If two points are at the same potential, does ts axe;,f;*jr/92 . ktrrdbzlg:gw ,frhis mean that no work is done in moving a test charge from one point to the other? Does t2z;bw*lx .;rjesagd,9gk: /rff , rt rhis imply that no force need be exerted? Explain.

If a negative charge is initially at rest i3 wmncf( vy/wyapy 2x.); nc6 zi)*fken an electric field, will it move toward a region of higher potential or lower potential? ym.wnn /w ze;k v3(xp) ia2fyc*c)y6f What about a positive charge? How does the potential energy of the charge change in each instance?

State clearly the difference;61 2:x trtexh3bueih4b- svo (a) between electric potential and electric field, (b) between e;heetotu:41 x 6xv2isbr h-3b lectric potential and electric potential energy.

An electron is accelerated by a potential difference of, say, 0.10 V. *js1amj -d*vbiw:e6u How much greater would its final speed be if it is accelerated with four *6vje i1u:*w -smjabdtimes as much voltage? Explain.

Is there a point along the line joining two equal positive charges where +gcixsg)e e:-a b8g:jthe electric field is zero? Where the electric potential is zero? Ej e: e:ia-cg+ x)ggbs8xplain.

Can a particle ever move from a region of low electric potentia4ht c((c- zuiql to one of high pou -((4izchc qttential and yet have its electric potential energy decrease? Explain.

Compare the kinetic energy gained qr svqh 0+ w6lks)4hen4 6vv*dby 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 lioxkjhs+ g /;a8nes cross? Explain.

Draw in a few equipotential lines in Fig. 16 – 31b 2 2mm xn6,ebw.viqx nu1lvw3g5 e9es:.

What can you say about the electric field in a region of space that haz- my :8pj0on 2voxv:rs the same poor-no zymv:p: 80vjx2tential throughout?

A satellite orbits the Earth along a gravitational equipotential line. Wh z )c+ c:b-rres26xfjehn3n4cat shape must the orbit be hn4fr+-j c cs6zb:r2n )xce3e?

When dealing with practical devices, w:0v .1nqs,o v7 zndqemm5jl/ ce often take the ground (the Earth) to be 0 V. If, instead, we said the ground was j7onqq1 z l d0vve sm5cn.:m,/ 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, whx0pbvo3srk ( 1y do the two plates acquire charges of the same magnitude? Will this be true if the two conductors ars01po (3vrbx ke different sizes or shapes?

We have seen that the q26w5 ru4ff 2 acjg1rbcapacitance C depends on the size, shape, and position of the two conductors, as well as on the dielectric constant K. What then did we mean when we said that C is a afb 2 rw2qu651c4r gfjconstant in Eq. 17 – 7?

  How much work does the electric field do in moviv)xha/4 le *u*n5xm snng a $-7.7\mu C$ charge from ground to a point whose potential is $+55V$ higher?    $ \times10^{-4 }\,J$

  How much work does the ee7)uf 4op2iq-hhx0dl 5e 0wfdlectric field do in moving a proton from a point with a potential of-w0 hfqexd2u)l07p o4 5 hdfei $+125V$ 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 accel98r iq8qtms 8c dv5be/erates through a potential difference of cm9 q/ dvrsieqb5 88t823,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquirest0k ;hbxy4 f/s $7.45 \times10^{ -16}\,J$ 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 5.8d6m.8 1up( m2 zgzqwlwsxe8 h:x; py6fck1v5x mm apart if the potential difference between them is 2208 (p1pmmx2xws5l xedhz;q z y:f66kvcg1u8w. V?    $ \times10^{ 4}\,V/m$

  An electric field of;bq k ba cz9(k3x -ubctzd6k87 $640V/m$ 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 45-V battedzg06k )*avwg2c 1jipry is $1500V/m$ How far apart are the plates?    m

  The electric field b:72uu mhgi -qoetween 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 ,zxhumn4a noypd+7 17-d -f0 ynzpkkp:4 e1uvgive a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, are separatedfx1 ik1i r48c i m(.mzc+ow3yf by an air ga38r(fo1iiw i1fxmy .c4z+ ckmp. 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 ei82r3gpe-z un xternal 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 ev: hlfv)+o0d3lv) ftxlectron with kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a prowjf 1gyrr ..)7vfklo e+xd 3*gton whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nucleusq hj-zdrt cceizk7h4ttz;* ):89 e2b i, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric potential 15.0 cm from a r )x,nttye* kshsrb7;5k. -of$4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an elecoo: mc:hp1xq2tric 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 )l2ic4*(xk, jsq l d*e yfjmv8of a football. This conductor carries a net negativj8l,2vyf(4l*ik mjdsq *)ce xe charge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a dis-uhglks ni ,o9ug;czer45z*; tance 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 yy co20eqlx8, square of side L as shown in Fig. 17–25. What is the potential at the celyoxq2 y0,8 fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed point ssp3 d9:mfw(t)o, pmw q:d*lc 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 lf4qz(8zi3um(8 hht jfrom a great distance apart t(88zlhu4h(iz3 jqmtf o $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a whicz rbs/m, ja:8ov: k qio4xev:ikc5)n4h is 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 usede1i *ns5 oxz *)r(mtbt to accelerate 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 seu,1) eyg* .dz/di gqptparated by a distance d, as shown in Fig. 17–27. Determine a formul,dy)g1edpuit g q.* /za 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 pro.pl)bo nh.w6*n0b j joton (the nucleus)*bo jpwb 0nhnl) ..o6j in 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 pr:t2 m+49tri qmqus)wkmv: 3anoton 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 pot 7vhj,0 *pq5 jumyupf+i+ sxy(ential 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, considered as a vector, poize3lxm5ok4vw8 wn3uov 4 gpis7*di 53nts from the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be considered as the vector sum of the two dipn7vgu8o p3 i3eodl 5 x5iwvsk43w 4zm*ole 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 (2aiuo2n gw e5hold $+2500\mu C$ 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 ej *:) e)rnkzocapacitor 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 pluss0u 6 1s-k6) laqd p)x-)iyp)z enybci and minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential differ ix me30w +( msvgrfrqk405o;mb j/ hl;3b7tmnence between two short sections of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is the capacitance of the tm5w0;h4 k lmeb g omftb3/(s7vrj+r0mxi3;q nwo wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of a 12.0-V battery when it k8g(8nf4vipeqll /p/is connected ton 8plvei//k8 lgqpf( 4 a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area m7-,mf fyx7x+w ts k5ej0miyb -ust the plates have if they are to be separated by a 2.2-mm 0imk5me-sy-xt7,yj xb fw+7 fair gap?    $ \times10^{ 7}\,m^2$

  The charge on a capaci72 cnt3 l pwklz0u2x4ttor 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 * bmb2 t58ahmr$8.5 \times10^{ 5}\,V/m$ 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 opposites f4+ 71louynr $5.2\mu C$ 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 3vo;.en1 ecfa ow8eu 0au5;sg 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 battery (Fig. 17–29a) and then is disconnectvvfl*51:hr yd vvylr *1fd5:hed 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 parallel plates 5.5 cmne i87tzf b j do2;c-)zpn(jj,kx42pr on a side that are separated by 1.8 pr,od-742 jtbz(c; i2jn pxj)zf8 knemm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a radius of4vetngv2. r/ th 6brg, 5.0 cm separated by 3.2 mm of grrng4vetb,t/ 26vh. mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22- f-*nqfxcnwz2 :u 2f(lV battery. If a piece of mica is placed betweenw *cuf2x z(nf nl-q2:f the plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of/ftp 3 ia -9jv5ve-ymu 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 std. eo2:f;l awvz2kd1d ored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is use;2kh wlzn2.ifvdk v mz4f)8 /n+mh8ffd to shock a heart that is beating erratically. A capacitor in this device is charged to 5.0 kV and stores 1200 J of energfv+n4m ffz8;8)hw /l2kfvni km2d.zh y. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the yr8g cxqhro9,+z5s7y yn9qa2 electric field between two square plates, 8.0 cm on a sideqqx,cygna8h7z+ 992yso r5yr , separated 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. ,majkc ) 3x-hj8pkz y1pie pans 5 cm apart and connectinhxk,-c aj8 mp3k1yj)z g 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 hask bnewi1zm-s, b,y 7ior1m9m7 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 stored in a capam 1m s24pwbq1h. z0prdcitor change if (a) the potential difference is do04zmp2w qsp.1md 1 brhubled, and (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 acc52i o/3bdb0km( kt oldelerated 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 reach the screen top 220k(/o5i mbto2dbld3 k cm away, 11 cm above the center. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6jb5 y+o-rx 1rdrzsw:(ez4cp1.0 kV in a CRT. The screen is 30 cm wide and is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizontally deflecting electric field vary to swd pzzr1 rjb :5o1cs +-rwe4(xyeep the beam fully across the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from8 j+xc fmj a(+7bq)qki rest acquires 6.3 keV of KE in moving from point A to po+b8 qijm j(7axck+ q)fint 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 4.0 C of chao9/ 5wixdt:ev wjr:2 -/iutsgrge 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 id9l+ ( pvw;hjis 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 voltsd 7nqk9s3r2rw7ob o 9d through a vacuum. If a television set were laid on its back,ron 79rwq7s o2k9 dbd3 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 store(j 7(i ot f spsjjg:-m,z9j8cnd 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 8/vwesb. ay;xis connected to a 24.0-V battery until it is fully charged, after which it is disconnected xvys;a .b/e8 wfrom the battery. 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 theiemc)mdvyd6368; z)mkwr m6 a 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 inr,aijs+q- 1b/h7vur ni j xaqp. 5x:y8 Fig. 17–30. Determine the potential u/ rxa n:qpv,qj+jr81ay5 s-b.h7xiiat 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 fj:g a-v77uaq is connected to a 9.0-V battery. If a piece of Pyrex glass is placed between the plates, how much charge will then vj-7:7u aagqf flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest inh qblh;nac/lr5zr6 ax, 527u p a 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 that have a potential differera xbzr u2qa5lh/7 ;phcn,5 6lnce 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 capacitp3izsdh* t2+zance $C_1$ 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-fbhjc o*i8t 5h ;3unzsczi*8 d-illed parallel-plate capacitor for a circuit you are building. To make it a reasonable size, suppose you limit the pla8 *8sd-ih ct*u53ohi j bzcz;nte 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 isuji0km ,led,l3m f79s 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 laser has ab+ 3sb3 ( p8ncxl)a,*aazq gcj $0.050\mu F$ 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 8 yvnhy;-ca t3between the Earth and the bottom of the thunderclouds can be as high as 35,000,000 V. Ty; yv htan3-8che 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, ultravz2rl6 s(zw7(f+juxk9 ,n lwr ziolet (UV) light provides 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 electrons, another plate above the barium surface is kept at a negative enough potential that the emittedzl6znrw7((z fsjlkw u r2 +x9, electrons are slowed down and stopped, and return to the barium surface. If the plate voltage is $-3.02V$ (compared to the barium) when the fastest electrons are stopped, what was the speed of these electrons when they were emitted?    $ \times10^{6 }\,m/s$

  A point charge is placed 36 cm from an idjijlu .4;lp y/a+ltr 2 wbr :f1h;gyz1entical $+33\mu C$ 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 sepjc bio ;7rkd0+arated by a 0.15-mm-thick piece of pkb +rjd o7i0;caper $(K=3.7)$ 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 capax*lwma70ubaj:f*ta 9citor with plate area $2.0cm^2$ and air-gap separation 0.50 mm is connected to a 12-V battery, and fully charged. The battery is then disconnected.
(a) What is the charge on the capacitor?    $ \times10^{ -11}\,C$
(b) The plates are now pulled to a separation of 0.75 mm. What is the charge on the capacitor now?    $ \times10^{ -11}\,C$
(c) What is the potential difference across the plates now?    V
(d) How much work was required to pull the plates to their new separation?    $ \times10^{-10 }\,J$

  A $2.5-\mu F$ capacitor is fully charged by a 6.0-V battery. The battery is then disconnected. The capacitor is not ideal and the charge slowly leaks out from the plates. The next day, the capacitor has lost half its stored energy. Calculate the amount of charge lost.    $ \times10^{-6 }\,C$

  Two point charges are fixed 4.0 cm apart from each other. T) uowea2gwy279 y i/2plwpy0fheir 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 plac5h q1x:3nvpnfvrgbjrbd 4,.:ed as 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$