If two points are at the same p jm91lgasx36fu *ght3otential, 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 exerted?sglmt3a6g3u*h x1j9 f Explain.

If a negative charge is initially at rest in an electric field, ijb p8c3rw2:xx+5c ijwill it move toward a region i3ji5cr:w p2xxj cb8+of higher potential 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 potentiali n,mka 8(1h+t -o uhqqjbykd15*5o ah and electric field, (b) betweenkq mqoh-5hjbiyta1,*k+a(ou1 h58n d electric potential and electric potential energy.

An electron is accelera7t92gan eifsm )pu71ox7* ohj ted by a potential difference of, say, 0.10 V. How much greater would itsoux s9efn 71gao)7th2m pi *j7 final speed be if it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining two equafv0twx 0+ dzt.l positive charges where the electric field is zero? Where the electric potentiaz0 0td fvx.+wtl is zero? Explain.

Can a particle ever move from a region of low electric potential to one 3fgs2ptr qsm0m uhpp10.p 5 0uof high potential and yet have its electric potential energy decrease? Explainmsm.2rh00p gqp 0u5supp3f1 t .

Compare the kinetic energy gained by v21em pe)ffcvk;l e i8qmz483 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 equipotentialvvp2 exbg k)2etfh1b /5 kwdn+)oics8ef 9;)r lines cross? Explain.

Draw in a few equipotential lines in Fifhb01. k7 qeji0ad( 7cuzgu4q2 qeg/n g. 16 – 31b.

What can you say about the electric field in a region of space that has ni4ehqs n99sc:;,, bx; jnjukthe same p,xu9ies 9 ,h4cj; k:qjnn;snbotential throughout?

A satellite orbits the Earth along a gravitational equipotential line. i(c7ltxmh 0.i2za / pxWhat shape must the ort0calmxhzii (./ 2px 7bit be?

When dealing with practical devices, we often take the ground (the Earth)gym3 6)xo 2u8-nv ttaw to be 0 V. If, instead, we said the ground was how would this affect (a) the potential V mtt 3x2)-uwnvyg 8o6a, and (b) the electric field E, at other points?

When a battery is conner(3u 9e(f4zqqz nb m;kcted to a capacitor, why do the two plates acquire charges of the same magnitude? Will this be true if the two conductz mqenr(9uq4k; 3fzb(ors are different sizes or shapes?

We have seen that the capacitance C depends on the q-ahkwshg)vl36/ rd*lyqyax(lm5::size, shape, and position of the two conductors, as well as o)6 y-l q h/m rg3hs(dq*a:l:yxav w5kln the dielectric 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 d(*tk im , e2g3-ali;2jx hloaho 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 a pw (t6( 3o l-pxk1iqtusroton from a point with a potential o tlio3q1t( xsk -wup6(f $+125V$ 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 electrywk3h kg2 .w f2ljtz.*z:ycl4on gain (in joules and eV) if it accelerates through a potential difference of 23,000gk .yt2h3 wlfk:yjz. *l4wc2z V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires av/rzb kl0x; .dq8i 8,mgczj 8$7.45 \times10^{ -16}\,J$ 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 theum h6,x:hmkg f+zr4;;5j bjqz potential difference between them i +:hj 4zu5mfxqj ;g,kzr;m6b hs 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of oppnsm f)l)h/j3xi6i +w0yv. $640V/m$ 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 to a 4rv:w;/gm sug z 02tq1x5-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallelb1b/h/a6jms6a( o jru plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to gn6g*u d+om1ogive a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connsfenm.mgk : .;53*v- hfwsh-kz5ebaj ected to a 200-V power supply, are separated by an air gaphfn.5w5- vm e-z;k* gkb .hf:s3emajs. How small can the gap be if the air is not to become conducting by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force 6bdxi r m:3h cv.xif)7.+sdpf .x trgj4j35y hto 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 x)* xniy6xd*celectron with kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of8oi*wwmfy*cs vlu6. 7 a proton whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nucleus, )x t7c-za03fpy krh2 z$Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric0r)h)vdv +3xa1 sx mwm potential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric potentia ;o 0rcbagy1 -y3lwi4rl 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 sha0s/3 fw0l lebbpe of a football. This conductor carries a net negative chargb/ 00ebf 3lswle, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a distance of r76wc 3s9avul$ 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 3rj(tyne2me; bj b:/c corners of a square of side L as shown in Fig. 17–25. What is the potential at the fourth corner (poin e;tr3cenbb y(: jm/j2t A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed point.wk 1ek6xmh7rl( diz+/u a-sn charge with $Q\,=\,-0.125\mu C$. How fast will the electron be moving when it is very far away?    $ \times10^{7 }\,m/s$

  Two identical $+9.5\mu C$ point charges are initially 3.5 cm from each other. If they are released at the same instant from rest, how fast will each be moving when they are very far away from each other? Assume they have identical masses of 1.0 mg.    m/s

  Two point charges, $3.0\mu C$ and $-2.0\mu C$ are placed 5.0 cm apart on the x axis. At what points along the x axis is
(a) the electric field zero    cm leftof $q_2$
(b) the potential zero? Let $V\,=\,0$ at $r\,=\,\propto$.

  How much work must be done to bring three electrons from a great distance apartonkc6jl;:g pgez6+7 q. eafw. to zgee: n;o l7.ca+ f6pj.wq6 gk$1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm north of1fkzqfjb/q kmz.(a :m9 +(oa:m6kwt s 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 accelerate a proton (rad as8 xxcg jkn+:nd 5dd0/2 -k*esyf+epius $1.2 \times10^{-15 }\,m$) 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 disq.7(fektc 6re tance d, as shown in Fig. 17–27(67ecqtef r. k. 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 hydrogb1c*h1vo/b,b3 tw e cd- rs.aten atom, an electron orbits a proton (the nucleus) in a circular orbit/1- c3hbr.bc1dw,bv* t oetas 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 amsp, bc06a q4ao /go 6nm77ctgre $ 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 dipole moment is+je sbl0 z+k83xhc2f;vyv* ie $ 4.8\times10^{-30 }\,C\cdot m$ at a point $1.1 \times10^{ -9}\,m$ away if this point is
(a) along the axis of the dipole nearer the positive charge;    V
(b) 45° above the axis but nearer the positive charge;    V
(c) $45^{\circ}\,$ above the axis but nearer the negative charge.    V

  The dipole moment, considered as a vector, points from the negative to the p4rpk 415rasq positive charge. The water molecule, Fig. 17–28, has qra 4 54pp1skra 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 cap ;ylqm p8o4h(nacitor hold $+2500\mu C$ and $-2500\mu C$ of charge, respectively, when the potential difference is 850 V. What is the capacitance?    $ \times10^{-6 }\,F$

  The two plates of a capacitor vs91dp uik n3*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 and minus charge35j 7r.ekbhl-p z kf2xs of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of parallel wirep;l6)jwqwl1b+.9kg .m m rfux in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is the capacitance of the two wires? .rl9 + jfwmbmx6; w)1q.ulgkp   $ \times10^{13 }\,F$

  How much charge flows from each terminal of a 12.0-V battery whyox82m6p86r 3 +a k , )yikqcpd1nybwden it is connectec3 b8 p2dqa pyk )nk6md+ryiw6xo18,yd to a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must tscbg*s69 xmqk.64r c ahe plates have if they are to be sepa.cb4 kmaqxsr *6c9 sg6rated by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor incre0 8: t.kbc:wsj o07qoz(zwdcgases 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 lb( ,fjh-i.z m$8.5 \times10^{ 5}\,V/m$ 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 opp iul+ts57.jsx osite $5.2\mu C$ 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 betwev4znp(yxt q xsfz,esd -lg+s0u*p 56,en the plates of a $0.80-\mu F$ air-gap capacitor if they are 2.0 mm apart and each has a charge of $72\mu C$ ?    $ \times10^{4 }\,V/m$

  A capacitor is charged by a 125-V battery (Fig. 17–29a) and then t zp30rqr71 8(y:jpj,prmhiu is disconnected from the battery. When thisr hjp,3rjzy(u 8 qitr1ppm:70 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 pl:p0 p5n +fnbodcwo/ 0ob(h+uxates 5.5 cm on a side that are separate5p(n0 xbno updfob+0h c/+wo:d by 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates waf y4t*,7rlvbith a radius of 5.0 cm separate rt*,47fb lvyad by 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. If a piece of mne r t64ffdh1 2, cfut4/ifams7p 09srica is placed between the plates, hhftfrrmf2s, 47tsupe6f 4/i09 c an1dow much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates o -*i*j laeqm,vr*wvul61oz p+f 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 muchwvfp0kvfv( 61g6l3 zi energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a hevs5y9wt2ucz ( art that is beating erratically. A capacitor in this device wy (c5utvzs29 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 fieldj lg1cv: m ke e7u.8gxcg2a,7a between two square plates, 8.0 cm on a side, separag7l v:ccaeggxje2,m k .ua718 ted 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 placing two 9-in. pie pans 5 cm apart andz(2c qz *ml/br con l*q/b zc2mz(rnecting 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 capacito6dp)z4ikq tnw q27.ajr 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 sto;wit.grh. 8k dtie2sj ;f cb)*red 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 ba; *ehtgd;fsj w8.iit.rb) k2 cttery?

  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 acottl2d*lw f4 +celerated horizontally by 7.0 kV. They then pass through a uniform electric field E for a distance of 2.8 cm, which deflects them upward so they reald2 o+flw*t4 tch 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 34+gp6+gawp g d1 cm from the 2.6-cm-long deflection plates. Over what range must thg+ap+g 61p dwge horizontally deflecting electric field vary to sweep the beam fully across the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting5m(pbd .y jjt0 from rest acquires 6.3 keV of KE in moving from point A to point B05 dbjy.(mtjp.
(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 1: ,tnw:cn1 aet wror: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 magm *h: yo fw:xi-h6 +8jqatb kd8p/rj1lnitude 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 thousands of voltslo(fksp lhmyw jp 6b7cfx 0j0217z(*x through a vacuum. If a television set were laid on its back, would electrons be able to movfcfspb7p k((l 001 o*lj2m6h jy 7xxzwe 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 enculw 8tu( ju2zxiz)+2qy62foough stored 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 batte::m goz+ei1y ;mpgz,c ry until it is fully charged, after which it is disconnected from the battery. A slab of paraffin is then inserted between the plates. Wha:mgzy ;m z,e cog1i:+pt will now be the voltage between the plates?    V

  Dry air will break down if the electric field excj-n2 at2ss am/eeds $3.0 \times10^{6 }\,V/m$. 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 st ro/td:p3tj / wb vn)udbq 2js7e50t6hown in Fig. 17–30. Determine the potential at the midpointqdwo2/s05et6 b7rjv) pjnt:ub t 3/td 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 Ppx lqr8h9c**f8u shy;yrex glass is placed between the p8hf8h* lsyxqp;c* 9urlates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in a tel was j)j8(yi*/irb qm0szo36kmig. .cevision picture tube by a potential difference of 5500 Vii/i.zsj0) a sq(8m*wk3ybm6crj o.g. 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 capacitanc5r9d:ux egcx+w po: -we $C_1$ 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 bi(w ahe-wqibq/nc+u+q7 6y2c o g a farad is, suppose you want to make a 1-F air-filled parallel-plate( qu- ihqaqb62ww +c oc+7/nye 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 plates? Is this practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there is an electric field of ap;9oj 9iev;pvo/r ibd55rai ;ry 0w2mbout $150\,V/m$ 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 p.bkh6;(ksd7ebno mhc7h(91 4d oz kqlaser 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 potee.ms+4ty qr wb9 *kaz6ntial difference between the Earth and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are typically 1500 me yasrk9+bz.wm6t4*q 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 ele*l 2-vs9qo beictrons 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 at a negative enough potential that thvqs 2*ibe9- ole 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 .f4h 7k6j 7tcnhxl+z 6n(efzu+wwgd/ 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-diamet7sf zrm2wxf 7 rb4a2f+er coins separated by a 0.15-mm-thick piece offf7b4 2m+fr2 ra zs7wx 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 area a k969ep c*s kw2v5xmsdp07 hh$2.0cm^2$ 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 jc0 f v/nfi.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 sho bh1t48f/ yu +i7riinswn 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$