If two points are at the same poten;s+q1zsw+ qn)r3rj nqt)ea( etial, does this mean that no work is done in moving a test charge from one point to the other? Does this imply that no fjn3zw + (ar tr1;)ssqnqe+q)eorce need be exerted? Explain.

If a negative charge is initially at rest in an electric zw:/b9t1io *lyhn- p5oyt 9l vfield, will it move toward a region of higher potential or lower potential? What about a positive charge? How does the potential energy of the charge change in each ins19w oyyotit h z bl/l9-:5nvp*tance?

State clearly the difference (a) between electric pot rf+1-yde:hq.x kb.pcential and electric field, (b) between electric potenhf1+e- q.y. rxckpdb :tial and electric potential energy.

An electron is accelerated by a potential difference of, say8u,ow2l lo 5nh, 0.10 V. How much greater would its final speed bo5hu n82l,lw oe if it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining two equal pos-,g cc 5bje9ifitive charges where the electric field is zero? Wh-9 ce, 5jcbigfere the electric potential is zero? Explain.

Can a particle ever move from a region ofwie 8rj5ox1*p. ce6wg low electric potential to one of high potential and yet ha 1* .gpi8joerx 65ecwwve its electric potential energy decrease? Explain.

Compare the kinetic p, mq6le.vjfd32 bnp+72zanoenergy 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 $\vec{E}\,=0$ there? If $\vec{E}\,=0$ at some point, must $V\,=\,0$ at that point? Explain. Give examples for each.

Can two equipotential line5xo3x7as ;f 0/d )botcv;dq trs cross? Explain.

Draw in a few equipotential lines in Fig. cw eq cj1+0r4dnf7,lb16 – 31b.

What can you say about the electg8v1 xx.pa 6xaric field in a region of space that has the same x.v6a1gx8x ap potential throughout?

A satellite orbits the Earth along a gravitational equipot75(gdj(sv 1dv ;jbnstential line. What shape must the orbittn(v1 sb7gjd;(j 5s vd be?

When dealing with practical devices, jsd :b+/rdjhrk(n**z)c c r1b 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 ejc d bd: r(*c h1nzjb)k/rsr+*lectric field E, at other points?

When a battery is connected to a capacitor, why do t5lj32act;bes he two plates acquire charges of the same magnitude? Will this be true il3taj ecb5;2s f the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on qplrnc:2poq( zro;-, the size, shape, and position of the two conductors, as well as on the dielectric constao ;zn qq,prr(:opc2l-nt K. What then did we mean when we said that C is a constant in Eq. 17 – 7?

  How much work does the electric field do in moovz7;f0 yam(trf6iz 1ving 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 movingof 0 8gog j9gty7;m2zd a proton from a point with a potential of d;g9yz 0gojfom82tg7$+125V$ 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 rx :g30ubxwm y0qc)glrc +xvew3*4l9 electron gain (in joules and eV) if it accelerates through a potential difference of 23,000 V in a TV pi*3rm +u l:0 )ww3cqxl40vx9by exrcggcture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquiressd y7(us9b gzygcgidvm01f ,p e.:54w $7.45 \times10^{ -16}\,J$ 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 elewf yi6- cd+bwp+*y3l9/omhelg2ur 3wctric field between two parallel plates 5.8 mm apart if the potential difference between the i3 ol g2fwpbyuel*h6mr +c+yw 3-/9dwm is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of/sx+zvvk6j+lq+9gy 8cpra o :pq5z- v $640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two parallewxzb fo,,u :.8b.oml bl plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two (ux 6n)7epf:eorda j- parallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give9 qqzwcx/3mb)jpw-v ; a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, conn fu r*/1,/ov8kri dkdsected to a 200-V power supply, are separated by an air gap. How small can the gap be if the au81rkd/i vo */k fd,srir is not to become conducting by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an exte imnfz+1wa r9d 5 : /vr+t0inacmw1,cxrnal 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 it3,vbo aujv lh78hf 4r)h5fxg; ht ,3electron with kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a prz - lykxr+*d.e(2yethoton whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium 59e j2opl :bxs6)g5in dnhd8mnucleus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric potential 15.0 cm+qoxzhi f4m0yf78 ga ; from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates .58:p wdwli+g0fh 9 .bif tvupan electric 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 carriesv26 np;5 j.zlxiaqw9 t+ug zq6 a net negative chargzw 2l.p95+6g v; qti njxzqu6ae, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the elecf 8 pcfl+*z(l,fvayo +tric potential 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 a d. sy1t94gsmayo+m)isj7 wf(rranged at the corners of a square of side L as shown in Fig. 17–25. What is the potential at the fourth corner (po9s+ot.sm (wsajfm1i 7 g4dy)yint A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cyg;ut434u6sk idij ( qt43swxm 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 elecur:5rd/ .lwwt trons from a great distance apart wr :r5d w/l.utto $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm north of iitub ,g6+1 fgg- qt.oa $-3.8\mu C$ 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 ngo / zaw)o.vvlbp8gd5/;m)k 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 a7 opz 4czaze51qz6f0mre separated by a distance d, as shown in Fig. 17–27. Determine a forqez p0fcz o57mz16a z4mula 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 electronk*)ishfa(mn 7*uoy gp*;p /yf orbits a proton (the nucleus) in a circular orbit of radius fy;pikg u7on pm*as(y /)f* h*$ 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 proton ar8vc v7 ii- rz6w1k2gvfwj1mk/e $ 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 p ;qc l.9eye-/qrbj8fwhose 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, points from j mv+ xkz;7ew4mkl: rnn:z;t0the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be considered as vw:0zmrltm+nn j4 x;7; k:zke 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 3lycnhy9h)czf dtpx3o9 ;dhn( r 9h,3 capacitor 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 gh )sp 2 o)+zn49/prdc.u ojuchold $+2500\mu C$ 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 plus and z18qo uewz o6909jmkbminus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections ofzfi1(v :dugpbd3hz*v0 hgw19 parallel wire in air is 120 V. They carry equal and opposite chhdpi13b z9 1*dg zw0g vu:vfh(arge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows:k)0ke pkvisht;1mhv1lz,x 4 from each terminal of a 12.0-V battery when it is connected p v0l)keks14vmxt,zh;k1i:h to a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates hav);caoei d r4zv y9-8u:(2/o rvafpksh e if they are to be sepv( 4/:duhsvk;z8-)9 ryao2 icf a peorarated by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increasejv.i8n2 hhm4. sv igi8s 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 ofum n jr,yz8(olg -0t8t $8.5 \times10^{ 5}\,V/m$ 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 o3ohzii0m0b.,kln- gqmr y9-a wk3-c gpposite $5.2\mu C$ 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 between 7g8o-tr vfxa;i8/c yu8orrp*l,gjf- 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 (hb1u+gnls. t/q w: tff/sa 4y0Fig. 17–29a) and then is disconnected from the battery. When this capaci nq1.+a g:yluhf tw /0/fss4tbtor $(C_1)$ 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 para9 xf xr -vflxt,13m gkd,k)e+zllel plates 5.5 cm on a side that are sep) 9lx,+gk,d-3m frextk z fxv1arated by 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a radius of 5.j +rcijg.4i)ey dx77i0 cm separated by 3.jiiie)cd7 j4rx7y +.g2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. If a pi: ).q wsmaa.gs.k0a jiece of mica is plac.).q0:i awa jgsm.asked between the plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of m6k9 29p2sso/ v gojpda 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 2200-pF ca7oxss,rc r/1g52 ppus cyd4w e qp11:hxd*x 9dpacitor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart 5;vxem/c wni- r j9+clthat is beating erratically. A capacitor in this device is charged to 5.0 kV and stores 1200 J of energy. What is its capav;nj+ xm9lir5ec /wc -citance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field betweens;5 iqh oo+ 3ec)qzpb. two square plates, 8.0 cm on a side, separated by a 1.5-mm a53s; qo.h+qoce )ipbzir gap? The charges on the 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 apart anb 7c eoel 8i5iit,2i.2 kqjvg+d connecting them to the ti,q7c loi8ekev ib. g+i52j2opposite 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 chargesg23hx )f6qibucb:5ig $+Q$ 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 chaq)d/2o o h) ventb)7ptnge if (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as tnt)7)vp)2/ oqtbeho dhe 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 accelenm ;xp)dfa00 orated horizontally by 7.0 kV. They then pass through a uniform electric ap0nm ;f)0doxfield E for a distance of 2.8 cm, which deflects them upward so they reach 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 sf-o fqz qwt. jy :cc;8i3eq,radr3/m7creen is 30 cm wide and is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizontally deflecting electrawot7 8,3;rmj/fe.qrcfic:yq dq3 -zic 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 from p yem (a)y2 i;6nz4rypnlp6x a*oint A to poinp;m z*64(yeyi yxnl6 n2 aar)pt 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 of charge and 4.2 MJ of ; g bxp;lm(, 0faix(u8k umeh(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’ztnc 5u8j 9foq-t*0pq 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 arcnrhh,0 o,x:x4a(u rg e accelerated by thousands of volts through a vacuum. If a television set were laid on its back, would electrons be able to move upward against the force of gravity? What potential difference,a,rh(r0 uh:g n,xo4 cx 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 hearwjy)f:lvirn8xs(ucds) (.+; zbm 7et 2.5 kg 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 battery until it is ful) 0zgw8hkh7u rly charged, after which it is disconnected from the battery. A slab of paraffin is then inserted between the plates. What will now bekg0w87h )uzrh the voltage between the plates?    V

  Dry air will break down if the xculqaj1)iu(e fgev ,nrmf0:7 r1d) 6electric 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 equilwiz3x rnu3v) :4fxo- materal triangle (side L) as shown in Fig. 17–30. Determine the potential at the midpoint of each of the sides. -3:r)3x4w mfn ivxuzo

  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 cwj y(.gz8xp))c boiux y84;ua 4stx4v9dg(zionnected to a 9.0-V battery. If a piece of Pyrex glaii.4g)(t4uuzva xboz xc 9ps)8dj w(xy;4y8gss is placed between the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horipa*sht( cx5( jzontally 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 apart that have a potential difference of 250 V (Ficps*hj a5tx( (g. 17–31). At what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capacitan acn8-.a8qmvh d/ tb+tce $C_1$ 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*vnaaqa4h () o want to make a 1-F air-filled parallel-plate capacitor for a circuit you are building. To make it a reasonable size, suppose y*) vaho(a4qn aou limit the plate area to What would the gap have to be between the plates? Is this practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there is an electric field of abm(gn0l 8ex trx) om5c1out $150\,V/m$ 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 nitrogen laser has a ty87x dy )2sks$0.050\mu F$ 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 the bottom o g.lq69drqrf7 f the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are typically 1500 m above the Earth, a lqr. q7fd9gr6nd 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 enoug9ys 5bnb zex 53(62hqnfosmp-h 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 slowehm5 pn yb5ze6 3s2fsob(q9 -xnd 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 yy1n*jqx9b(fiu / hi3 36 cm from an identical $+33\mu C$ charge. A $-1.5\mu C$ charge is moved from point a to point b in Fig. 17–34. What is the change in potential energy? $\approx$    J (round to one decimal place)

  A capacitor is made from two 1.1-cm-diameter cobn*),u6vsbw k*f;el-gue 4 qsins separated by a 0.15-mm-thick pie*;v b,)lgeu*ks6buw s4n feq -ce 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 with plate */h qw hl34kvzarea $2.0cm^2$ 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 each other. Their chargaoj7+ u 3 ,oz-cro+uhxes 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. 17–4tz0cae2g aqu +e4+ne35 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$