If two points are at the same potential, does this fyaj s .ne(8vd(s7z :umean that no work is done in moving a test charge from one point to the other? Does this imply that no force need be exe (yjd (fs8su ae7nvz.:rted? Explain.

If a negative charge is initially at rest in an electric field, will it move- hkwtp0)( men toward a region of higher po-m wtepk (nh)0tential 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 g04u7jg qi 7)2 igtbtspotential and electric field, (b) between electric potential and electric potentiajg)7tgius t gb0 q4i72l energy.

An electron is accelerated by a potential difference of, say, 0.10 V. How much9 -bzarqgt8s *wzxv,0 greater would its final speed be if it is accelerated with four times as much aqsgz-0v x 9t8r,w b*zvoltage? Explain.

Is there a point along the line joining two equal positive chargebiaw(jhp6*uiq,u.5 b vf7sdqtop:0+s where the electric field is zero? Where the electric potential is zero? Ex,+ p7t5uvdjf.u o*s ap0hqb(b6q iw :iplain.

Can a particle ever move from a region of low electric7a 9 2njann2- o8lxp.hqay(ql potential to one of high po.9 aloa278p-h jnx(ny2 qnlaqtential and yet have its electric potential energy decrease? Explain.

Compare the kinetic energy gained by a tmcx* ,*myqc 6p:jk2g8(kle ylu(f (mproton $(q=+e)$ 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? Explail5g782ltn. iw9n7yx)a 4eb9tjgan f qn.

Draw in a few equipotential lineu*sl2z. mflx.n:brrs(v:4 t gwu6 a8p s in Fig. 16 – 31b.

What can you say about the electric field in a region of sp7,j6.pl q qxy9pyl i ugc-)u+mace that has the same poiyu g. lp6,qx )uq-c9p lmyj+7tential throughout?

A satellite orbits the Earth along a gravitational equ2v5u+ abhvzifw)k0 e2ipotential line. What shape must the orbit w zhifv+vu)k5ba 220ebe?

When dealing with practical devices, we often takz3 :u9lj:qz ta dtyfk dye:ua 6461cy.e the ground (the Earth) to be 0 V. Iflfua 9y az6uc.1yd :j3z kyqedtt6: :4, instead, we said the ground was how would this affect (a) the potential V, and (b) the electric field E, at other points?

When a battery is connected to a capacitor, why x:gz* idr z,4jdo the two plates acquire charges of the same magnitude?z*,i x:dgz j4r Will this be true if the two conductors are different sizes or shapes?

We have seen that the capacitance 3)rcx/tlw+ clkwz96a3 tf4xa C depends on the size, shape, and position of the two conductors, as well as on the dielectric constant K. What then did we mean when we said tar4l x 3afw36cx c)z9+ltt kw/hat C is a constant in Eq. 17 – 7?

  How much work does the electric field do in bd :xhi)3if(y lgb+qx8z/jozp 1g+ c4 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 poi(swuw/v (qglos)yo004lj, a j nt with a potentias0svujgy /oaol4w)l,w(jq(0 l 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 wijrh.g,s4 u5 5c+gokmm1 k7syh ll an electron gain (in joules and eV) if it accelerates through a potential difference of 23,000 V in a sm4+gkjy.h o7rh5g ,c1s5km uTV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires cfgz;c 087nks0 ,mzwz $7.45 \times10^{ -16}\,J$ 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 between two parallel plat u01oh*r:ooi:skv a ayp(3qt1es 5.8 mm apart if the1:o:y3o 1at* p(0hrk u svqioa potential difference between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field ofp0tpza*t( 9l k $640V/m$ 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 connectfv( 9+m7fqa))2 rf jev*tv kgaed to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parv;ai1:) /lkmziwnszqd 8cm2/c)c c4w ym, ml(allel 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 helium nucleusd*forhzlky m7mf46hqww,x xua79+4 8 $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 20q6l*;q.a7yi nvz zpc1bqn 4 e30-V power supply, are separated by an air gap. How small can the gap be if the air is not to become conducting by excvnqz z 1cnqey*ab4q;3pl.76ieeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force to ,s10zvt9zfaag:ya5kwv ) u 3 p9zv/nm 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 l2aut+f78p- 4*g5/ivphvnua* e njhjwith kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whose kinetic energy(krd5dho -xx-; i5duwq4f+ t y is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nucleus, 71h4fec igg +e)9b1vz fbg:n u$Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) 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 a nl6(ide a+l(c$4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric potential of qxc9lb rv.q 4tx/8f4g$+125V$ 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 carries a nc5 25cpgpk4 tket negative cha4kp 2cpk55cgt rge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a distance of 5d ybs)2ssstz).g6 -jt rgl2*x mq(wh$ 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 of a square oxwly22b2xddw2 s.( bjf side L as shown in Fig. 17–25. What is the potential at the fourth corner (point A)s(jwdw .2d bby2l22xx , taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixa7;uv19o(xi 3jozu /wic 3zloed 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 dxazz u3(5ib)lone to bring three electrons from a great distance apart tozz)5 i3u(lbxa $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is x3:4 (zf;it -cu,lxk8s akqp c72 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 used to accen07j1lx3 hl mulerate 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 sepx*3e ca 87e7tvmkd:eaarated by a distance d, as shown in Fig. 17–27. Determine a formula :3aa de7e 7*tvexk8mc 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 protonj t4q*os*g/b cru,l+h (the nucleus) in a circular orb,r*4uojg lhtb/qs c +*it 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 proton ahi0udz8 vtyi, kryo/2 3oop65re $ 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 y ;(wotbur)s+to a dipole whose dipole moment is $ 4.8\times10^{-30 }\,C\cdot m$ at a point $1.1 \times10^{ -9}\,m$ away if this point is
(a) along the axis of the dipole nearer the positive charge;    V
(b) 45° above the axis but nearer the positive charge;    V
(c) $45^{\circ}\,$ above the axis but nearer the negative charge.    V

  The dipole moment, considered as a vector, poin1yjw5eao zy4) ts from the negative to the positive charge. Th) e1w5j4ayoyze water molecule, Fig. 17–28, has a dipole moment which 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 hold gri-twy;m t px wn g q;n(ut43)h/.c gc9ql8p2$+2500\mu C$ 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 cay4:qq 5f 6i*z /fezyzlpacitor 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 andsi u,k 5e4apa( minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference be9:yhba.uowuj7vnx0d2tv tm :xt 2f-/tween two short sections of parallel wire in air is 120 V. They2.jyuh0-u/9of2tvt a:xxvt:m7d bnw carry equal 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 when it is *sc0 v,wqn9afconnected ,n csvwq9fa0*to a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is de;;r-j pdodb1 nsired. What area must the plates have if they are to be s-do;b jn;rd 1peparated by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor dpp0c;qb,1whincreases 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 r)-z2cyg ldzi69 2tuz $8.5 \times10^{ 5}\,V/m$ 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 oppositdsmzf b(of9.-)u,h qie $5.2\mu C$ 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 plates o-f -ykkmqi5qnge0 8wv;q (5bcf 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. 17–2p /id,i s v s.irn3kcf6qe+28j9a) and then is disconnect/n+k.,p62j is3f8 isired cvq ed from the battery. 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 squar4 pst)(o b,tfse parallel plates 5.5 cm on a side that are separated by 1.8 mm of o4 t),fbstp(sparaffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair ooieapfd ;+ rp744 ev1jf circular plates with a radius of 5.0 cm separated bye1ero f+pd;a4j4 i7pv 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor / w2fred2mk)s9rbh ywi u/3 )vis connected to a 22-V battery. If a piece of mica i)wr i f/2/2h9be3 r )uvwskmdys placed between the plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field betwe )xrk 6pj6u/znen the plates 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. Hb-1 brpcf uc,5n6 uvp-ow much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator pvrw4u)9o d0 mzf5m)i is used to shock a heart that is beating erratically. A capacitor in this device is charged to 5.0 kV and stores 1um4f)w ozm50 9drvp) i200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between te*6wbu tl8cb6,en 5htwo 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 6n6u wh8,tbt5c*ebel magnitude $420\mu C$.    J

  A homemade capacitor is assembled bhu/a o l6/9upiy placing two 9-in. pie pans 5 cm apart and connecting them to the opposite teruil9/ha 6ou/pminals of a 9-V battery. Estimate
(a) the capacitance,    $ \times10^{-12 }\,F$
(b) the charge on each plate,    $ \times10^{-11 }\,C$
(c) the electric field halfway between the plates,    V/m
(d) the work done by the battery to charge the plates.    $ \times10^{ -10}\,J$
(e) Which of the above values change if a dielectric is inserted?

A parallel-plate capacitor has fixed cha70bmkv(6c7 g w.peq eou -pic(rges $+Q$ 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 (a) the poopz 30l6lg, yh4dv w +w6pttw(tential difference is doubled, and (b) the charge on each plate is doubled, as the capacitor remains connected to a battery?wpgd l(wh t3o,6w t0+zp6vy4 l

  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 kV. They then pa wvk97hvn*m; qss through a uniform electric field E forh9v7*n; vqm wk 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 d,-- i ( wn.70ny akkmylai.tsa CRT. The screen is 30 cm wide and is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizoks .y-mid,a. (ik7ly nwnat- 0ntally 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 c vpd-ntf-fm(g; t/5racquires 6.3 keV of KE in moving from point A to poinvm5tc / fr-p- gn;tfd(t 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 4q+ vj/tp2( pkw.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 the Earth’s 97mb5*zlihj nqbt 4ugw; +zl4cq 3(wj surface whose magnitude is about $150\,V/m$ How much energy is stored per cubic meter in this field?    $ \times10^{-7 }\,J/m^3$

  In a television picture tube, electrons are accelerated by thousanmhe+ny 3c9c 0kds 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 ele n9ecy3h+kc0mctron would remain stationary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough storv wwul ob zt.b93wt l9gf;a8+/ed 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 is fullyk np,4lkui*+p0b clq49tc)w/zhv1 it t3: djy charged, after which it is disconnected from the battery. A slab 30qn/4 w l9 ph kvk,*d+pc:yilcztt)i t4u 1jbof paraffin is then inserted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down if the electric)akz;f5v fhvnb4.j7z7fd r:b 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 t5-ei 4tnn gh9uriangle (side L) as shown in Fig. 17–30. De 4guht9nei5-n termine 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 capa6.6cnhe4 j ahycitor is connected to a 9.0-V battery. If a piece of Pyrex glass is placed betw4y.h6 ca6jnheeen the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerat08cufr:cz8f9)a;v rvw 8n o hted horizontally from rest in a television picture tube by a potential difference of 5500 V. It then passes between two horizontal plate)czc:o88 r0vff8; rnwauvht9 s 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 capacitanw f(j )pjx82lgce $C_1$ 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 w )q+b6+uhyhbwdc bv*2d)8ek farad is, suppose you want to make a 1-F air-filled parallel-plate capacitor for a circuit y bdbcw 8v) 2hu +hewqbd*6k)+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 Eak1y:vg1 :mhnoayqm8 g5.r-z9 fof qy 6rth there is an electric 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 for06c kgqxn.elh g+aav 9,g5y +q a pulsed 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 potenuq w)p31*s5 *pcycnxqtial difference between the Earth and the bottom of the thunderclouds can be as high as 35,00p*yq)cc5 3w x*1nqsu p0,000 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) lighst6kcg.f n)- gt provides enough energy to some electrons in bark s-) c6f.ggtnium metal to eject them from a surface at high speed. See Fig. 17–33. To measure the maximum energy of the electrons, another plate above the barium surface is kept at a negative enough potential that the emitted electrons are 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 ansd1nmx(,o- u:r*; rujre3s1flqlo ; d 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 c ib5+(8yvf7;n l waxr0.15-mm-thick piecyvf5( c7xilw8a r+nb;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 capacitt8p *dok)2jkl-dz 8hmc. vm( mor 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 4.0lub:3vxkn :h2 lrxsv*3 , br3w cm apart 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 shown in Fig. 17–35 with-l6+-pftkq ye $q_1$=$1.5\mu C$ and $q_2$=$-3.3\mu C$ Find the potential difference between points A and B.    $ \times10^{ 5}\,V$