If two points are at the same pwy (0co7er-jj otential, does this mean that no work is done in moving a test charge from one point to the other? Does this imply that no force need be e (cy0j- reowj7xerted? Explain.

If a negative charge is initially at rest in an electric field, will ah71 faz hghuvd ;c*(-it move toward a region of higher potent-* h(z;h1uh7dgc af vaial 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) bewu .)xxd8j) zttween electric potential and electric field, (zutj x d.x8w))b) between electric potential and electric potential energy.

An electron is accelerated by a potential difference of, say, 0.10 V. How mucs 7ovc y8cop,qrw3) r8qu 1a9oh greater would its final r3,yqc pv uoa78r w9oo1sq c8)speed be if it is accelerated with four times as much voltage? Explain.

Is there a point alon.8bwcz 4ee v1fg the line joining two equal positive charges where the electric field is zero? Where the electric potential is zero? Explainv4 8e1eczb.wf .

Can a particle ever move fr0f3ork kyeu0aei*h9tgv4pk0 wm-c 0,om a region of low electric potential to one of high potential and yet have its electric potential energy decreasey0roif9*gw- 0,kt0kpe aev04 ukh3m c? Explain.

Compare the kinetic energy gzsc de/;o./o5aq *ogy ained 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 lines nb)e2 nki+;s lcross? Explain.

Draw in a few equipotential lines c.gy32qxh0k 9 ayz+s ( 3nqdo;x*bfooin Fig. 16 – 31b.

What can you say about the electric field in a +lt(y 0;k( (nwp9upjtb,sou uregion of space that has the same pot(o uw(;syubt(tlnp p, j9k+ u0ential throughout?

A satellite orbits the Earth along a gravitational equipotential line. Wqx 3 e.fcqw+ har(2w*khat shape must the orb32q ak.rx w ew*c(+qhfit be?

When dealing with practical devices, we often take the ground (t (:yvz4z97x;bumj c ywhe Earth) to be 0 V. If, instead, we said the ground wa7:;9yz4 yjmzxc( bw uvs how would this affect (a) the potential V, and (b) the electric field E, at other points?

When a battery is connected to a capa0 5d r1a(shbhfcitor, why do the two plates acquire charges of the same magnitude? Will this be true if the two conduh01dba(sfr 5 hctors are different sizes or shapes?

We have seen that the capacitance C depend:-i193c3luv6.,vaxrc fq y aizq7rxwe /a0ics 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 that C is aw c63.x vv-ra, zeq/ac9a03x y7 uiirc:lqif1 constant in Eq. 17 – 7?

  How much work does the electric fv2b+49j/ /fhw:ygrf2zlqbae ield 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; k+7ay/qpiefs u5i,y a proton from a point with a potential e qay, s7/pi5ky+ ifu;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 w bn;v6 de2bs.*l ai0jnill an electron gain (in joules and eV) if it accelerates through a potential difference of 23,000 V in a TV picture tain b;j.v2*0 bsl d6neube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires knx; vwxx439s$7.45 \times10^{ -16}\,J$ 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 benq q6:.i*gx3n +i5(nx hgoxby tween two parallel plates 5.8 mm apart if the potential difference between them is 2nx6+x(5inh3yo:*n igx. q b qg20 V?    $ \times10^{ 4}\,V/m$

  An electric field ofocs8e 4dss+8w+ cw6 qf $640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two p lb3i tccaf6,*arallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between. y6oatur7q iiasy+;( 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 heliumxt*q4ov, / q10e2 iag krv)wsn nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, are separi+z 7h9ml9g kyated by an air gap. How small can the gap be if the air is not to become condu9m glhi+y9k7 zcting by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force to b9 ataajr q ,-r;4if9emove 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 kineticirzkv1o e l6;1 energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a pron r;g0zd5pj di-df- l5:pi4kpton whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is5gs /jd: snzyhe:gc:hs ,)l*j 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(/ i /z4t sw:v*sat 2jzkn:zca potential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric potential of k, otag6 m9rh/gt.n .i$+125V$ 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 rqxk)l h,-o0h a football. This conductor carries a net negative , lhqo-0)khrxcharge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potene4 l17uc7v kqprzu .5stial 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 cm3mym3 5-vta w0d3 1u,gval imorners of a square of side L as shown in Fig. 17–25. Wh530ummmgv3 1-ta 3 lvawim, ydat is the potential at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm fro v+ **k; nyxye/p6vluom 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 electroyf6dpm*z)i4.jtdo l3 (. xw.+t+ now on tia0uns from a great distance apart to ot4 6.w(.no.d0 +wpd tu)fxyij*m+lnat iz3o$1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which isl64 9isna 0feu 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 used to accelmxi;)k-jgh6 ob8 s(tz 7bj:x yerate a proton (radius $1.2 \times10^{-15 }\,m$) so that it has sufficient energy to just penetrate a silicon nucleus? A silicon nucleus has a charge of $+14e$, and its radius is about $ 3.6\times10^{-15 }\,m$. Assume the potential is that for point charges.    $ \times10^{6 }\,V$

Two equal but opposite charges are separated by a distance d, as ru i g-gca,2i+k u+v9s55qc7b k/duwushown in Fig. 1qu c++u -argu5ii5d ,bwk9k/ sgc 7u2v7–27. 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 electron orbits a proton3(zy1zxh akt,:vct3y (the nucleus) in a circular ok:vayzt (cz1t3, hxy3 rbit 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 are h( coaq 5tmz-i2u chrpf*:h4 ($ 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 dzgbu4f 86b a+gipole 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 yrv)8;w v:fb( idp; dyas a vector, points from the negative to the positive charge. The water rdvb)i y(p8 wfyd:;v; 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 hol)nogub/ 7 ,ugsd $+2500\mu C$ and $-2500\mu C$ of charge, respectively, when the potential difference is 850 V. What is the capacitance?    $ \times10^{-6 }\,F$

  The two plates of a capacitor eikm4zg3p 2v dbb6hap52h+1bhold $+2500\mu C$ and $-2500\mu C$ of charge, respectively, when the potential difference is 850 V. What is the capacitance?    $ \times10^{-6 }\,F$

  A 9500-pF capacitor holds plus and minuska s82nvz7f5c charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short e e; (*d6/kptlbd: prhsections of parallel wire in air is 120 V. They carry equal and opposite charg /kppberd:e 6th(l d*;e of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each termina-3,rvxrwp wh6s3rrga vsyj 27+ - y/cal of a 12.0-V battery when it is connected -+ ,jwr gar rs7w/pv hyyax 3vcs362-rto a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What akf -4(tbwhi)n rea must the plates have if they are to be separated by a 2.2-mm air gatw( )k4 i-hnfbp?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increb2wpu+.n ,amqv-* hkg2ab-xtf 0*wo; -hpzlu ases 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 0 w0 m6wsukstty0n:6a.) ugpj$8.5 \times10^{ 5}\,V/m$ 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 s c-rfnpwb.k t +4)2ce$5.2\mu C$ 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 electr +jl4;k 2 ;i7jzn pz, nmn0mgqs7b0yxric field between the plates of a $0.80-\mu F$ air-gap capacitor if they are 2.0 mm apart and each has a charge of $72\mu C$ ?    $ \times10^{4 }\,V/m$

  A capacitor is charged by a 125-V batteq7 j jqc3cp7 dtn9z/:try (Fig. 17–29a) and then is disconnecte/c7z qp:tnqc7j d93tj d 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 square parallevmvkbtc -;g (+l plates 5.5 cm on a side that are separated by 1.8 m m(; vg+t-vkbcm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a radius of 5.0 cm sesvme (c;2qxp * +c)zfdparated by 3.2 mm oxqm) (c;+c* zefpvs2 df mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor ,oob4p:4khtl is connected to a 22-V battery. If a piece of mica is placed between the plates, how much charge will flow f4 ol4k bhtop,:rom the battery?    $ \times10^{ -7}\,C$

  The electric field between v,/(k,o c6; jqdm xolythe 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. How much ene2vbx.,vxhb/ixxo u;- rgy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is usedplo 4u.ebl,c)ocx)gt 2ilr9 8 to shock a heart that is beating erratically. A capacitor in this device is charged to 5.0 kV and p2 ol4e llro)gibx,9c8.)ut cstores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored jz )o.pa0y .cr5w mvv*by the electric 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 magnituz.*wm0 yav5cp) o.vr jde $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in. pie pansa3k7 q 8pyy0ubgu :(rp 5 cm apart and co 8p 0(:u7bygyuqrakp3 nnecting them to the opposite terminals of a 9-V battery. Estimate
(a) the capacitance,    $ \times10^{-12 }\,F$
(b) the charge on each plate,    $ \times10^{-11 }\,C$
(c) the electric field halfway between the plates,    V/m
(d) the work done by the battery to charge the plates.    $ \times10^{ -10}\,J$
(e) Which of the above values change if a dielectric is inserted?

A parallel-plate capacitor has fixed chargl b9i ut08zd1zcz.sr5es $+Q$ 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 potential e jow*vynm;( mq 4um,r.me c+z) nuz3/difference is doubled, and/u.my 4 q,vm(rj;mcem+nz)ze *w n3 ou (b) the charge 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 77sf.dpsxl( z;cil*w9 .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 center. Estimate the value of E. l7 l.wdp i9fsx*scz(;   $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a CRT. Th(f 9nodk e)p z6bv37qve screen is 30 cm wide and is 34 cm from the 2.6-cm-long deflection plates. Over what rangenb6 k3)p9f7 d(q eozvv 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 restxgmex cv;. 2k5fu5n8i acquires 6.3 keV of KE in moving from point A to 85 mxek5fx2.iv ;gucnpoint 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( 4 t 9ekw uhra;o ,6szgzmp.bb7b44bo.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 surface whose magnitude w-;z-xii rp3 d1e b j8) 8l)lnfycrli.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 ar- 8 ilt7*5etbj.5sucvkh6bare accelerated by thousands of volts through a vacuum. If a televisij6ae7 -bt5kcbs8*.l5iuvrt h on 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 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 wa -bf.tv;qe7+ulmst *+wtl q/cter 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 fullk ub4kale l8z 3m72tye/na a6b*ma,k0y charged, after which it is disconnected from the battery.ma/ae 4t ya7lkk6*m3,al bu8ekn2b 0z 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 th(to 1vczz+0xgsq f h):-8ej gge electric 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 trian(yph8hcdyw9 : 2cmru 9gle (side L) as shown in Fig. 17–30. Determine the potential at thm98crpwy:2ud c9h(h ye 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 ixytvu4h+/k24r rx dp,;wrc) o s connected to a 9.0-V battery. If a piece of Pyrex glass is placed between the plates, how much charge will then f+ tr c4 4 2ykwxh/por,xvur);dlow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally fmcmb4ci+o) 7s 6/ dvh1as0 w0l lj)tdrrom rest in a television picture tube by a potential difference of 5500 V. It then passes between two horizontd0 )j1+ barms6 ccsd7/4 i vmlo)lwt0hal 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 capacitanc m qzp)g-kia*zr2 -k6je $C_1$ 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 a 1-F air-filled paiq92fb,e ui+qr1gbp* v)kmwy:)ol2*/hf qr arallel-plate phlowr+ e)q,b*qifa r19f /km2 b*:v )u qyig2capacitor for a circuit you are building. To make it a reasonable size, suppose you limit the plate area to What would the gap have to be between the plates? Is this practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there is an electric f.ikwva0:dz hn 9be3.mield of about $150\,V/m$ which points downward. Two identical balls with mass $m\,=\,0.540kg$ are dropped from a height of 2.00 m, but one of the balls is positively charged with $q_1$ = $650\mu C$ ,and the second is negatively charged with $q_2$ = $-650\mu C$. Use conservation of energy to determine the difference in the speed of the two balls when they hit the ground. (Neglect air resistance.)    m/s

  The power supply for a pulsed nitrogen lagz6e p:ls5pi+qy67i7jua77 uhmr0ouser 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 p:;f xt6wzsyf0ie c ;d.otential difference between the Earth and the bottom of s;z fe:y;wf.xc06 itdthe thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are typically 1500 m above the Earth, and can have an area of $110km^2$ Modeling the Earth–cloud system as a huge capacitor, calculate
(a) the capacitance of the Earth–cloud system,    $ \times10^{-7 }\,F$
(b) the charge stored in the “capacitor,”    C(Round to the nearest integer)
(c) the energy stored in the “capacitor.”    $ \times10^{8 }\,J$

  In a photocell, ultraviolet (UV) light provzz;x)ges)griu 1 dde,y i14h;ides enough energy 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 electroi1gsid e;y zd ));xrzghe,14uns, 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 fr::h v6nj larfog* 7nv2 5bk)rsvo 76cgom 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 u x :tj6i:/ily ln2hc6separated by a 0.15-mm-thick piece of i /2l :yjxucn6hlti:6 paper $(K=3.7)$ A 12-V battery is connected to the capacitor. How much charge is on each coin?    $ \times10^{-10 }\,C$

  A $+4.5\mu C$ charge is 23 cm to the right of a $-8.2\mu C$ charge. At the midpoint between the two charges,
(a) what are the potential    $ \times10^{ 5}\,V$
(b) the electric field?    $ \times10^{6 }\,V/m$  ----待选择----leftright 

  A parallel-plate capacitor with plate a /n wyt/mkhp*h.um 9r(hc;ns(t11quo rea $2.0cm^2$ 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. Their charges l8.fmzf4(ei;6p qj 7advj9zhr b6r p, 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 wi(o1.f kpdzudf /jsfn s t++1z/th $q_1$=$1.5\mu C$ and $q_2$=$-3.3\mu C$ Find the potential difference between points A and B.    $ \times10^{ 5}\,V$