If two points are at the same potential, does this mean that no workw,r i0vm(1ayn ; 3wdcy is done in moving a test charge from one point to the other? Does this imply that no force need be exercwmvyd;( 0i 1ny3, wrated? Explain.

If a negative charge is inm z+oo4s c;eg 8g;1ujhhu,3elitially at rest in an electric field, will it move toward a region of higher potential or lower potential? What ah he1jz co;go;gmu3usl 4,+8ebout a positive charge? How does the potential energy of the charge change in each instance?

State clearly the difbj-kd 4h )geve *+ihq,(1dn5 t/;gp )uqgmkwlference (a) between electric potential and electric field, (b) between electric p-gpke ;bjdh q5h+num d)g4 )ti/(l,*qgw 1kevotential and electric potential energy.

An electron is accelerated by a potential difference of, say, 0.10 usmza83k)f6pr r7;o vpjki a1a5+h4qV. How much greater would its final speedf1k3+6) pa k48uoqj 5ip ;a7avhr mszr be if it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining two equal positive cxuw kgxq,3:o 6harges where the electric field is zero? Where the electric potential is zero? Exp, :oqxg ukwx63lain.

Can a particle ever move from a ref l3- g3y mmil-.nrtjb(dr(i(gion of low electric potential to one of high potential and yet have its electric potential energy decrease? Explain.dr.tgmyb (j li (- mn3-(fl3ir

Compare the kinetic energydbb 5n +shj.tnaf9d2v148ix z gained 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 $\overrightarrow{E}=0$ there? If $\overrightarrow{E}=0$ at some point, must $V=0$ at that point? Explain. Give examples for each.

Can two equipotential lines cross? Explain.rngd --hy,rsdif)p 1,

Draw in a few equipotential lines in Fig. 16 aa db, 5p* y,axd8bixo;q(l; f– 31b.

What can you say aboutmrspt/e,0l 0ns 1f27sb id/a b the electric field in a region of space that has the samefim071//dstr ,0spa elbn2bs potential throughout?

A satellite orbits the Earth along a gravitational equipom o)rfxx80uklk*p6 v1qo 5xq2 tential line. What shape must the o)6 8mq5x0kk1 prx2q lofxuo*v rbit be?

When dealing with practical: yf;nh mfq ),)yqqek: devices, we often take the ground (the Earth) to be 0 V. If, instead, we said the ground was how would this affect (a) the potential V, and (b) the yf,: qk mq) fhqy;e:)nelectric field E, at other points?

When a battery is connected to ax; hpcqpnm/:rek.x cd(ax7x /h 0+zj5 capacitor, why do the two plates acquire charges oam;x5k/ qz 7 e.xxphncdc+x0 p(/h:rjf the same magnitude? Will this be true if the two conductors are different sizes or shapes?

We have seen that the capacitance;elzbaqja8 *szy3s)h hx;5 3s C depends on the size, shape, and position of the two conductors, as well as on the dielectric constant K. What then did we mean when we said that C is aayh 8s s;h xq lzzejb3s3a5;)* constant in Eq. 17 – 7?

  How much work does the electric field do i8 uybk.b 2r1 9llope5on moving a $-7.7\mu C$ charge from ground to a point whose potential is $+55V$ higher?    $\times {10}^{-4}J$

  How much work does the electric field do in moving a p1u d9yin:xe(oroton from a point with a potential of(9ynu:x 1eoi d $+125V$ to a point where it is $-55V$ Express your answer both in joules and electron volts.
   $\times {10}^{-17}J$
   eV

  How much kinetic energy will an electron gain (in joules and eV) if ibp+(-*2gki ad9:n ctsi1avw nt accelerates through a potential difference bw-gvin 9n2:( 1 s+ct*aaidpk of 23,000 V in a TV picture tube?
   $\times {10}^{-15}J$
   eV

  An electron acquires ,s 1zh)kv7p nn:uj/vn is9/sg $7.45\times {10}^{-16}J$ 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 platesfyk8 c3a1u vn26 7 fhde+z -ayfs;r5dw 5.8 mm apart if the potential differe;dnh8uff6az3c 5ref7kswa +2 -yvd 1 ynce between them is 220 V?    $\times {10}^{4}V/m$

  An electric field of 5p gx 1.( sltl)yflq42hcu)ho$640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two pa- i*e jiaaxxz4xp-t.6 rallel 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 batvafd i7+uvpjw.n ,l. *tery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed t j+ki:8r1ia dun), m, dfa3+otto8bkto give a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $\times {10}^{4}V$

  Two parallel plates, connected to a 200- 1q rl vc4+j:ylmll0d99 kwm6wV power supply, are separated by an air gap. How small can the gap be if the air is not to become conducting by exceeding its breakdown val9 60lymd4 lq 1:lwjm+9rvcwklue of $E=3\times {10}^{6}V/m$?   $\times {10}^{-5}m$

  The work done by an external forces meqs)zbhbx- :i4m7( to move a $-8.50\mu C$ charge from point a to point b is $15.0\times {10}^{-4}J$. If the charge was started from rest and had $4.82\times {10}^{-4}J$ 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 e:g-/yb0q. bnthzvkkeb )s5*f o* w lm(lectron with kinetic energy
(a) 750-eV,    $\times {10}^{7}m/s$
(b) 3.2-keV?    $\times {10}^{7}m/s$

  What is the speed of a proton whos ejb pv1j,08qr0v3kl le kinetic energy is 3.2 keV?    $\times {10}^{5}m/s$

  An alpha particle (which is a helic ( yj-dj qgum.yu9(m6um nucleus, $Q=+2e$, $m=6.64\times {10}^{-27}kg$) is emitted in a radioactive decay with ${}_{KE}$ = $5.53MeV$ What is its speed?    $\times {10}^{7}m/s$

  What is the electric potential 15. jh9zg ;ig,)7sdymt;n; st 3,wrpwyk6 0 cm from a $4.00\mu C$ point charge?    $\times {10}^{5}V$

  A point charge Q creates an electric potentiagy2h ee+jphn 1zk6we; p ag61-l of $+125V$ at a distance of 15 cm. What is Q?    $\times {10}^{-9}C$

  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 ozhtnlcof4zq1 5:; /hfootball. This conductor carries a net negative charge oc:h/l5fqon z; 1zth4, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a distance ofnxv2u9dc7w / k $2.5\times {10}^{-15}m$ away from a proton?    $\times {10}^{5}V$
(b) What is the electric potential energy of a system that consists of two protons $2.5\times {10}^{-15}m$ apart — as might occur inside a typical nucleus?    $\times {10}^{-14}J$

Three point charges are arranged at the corners of a square of side L as o2 * v*jq7qiuzdvk5 2og3a j+dshown in Fig. 17–25. What is the potential at the fourth corner (point A), tako z*q d2j au2q k+7dv5gvoj3*iing $V=0$ at a great distance?

  An electron starts fr+ gp/0byuol +qom rest 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?    $\times {10}^{7}m/s$

  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 fh :c b;tu3cdma) k4t2erom a great distance apart tdca3t 2e):h 4mc t;bkuo $1.0\times {10}^{-10}m$ from one another (at the corners of an equilateral triangle)?    $\times {10}^{-18}J$

  Consider point a which is 72 cm north on-efpcx 17d (a vu8vk4watz: 0f 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) ${\overrightarrow{E}}_b-{\overrightarrow{E}}_a$ (magnitude and direction).
   V/m
   ${}^{\circ }$

  How much voltage must be used to accelerate ac 9 i+eed:/ne(y knn:u proton (radius $1.2\times {10}^{-15}m$) 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 $3.6\times {10}^{-15}m$. Assume the potential is that for point charges.    $\times {10}^{6}V$

Two equal but opposite charges are separated by a u2,0fzyvuj 59isc1v-uw 5 vw rdistance d, as shown in Fig. 17–27. wc v v,z5 1juufr05 vys2-u9wiDetermine 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 orbs 6v qa / mi8 fh)1dsioxgk//g(4rpc+gits a proton (the nucleus) in a circular orb8msga(fr/p1v go)kq /ici4hs d 6x /+git of radius $0.53\times {10}^{-10}m$.
(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?
   $\times {10}^{-18}J$
   eV
(c) What is the total energy of the electron in its orbit?    $\times {10}^{-18}J$ $\approx$    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.   $\times {10}^{-18}J$    eV(Round to the nearest integer)

  An electron and a proton are 7bde./pxfr i/6wy)an $0.53\times {10}^{-10}m$. apart. What is their dipole moment if they are at rest?    $\times {10}^{-30}C\cdot m$

  Calculate the electric potential due to a dipolht8gmg./n:. otmmc qeb - (k6je whose dipole moment is $4.8\times {10}^{-30}C\cdot m$ at a point $1.1\times {10}^{-9}m$ away if this point is
(a) along the axis of the dipole nearer the positive charge;    V
(b) 45° above the axis but nearer the positive charge;    V
(c) ${45}^{\circ }$ above the axis but nearer the negative charge.    V

  The dipole moment, considered as a vector, points from the negatbaq-6ax(( e9tjm ao(tive to the positive charge. The water mol9q( (t6ao teaxmj-(b aecule, Fig. 17–28, has a dipole moment which can be considered as the vector sum of the two dipole moments, ${\overrightarrow{P}}_1$ and ${\overrightarrow{P}}_2$as shown. The distance between each H and the O is about $0.96\times {10}^{-10}m$. 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 $p=6.1\times {10}^{-30}C\cdot m$ Determine the charge q on each H atom.    $\times {10}^{-20}C$

  The two plates of a vd g)8 ,j-u2pe;xgr7m4bspahcapacitor hold $+2500\mu C$ and $-2500\mu C$ of charge, respectively, when the potential difference is 850 V. What is the capacitance?    $\times {10}^{-6}F$

  The two plates of a capaci .tp0lw59ek;jut* fiptor hold $+2500\mu C$ and $-2500\mu C$ of charge, respectively, when the potential difference is 850 V. What is the capacitance?    $\times {10}^{-6}F$

  A 9500-pF capacitor holds plus and minus charges ofy hmzx/siuiw13vpiuv4,4 , m4 $16.5\times {10}^{-8}C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of pauu. n2ii5 0 vfhi(xep9xzy*i1rallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC h p(fui9x2i nizuy.i e*15x0v. What is the capacitance of the two wires?    $\times {10}^{13}F$

  How much charge flows from each4p ec0nb5a) guw; qyy4s((eqv terminal of a 12.0-V battery when it is connecteb qn)wypces qe y;4ua4 0((5vgd to a $7.00-\mu F$ capacitor?    $\times {10}^{-5}C$

  A 0.20-F capacitor is desired. What area must the plates have if they are to beklx.7(bad6s.w /- wsvuejzbp4h8s-if 0b- le separated by a 2.2. bijess hb(4kdxpl wl--z-ab 6wes7. 0/ u8fv-mm air gap?    $\times {10}^7{m}^2$

  The charge on a capacitovowo2bhum-t2z44fkx)9xb8+x yva8 x r increases by $18\mu C$ when the voltage across it increases from 97 V to 121 V. What is the capacitance of the capacitor?    $\times {10}^{-7}F$

  An electric field of 5z 3glbj.fphgz q* 1 0*nx-xot$8.5\times {10}^{5}V/m$ is desired between two parallel plates, each of area $35c{m}^2$ and separated by 2.45 mm of air. What charge must be on each plate?    $\times {10}^{-8}C$

  If a capacitor has o2 v tnb(ojs;w, moze/6pposite $5.2\mu C$ charges on the plates, and an electric field of 2.0 $2.0kV/mm$ is desired between the plates, what must each plate’s area be?   $m^2$

  How strong is the electric field between r -)4 xjp 6gah,.g:fblnzw,ax the plates of a $0.80-\mu F$ air-gap capacitor if they are 2.0 mm apart and each has a charge of $72\mu C$ ?    $\times {10}^{4}V/m$

  A capacitor is charged by a 12 hk , 8m8brqs7usgp,:q5-V battery (Fig. 17–29a) and then is disconnected from the batteq8:gsrk s quphb7,8,mry. 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.]    $\times {10}^{-5}F$

  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)
$\begin{array}{l}{Q}_1\\ \text{ initial }\end{array}$   $\times {10}^{-3}C$
$\begin{array}{l}{Q}_2\\ \text{ initial }\end{array}$   $\times {10}^{-3}C$

  What is the capacitance of two square parallel plates 5.5 cm on a side tha jpjqk plj *juy,*o5(8t are separated by 1.8 mm of p*jk5oj* uj ,(ljpypq8araffin?    $\times {10}^{-11}F$

  What is the capacitance of a pair of circulaat* fso2hx ;0ar plates with a radius of 5.0 cm separated by 30o ta;f2*xash.2 mm of mica?    $\times {10}^{-10}F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. I5ag l 3wbi6sie086/m++v4l jn j5 k fgbw-iantf a piece of mica is placed between the plates, how much charge will flow from the batteb6wlka-ng+g+ 5w6e ij54 fl3ntb/si ia08vmjry?    $\times {10}^{-7}C$

  The electric field between the plates of a sc od0 ; qwjxpw-tu-o2dga+.nw20rl: paper-separated $(K=3.75)$ capacitor is $8.24\times {10}^{4}V/m$. 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.
   $\times {10}^{--9}F$
   $m^2$

  650 V is applied to a 2200-pF capacitor. How urblw gq*5;4n07bz yf much energy is stored?    $\times {10}^{-4}J$

  A cardiac defibrillator is used to shock a heart that is bearwrz; 6.lx c5ating erratically. A capacitor in this device is charged to 5.0 kV and stores 120l xr;w .a6cr5z0 J of energy. What is its capacitance?    $\times {10}^{-5}F$

  How much energy is stored by the electric field between two squan6 y( z4sjf9of s:rak:re plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on the plateosanzs6(4f:k9 : fyrjs are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in.-jkn+: vgwe 6l pie pans 5 cm apart and con+lgjn6w -kv:enecting them to the opposite terminals of a 9-V battery. Estimate
(a) the capacitance,    $\times {10}^{-12}F$
(b) the charge on each plate,    $\times {10}^{-11}C$
(c) the electric field halfway between the plates,    V/m
(d) the work done by the battery to charge the plates.    $\times {10}^{-10}J$
(e) Which of the above values change if a dielectric is inserted?

A parallel-plate capacitor has fixed chargeaj:an v8yw, 1 hp3.dits $+Q$ 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 h2r+7tkogj-ub;mmj7 if (a) the potential difference is doubled, and (b) the charge on each plate is doublhtgb 2;7 -+jomrkuj7med, 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,    $\times {10}^{-4}J$
(b) after they are connected.    $\times {10}^{-5}J$
(c) What is the change in energy?    $\times {10}^{-4}J$

  In a given CRT, electrons are accelerated nx8f-q( yz6h3sy +s guhorizontally 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 screen top 22 cm away, 11su3yhz-yq xf 6(gs8+n cm above the center. Estimate the value of E.    $\times {10}^{5}V/m$

  Electrons are accelerated by 6.0 kV in a CRT. The screen is 30 cm widhn8.l 87vsof cvxk .p9yn5o k8nvg8+qe and is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizontallnhnyg8.pov 8nsok.59 vxl+qc88v7 kfy deflecting electric field vary to sweep the beam fully across the screen?    $\times {10}^{5}V/m$ to    $\times {10}^{5}V/m$

  An electron starting from rest acquires 6.3 keV of KE 1p,x(qjnalvik2 zmh8x4 s i96in moving from point A to point B6ikza9 xx(,8s1 i 2plmv jn4qh.
(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 h +vokxw36zk)km r c;/4.0 C of charge and 4.2 MJ of energy to the Earth.
(a) Across what potential difference did it travel?    $\times {10}^{6}V$
(b) How much water could this boil and vaporize, starting from room temperature?    kg

  There is an electric field near the Earth’s surface whos0hc19 6tndv45(yh0 z g uyyqlre magnitude is about $150V/m$ How much energy is stored per cubic meter in this field?    $\times {10}^{-7}J/m^3$

  In a television picture tube, electrons are accelj3/ww 8i,*ei..qpoma:j y pqgerated by thousands of volts through a vacuum. If a televisionyi: w, jom8iqpa*3./wp.gqej 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 field is uniform.    $\times {10}^{-12}V$

  A huge 4.0-F capacitor has enough stocdlrer)v4 1kz v8 3 f,(i 8heb+3ijbdxred energy to heat 2.5 kg of water from 21${}^{\circ }C$ to 95${}^{\circ }C$. What is the potential difference across the plates?    V

  An uncharged capacitor5 5wbdq,uzm x.9v p19j nigz(z is connected to a 24.0-V battery until it is fully charged, after which it is disconnected from the battery. A slab of paraffin is then inserted z zi9vwd5,gxqum5 p z( j.n91bbetween the plates. What will now be the voltage between the plates?    V

  Dry air will break down ec7;dx5 ozg 89vy5jpi if the electric field exceeds $3.0\times {10}^{6}V/m$. What amount of charge can be placed on a parallel-plate capacitor if the area of each plate is $56c{m}^2$?    $\times {10}^{-7}C$

Three charges are at the corners of an equilateral 4nlse6ne 7 a(.mx)uehtriangle (side L) as shown in Fig. 17–30. Determine the ph4nx) 6nus7aeme( l. eotential 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 to a 9.0lw + 7c)auq3xlx7b 1vl0c9 ebs-V battery. If a piece of Pyrex glass is placed between the plates, how much charge will then flow from the batlb9 qsc)ac lx7 +be1 wl7v3u0xtery?    $\times {10}^{-8}C$

  An electron is accelerated horizontally from rest in a television pk m0fbucpn9zzc3 j*j h4a)h0: icture 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 have a potennz9 hcm*ka)b zfjc0up4 jh30:tial 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 capacitarqq+ ;1zvpzqm a+2z*x 0.ikajnce $C_1$ 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 10v r/z 3m8yr)mew *msr-F air-filled parallel-plate capacitor for a circuit w3rv*r y8/ rsme )z0mmyou are building. To make it a reasonable size, suppose you limit the plate area to What would the gap have to be between the plates? Is this practically achievable?    $\times {10}^{-16}m$  ----待选择----YesNo 

  Near the surface of the Earth there is an electric field of abo: x khgj7;flbsw3* uhv2 -wk-dut $150V/m$ 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 nitrogencio.3 -aa8x8 ql z nb-/lwgtz+ 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?    $\times {10}^{5}W$

  In lightning storms, the potential difference y-mk7y9p8v8iu00h rewny sj,between the Earth and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are typically 1500 m above the Earth, andumjnyps,yyk 0h0v er w-9788 i can have an area of $110k{m}^2$ Modeling the Earth–cloud system as a huge capacitor, calculate
(a) the capacitance of the Earth–cloud system,    $\times {10}^{-7}F$
(b) the charge stored in the “capacitor,”    C(Round to the nearest integer)
(c) the energy stored in the “capacitor.”    $\times {10}^{8}J$

  In a photocell, ultraviolet (UV) ligs/fk ; li;3goaht provides enough energy to some electrons in barium metal to eject them from a suro/gki;l s 3f;aface 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?    $\times {10}^{6}m/s$

  A point charge is placed 36 cmaem;+q7 p f 5iyrxgpzn-:kz+3 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-di5f6o yhe7m 3 dc0j1ps2j toi2tameter coins separated by a 0.15-mm-thick piece of pajj 5mpy2i2s7 h0eco 6ft 3dto1per $(K=3.7)$ A 12-V battery is connected to the capacitor. How much charge is on each coin?    $\times {10}^{-10}C$

  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    $\times {10}^{5}V$
(b) the electric field?    $\times {10}^{6}V/m$  ----待选择----leftright 

  A parallel-plate capacitor with plate arj(bis4b)u r5 hea $2.0c{m}^2$ 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?    $\times {10}^{-11}C$
(b) The plates are now pulled to a separation of 0.75 mm. What is the charge on the capacitor now?    $\times {10}^{-11}C$
(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?    $\times {10}^{-10}J$

  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.    $\times {10}^{-6}C$

  Two point charges are fixed 4.0 cm apart from each8 j8lte:vxa j *+8nshqsqie/ 3 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 wz 0hw :ixgr:q qne 3vnqb0l,/8ith $q_1$=$1.5\mu C$ and $q_2$=$-3.3\mu C$ Find the potential difference between points A and B.    $\times {10}^{5}V$