If two points are at the same potenti+dh-/6c efws5cbhnkh a 5bv7 *al, does this mean that no work is done in moving a test charge from one point to the other? Does this imply that no force vh*bbc7hhfwnkd -a5 6c+5/esneed be exerted? Explain.

If a negative charge is initez d 9e sgyt:1tl-ga0is w;z-;ially at rest in an electric field, will it move toward a region of higher potential or lower potential? What about a positive charge? How does the potential e1s-g e0l-ad 9ie gtyzzw:;s;tnergy of the charge change in each instance?

State clearly the difference (a) between electric potenti v)e ml3/ggay+al and electric field, (b) between electric potential and electric potential energy. g 3layvgm/+)e

An electron is accelerated by a potential difference of, say, 0.10 V. us ;-eove631bxos1w 3,rvvf;;fsyytHow much greater woultbs ; xrfvy3wyv1, euo;o6fv-s3 ;se1d 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 chay cn9jyqsmz 1r0(:n4mrges where the electric field is zero? Where the electric potential is znr nyy4 sz90m1(jm: cqero? Explain.

Can a particle ever move fv;uq s*9 hd+jsrom a region of low electric potential to one of high potential and s v*q+sd;huj9yet have its electric potential energy decrease? Explain.

Compare the kinetic energy gainea(p bs-z dyt(073bkccd 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? Explaiw t60)tm kaaihj2)-ae x,x)san.

Draw in a few equipotential lines in Fig. 16 – 31b1bwll5fi 3ime )rpis;1+ xt; c.

What can you say about the electric field in a region of spa5 .s(j,idhzz1by*t2m6g znn nvmg;3-p l 1nphce that has the same potenzg21hbdn,3*sljhzznp.nv1y (mg i; m 56-p tntial throughout?

A satellite orbits th i(eazmnv9x - /wrmr3*e Earth along a gravitational equipotential line. What shape must the orbit b mrne*-a r vi3(wxm9/ze?

When dealing with practical devices, we often take the ground (the Earth)ob61 s: cvnd70mbr *bw to be 0 V. If, instead, we said the ground was how would this affect (a) the potential V, and (b) the electric field nrwbv7co *m b1 bd0s:6E, at other points?

When a battery is connected to a capa8c y;pzx3 8m 4yqbjn*gcitor, why do the two plates acquire charges of j c*yz4 q; n3y8mp8bxgthe 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 s ;-datj6no0ks 85rmg dk:k+ohize, shape, and position of the two conductors, as well as on the dielectric constant K. What then did we mean when we said tm:5ho+ g ok8a6sd rd0ktk-;njhat C is a constant in Eq. 17 – 7?

  How much work does the electr)w myb kx2wk:)ic 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 electri5h b3 z+(wm*tc ftzw3kc field do in moving a proton from a point with a potent3wbt*zfm+ztw c(hk35 ial 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 job6t +rum3+xz -eoe/oyules and eV) if it accelerates th-6e/m+e3 o b rxuyozt+rough a potential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires 1dn ryd3:kc7 l$7.45 \times10^{ -16}\,J$ 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 elec/ 6g n8xu8v ckg1hzvjx2-5 dgxtric field between two parallel plates 5.8 mm apart if the potential difference betwe82n8-xughg 5v vcxzx6 d1jg/ken them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of d80xqf s11c x w uxcpxr,/l:,h$640V/m$ 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 connectedk6 w-kg5e 4yp(t zxq1b to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected to a 45-V battery isy3ad*.5(e n fp. ksvhd $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to giveow o5 3qitb.2k a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, are separated by anyybjm/:28 owag tf)q2 air gap. How small can the gap be if the air is not to becow2oyt8qgm2 abyj) f /:me conducting by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force to move a by/l(djc t- 2v5tz5xm$-8.50\mu C$ 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 kine3yb(pcnr/ev)a nk2hy3m4l 0 sgj( d 8ytic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whose g ousfu+s,r m aa;+z,w(zi27pkinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nucjqoi6.sv2d: l leus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric p t cp48uc0 zy epuxq*j41obfv-tp926wotential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric poteo h1i q)cs0gd9ntial 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 yij066)q nqskm9r ps1 net negative chary0 ir916nk)sqjsmp6 q ge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a distanyv8 dz-j-a qu1csl9x -ce 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 qai(c*g;3 .sh errym:shown in Fa3ir:.srme ;( gyqhc*ig. 17–25. What is the potential at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed point charge wiq6k ga rh+rbe3: j1s5jth $Q\,=\,-0.125\mu C$. 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 donedbx7,.bq5wdgd2 z m a. to bring three electrons from a great distance apart toaqdmw5,72..b dgbz x d $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm o1ma l7m/l1l0x+ lxpdnorth 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 (radiusz5ilusf w5 g l:poa0aofo0(jsqqp: .5o(6* de $1.2 \times10^{-15 }\,m$) 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 dispa x 6c2tf.j7ttance d, as shown in Fig. 17–27. Determ.7ac j 6t2pxftine a formula for $V_{BA}\,=\,V_B-V_A$ for points B and A on the line between the charges.

  In the Bohr model of the hydrogen atom, an electron ssha+4*/ 0 stz+ekmz morbits a proton (the nucleus) in a s s *mz/+ms+e0 tzakh4circular 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 protone k,, 4gz* p2zdhh-r9+omsii w 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 whosaal(/pl w- 7nnv yx)l6tf:a; *p0brbye 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 4icmu1qym6fd x -ym) *vector, points from the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be considered acxm )1*qiy dym4 -6mufs 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 c8qft5 k0t:47g hqams gapacitor 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 capaci/ ceylk x0 lhn*6laus3s- i1(ltor 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 h. *9x*n immuooolds plus 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 parallel wire;zcgy71o90; alya/:wer3;s g hdk boy in air is 120 V. They carry equal and o7;y ;arbe a3 yl k1so9;hz0ydogwcg /:pposite 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 it is conne4-)quig7 kpaz/ jm sv+ctedqj)gm4/ -u pkiav+zs7 to 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 to by- pat 7y skw8w8 g9; lap0z6lo-r0dvge separateza87g 8-st wp;ldglwo6ypvra k90 - 0yd by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increase gz3m1ktrd) :0i bibq 7qg7.vls 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 l9j)c-mmw qh dfot,,7 $8.5 \times10^{ 5}\,V/m$ 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 op d3+jm*f ie;/u4kqylt 0 bfn) tdml0;hposite $5.2\mu C$ 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 bet+uyzakshuir kt 7/- 0(ween 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. dd tqci9x4t(r( q 7dh*17–29a) and then is disconnected from the battery. When this capa97( d*r ixt(q4hd cdqtcitor $(C_1)$ 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 sc9hk/c 2pvgpg sj cf69 m;jc*-ide that are separated by 1.8 mm of/;ppc2vsmf k*99g 6g jjccc -h paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a p tn:9ka l+4gjk7jly;mair of circular plates with a radius of 5.0 cm separated by 3.2 mm of mica? nal j4 ylj;m9+k gk7:t   $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. e8 ix30vk1jtf 5bdlj9twmb)4u ztpbn7) oc:9If a piece of mica is placed between the tb0k w 54)e 3tc vod)mflj9t7pibjn 8b:uxz 91plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plb ol ;ll l5mlo(,*am28.qgoujates 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 2kg8d2f :mu 3nh200-pF capacitor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator qyxdv 7/jf9 lg*( -xbp1g otl-is used to shock a heart that is beating erratically. A capacitor in this device is charged to 5.0/ g(l jo1x-* t yblgf-pvq7d9x kV and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between two square plat 0vii1u ug()g5wff. hees, 8.0 cm on ag(e.i uh 0uvf)w5f1ig side, 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 assem esxkqt *pxx 65zf,v7;bled by placing two 9-in. pie pans 5 cm apart and connecting them to k;v 6 f7xszxtxp*5,qe 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 fixed charges;frjo3his+bt;3 55,zvnqc n j $+Q$ 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 capacovy/.sk-k 8d eitor change if (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as ksvkeo -.8dy/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 then pavp ow*or3t;s/5fbu3 fss 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, 1f /;rp*boouf3vt 5sw31 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 is 30 cmomh *ns; d(sl(pc58p7 /cyfmu wide and is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizontally deflecting elem5c *hsdlo/c7fy8 npu; m(p(s ctric field vary to sweep the beam fully across the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from rest acquires 6.3 keV of KE in moving fromj bjyy* *1 p0ak 10ek2q8gxxoq n+fms0 point A to j+2y a8jeb0o*fm0x*q gknkq01p ys1xpoint 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 og xj;-ea.dczb2k*+ -nxu 2jzqf 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 Earth’s surface werl;729 +fife ekns9 hhose 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 accq(lby-44w d q,p /xnxcelerated 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 gravl,bcpy4 4nwqx/ xdq(-ity 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 oy+uirbj k55p0f 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 vod;i6 8i 8h8tx:2ir;vrihn sis fully charged, after which it is disconnected from the battery. A slab of paraffin is then inserted between the plates. What will nohiivtd 8nhv6 8 8x;ri2;:roisw be the voltage between the plates?    V

  Dry air will break down i)d y)o1l9aw yc/) jseef the electric 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 oc,t b a..s2**rhdufmi f an equilateral triangle (side L) as shown in Fig. 17–30. Determine the potential at the midpmi d.ft.u ca*rsh*,b 2oint 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-V y63wjpt+5 ihsbattery. If a piece of Pyrex glass is plyijt5s63wh p+aced between the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest f(hx+kbto,) o 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 apart that havo)(t+xkfbho , e 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 capac8d(1 /1veax ebf f7y4w6wftjmitance $C_1$ 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 ac+ib+ uvp zdezm3-s3.mo- :mto make 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 would the gap have to be between the plazdm3e+-p+: a i.3bmumz s- voctes? Is this practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the E3eg. c5 vvfueil1t.d r8+b sxap1rc2) arth there is 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 a pulsed nitroge il.tuaur3di 3:x5s y;n 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 between the Earth and a1p l:ph8qoq /the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the t8oql :1papq/hhunderclouds 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 (m iy:,(oryf2btp6 pp(UV) light provides enough energy to some electrons in barium metal to eject them from a su((pp,pboi6 yt :rfym2rface 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 2qjc.6knd9 yg 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 by a dleq/sh. l m :h6o9yv zsfy6.7z*8taz 0.15-mm-thick piece of papel6al9md/zehvs qfz zs.*:y.h8y6t 7 o r $(K=3.7)$ 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 witawqb )n ctn.e6zdsg+gu v*u:9 (,pd1xh 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 0 3(nwbl9utfknh/. p weach 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+ gsz1fxbcs24 as shown in Fig. 17–35 with $q_1$=$1.5\mu C$ and $q_2$=$-3.3\mu C$ Find the potential difference between points A and B.    $ \times10^{ 5}\,V$