If two points are at the same pot7/u dpuy7) utpential, does this mean that no work is done in moving a test charge from one point t 7t7)ud/ypu puo the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at reag p 3q,m,j/d -.dqv 4wr5( h4yrkidrdst in an electric field, 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 changeakjmd5 v g3,d-d/id,w(4r hqpqr.r4y in each instance?

State clearly the difference (a) between electric potential and pvfj0p -jlx232ms+q( e- ktdh 2ni.fkelectric field, (b) between electxl+k fikn2d(pemsq vp-0 3f2.-2 jtjhric potential and electric potential energy.

An electron is accelerated by a potential diykm 9j.qznek f:06pk)mm09lpfference of, say, 0.10 V. How much greater would its final speed be if it is accelerated with four times as much vo k0qp)mzk fmmpey j:n9kl.6 90ltage? Explain.

Is there a point along the line joining two equal positive charges6w .ru4qt:ye f where the electric field is tyr:.e6q 4f wuzero? Where the electric potential is zero? Explain.

Can a particle ever move froyi lzc0 :l jtz9hh:w6( 8el3f5q(y ofrm a region of low electric potential to one of high pot96 (yll j:80rcq 5 tzf z:h3whl(yfoieential and yet have its electric potential energy decrease? Explain.

Compare the kinetic e 2 4hitq)rgt,z5x;eu ug om)2anergy 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 lm ke-dv06d(kc ines cross? Explain.

Draw in a few equipotential lines 9uop; xn jis .g0r0;jgin Fig. 16 – 31b.

What can you say about the electric field in a regiod0lryxma h3ch *lfs9stf 42-+ n of space that has the same potential rx+-fsal*294 0scml 3fdt hyhthroughout?

A satellite orbits the Earth along a gravitational equipotential line. Whaj .y4dpglkt qp*zq1; (t shape must the orbipdt 1j(p4l q* qz.ygk;t be?

When dealing with practical devicevq9s2zs mxk7 /7l4de us, 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 el/47d9zx7veu2 s kqslmectric field E, at other points?

When a battery is connected to a capacitor, why do i* h5jt78bb rlthe two plates acquire charges of the same magnitude? Will this *85bl7 b tirhjbe true if the two conductors are different sizes or shapes?

We have seen that the capa ;5nks u(x)x jkebk62rcitance C depends on the size, shape, and position of the two conductors, as well as on the dielectric constan;b(usk)rjn2e 6kk5x xt 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 td06 i6s p cb o.gcal07c-- uidrgt1,qin 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 p mho8gv,n .-+(qb7u6jhf zzrm1 oaf(rroton from a point with a potential ofzh -(gu1 8jh(,f qnb+mroz6f. v7mr oa $+125V$ 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 aql- ggw2cs:wbmr6 pof4/bf- 9 n electron gain (in joules and eV) if it accelerates through a potential difference of gbgl2/f mbrw o9pq-f:s- wc6423,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires,0y+qg dys4i f $7.45 \times10^{ -16}\,J$ 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 betwep i0o yb+;ee+men two parallel plates 5.8 mm apart if the m 0ebo+y+i ep;potential difference between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of a yb+chxz5(a*$640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two pa uw4-rvtb6+dm lg +op-)xd)i arallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between45tqzfnoldpq :5/ +jh two parallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference iz, h,( 4goj po-oyu5kus needed to give a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, are 8jcqm-n/7csqseparated by an air gap. How small can the gap be if the aq/qcn s7 8mc-jir 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 external force rdf, */p z5g; (rzh5u ;kpcww2qq4ltkto 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 electron with kinetic ena+b,+t4a ggowixe7j : ijzd4*ergy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a ds6ez*hok78sez nufsd 44;8d proton whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nucxf l.t7 dbs00c716l rkxp voa0leus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) 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 from af0*zzngh +vbv4d;, wsai2va- $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creat4 y 0ws sf0h0*qrx;yztlhnxd* h(16m08oo cqk es 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 conductor carrief us,/dt;7lp o)jw59 3h wdz2x u7uyxbs a net negative chargexh5b;73dos/7 ljzwy uxf,uw2 du9p)t, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potentv(bih7q 3vshr+ 7p+hvial 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 arranged at the corners o;aks o +t1e*a )iw1jewf a square of side L as shown in Fig. 17–25. What is the potential at the fourth corner (point A), ekoa1+ ;ea * 1tswijw)taking $V\,=\,0$ at a great distance?

  An electron starts fra6k a sdtuz;+4om rest 32.5 cm from a fixed point charge with $Q\,=\,-0.125\mu C$. How fast will the electron be moving when it is very far away?    $ \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 gra5q;*;si zqoneat distance apart oq;q zai ;s*n5to $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is0 zu e3vn*mlk41at/dm 72 cm north 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 usytlw4+riph0v w;3 nd.ed 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 7.y hup(xmj3ad, as shown in Fig. 17–yx3u.j7m pa h(27. 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 atom, an electronw -yjjol)h3.nq azz)2 orbits a proton (the nucleus) in a circular orbit of j.n- z y)wh2oz) qal3jradius $ 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 protcp0grk a csc3*:a4 lc3on 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 d)a 0.1kxf 9os0yy/kgepni0vu7a- mf kipole 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 negative to l u;7,ctvwhm/the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be considered as the vector su vc7tlhu,; /wmm 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 capacxwfazz. )a8 wr dx4 f,ola;-)sdaoy/(itor 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 capadb tcn1 v2xch2 twj6tv0pyq x+86i8/tcitor 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 holncynqn33z6 8z ds plus and minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference betwevpm3*5vb z 6 fltnx/9sen two short sections of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is the capacitx*6tsp vb3mn9 5zfl/ vance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of a 12.0-V w,j ;2tks;(9l.qncycl8 afof battery when it is connected to a al(9n os.yk2c 8j,fc;lq;t fw$7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates havuyc0b tg 4 ,*ux3ow8zbe if they are to be separated ozuxb 8u03w,*g 4tbcy by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increases ()ty :qtd8h hzby $18\mu C$ 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 ofdm h dzkrzj;)jt45;p r 9-(8*oyx tmut $8.5 \times10^{ 5}\,V/m$ 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 om l2 vle3+7,)ubsax nnpposite $5.2\mu C$ 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 be)g e/gbrt 5a py :ivc:0x9e*jjtween 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. 1nuade-2u):3cb; eyx j7–29a) and then is disconnected from the battery. When this capad) a3n c2xyeu:je -;bucitor $(C_1)$ 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 two1+ osq/zs xo:)nd t(mfq.a* qi square parallel plates 5.5 cm on a side that are separated by 1.8 mm of paraffa+) ( mnit/*zox o. qdssfq1q:in?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of cia*e(y0 ,bg0 wonift4n rcular plates with a radius of 5.0 cm separated by 3 iny0(ta e04w*n, gofb.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a l y(2cnq;nmigh /j+4g;qt ra122-V battery. If a piece of mica is placed beyn+4 i2n;g/tgj hr;m(cqalq1 tween the plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plac3tfg:6v0g+ym kzbd,/tob9 f tes 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 stoxo:6 x8l ctj6hred?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beating erratitbfh*eck+utsq4d;7 8cally. A capacitor in this device is charged to 5.0 kV and storcfe 4 ustdkt7;q *8hb+es 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored b0dvafim4,llik6g mhedjs x2+ 0 e(e1)y the electric field between two square plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The chargem2lexgm(ve 1s0ad 0fel,)i+46j dhi ks 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 fn(-i,jtig1o qq81n r apart and connecting them to the opposite terminalsqtrinngqo-,fj1i( 81 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 capan ( 5fjaaj7.gacitor 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 storxba c.lnvtf-8u * .jz,q(oi/g ed in a capacitor change if (a) the potential difference is doubled, and (b) the char/j (nf,x.8zv gouqtl ab c*.-ige on each plate is 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,    $ \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 by 7.0 kV7a2k hv ,7mz: snpe;cl. 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 center. Estimate the value ov kspz7h;7n: m,la e2cf E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a CRT. The screen is 30 cm wide and is 34eo;3mw ;ou cg- cm3gow;cum- eo; from the 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 acqu4 7ztmmm;ofjj lh9e,: ires 6.3 keV of KE in moving from point A to point B;4:j7z,lom tmme jfh 9.
(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 trkfk jvm*z6bd6u2ez3) ansfers 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 field near thp8;. vgizsdhh8d , l(fe 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, electrs hsl ei*wu2d. pzb+l7l+uv6sgj7o -(ons are accelerated by thousands of volts through a vacuum. If a television set were laid on its back, would e6e( s* 7bsp-js wu2.zol+hldi+7lv gulectrons be able to move upward against the force of gravity? What potential difference, acting over a distance of 3.0 cm, would be needed to balance the downward force of gravity so that an electron would remain stationary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough stored energy to heat 2.5 kg of water pnpl)ofa*.zk;2h b + zfrom 21$^{\circ}\,C$ to 95$^{\circ}\,C$. What is the potential difference across the plates?    V

  An uncharged capacitor is connected to ahiza 2-zt rk).u8 s67xkd(ox;wllf z + 24.0-V battery until it is fully charged, after which i l+.wzrt6zzd kx8h(f7 ix2 uo s;)k-lat is disconnected from the battery. A slab of paraffin is then inserted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down if the elecz*; pvr 5n;jextric 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 equilateral triangle (sdt;u( alk +bzw9cr( ;iide L) as shown in Fig. 17–30. Determine thz(i kw;bt9cl r a(du;+e 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 to a 9.0-V battery. Iff/(b.;noqvuj7)xs pjvj,u- y a piece of Pyrex glass is placed between the plates, how much charge will then flow from the x,v-fpnyb (uo/ujs 7);j j.vqbattery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in a television picz o*.oh wm:,rcture tube by a potential difference of 5500 V. It then passes between two horizontal plates 6.coo*h :z ,rwm.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 capact;to9l3. g uznu:yye4itance $C_1$ 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 wany8 mv,vo t5mt8t to make a 1-F air-filled parallel-plate capacitor for a circuit you are building. To make it a reasonable sizevy8 omv5, tt8m, 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 ofiehu5in/e -br3na34 z 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 pulsed nitrogen laser havhdv-lwiho// z6f x 5)s 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 between the Earth and th9m (m3jwxjxxkg--l 7ge bottom of the thunderclouds can be as high as 35,000,000 V. Tlj- m-wj x (9gkx3m7gxhe 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, ultraviolety0 j8p1(sz bg+es y3xh (UV) light provides enough energy to some electrons in barium metal to eject them from a z(sj +e 8s1px hygy03bsurface at high speed. See Fig. 17–33. To measure the maximum energy of the electrons, another plate above the barium surface is kept at a negative enough potential that the emitted electrons are slowed down and stopped, and return to the barium surface. If the plate voltage is $-3.02V$ (compared to the barium) when the fastest electrons are stopped, what was the speed of these electrons when they were emitted?    $ \times10^{6 }\,m/s$

  A point charge is pl6mq zjor,l,,jpg3t , qaced 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 f5/duoes ww fi xtu/w )9p0t0(vvr/(rcrom two 1.1-cm-diameter coins separated by a 0.15-mm-thick piv (fwtw(/xdu/orr5 t c)v00iweup s9/ece 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 capacitort;a a42j*nh 3q2mxot b 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 apart from each other. Theiy7bvv4trx; +xu p:z.hotk8 i:r charges are $Q_1$=$Q_2$=$5.0\mu C$, and their masses are $m_1=1.5mg$ and $m_2=2.5mg$
(a) If $Q_1$ is released from rest, what will be its speed after a very long time?    m/s
(b) If both charges are released from rest at the same time, what will be the speed of $Q_1$ after a very long time?    m/s

  Two charges are placed as shown in Fig. 17jr9-nmm qh 3w si8*9rd s2q uyxs9(ajw6o0k.e–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$