If two points are at the same potentialj v6 (euuvj1d,, does this mean that no work is done in moving a test charge from one e1dvuj6j (uv, point to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially l+-v; (jkyljw(ji iz +at rest 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 change in each instancy+( jj+ ;-illvw(izkj e?

State clearly the difference (a) between electric potential and electr w7l9e-uagf2ot8. z xeic field, (b) between electric potential and el 9 tuzee w8a7.o-fgx2lectric potential energy.

An electron is accelerated by a potential difference of, say, 0.10 V. H2*qiezq4-g qr ow much greater would its final speed bzegi r*-4q qq2e if it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining two equ :v1rz6/yh(0egvfgd6z 1 dzbzal positive charges where the electric field is zero? Where the electric potentialdd v1:6(e zbgv1rgyf60/z z hz is zero? Explain.

Can a particle ever move from a region of low electric potential to one4pz; + 3whktk,9h dvus of high potential and yet have its electric potential w;k43vd,9hps z k uth+energy decrease? Explain.

Compare the kinetic energy gaiz2ptd)sx (zv/4v f*fv d q9zui8 s;pp*ned 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 c5- k.9-*fvea d pnziisross? Explain.

Draw in a few equipotenti5i sz5sa-ke d9al lines in Fig. 16 – 31b.

What can you say about the electric field iy a i3y7,nyuq8n a region of space that has the same pote37ayy ynq,8uintial throughout?

A satellite orbits the Earth along a gravitational equipoten9v2j(a +cb quatial line. What shape 2c a9jv+(aq ubmust the orbit be?

When dealing with practical devices, we yhpxu-f,x k 9-lz4po8u43 tgl 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 electric field E, at other point4px,fu oph8-llx ty4 zk9ug3-s?

When a battery is connected to a capacitor, why do the two6pfa9c wwsn2 m /79idp plates acquire charges of the same magnitude? Will this be true if the two conductors are different7 n6fwp9c ms/w9diap2 sizes or shapes?

We have seen that the capacitance C depends on the size, shape, and position of.ztktrb*;, s cp*ri:b the two conductors, as well as on the dielectric constant K c;rzt*pi, .kbrtsb* :. What then did we mean when we said that C is a constant in Eq. 17 – 7?

  How much work does the ele +cei btmtoa:sjn(e y,a.usz:rc8 (+1ctric 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 i(.8 cs1m4n8qejdf xz vn moving a proton from a point with a potent( zmqdn8j. e 8v1cxfs4ial 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 gain (in joules g/:o -oc d1bzaand eV) if it accelerates through a potdb g-z/1 o:oacential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires;h c7z am/vom-m(yr*(7 1 csre qm/vcw $7.45 \times10^{ -16}\,J$ 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 elect ;oicd7u2 um+7 p iw6yhk+(betric field between two parallel plates 5.8 mm apart if the potential differen+(+u7 p ii6bmt yd2;hko7wceuce between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of9xbysrdb31*ndg/)u q $640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two parallel plalf (icrw ( mk0c*gf5w.tes connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallekb )akwo +hmoje3h7i*h5w t 717jwh :tl plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give atozop: xv6g. x8 a3bu( helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a q2/njy vq5 9 y0aq+pui 69nvot200-V power supply, are separated by an air gap. How small can the gap be if the air is not to become conducting by exceeding its breakdown value ofyvv2/n n pqo0j 5qya6iu9 tq+9 $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external for:(g y(t3t3dpyf9o zxn oh,a/ng)qn,s7/h fhmce 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 electron with kinetic enery0 jze-+uiax) gy
(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 is by 7n f.lbv+r33.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is apd/2p7 d4ml(wki w:q 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 pote 5;lymdxap/ jkwf+smq7r: y /1ntial 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an nqd 3qdmr+5d 51 o5pwcx7a:ifelectric 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. Thisf-usr,eir of )a 12kgq ,rynrx59h-0h conductor carries a net negative -f5yof1r9r), ,h urhg n2 e0ixkqr- ascharge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric poted4(nvrt0pv/:jom ( 2f bn 5/jcln4ouhntial 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 f((pow +k hmi2; tl+gvof a square of side L as shown in Fig. 17–25. What is the potential atovf l (piwhm;k(2g++t the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed point charge iv ouc 1.fwm4x0yt;i8 *eis kshb-,b; 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 distancekfa1-wrqx m90m0i7j c apart takcf r 7mx-m0q1j 0i9wo $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cmvk57 l*38*cmzc2kx 3y rx swuk 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 accelzws.y bt)/ m:gezlw2 7erate 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 a f7r8g56)lcxt4ruolof:b c t7re separated by a distance d, as shown in Fig. 17–27. Determine a formula6lc7o 8t4fl5obu7c r:g)t frx 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, a kgrtyjaqq, 0/5+7 iayn electron orbits a proton (the nucleus) in a circul7j5 0yqaqgr kyia +,t/ar orbit 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 kfq7sd(ik4 ,, wbe*cf 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 potenti+bv5 szzzgw(r9xd: c2+ mtjo1 al due 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, cons:sj91 d6ucnhczpkw3 5y(d xn*kjs 86videred as a vector, points from the negative to the positive charge. The water molecule, Fig. 17–28, has a y 1p*znk69xcwdj k6jdv3s sc5 8(nuh: 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 h q1 x+rhwgpe2y 2lndh(keaba,;h (g,in/o n ,0old $+2500\mu C$ 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 cap6btz5y;p .5- flwwwtionj 5u* acitor 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 v (aor/8jir,ijs tn459o a,eyplus and minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of parallelmu9/: mfnt :wgo,6bd l wire in air is 120 V. They carry equal and opposite c l9um ow/fnbd,6mt::gharge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from t(gn.,x2 jjua each terminal of a 12.0-V battery when it is connected tnx. 2,(tjjag uo a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must thgk,r*kxwmxpp ,r iv5+d/( n/he plates have if they are to be separated by a 2.2-x v+mw*/i5 n,k,ph pd gx(/krrmm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increases *m mlp j,. dzj6d;p(iyy:9lehh0:(zsl hn3a bby $18\mu C$ 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 ;*x zdz6)ysbk $8.5 \times10^{ 5}\,V/m$ 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 opposixh iga v7t(s+3te $5.2\mu C$ 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 pl jkrpu*9.8;ghv slj( yates 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. 17–2bbp9z0b y)*k f9a) and then is disconnected from the battery. When thib0bfb )z* 9kpys 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 parallel plates 5.5 cm on a sozm6ed1 c 1xm(4wb j,bide that are separated by 1.8 mmm,d4j 11 x6ob(z mwecb of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a radiuma(ym:vdaq+7vfy; r / jj te8i7u48uq s of 5.0 cm separam+7uqay m84uj iv/dqt:aerj (y8;v7 f ted by 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. If a4aq / bzl7sm*n2dto/x) w i.g.ga /vjq piece of mica is placed between thv7g.*d/a tam/glzjix/.2sb)w qoq4n e plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates e:/k*79n(ymixazyjvt/a 5pvv.j 7 gkof 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 energw 8t.9mlzlg ;wy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart0nc-ncvj)3; ub-oih juz4d;j that is beating erratically. A capacitor izb; )-jh;c4 vuj-u03jndonc 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 electric ,)k 75wx x5 qbom(nzvpfield between two square plates, 8.0 cm on a side, sep) vx(5n zp75woqxkm,b arated by a 1.5-mm air gap? The charges on the plates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by x 7ib7ms6kz cvxv94v6placing two 9-in. pie pans 5 cm apart and connecting them to the opposite terminals of a 9-V bat izvbv6m747 9scx kxv6tery. 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 chargeu-;bve0mjc/) idbl, t 4c u7urs $+Q$ 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 difdhfe 77 0zta/kference is doubled, and (b) the charge on each plate is doubled, as the capt7d zehfa/0k7acitor 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.trmevo88+;csft 0as o5,7op d 0 kV. They then pass through a uniform electric field E for a distance of 2.8 cm, which deflects them upward so t tcop8sro0 5f+a7sdmo8;tv,e hey 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. The screen is 30 cnny xh aw+y(t76uh,)0pw) uqnm wide and is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizontally deflectingy u,n+ t(a6)w 7h0x qwnupnhy) 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 K.lfhi; z0csm: E in moving from point A to point B. f:ch;mi0 zs.l
(a) How much KE would a proton acquire, starting from rest at B and moving to point A?    keV
(b) Determine the ratio of their speeds at the end of their respective trajectories.   

  A lightning flash transfers 4.0 C of charge and 4.2 MJ of eneroa*hu :zu)x5t5 5q6z)fjacfqgy 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 eoe8 h-qzaaa2oz fg+3 li- *5/l1d wjcfield 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, e:98xj pce-z7upuh +wi lectrons 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 g7z:j8p+x9c hwip e-u uravity? 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 ,m4nlew ,0a*cjazv9d 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 ryhkd70pb0uam, k5 2nis connected to a 24.0-V battery until it is fully charged, after which it is disconnected from the battery. A slab of paraffin is then inserted between the plates. Whk,ynrmk d0u0a75h2bp at will now be the voltage between the plates?    V

  Dry air will break down v*lr8/,x0+xawa lnp9 h 4 0,wtwtpd 7fqx,dfl if the 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 triangle (side L) as shown ib3oizl5piia4 d 6w0 q5n Fig. 17–30. Determine the potential at the midpoint of each of4i6 q5l3zipoi5d0b wa 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 capacito:6 nm 0lk),oeq:z hrhdr is connected to a 9.0-V battery. If a piece of Pyrexhdz0 ,o )lqk: hm:ren6 glass is placed between the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in an.2zfyxch1m; s6)a jj.h7v v s television picture tube by a potential difference of 5500 V. It then passes between two horizontal plates 6.5 cm long and 1.3 cm apart tha.h6)a;v v fx.27jshcjnm 1yszt 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 capacitancee2/nl zu7f0qm 23ggd d $C_1$ 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 aiyn 62 98)xg;kqromfdyr-filled parallel-plate capacitor for a circuit you are building. To make it a reasonam)8koyqn ;y9r6 x fd2gble 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 of a59q xz- sf2uanbout $150\,V/m$ 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 las (+k-2rj7fbz:e+e wgf/ rth (fx5d bbper 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 potential difference between the Earth andiet 32ve x9i/pbr5e.n0qt;h x the bottom of the thunderclouds can be as hi3i exbe eh t.ni5q 09vx2;p/trgh 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 provides enough energy t;jk7;i(vq 0s9 ve/o xpbsssu;o 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 ; kv;(vu/7p0ibq;e sssjx9o sat 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 ay4j6ds+/z cp36 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 wf;b(ij km/w7 a 0.15-mm-thick piece of paper (i/ jf7mkwb;w$(K=3.7)$ 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 areak0x2uyu.hz-+bo: p ah $2.0cm^2$ 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 otqe8z( 9 yuurr-jl;5zmher. 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-7)qm.,lqy6 rk flw 5y/;hf2amohm aj shown in Fig. 17–35 with $q_1$=$1.5\mu C$ and $q_2$=$-3.3\mu C$ Find the potential difference between points A and B.    $ \times10^{ 5}\,V$