If two points are at the same potential, does this mean that n 6q,d skxv/5o9s6i yhpt )xy7qo work is done in moving a test charge from one point to the other? Does this imply that no force sqx 7yp)k v9 6sq5hio/6ytx d,need be exerted? Explain.

If a negative charge is initially at rest in afo. h0z/ 7cq-dlzn yz*n electric field, will it move toward a region of higher potential or lower potential? What about a positive charge? How does the potential energy of the char y0olcd zq*-z. fnhz/7ge change in each instance?

State clearly the difference (a) between electri *7g0eg/ zrgubo vtbl0;h(x. ic potential and electric field, (b) between ve*70g xb oh uigb/;zt(0r. lgelectric potential and electric potential energy.

An electron is acceleratedw(cgnmk(v 3.dl+fq 4 p by a potential difference of, say, 0.10 V. How much greater would its final speed be if it is accelerated with four tim p3k+ lqwmn(4(dv.g cfes as much voltage? Explain.

Is there a point along the line joining two equal positive charges k1*epn dw3xz/where the electric field is zero? Where the electric potential is zero? Explanx/d z *3pkwe1in.

Can a particle ever move from a region of lq wo fg)cvp3:u :x*l4l j)dsh:ow electric potential to one of high potential and yet have xqjsuvc*4og:l: hwlpf)d) :3 its electric potential energy decrease? Explain.

Compare the kinetic energy gi +czoru0q nv,ftrjq,8: oo5y9vw/ju1 9u oo9 ained 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? Explaizp mcqvp8p.qamyu66zvo *g2+v85-kan.

Draw in a few equipotential linesiktzl3qr4qid:nm r/p ..)+z s in Fig. 16 – 31b.

What can you say about the electric field in a region of space tai2rq 37 3n8ylgor(yyhat has the same potential throughout?(28oy l aqin 7ryg3ry3

A satellite orbits the Ea .dwsn-a 4i/abs* :nxtrth along a gravitational equipotential line. What shape -da4nbx nsws.t i:*/amust the orbit be?

When dealing with practical device)t(whw5c*s: xwy ghm7e r+3jr s, we often take the ground (the Earth) to be 0 V. I srw3m)wj:g7ye+x5*(h t rchwf, instead, we said the ground was how would this affect (a) the potential V, and (b) the electric field E, at other points?

When a battery is connected to a capacitor, why do the two plates acquire chargp1cce2rp 2ul e 9h9hsh)b; 4ocf w+6a qsmdj6-es of the same magnitude? Will this be true if the two conductorsp 49so+wb- hp2rus d9;6ecahmch1) qf 2 le6jc are different sizes or shapes?

We have seen that the capacitance C depends on the1bjw a) zrw3v(js2dhh +2x4 pl size, shape, and position of the two conductors, as well as on the dielectric constant K. What then did we m zvrp1s xh3wjh+2 2( d)wal4bjean when we said that C is a constant in Eq. 17 – 7?

  How much work does the electric 8if7d8xq + jypfield do in moving a $-7.7\mu C$ charge from ground to a point whose potential is $+55V$ higher?    $ \times10^{-4 }\,J$

  How much work does the electric field do in moving a proton from a point witmygakrj ik: 32g//7 bsh a ykk3sgb :7/m2irj /gapotential 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 ellg +,j3q szo8bectron gain (in joules and eV) if it accelerates through a potential difference of 23,000 V in a TV pqlsob+ gz,j 83icture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires7ip,x+(vups cveqi8, $7.45 \times10^{ -16}\,J$ 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 twwcemcn5 gi7/51zh3b c o parallel plates 5.8 mm apart if the potentgz3n i7b5 mh5 e/c1wccial difference between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of)w/ 5 hrt(llnx $640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field be1,lbt *3 fs rsna*x5petween two parallel plates connected 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 c4fe0m z 1du+ais $1500V/m$ How far apart are the plates?    m

  What potential difference is neededk) (.8 r8pihzj2c bbeb to give 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 u255jqw ,i3imjawdb 5an air gap. How small can the gap be if the air is not t wb jd iuai2jw5q,355mo become conducting by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external forcf ism5 .*zdto2zs,h9x ol d4q)e 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 kfhhnrr+/qxyyu r -;);,jhyg9inetic energy
(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 is 3.2 kzud/3n 8m xge qo+w7t(eV?    $ \times10^{5}\,m/s$

  An alpha particle (wkt:fn*zlbjc7,wd 91t hich 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 electricxt- j 8zkff(3ncc bv3: potential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric pokn;a0tr4 7zmkb/q3ku tential 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 carriboz 6l5tv6c .oa2aet/es a net negative chargeeazt/alt v6.ob2co 56, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric pctd .egv(t5s 7otential a distance of $ 2.5\times10^{-15 }\,m$ away from a proton?    $ \times10^{ 5}\,V$
(b) What is the electric potential energy of a system that consists of two protons $2.5 \times10^{-15 }\,m$ apart — as might occur inside a typical nucleus?    $ \times10^{ -14}\,J$

Three point charges are arranged at the corners of a square of side L as shownv usa(e7 81oin in Fig. 17–25. What is the u e78an1ov(sipotential at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm f 17db-j+mn):qfvu dc nrom 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 electronskon3sb(v5.nwe;; en e from a great distance apart to(v3n. ;n eonb kse;w5e $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm north of 4 r2gv00l3c kxt in,kca $-3.8\mu C$ 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 be5 k4 zum+-6tr(.fp h s1jnk.bt prwjd9 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 swvyol) 4r/m+ 8o 0xdeueparated by a distance d, as shown in Fig. 1m )vo/ wr084edluxo+y7–27. Determine 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 orbits a proton (the nucleuylk kov0-yd:q)7 nl1 ys) in a circular orbit of radius y)n : 1dkl lo7-qvy0yk$ 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 prz zca.ho,p; k.oton 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 jd .-y x)vc+fapotential 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 vector, 9gmo9 *dm yle7points from the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole 9ldemy7gm 9o*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 capac7ikiym:a + cxxvay-n. *e8 xr6itor 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 capjwg: uywv+// dmelld;ol3+mn0 0hoj: acitor 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 plucv.chru 2 7 onvco706hs 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 pal)maq)t.yz )y rallel wire in air is 120 V. They carry equal and opposite charge of magm))a)yy tl .zqnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal fy. aokd+/4) k2pcfxydoxp3 8of a 12.0-V battery when it is connected f/ypo o xcpd)3d2kx k.a+ 8f4yto a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates have if they ayhv)(o+ e ncz/qznpc;r *5td* re to be sepannpy*5 *o +vde;rqzct/h( cz)rated by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increa/-ikck7 jth:xses 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;d s)-zbiw*2+sohp 5halt1k b $8.5 \times10^{ 5}\,V/m$ 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 opposit-oa;n so3)fcklg p( l+e $5.2\mu C$ 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 fies-n box2.qiyvw7/ od( cn(2f sld 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 dv :-37y - l8wngnan/yg x6lxhwokf,2zisconnected from the battery. vka w-8lg / 7xn: o3y6x-n,lz hynfwg2When 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 tr4,vrz vsfyovzb37 c 4ao2*l ;hat are separated by 1.8zo;vay ,l 3zvf*b ovr4src 724 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitanco 7;l/wnh iyzgbd7 pl-889syve of a pair of circular plates with a radius of 5.0 cm separated p;7vgz/y bl n lh7osw9i88-ydby 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V d+ic2r g 6hci7z:k p;k9uy/sabattery. If a piece of mica is placed between the plates, how much charge wih aku7rk+6 ii2 dzc9pyg cs:;/ll flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a paper-sepqp *bo2z;7sp, dr3vu aarated $(K=3.75)$ 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 /0l,j jeo-d2i fssf(b capacitor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is u /d;k dw5psd5rsed to shock a heart that is beating erratically. A capacitor ipd55/ rd;w dksn this device is charged to 5.0 kV and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the el2nb*()d 5d(dodn;-b4n lrafjv-ak oj ectric field between two square plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on (n(vdjfdknoa -dd b-j54b l)2nar;*othe plates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assemblcbr )xgyi 4(0wed by placing two 9-in. pie pans 5 cm apart and connect 0)gry b4xiwc(ing them to the opposite terminals of a 9-V battery. Estimate
(a) the capacitance,    $ \times10^{-12 }\,F$
(b) the charge on each plate,    $ \times10^{-11 }\,C$
(c) the electric field halfway between the plates,    V/m
(d) the work done by the battery to charge the plates.    $ \times10^{ -10}\,J$
(e) Which of the above values change if a dielectric is inserted?

A parallel-plate capacitor has fixeye 7-snyn5 yhfydk ri 50+vj,;.lrx l-d charges $+Q$ and $-Q$ The separation of the plates is then doubled.
(a) By what factor does the energy stored in the electric field change?
(b) How much work must be done in doubling the plate separation from d to 2d? The area of each plate is A.

How does the energy stored in a capacitor change ukay2l /r q74aif (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as the caa4al2rkqu7/ ypacitor 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 horizocfkw1 e-/ )kvfntally 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 reach the screenwk/)ve- fkf1c 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 is 30 x0flv b 2mpq*b dgu(va 38v*1ncm wide and is 34 cm from the 2.6-cm-long deflection plates. Over what range must g (b*xv0*fqvu l3bpmd82n v1a 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 acquires 6.3 keV of ywf--4qm w,8qu;sqa z KE in moving from point A to poiny8q -msfa;w zu q4,q-wt 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 transfer 7j:qd fpj8h+ts 4.0 C of charge and 4.2 MJ of energy to the Earth.
(a) Across what potential difference did it travel?    $ \times10^{ 6}\,V$
(b) How much water could this boil and vaporize, starting from room temperature?    kg

  There is an electric fielts*be).ve k) h9s fv4rd 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 tube, electrons are accelerated by thousdl( mnf.df-zg8e07 khbhmb 8i+ -; qieands 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 rem-h l;bbe(0 8fdqh zemgm+f7i 8i-n.kd ain 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 of wat8pl zgaic4t-p9-v /mgsy1s p0 er 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-xcc3 acg (hh zx6jh: j)u+5g;lV battery until it is fully charged, after which it is disconnected from the battery. A slab of paraffin is then inserted z h3(lhh c6xcjxj5c+g)au g;:between the plates. What will now be the voltage between the plates?    V

  Dry air will break d48+a wvo 29imquf yuf-own if 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 of an equilateral triangle (side L) t)27ehmkq d abjq(00las shown in Fig. 17–30. Determine the potent jab)q72h leq0dkm0(t ial 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 issvbm,hsqq/8d y;yp9o ax h0-e msf: 62 connected to a 9.0-V battery. If a piece of Pyrex glass is placed between the plates, how my : hs d y209s,q 8-ae6phoxqfv;msbm/uch charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horisbbjxqk /lxn8e**- 1j zontally from rest in a television picture tube by a potential difference of 5500 V. It then passes between two horizontal plates 6.5 cm long and 1.3 cm apl18/b bj jqxexs-** nkart 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 capacir:,flzp**o 2u ptx2 s:xtac0n g*d0sg tance $C_1$ 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 9 ydmg fk:2mc0to 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 plates? Is this practdf0gm2mky c9 :ically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there ispmp 9 ovbi1z3/ 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 ni/ r6-yjr xhjxpy a73jxk9;k5la )3 qvttrogen 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 Ea g itr;(yr3)jhrth and the bottom of the thunderclouds can be as high as 35,000,000 V. The b)yjg( ithr3; rottoms 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 enough energy to sob)- 6f6xfqk0pqq qk3 nme electrons in barium metal to eject them from a surface q )b -66qkn3qfpqx0 fkat 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 3ceeizm h +r;f ju /m5l69n:hi( jx4.he6 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 1.1-cm-diameter coins sepa2qr+i iw/9zkqn;n; yf rated by a 0.15-mm-thick p;n9 w/f2yqnz i+i kq;riece of 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/ rnq0o q3 4xurjl7i+v with 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 v ox: imwz- c.g5oe6.ifrom 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. 17zt)xmuy./ s3 ;v+ uw wimwyzjvb.6 r+)–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$