If two points are at the same potential, dcs wi 6)x(2wyrdt-f f2oes this mean that no work is done in moving a test charge from one point to the other? Does this imply that no force-(x rcd2 2wws6fy)f ti need be exerted? Explain.

If a negative charge is initially at rest in an electric field, will it move 4kvi/w;2 j(ah ,eipqktoward a region of higher potential or lower potential? What about a positive charge? How does the potential energy of the charge cq /2e ai,kjp(4i w;kvhhange in each instance?

State clearly the difference (a) between electric potential and electric fi2wf .sjby /8n 9;rs dfau23vhreld, (b)w98b;f urhnardjf/ 232y.ss v between electric potential and electric potential energy.

An electron is accelerated by a potential difference of, say, 0.1 g/s5fzyz vov*c7f6 e:b1 wz-e0 V. How much greater would its final speed be iz v5/e zv s6f71ozgbe:fcy*w-f it is accelerated with four times as much voltage? Explain.

Is there a point along the line t(h* (ray 5ojdjoining two equal positive charges where the electric field is zero? Where the electric ay(5jhto d (r*potential is zero? Explain.

Can a particle ever move from a region of low e7 ot6 .mpan7og8xhbf+lectric potential to one of high potential and yet have its electric potential energy decrease?pf87m .+gx76ht noao b Explain.

Compare the kinetic energy gained by a f, )lllbgx/s/proton $(q=+e)$ to the energy gained by an alpha particle $(q=+2e)$ accelerated by the same voltage $V$.

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

Can two equipotential lines cross? Explyh5 ri bios2xknt zf5:e,7;b9ain.

Draw in a few equipotential lines in Fig;jdevji :9y4y . 16 – 31b.

What can you say about the electric field in a region of space that6(m wj(bsm- 7. sp due2,aoscn has the same potential w7sm6cdjb(uas2( p-,osem .n throughout?

A satellite orbits the Earth along a gravitational equipotential- 6kc )d1wqpsb line. What shape kp1d)w-b q6c smust the orbit be?

When dealing with practical dd- jbyykt2 c026/lwtcevices, we often take the ground (the Earth) to be 0 V. If, instead, we said 6 0j2ydlbckc t/t2w-ythe 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 do the two plate()u/gwyx x d/cebl/)qs acquire charges of the same magnitude? Will this be true if the two conductorsugy wq/ edc)l)x(/bx/ are different sizes or shapes?

We have seen that the capacitance C depends on the size9v6lo h- uvid(, shape, and position of the two conductors, as well as on the diellhiuvd9 ( -6ovectric constant 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 in my*s3xr-b v cm+oving 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 aulfz6 taxaw3nf4 7can1( l79roton from a point with a poflua 749( wcant7 1zaaxfl6 n3tential 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 and eV) if it accfdx lgf)8tpr nz:.50 lelerates through a potential difference of 23,000 V in a TV pictu5nzlrpxl.d g: 8f)f t0re tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires8nejac9dr, g 6)w,u/w kp ,vv -v3haea $7.45 \times10^{ -16}\,J$ 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 plates 5.8 mm apart if tj9/e8oe;iu(jl1 i9ork1,d qa eao0vrhe potential difference between them is 220 r q1 oek1jo,e8 vaau0jr(9le 9i;/odiV?    $ \times10^{ 4}\,V/m$

  An electric field of a j ekx;dd:(s7$640V/m$ 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 connected 42sdrfyr.mw/ :xddqx s6-o 0rto a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected to kswiyubxi)4250uxa :a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is need:.lqx3 jf1uyye2 7yqqc --r wjgsw2d2 ed 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, a * rx*2liqabb5re separated by an air gap. How small can the gap be if the air is not to become conducting by excal irb**5 b2xqeeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an externalen h.-pa8q)tq force to move a $-8.50\mu C$ charge from point a to point b is $15.0 \times10^{ -4}\;J$. If the charge was started from rest and had $ 4.82\times10^{ -4}\;J$ of kinetic energy when it reached point b, what must be the potential difference between a and b?    V

  What is the speed of an electron withx:sx z tgf 0n;km0sz6a+sq(t/ 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 e.hm;wm)r3 r,j 04xg5g etvr aznergy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is ui5h p.+)5,cp+0j*gt8dhf: zygtb sthk o(hba 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. jajk1*.y3z prx9 blhk9;jqxntial 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric potentialvg+apl9 pd/ t; 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 sh6z0mss-, rtxz x30nq hape of a football. This conductor carries a net negative chaztxn zr0mq0xh 6-,3ssrge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electfb h :7qwec2h;gx7gt2 9j,pwq ric potential 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 of a square p w7 dy-wo(zs.9vyzz2v taz* (of side L as shown in Fig. 17–25. What is zz (t9dv(z*p.vyw oz7yw-a s2the potential at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed poqdq(1(f,b6,.c yjb wdjf9yzj int 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 brinwr4a 4f /wa6zgg three electrons from a great distance apart to zrawf4g4/w6a $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm nofd. xp4kr9)s wrth 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 acceleg.pmcth (7jtn u8x.ft)x s2+k)b0ghr rate 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 opposit //-r1w1c;kxezc ;xy zzvbup+e charges are separated by a distance d, as shown in Fig. 17–27. Determine a forwc;pz/y1br;c vk +/xu ez1-x zmula for $V_{BA}\,=\,V_B-V_A$ for points B and A on the line between the charges.

  In the Bohr model of tj7e ai9nlf 5y2he hydrogen atom, an electron orbits a proton (the nucleus) i2y a9 filen5j7n a circular 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 proto0x4 gfmz3o ll8n 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 dipolegxw.2654wjdqb 1)yun qm hl )r 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 t7lmk)k9 z2/wozh wl ,phe negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment whichowz2wz)khml 9k 7lp ,/ 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 h6h3ea:m e va1lold $+2500\mu C$ 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 cdnqc +sk d/g3he zukb)tz )x+f/8de+ +apacitor hold $+2500\mu C$ and $-2500\mu C$ of charge, respectively, when the potential difference is 850 V. What is the capacitance?    $ \times10^{-6 }\,F$

  A 9500-pF capacitor holds plus a 2.jmd j b.0dl mu7/ms6tjii u,mdy7g5nd minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference betwltfwm ,r8i- szb-67ow *in v*p2xppo( een two short sections of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is the capacita-xnm *svf b,tplop-i2wiow86* rp7 (znce of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of a 12.0-V ba; dfu8.qjy 5c8g xdtf7a+1mjz ttery when it is connected to f ;1j88.md+57 fjdaqztc u xyga $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the platbyf67nnx 42 xvsczzz: p 4v943nq3ulkes have if they are to be separated by a 2.2-mmnq2xl: n4vsv4 zf67pbukyn9x3 z4cz3 air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor wj0u: rn2rhz/ increases 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 d8 iz3tv5 *c*eizbr3k $8.5 \times10^{ 5}\,V/m$ 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 oppokf w txw8,t-eilw39 x4site $5.2\mu C$ 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 t1b :7j2g3d colyh9 rg 9eei4jof a $0.80-\mu F$ air-gap capacitor if they are 2.0 mm apart and each has a charge of $72\mu C$ ?    $ \times10^{4 }\,V/m$

  A capacitor is charged by a 125-V battery (Fig. 17–29a) and then is disconnec7ut t.4a 4edjtted from the4u.tjtt a 74de 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 parallel plates 5.5 cm on a side that area6 ethb8nct)xgi.h18 ifh+.5lvn z f. separated by 1.8 mm of paraft8vhg1.hhi).fafn.cn xei6l5+z8 b t fin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a radius of 5.0 cm1w dli,gdw 11f separated by 3.2 mifww1dl,1dg1 m of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. Ifgg3.w ,g;-kx; din kup a piece of mica is placed between the plates, how much charge will flow from .kwgggpd; 3,nx; -iukthe battery?    $ \times10^{ -7}\,C$

  The electric field between the platevnv.5f:bf 7kj cefiysk( 81t /s 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 st j c7--;pwo;powzzze6ored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heartq d, lon6p/y3hdp+ ;5 /xotahx that is beating erratically. A x/h,dpo x6ld ht+p5q/;3a ynocapacitor 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 fiew x x.iq;p;v 2;n gefz-:kmxpt*x**nald between two square plates, 8.0 cm on a side, separated by a 1.5-mm air gap?p f;g**ixpqnvwxzm-t 2x .:ken; ; a*x The charges 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 p0i cv9j : )-phfhxrry3ans 5 cm apart and co:9j)c3xfi rhr0vhy-p 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 capacfx7 ,eyk eb(f cmeba-(y)(ae6itor 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 storedrmj bxpib38n)lg y3 1y2 sq6c6 in a capacitor change if (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as the capacitor remains connected to a battery3 ci)lps1q6 gbx3y6jnr 2 mb8y?

  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 accelertrdti6a ;w,u) ated horizontally by 7.0 kV. They then pass through a uniform electric field E for atu;i6dw)t ,ra distance of 2.8 cm, which deflects them upward so they reach the screen top 22 cm away, 11 cm above the center. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a CRT. The screen is 30 cm wide and is iq9,qvru ;* sx34 cm from the 2.6-cm-long deflectio9r ,qu;sx*vqi n 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 a r15io;(soygxl;b w. - d0q6vrfxw4lycquires 6.3 keV of KE in moving from point A to point B. wf.vwqb-g lr sdxr(;; l6 ox iy41o5y0
(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 cy-mj l3pl:rqas3x7 ; 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 sf0-/.fiw b ngsurface 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 t(-jx xfo0jn3 br6q f9nhousands 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 distann n-b39q ojx( jf6rfx0ce 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 sto3iln a9ct3n s b9;zxv9red 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 capacit2u qq.9do7fv p /yml (k8+femeor is 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. What will now be the voltage between the . f9eku78mm qqv/+lef(2py doplates?    V

  Dry air will break down j80qgwhnn/m 6 ix-r d3if 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 cornerq6xoo31 r,e 5 9bs)onvf i88kxlqm,hks of an equilateral triangle (side L) as shown in Fig. 17–30. Determine the potential atk6kh89,1mq5o ox), 3lvenqsoib fx8 r 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. If a piece of Pyrzq .bko+tsucu 1c:k*.ex glass is placed between the platestk:ucqoukz1s. c.b*+ , how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizsz e 0iw9air1,2k ixokkt c90+ontally from rest in a television picture tube by aiacksew1xi , tz90k+rk0 i92 o potential difference of 5500 V. It then passes between two horizontal 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 capacitan 3xppk1js*o/ uce $C_1$ 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 wantmae u92 do1pq- to make a 1-F air-filled parallel-plate capacitor 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 platesmea u-qo29d1p? Is this practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the .0 h vltc01y7 znn:xouEarth 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 for a pulsed nitrogen las8mjn9l m8gz 0 k7nni/eyz5ru8er 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 pox d6x d30go5nybi kq.:tential difference between the Earth and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms oon i0kx 5qx6b:g3.dd yf 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 to some elecyic- -vmz -m4mkq r(7wtrons 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 surfac-y w4 cmq-v(7zkm- mire 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 36mt3uws v:0y,7pqf jhqj0*i-u vhe:9 y cm from an identical $+33\mu C$ charge. A $-1.5\mu C$ charge is moved from point a to point b in Fig. 17–34. What is the change in potential energy? $\approx$    J (round to one decimal place)

  A capacitor is made from two 1.1-cm-diameter coins separated by a 0.15-mm-t1v yr) )r bcx,j:zh4yjhick pieb4r)x:jy1 v zyc,jh)rce 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 capacitor with plyae 3q nunx67r/b3,gtate 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 othpw 5xd g8zvu38er. 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. 17oqb1wr+ i7g .hwtqre 7v3 .e/+ abkdw5–35 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$