If two points are at the same poten ;g2wjdlv.oj*(bzu. d tial, does this mean that no work is done in moving a test charge from one point to the other? Does to z2ldjj;u(w .*bv gd.his imply that no force need be exerted? Explain.

If a negative charge is initi59 +2lwspla q shxr*yinsl)1r/f +w6 yally at rest in an electric field, will it move towas*w5l+xp1 l)62ws+qin srr y lfa9 hy/rd a region of higher potential or lower potential? What about a positive charge? How does the potential energy of the charge change in each instance?

State clearly the difference (a) between electric potexvbsv-ynm9 66 4(xksif s.x/cntial and electric field, (b) betwee bxyk/6xs nxcf i4v.vs-96 s(mn electric potential and electric potential energy.

An electron is accelerated by a potential difference of, samhq x/k 7 ,wbxd8opb95y, 0.10 V. How much greater would its final speed be if it is accelerated with four times as much voltagmoxxqw 9kpb , 75/8hdbe? Explain.

Is there a point along the line joining two equal positive c-o3 aj6mdtd +charges where the electric field is zero? Where the electric poten-tjcmad+o36 d tial is zero? Explain.

Can a particle ever move from a region of low electrfpki;-l h4egszh 79)kic potential to one of high potential and yet have its electric potential energy decrg4sfhhk)izl9-k; 7e p ease? Explain.

Compare the kinetic energy gained by a 7e3ri7 kl8.amwk q/ud proton $(q=+e)$ to the energy gained by an alpha particle $(q=+2e)$ accelerated by the same voltage $V$.

If $V\,=\,0$ at a point in space, must $\vec{E}\,=0$ there? If $\vec{E}\,=0$ at some point, must $V\,=\,0$ at that point? Explain. Give examples for each.

Can two equipotential lines cross? Explaiv / fh+.(waxqz t/5sv9hywr/vn.

Draw in a few equipotential line-zutr0w bsh*8/t* r: ;c9dw:bluuc e hs in Fig. 16 – 31b.

What can you say about the electric field in a region o53ljy(: n8prvj )nnvl f space that has the same potential thr l58 vp)vj3: nrjnynl(oughout?

A satellite orbits the Earth along a gravitational equipotential 1 uk,baoq74 7hyus q2nline. What shape must the orbi7u 2b1kq hq7o, 4suyant be?

When dealing with practical devices, we often take the ground (the Earth) to be k 8)p.g:irsb x*d y)vw0 V. If, instead, we said the ground was how would this affek:)v8s.pg *bxi)yd wrct (a) the potential V, and (b) the electric field E, at other points?

When a battery is connected to a capacitor, why do the ,mmdo0 f x:xb1two plates acquire charges of the sam : 1b,0ofmxxdme magnitude? Will this be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on the size, shape, and positiov1 vrhvw7gzoyb5ik(a/4y8 mex.y 9o. n of the two conductors, as well as on the dielectric constant K. What then did we mean when we said that 57y vkbygv.m 9 wz/ rha(8oo.iyx4v1 eC is a constant in Eq. 17 – 7?

  How much work does t(yjul2y pqd d24u(93 -etai,xgr avo-he electric field do in moving a $-7.7\mu C$ charge from ground to a point whose potential is $+55V$ higher?    $ \times10^{-4 }\,J$

  How much work does the electric field do in moving a proton from a point wi0w:vl.aryo )prq7e 7sd-dn y5j (bdu6th a potentidd7(q rp lj -ydusyra: n5o06)7eb w.val 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 wi hsqoy hc;8u(g*a 2-gain (in joules and eV) if it accelerates through a g*uhwh;siac- y 28o(qpotential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquiresa ge(z py3k00d $7.45 \times10^{ -16}\,J$ 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 xv(x/i:rgzs z.y-ym zie/so 2tx96w4between two parallel plates 5.8 mm apart if the potential difference between -96 ( :rozwx/gs. ixv4tzs2/zmexyiythem is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of51xy2rfck b ,j:owv(o $640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field betweeeb7m f1.yge 1rh6wowe 75h5wr n two parallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field betweeaz7. o+o .dlgj*2w 2jzwrhrg:n two parallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a jy20m 2qrzw( shelium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, are mmy-vp hn4eyaq809 d,z(-hre separated by an air gap. How smazh,m q-(ea9r84 ynev d0 hm-ypll can the gap 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 extn3ns 4b9 -z cr)t-keldernal 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 etpu. 7pmg a:4mlectron with kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a pro sqivth 7jz*8w*a;w,eton whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which itu hq5 ejau199as/a 9ss a helium nucleus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric pk9pbp6 i2jqx 1otential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric bk 4 34f3m+yk2aqlvx o )m9dzlpotential 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. rvid97zh4t 7c This conductor carries a net negativ79i4d rzht7c ve charge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a d.zwcgg)9td. z(eat w/istance of $ 2.5\times10^{-15 }\,m$ away from a proton?    $ \times10^{ 5}\,V$
(b) What is the electric potential energy of a system that consists of two protons $2.5 \times10^{-15 }\,m$ apart — as might occur inside a typical nucleus?    $ \times10^{ -14}\,J$

Three point charges are arranged at the cornersx q0obt9(ek b( of a square of side L as shown in Fig. 17–25. What is the potex9(0 ko(bqte bntial at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from re468wb6 ac 0 s c:4oqglym8ddedst 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?    $ \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 electrons from a great distance apart 93ehu ,i8rqhj2dynm* to 3,rujhyn 8*he 9q2di m$1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm north of i cb-pdo5/lo+ja;5 zwv))lo ua $-3.8\mu C$ 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 proton (r5i v m tlh3c0wiq+7nw.adius $1.2 \times10^{-15 }\,m$) 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,+u5es m0wa k(nz2zcp 3 as shown in Fig. 17–27. Determi5230ns(w+ezmuza cpk ne 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 orbitsw5 dvjm3c2g :n fx8x,q a proton (the nucleus) in a circular orbit of radij8qc: d 5w3x n2xm,gfvus $ 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 pro9(*u 0ze3larxiq0k;ufhf a4bton 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 dipo 1+uvaiy3j7dile 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 the o1df4)l 2 iy.snsaln5 negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be considered as the vector sum of .o lnyns5a) 2il4sdf1 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 hye/dcrdfa+o(q b n1(y, as68iold $+2500\mu C$ 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 capc0 w6ub)dh fizh; ku(o e/sa;4cvi(1 iacitor hold $+2500\mu C$ and $-2500\mu C$ of charge, respectively, when the potential difference is 850 V. What is the capacitance?    $ \times10^{-6 }\,F$

  A 9500-pF capacitor holds plus a ++ eupydhv4y,1p ly dw(opga+*/)(lym tho3cnd minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential differ t +yj) yaox/qdq4 (isjw+m;nky*2 hg/ence between two short sections of parallel wire in air is 120 V. They carry e gaw2ty yjs*;4qjn+y /q+)/m(xkoid h qual and opposite charge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of a 12.0-V battery wj.k48str nsj i 85b3xahen it is connectedbjstx8n .43 jr58ia ks to a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must 6qrrrr4p d6g5:p 2symthe plates have if they are to be separated by amy62 r54drs: rgq6ppr 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor incjw/7 fakm,3 pwx,hdq3reases by $18\mu C$ when the voltage across it increases from 97 V to 121 V. What is the capacitance of the capacitor?    $ \times10^{ -7}\,F$

  An electric field of *v v5 ix gk:-q(cxufw*prf a4)$8.5 \times10^{ 5}\,V/m$ 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 opposite kf f kfetb;f4)4+kwb*$5.2\mu C$ 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 the platousi4u/h q8 bl by0.p6es 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 1w gktfv ;nh34then is disconnected from the battery4fwn1;gt 3kh v. 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.]    $ \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 squars vodgb j8: m4tzxw0ah0l7p) 08jae 1ue parallel plates 5.5 cm on a side that are separated by 1.8 mm of par00o1 lm88xa0ptjh : uzgjsab wdev74)affin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a radius of xngxjd : 6lz4jn(1 c2p5.0 cm separated by 3.2 mm of m:g4c 1jxnjz2pnd(xl6 ica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22em h;9 q/cpc7ugdd0dtg8dct2xp1 :k- -V battery. If a piece of mica is placed between the plates, how much charge will flow from the bat7kpem-c2 xg t d0pq9hcddutgc ;8/d1: tery?    $ \times10^{ -7}\,C$

  The electric field between the plates: .ovmsk h8 afn8n7d;1av6dx y 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 energy is store(svu+j x x.ofma+ qp2p;d/ pd39ntt.td?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is us 5y9rzvb7 e:qhp g4b-sed to shock a heart that is beating erratically. A c:q9-pgsz vyr 4ebh7b5apacitor in this device is charged to 5.0 kV and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electrx 1a)jaiz 1rf9 ur5z:pic field between two square plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on the plates are equal and opposite and of:)9p a1r r5xzia1 zujf magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in. pie pans *lqu 6.xmvx/zg; xht 3qv- p8u5 cm apart and connecting .g8 zxpuxq- xtm;vu6 3/qhl*v 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 capacitot4dn)s h,sk j,r has fixed charges $+Q$ and $-Q$ The separation of the plates is then doubled.
(a) By what factor does the energy stored in the electric field change?
(b) How much work must be done in doubling the plate separation from d to 2d? The area of each plate is A.

How does the energy stored in a capacitor change if au5nunl:- uv/ (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as the capacitor remains connected to a batte:5u-l uunvn a/ry?

  A $2.70-\mu F$ capacitor is charged by a 12.0-V battery. It is disconnected from the battery and then connected to an uncharged $4.00-\mu F$ capacitor (Fig. 17–29). Determine the total stored energy
(a) before the two capacitors are connected,    $ \times10^{-4 }\,J$
(b) after they are connected.    $ \times10^{-5 }\,J$
(c) What is the change in energy?    $ \times10^{-4 }\,J$

  In a given CRT, electrons are accelerated horizontally( el 7m*wj2gda by 7.0 kV. They then pass through a uniform elecdw(*gjmea 72ltric 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 center. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a CRT.xbjfs,*lll;)c8 bf y * The screen is 30 cm wide and is 34 cm from the 2.6-cm-long deflection plates. Over what range l*x8sjbcf,bl y l)*f;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 keV of KE in moving from point A tojzmg1(y)bv7 9 y( o/ dkdns4im (ys mkm) n1y b/ dvzjdg7(4io9point 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 transfq)9c f g*n ue2rexcx;:w-l+qmers 4.0 C of charge and 4.2 MJ of energy to the Earth.
(a) Across what potential difference did it travel?    $ \times10^{ 6}\,V$
(b) How much water could this boil and vaporize, starting from room temperature?    kg

  There is an electric fib o2 mqrlns.:-;iz,tyeld 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, electronkixor ) ( 7)on,aevly: 6mfkp)s 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 a())rnky6,:7)oikxm loe p vfforce 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 jbcfh(a8. j,estored 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 it i;*:grpkfjfl;ba7/t3l/-rdzn /z d n/fcm yo: s fully charged, after which it is disconnected from the battery. A slab of paraffin is tdrnj mzt/3nfgll ;r-*d bzf/7pk;f:oc/ a:y/hen inserted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down if the electric field exceeds 4seguu5m(2y g; vg.vj $3.0 \times10^{6 }\,V/m$. 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 b-vt+z l xwxd7se2k / ja,)*xc(side L) as shown in Fig. 17–30. Det/2vs x),x adb -jk*cw xlzt7+eermine 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 connejgzgyt5r9b+7 h: j*o cvmqr/ 5cted to a 9.0-V battery. If a piece of Pyrex glass is pla gg zqot* rm/b:7c5y r9v5+jjhced between the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accel*s+3l9bz2 sjvlsf cu 3erated horizontally from rest in a television picture tube by a potential difference of 5500 V. It then passes between two horizontal uj3ss2fvl*lc +s93bz 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 capacite7ehosmk,v 33avi 5z;ance $C_1$ 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 ;ls::isyf p))co kk.ia farad is, suppose you want to make a 1-F air-filled parallel-plate capacitor for a circuit you ;::fs p.)coikl)kisy 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 electric field ofavt 4ny 1aeu wt0wf: )7/k3xai 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 pkm7t u hq mvumvuq,*aq7; 07n;ulsed 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 potentiae3c + d.i/plpv8u-s-7pee tqxl difference 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, and can have 8i. - uep3dv7+ /ece-qpsxpltan 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 energyh9 8ju *p9r1 8af+vtprdtucd. 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 electfd1vtc8u j h. p+dp8 *r9rtu9arons 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 : rvhr-m,1qmmf*i+, bxm4nrh 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 coins separated by a 04 j/aco//ek jtvjtly dl( y3g3g. 5btwj6w.h4.15-mm-thick piec5l .vwyg3b(6yhwet/j./tjjc4gd/taj kol43 e 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 capacieu6.xlj l0 dg9tor with plate area $2.0cm^2$ and air-gap separation 0.50 mm is connected to a 12-V battery, and fully charged. The battery is then disconnected.
(a) What is the charge on the capacitor?    $ \times10^{ -11}\,C$
(b) The plates are now pulled to a separation of 0.75 mm. What is the charge on the capacitor now?    $ \times10^{ -11}\,C$
(c) What is the potential difference across the plates now?    V
(d) How much work was required to pull the plates to their new separation?    $ \times10^{-10 }\,J$

  A $2.5-\mu F$ capacitor is fully charged by a 6.0-V battery. The battery is then disconnected. The capacitor is not ideal and the charge slowly leaks out from the plates. The next day, the capacitor has lost half its stored energy. Calculate the amount of charge lost.    $ \times10^{-6 }\,C$

  Two point charges are fixed 4.0 cm aph0q 4d56uf gfeart from each other. Their charges are $Q_1$=$Q_2$=$5.0\mu C$, and their masses are $m_1=1.5mg$ and $m_2=2.5mg$
(a) If $Q_1$ is released from rest, what will be its speed after a very long time?    m/s
(b) If both charges are released from rest at the same time, what will be the speed of $Q_1$ after a very long time?    m/s

  Two charges are placed as sh-q 5ql*)edtb oown 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$