe;4zzeien 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 poten3)i1atg c i8(mpel sp.tial difference between the Earth and the bottom ogipm1c pli38 as)(e .tf the thunderclouds 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) li r 2)2lrv5gwp8 rd4oomght 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 lr84 pmd2 goo)5vrw2r 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 cl9:3dlkjznu fw9fx w:g cn )46m 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-cm-diameter coins separated by0r k/p ceqs, um,ju:nf--h1mg a 0.15-mm-thick piece of eq p, ,f-n/sr1jum0um: kchg- 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 withas. h,z .jap 1u8wgu8f 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 ari n:pld+h 6 9+5sqxw2op85 lclnpln,we fixed 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 witha jp:m)//vk+8 qt hcsk $q_1$=$1.5\mu C$ and $q_2$=$-3.3\mu C$ Find the potential difference between points A and B.    $ \times10^{ 5}\,V$