If two points are at the same potenti6r7mn h r;7lz 4j4ncqcal, 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 need be exerted? Exp;mc4q7 rh 7lrznj 6c4nlain.

If a negative charge is initially at rest in an electric field,yh ,nv6p:uf p.c dlc i2b*i)a- 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 eac pblv:c pc-h.)f26 n i,i*adyuh instance?

State clearly the difference (a) between electric potdqc1:2jko a mvap-p;t; / bvv/ential and electric field, (b) between electric potential and electric potentidv t:o;/m v1j-c p/2pkqaabv; al energy.

An electron is accelerated by a potential dazdj)( ph43bqf4thm, ifference of, say, 0.10 V. How much greater would its final speed be if it is acceleratedafbzd4(4 3, mqp)ht hj with four times as much voltage? Explain.

Is there a point along8up yfbbe6nps.t)y;a .v-f we chy510 the line joining two equal positive charges where the electric field is zero? Where the electric potential is zero1c0ebapve6.ptf8-fn;yywb h uy )5s.? Explain.

Can a particle ever move from a racc (l)m bia3u igdij+3 8z-8tegion of low electric potential to one of high potentialt bda+ (uzi8i3ga- c3c8 jim)l and yet have its electric potential energy decrease? Explain.

Compare the kinetic energy gained by a prot;6 kl-+fmiuwek x3e s.on $(q=+e)$ 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 l ejd2,w cs9yg:)j4soc+ ft1xdines cross? Explain.

Draw in a few equipotential lines in z1ouv1./g4; rw9dpejvw8p v rFig. 16 – 31b.

What can you say about the elect3gfby4 3 exh2mric field in a region of space that has the same potent y 32gm43ehbxfial throughout?

A satellite orbits th8ml jp6/zcp(*d1i rye1795z jaaiupve Earth along a gravitational equipotential line. What shape8azm6ueyz9l 75dpii1 pc1prav/*j ( j must the orbit be?

When dealing with practical devices, we often take 9 shg8/ dw9loythe 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 electric field E, at other pointw9ghldo/9 ys8s?

When a battery is connected to a capacitor, wwq,/ajd o9m( bmk yro; d777hkhy do the two plates acquire charges of the same magnitude? Will thisk7 /awbq do,97o dm;h (kjmry7 be true if the two conductors are different sizes or shapes?

We have seen that the ca7ux kwp )affnxvky)- 5.9klw) pacitance C depends on the size, shape, and position of the two conductors, as well as on the dielectric constant K. Whafak9x. lk vx)unpk7)- w5 )fywt then did we mean when we said that C is a constant in Eq. 17 – 7?

  How much work does the electric field ekjcmxw x6 725do 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 ele ( 7 uut+)gsusitwc; gl(f8/qqctric field do in moving a proton from a point with a potentiawt(/+tl ; uqguf)cug8is 7(s ql of $+125V$ to a point where it is $-55V$ Express your answer both in joules and electron volts.
   $ \times10^{-17 }\,J$
   eV

  How much kinetic energy will an electron gain (in joules and e 3i;,68wjx ,yb wquphlV) if it accelerates through a potential differe8ybw;hu 3,6, i wplqjxnce of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires l(-gkap:v/9 poxrou 8 $7.45 \times10^{ -16}\,J$ 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 betweenj t /5ukem9v)c two parallel plates 5.8 mm apart if the potential difference between them is 220 V? k / vmtc9je)5u   $ \times10^{ 4}\,V/m$

  An electric field of cb93wh)yg;y5rfk yb ($640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two paral3zkqj b* 5(;n0b fzlfolel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between tw:ylyc:ry m88+ (;dz -ibfqnqfo parallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is neexlfpt3 5 j)t jl-ig72nded to give a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connectt *ia2*mm ih4jed to a 200-V power supply, are separated by an air gap. How small can the gai*2 aj4t mih*mp be if the air is not to become conducting by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an expfog ca ky3(b:t+, lv4ternal 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 af 8*gm57bu ez01e hkxyn electron with kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proti slcz6. (xw,w;oj yk 26j4rhqon whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nucleus,am f+ ,ovaban:7/;qe7f kp*ec $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric0lwah8 fqje;r :j w3e5 potential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q createsa1avo xn5wfb:8vc)w.3 tml f2ll we:8 an 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 con*el. j.pc11j3cjb afn ductor carries a net negative chargpl1c.f b31aj.jej n *ce, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a distance of kt j7s9:d.g/4xxp0xk t : e8 ikjx2d7x 7umtgx$ 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 arranged4 mxj*rocg36t9 hw3 oh at the corners of a square of side L as shown in Fig. 17–25. What is the3whghmcj3t49* 6 ox ro 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 with . e:zl-u id3si$Q\,=\,-0.125\mu C$. 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 elect( u0pazb 0gc6drons from a great distance apart togdb 0pz u6(c0a $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm norq/g6 g rhx8qq,th 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 usea asu)g08 f-rqd 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 separated by a distance d, as shown in Figa3vlyn6k /uk:).smot e a9 cci..2cte . 17–27. Determ 6v c2.es.tka/9 l) t ik.oucmc3nea:yine 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 nudv,ly g73bth sp2, 3kicleus) in a circusp,7htiv gy b2 ,k33dllar 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 protoli)wck ukd :x5l*s) t2n are $ 0.53\times10^{ -10}\,m$. apart. What is their dipole moment if they are at rest?    $ \times10^{-30 }\,C\cdot\,m$

  Calculate the electric potential due to a dipole whose dipole 4( 0 drlp. qp,vj,amelmoment 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 the negative to the posivxqyvgt3,5-z l1 -ytpjl,t9a tive charge. The water molecule, Fig. 17–28, has a dipole moment whiy,atllp t1zj-tq5 vxg v 3-,y9ch 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 capacitor holzs1xnq- e/0vlwll *) wd $+2500\mu C$ 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 holtv mrj ,;;u((myiv zw-d $+2500\mu C$ 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 minus charges oaedua3 )fn:2s;vaq vy 88dw1 bf $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of parallel wire in ai4ihj);gg 1aow vyl2 m4r is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is 42lv gm ;j wg14)haioythe capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of a 12.0;egsz h 81zs r*d 9/*jr7uoi1vmqgsb7-V battery when it is connected to a;97 rrvg ozm8*s*eb1gzh u 7ssji1/qd $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must zc5+;. ivw4 ih*5tc:ucch ep z2(lidf the plates have if they are to be separated by:u li24 ih(zc+c .pdv;5 f*cizce t5wh a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacito621j op;npvrn 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?    $ \times10^{ -7}\,F$

  An electric field ofiujeg017pct 3k(5q j16za i rc $8.5 \times10^{ 5}\,V/m$ 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 opposij3fn:.8(u jadixxc 7w te $5.2\mu C$ 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 fl,;wiwu-i i87 fo.uioield 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 tcaqmbkm t6je++))m nl 2f 9s6mhen is disconnected from the battery. When this c+m ak2mq 6fjb+6)n9lme scmt)apacitor $(C_1)$ 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 squarf/ejmn8 o 74ztg79t;j p/belke parallel plates 5.5 cm on a side that are separated by 1.8 mm lfke /jm9 bzetj;47pnog7 8t/of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular p eo3x9o0*ssc rxr kli*/stj cz0m2b6 /lates with a radius of 5.0 cm separated b*z2co0 c/s 9m0rbksls/t xo*6 ije3rx y 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. If a piece of miciid ws88t e,7m cbja5+a is placed betw87te5mswi8,icb+ d j aeen the plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the platei,(doyro2rij-.tq v)s 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 2200-pF capacitor. How much ener33l-( vev dv7bkrx.prgy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shozvawhg+a :nhxid:6, 20h drfv1 d2: wlck a heart that is beating erratically. A capacitor in this device1 hvv ifa06hlxz2 r,dhaw 2g:dw :+dn: is charged to 5.0 kV and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored 77jmpm3yad y2by the electric field between two square plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The cy7 ayjdmp3m72 harges on the plates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled w6dbt /0m73wpnxnp m 6by placing two 9-in. pie pans 5 cm apart and connectnt dbp3/ 7 6pwm6nxmw0ing 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 fmhhwf+ ;k d,iaa g73h3ixed 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 capacitko gd, ;7ls +lpwb(kr excf.,-or change if (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as the capacitor r7d(xpfeob,,wsl-+r l;. gck kemains 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 i ( hq*cpg2.w +,qt8zntxfng3are accelerated horizontally by 7.0 kV. They then pass through a uniform electric field E for a distance of 2.8 cqigq p( n+2 8c,gf nhwzxt.t*3m, 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 screeibdlg ebn4p.p+ w1q3 ,n is 30 cm wide and is 34 cm from the qpgp 3+.i d4 nbb1lwe,2.6-cm-long deflection plates. Over what range must 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 keV6rg y8 gaur)zn60k, us of KE in moving from point A to point B. uyuz gks,866r n0 ag)r
(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 energy to the Earth. hsgxf3.m/ l( u5bg3rx
(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 - sdd4e /njqww.+ p:cujr.2 mxfield 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, electrone 4y 8 vtx5n,e:*qotmks are 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? What8 *4 e:etxvmn,oy5tkq potential difference, acting over a distance of 3.0 cm, would be needed to balance the downward force of gravity so that an electron would remain stationary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor hoks* -.plj3wd:sp,wkhg 8)c kas enough stored 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 capacitor is connected to a 24.0-V battery until it9bw50edxsu k 6 :jlupr(sp:;k is fully charged, after which it is disconnected from the battery. A slab of paraffin is then inserted between the plates. W9dxsb 5 r0e; (up:swpk6k:u ljhat will now be the voltage between the plates?    V

  Dry air will break down if the electric field exceedm xq-* biujl 7p,np3(ws $3.0 \times10^{6 }\,V/m$. 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 (sidqo sk.f.jt 1qb94y:4a tj ulp7e L) as shown in Fig. 17–30. Determine the potential at the midpoint of each koy tu.:bj7t4qapfqj .l94 s1of 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 battery. If a piece of Pyrex6bvcqp6ea,4tulchi.2 j j9 d3 glassb.d6c heq3a4u6tj vjl,c9p i2 is placed between the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelw5 la0cdj 6r0aoi0fr2 erated horizontally from rest in a television picture tube by a potential difference of 5500 V. Itw02lif rocj 65ar00 ad then passes between two horizontal plates 6.5 cm long and 1.3 cm apart that have a potential difference of 250 V (Fig. 17–31). At what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capacitance*7j lpf;ctd3a) ecp (ac+x6 ir $C_1$ 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 ma) 7so v+t(p3ezf hx2jb)v3va cke a 1-F air-filled parallel-p3) vobsjxpa2+ eh vc(f73t z)vlate capacitor for a circuit you are building. To make it a reasonable size, suppose you limit the plate area to What would the gap have to be between the plates? Is this practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there is an eledk 5k,a3k im0lctric 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 pulsc*o*casj6y+ ced nitrogen 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 betweev/ 19nj-tp4 fd- huzxtn the Earth and the bottom othf-/u9xpj1v 4-nz tdf the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are typically 1500 m above the Earth, and can have an area of $110km^2$ Modeling the Earth–cloud system as a huge capacitor, calculate
(a) the capacitance of the Earth–cloud system,    $ \times10^{-7 }\,F$
(b) the charge stored in the “capacitor,”    C(Round to the nearest integer)
(c) the energy stored in the “capacitor.”    $ \times10^{8 }\,J$

  In a photocell, ultraviolet (UV) light provides enough energy to som6en5 vc 3.8mu/6zdndzeguln+e electrons in barium metal to eject them from a surface at hi.+ gn/vm6 3ndznud8u ecz6le5gh 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 an i1d+(m tidjyugne m8t89+gy 1tdentical $+33\mu C$ 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 0.15-mmj5hb, qn0bg8v- tma j)-thick piece of,hta5m b8 jn-v gbj0q) 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 pd6glgupr4ji; ye13+rn 7p778y uts e dlate 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 each other. Thenf4 ;2tbono 4sir 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 astwcfcf 3y)tpp7v;o2/ 8a ;dos 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$