If two points are at the same potential, does this mean that no wobc en2 .(8ycntrk is done in moving a test charge from one point to the other? Doeb 2tnyc. 8ne(cs this imply that no force need be exerted? Explain.

If a negative charge is initially at rest in an electric field, will it mov vqm9gho,o-d-4/dhi n e toward a region of higher potential or lower potentiav9nh,-o ddi hmg/4-qo l? What about a positive charge? How does the potential energy of the charge change in each instance?

State clearly the difference (a) between electr9 (/nschp h/-8 mpnwcvic potential and electric field, (b) between electric potential and electcp98 mnc/w- /n(hsh vpric potential energy.

An electron is accelerated by a potential difference of, say, 0.10 V. How - 2shgk4z+poe zhp 37zmuch greater woulzk zohs4 zep3h-7+ pg2d its final speed be if it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining two equal positive charges whe;nmq z0) dt2/r zh:*du.fyquc-wgtg 7 re the electric field is zero? Wheuznqd: t d -2mhctrg f07w;q *zuy.g/)re the electric potential is zero? Explain.

Can a particle ever move from a region of low electric potentia.cir)vuv+ bu.t /mkz4l to one of high potential and yet have its electurzv.cti ub/m. v4 )k+ric potential energy decrease? Explain.

Compare the kinetic encz5s3, 6l5wp/istm l jdb+:qvergy 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.wt(t /)uqsdr 5

Draw in a few equipotential lines in Fig. 16 – 31b.d( vfy 6grx/4s

What can you say about the electric field in a region of space that has thed5h5j:o.cftb m qr8jf z yz-;* same potenti r5d o; q:mfjf-*t.58zchjzyb al throughout?

A satellite orbits the Earth along a gravitational equipotential line. What shap p i0wcrv bl;(4-/hhlve must the orblb/;4vc-w0p(h i rvlhit be?

When dealing with practical devices, we often take the ground (the Earth) to nza(-,l;wv mko+ufi;be 0 V. If, instead, we said the ground wa, lv(o-unzki;f+ a;m ws how would this affect (a) the potential V, and (b) the electric field E, at other points?

When a battery is connected to a nd6+cb,r6 phacapacitor, why do the two plates acquire charges of the same magnitude? Will this be true if the two conduc6rpcb n,a+6d htors are different sizes or shapes?

We have seen that the (4zsh)* ah o,y dd1moucapacitance C depends on the size, shape, and position of the two conductors, as well as on the dielectric constant K. What then did we ms )dy 4(a1zmho*odhu, ean when we said that C is a constant in Eq. 17 – 7?

  How much work does the electric fv+nrvi2gh/vp,; sct 1ield do in 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 proton from :4r5 xn,r6ja.o;nq aadhuknqn8 v6e d f ;c8b8a point with a potentialnqnnnjva;8akd. d o6u4xhr:q c5r ,b6 88af;e of $+125V$ 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 jo)t;qolj:p 6i pules and eV) if it accelerates through a potential difference of 23,0;)popjtl:6 qi00 V in a TV picture tube?
   $\times {10}^{-15}J$
   eV

  An electron acquires eu-s i r*48gjq 9y.nha$7.45\times {10}^{-16}J$ 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 plates 5.8 mm a:vxapea7 w-dl7w , x), /pfx 4krx*zlbno*/lfpart if the potential difference between thea: fxl-z/ r b7,4dpow7we)flk ,* np*xxaxlv/m is 220 V?    $\times {10}^{4}V/m$

  An electric field of 5.ktypl/ : ykoj ugc o+w)2w0h$640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two parallel plates connected tuomd3 . 3xg5y94hczjzo a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel pla 6vfb 0rtf/.0 mqhqp(dtes connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is neek dgu- z 2,ini4tf,(bwded to give a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $\times {10}^{4}V$

  Two parallel plates, connected to a 200-V power supply, are separat z++7g3) u/zfj3ij*6 liv okgcmdtf *hed by an air gapf+c) vjtm6z/ +f*lzi3ugi j gd7 ho*3k. How small can the gap be if the air is not to become conducting by exceeding its breakdown value of $E=3\times {10}^{6}V/m$?   $\times {10}^{-5}m$

  The work done by an external force to 26, qswv0 ofclmove 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 electron d80swxp+2g pmwith 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 wh1wko 3q(zy2fv idq,)toh/yg8 ose kinetic energy is 3.2 keV?    $\times {10}^{5}m/s$

  An alpha particle (which is a helium nucleus,*m(zx v,w,wgslx0uvu f:/gzs n0y7.kd 4)wbg $Q=+2e$, $m=6.64\times {10}^{-27}kg$) is emitted in a radioactive decay with ${}_{KE}$ = $5.53MeV$ What is its speed?    $\times {10}^{7}m/s$

  What is the electric potential 15uj9 mase /:+dn.0 cm from a $4.00\mu C$ point charge?    $\times {10}^{5}V$

  A point charge Q creates an electric potkoul/lvm(kb(n -u s8)kb,m6c ential 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 football. This condwn. r5bv a*xu3uctor carries a net negative cn* w.5 xvb3rauharge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a dis*x,:v2rr(+sojhg 9d3btyc b)sp pgo-2iz s.ztance of $2.5\times {10}^{-15}m$ 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 arrang0 ;j r-uvpmw;-g+li5atd ewh, ed at the corners of a square of side L as shown in Fig. 17–25. What is the potential at the fourth pv 5 wm;-airg+0d ;jhlt-eu,wcorner (point A), taking $V=0$ at a great distance?

  An electron starts from rest 32.5 cm fro4 t/)pxj k.uf.,:ts oj9lcuqjm 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 txl r-;s.w:ry0 ip d/, vlc;h76polobvhree electrons from a great distance apart to vc,x vdrwb. io;osly6lr - 70p;p/hl: $1.0\times {10}^{-10}m$ from one another (at the corners of an equilateral triangle)?    $\times {10}^{-18}J$

  Consider point a which is 72 cm north of t ht0jztcjd .7n):hk 0a $-3.8\mu C$ 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 u*vl qb us;+pdnp8s 91nsed to accelerate a 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 distance d, as shoi 1t2pgr ;w)jown in Fig. 17–rt2i p1;wo) gj27. 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 atogz ult89k u 1 czngm06zu:73ngm, an electron orbits a proton (the nucleus) in a circular orbit of radznlm08 zc 39 u1ug6kggt:u7znius $0.53\times {10}^{-10}m$.
(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 proto:pi8 r+gf ym)h.h snf*n are $0.53\times {10}^{-10}m$. apart. What is their dipole moment if they are at rest?    $\times {10}^{-30}C\cdot m$

  Calculate the electric potential due to a 1 dgh55mfc la:dipole 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, condx* h64 kwg2xrb ime,5sidered as a vector, points from the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which cank,x5mg 4x 2rieb*h wd6 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 capacitor-1gylx p4/ dly 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 capac czk*1 9c5rcfyitor 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 plusydz167bsun*k(q p (lhv ,+aq v and minus charges of $16.5\times {10}^{-8}C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of paraljw0uug7 vsd; m0mc vq0fl859 klel wire in air is 120 V. Th0 mdg597; j080 svmvukl wfcquey carry equal and opposite charge of magnitude 95 pC. What is the capacitance of the two wires?    $\times {10}^{13}F$

  How much charge flows from eaquc0vy kf/he; fq+)5ach terminal of a 12.0-V battery when it is connected to f+h v/qc;5 fk y0)eqaua $7.00-\mu F$ capacitor?    $\times {10}^{-5}C$

  A 0.20-F capacitor is desired. What area must the plates have if they are to tt -j3*wh tk0nbe separated by a 2.2-mwh3 *tkt0t-jnm air gap?    $\times {10}^7{m}^2$

  The charge on a capacitordusmup/7;6y1t rzwjh2 . vh:d 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 wwgx1 k3:b,bg:g ta p1$8.5\times {10}^{5}V/m$ 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 oppositelz9 +5va0f mmv $5.2\mu C$ 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 the ps-xl p9:pf)v -5l0i qn2 yxxselates 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 125-V battery (Fig. 1f5 a6d)d d 9cnsjd:cu(dsc5 0b7–29a) and then is disconnected from the battery. When thisds j09un6adc) dbcf d(s5d5c : 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 that aid3o0bg7:gn are separated by 1.8 mm of p o:ingd0a g3b7araffin?    $\times {10}^{-11}F$

  What is the capacitance of a pair of circular plates with a radiu01g hx)8v waphs of 5.0 cm separated ha01wp xh gv8)by 3.2 mm of mica?    $\times {10}^{-10}F$

  A 3500-pF air-gap capa4gb r0pqbi k*fccjv)zpc .n419;l h6jcitor is connected to a 22-V battery. If a piece of mica is placed between the plates, how much zh;pjl9 q*bc igrnc6jck.p0 v41 4f )bcharge will flow from the battery?    $\times {10}^{-7}C$

  The electric field between the plates of a papern drj+xbdma d8(6j /w+-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 capacitj5b. svkd j4azfp9e.2or. How much energy is stored?    $\times {10}^{-4}J$

  A cardiac defibrillator is used to shock a hxn tka;sd ddt+(a (m+ r,)uy4deart that is beating erratically. A capacitor in this device is charged to 5.0 kV and stores 1200 J of mst adxa )+k4 t(,u;+nd yr(ddenergy. What is its capacitance?    $\times {10}^{-5}F$

  How much energy is stored by the electric field between two square r 66gdzu4qfht+kbbwz,y6s+.wh o.6vplates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on the plates 664hvbzr b6d.w u h. stzg,wkoq6y+f +are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing twijl 2w4.q l+vm*sto7 kd*w-eh8ys/io o 9-in. pie pans 5 cm apart and connecting them2omwoi jlhlsk/dis8t7. *q+ v*y w e4- 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 fipy e)xk*d bmy cs.()b+xed 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 capacitorhz90* thx1vi- )q: yvdtug4x t change if (a) the potential difference is doubled, and (b) the charge on each plate - ytt:9v)i xhq h1vx d04tu*zgis doubled, 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 horizontally by 7kh/lsbldjb1n72s 31 w .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, 11 cm above the kd1/231l sbljbn7whs center. Estimate the value of E.    $\times {10}^{5}V/m$

  Electrons are accelerated by 6.0 kV +vjt)gy,-eib in a CRT. The screen is 30 cm wide and is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizontally deflecting electric field vary to sweep the beame-bt+ )vi,yjg 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 sm 74xf6dywn8p,qlk9in moving from point A to ponl p sf498dxy ,mq7wk6int 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 energy to the E)zn maoro+5xy0i o44tra w;g;arth.
(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 surfac8-(g/ zyfkkkk e whose 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, elecugj/v ut)wp7q xf)0t(,z y 0wgtrons 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? 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 thzf) gv,(ww0x) 0j y/tgu7 pqtuat the electric field is uniform.    $\times {10}^{-12}V$

  A huge 4.0-F capacitor has eno7/yt.,htz 16;kohi2em.rww uh agx x-ugh 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 +7. uk q alfpk t0)36db tjqko.d*1grf24.0-V battery until it is fully charged, after which it is disconnected from the battery. A slab of paraffin is then inserted between t3k) pr*b6ot +q .df j kadt.f7qu0l1kghe plates. What will now be the voltage between the plates?    V

  Dry air will break d- jq5up7,m3c:hrwg ip,3i cxk own 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 triangle (side L) as5:him ;zi7 1a3oytpwj shown in Fiz5y :1imjpt ih;7wo3ag. 17–30. Determine the potential 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 t95gl c4shgy2p+l nu 7so a 9.0-V battery. If a piece of Pyrex glass is placed between the plates, how much charge will tgghl p4ys2lu7 9cs5n+ hen flow from the battery?    $\times {10}^{-8}C$

  An electron is accelerated pz3m0o9)kafnhorizontally from rest in a television picture tube by a potential p9n k30zo)fam 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 (Fig. 17–31). At what angle $\theta$ will the electron be traveling after it passes between the plates?    ${}^{\circ }$

A capacitor of capaci qh me;r-,l-kgtance $C_1$ 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 a3xm7 2w h jqeeby8+wfgi5c77e 1-F air-filled parallel-plate capacitor for a circuit you are building. To make it a reasonable size, suppose you limit the plate arexi+3yqebm 77ej5 f2wh e87gcwa 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 electrikr3w,.q,olc7 xyxa-p g j:mv*s9 dnw2c field of about $150V/m$ 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 nitrogen laser hasv,q)k. y 0n-e qkv7vbv 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 between the Earth a,p /9bedhbd8wp;r o ,wn.yuj/nd the bottom of the thundercloydw/pohd,bp j.bw e9u/r 8;n ,uds 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 $110k{m}^2$ 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) light providesb/ qtsti 3hgi+ ketj *,a4t*)r enough energy to some electrons in barium metal to eject them from a surface at hi+ )ehq ,gsirtt b3j4iat*t/k*gh 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 cm froxx9af1f9yc+*69q u0g k ytokcm 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-cvip 6a3a 3 izzc-;fp2nmsu9w-m-diameter coins separated by a 0.15-mm-thick piece of pape-ma;2 cnvw-ifzpui9 3 pa6z3sr $(K=3.7)$ 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 capacg tne5.lia7.q itor with plate area $2.0c{m}^2$ 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 each other. Their chargeszyml r6(a8baj89o;l e 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 ))t tfxjdm/t 0v+e7jpas 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.    $\times {10}^{5}V$