If two points are at the same potent0y-mw;;st lni hjy9i3 ial, does this mean that no work is done in moving a test charge from one point to the other? Does this imply that no f;3nh t9;i y 0jym-sliworce need be exerted? Explain.

If a negative charge is ink2 eux wef5(q 2iuurcz5:qb75itially at rest in an electric field, will it move toward a region of higher potential or lower potential? icz5e r 2euqf7:ubx2 u( qk5w5What about a positive charge? How does the potential energy of the charge change in each instance?

State clearly the difference (a) between electric potential and electric fb)+hj g-ad41z *gcd zpkj-l8vield, (b) between electric potential dk 1 jj-hg)z4-+bgzv*pa8d lcand electric potential energy.

An electron is accelerated by a potential differeozrk2.;n0lm qoqg;te0p: do ) nce of, say, 0.10 V. How much greater would its final speed be if it is accelerated with four times as much vol .q; p om;l )tkq:ro2dn0oeg0ztage? Explain.

Is there a point along the line joining tbod5 .g7ix ngwd:.*rr wo equal positive charges where the electric field is ze :.*io5g7 dnbrr .dxgwro? Where the electric potential is zero? Explain.

Can a particle ever move from a region of low electric potentialh *zg* qphflp;y, +t5g to one of high potential and yet pt,qz* g+*5hfh;y gplhave its electric potential energy decrease? Explain.

Compare the kinetic energy gained by a proto33js ,a9,7vocx4g ktohq;qjun $(q=+e)$ 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 lu(;gvh z5km 8zines cross? Explain.

Draw in a few equipotential lines in Fig. 1+a,ypz4wn( hc 6 – 31b.

What can you say about the electric field in a region ofclenhsg-js 2+8h3hn+ loxp i(b.;o5 p space that has the same potential t+o8jl-( lh 3honhb;c2ine+ p. pg5ssxhroughout?

A satellite orbits the Earth along a gravitational epn) 5l/wt.zy8;oz 0n bpai-ywquipotential line. What shapbt )p;p/lywoyn8w -a zn5.z i0e must the orbit be?

When dealing with practical devices, we often take the ground (the Efvdafn ztkjb)4r( .pn 67tl43arth) to be 0 V. If, instead, we said the ground was how would tnl fd76pk4 ta 4bn.()zv3rtjfhis 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 t 3 y.6;cszejhvwo plates acquire charges of the same magnitude? Will this be true if the two conductors ar 6jyvehzc.3 s;e different sizes or shapes?

We have seen that the capacitance C depends on the size, shape, and position of 1 azzu4f0 yj y8,-ceyithe two conductors, as well as on the d,yz ec -10zij4fua8yy ielectric 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 inl3)ou;2-c v pnutmq0wiq-e( v 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 fie+etisl e18r( wb: 3qsrld do in moving a proton from a point with a poq(+ ri3l8bers1te sw: tential 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 jouae.9/d9u p/z0b8wrx xj,w a uwles and eV) if it accelerates through a poten wup9wu8 /az/xaj90 we.d,rxb tial difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires s9mj68c( my ya$7.45 \times10^{ -16}\,J$ 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 electrx8a:o5ykwh 2uic field between two parallel plates 5.8 mm apart if the poa5w:yh ou2 kx8tential difference between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of +2 jyumles7/m; ux9i crr/sj ,$640V/m$ 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 battery b c96ap) y(lznis $1500V/m$ How far apart are the plates?    m

  The electric field bet,f)xxi3z 2pnm ween two parallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed :0hgn-vs s8 .a*zfnib43j hon; cgb/ rto give a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power 0)ytuuiavg l01i p7d 3supply, are separated by an air gap. How small can the gap be if the air is not to become conducting by exceeding iipv 0y 73duglt1i0ua )ts breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force to movetk)jm 0w7p. m4 -oiuje 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 kin k9-y- 7akygenetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a protonju+) uhr8jm 1d whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nucleu). y24hn e;mjz3ju hjls, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) 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; m4t jj 8njcf2m8yfn: a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electrici.l :lyzc40irqb u4a 4 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 .uu5 jex/n y3v3wi/pn the shape of a football. This conductor carries a net negative charge/j nyv3.x/p w3ien5uu, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric po2 2p8aedko2h otential 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 e5 (n u+gm.ny;,ona*s)gwrar are arranged at the corners of a square of side L as shown in Fig. 17–25. What is the potentialne 5umrn*;s,ngygrw.o)(+a a at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from res*of)smkw3j6hfr92krfg b48 zt 32.5 cm from a fixed point charge with $Q\,=\,-0.125\mu C$. How fast will the electron be moving when it is very far away?    $ \times10^{7 }\,m/s$

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

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

  How much work must be done to bring three electrons from a great distancenqb+d f1m3j q0 apart 3j+bqq1dfn0m to $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm north of . jqn6rc+lq37ho6 eeh5umoy2 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/hf 0t.akg4zg q t7n0o (radius $1.2 \times10^{-15 }\,m$) so that it has sufficient energy to just penetrate a silicon nucleus? A silicon nucleus has a charge of $+14e$, and its radius is about $ 3.6\times10^{-15 }\,m$. Assume the potential is that for point charges.    $ \times10^{6 }\,V$

Two equal but opposite charges are separated by a disq v o d)c*k4lmj ukfl28ape8 +8z8shh4tance d, as shown in Fig. 17–27. Detervmp d842ujk8 s f4helq)8z lco8+ha*kmine 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 thepa j9s.ltuo b8)u* f)7uoz7 af hydrogen atom, an electron orbits a proton (the nucleus) i a *zf87au)p 9otluofuj) bs.7n 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 pro*2xczyplue72. h ;r pnton 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 dipoletl2sk s+fp -tzh+qh; 8 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, points from the negative t,ae 4 s:57mvasnnib9 fo the positive charge. The water molecule, Fig. 17–28, has a dipole moment whiim,59nean:fs47 avsbch 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 ,os 4 v,vm/u*9 okmngfcapacitor 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 casbips*o9o5svv m(72lpacitor 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 ;,, /mu:quk3rdpc ud)(lz iopminus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of parallel wire in air is3loeqf j v6;0pypcl -l;g ;84sw+fbiv 120 V. They carry equal and opposite charge of magnillje-0;4f fv;qv8pp oil+cb; 63 wgsytude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of a 12.0-V battery when itb id4x8 zs)fwhq6 .l;wd/3gxg is connecte ;id hb6s d.)w4xf/gzlg3x 8wqd to a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates have if they are to bgkgfx2j5w3--l 2yqxhgz: m 7de separatel23 ggwk7:f5 xqz 2 gdjmxhy--d by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor incream0bpl z eg9:3bses 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 w3v8vb 1urmpk l4vs7g:f) v5j$8.5 \times10^{ 5}\,V/m$ 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 o6221w+,bskax pew oyepposite $5.2\mu C$ 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 fiel7awnwpx kc qul25 m 37jk;-e6ed 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 12xmc6/3 6flvdy 5-V battery (Fig. 17–29a) and then is disconnected from the battery. When thlm3c/f6 xv 6ydis 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*qe uvvg, y-j/w fn 5-2p:6algkzi59q2ibwlp plates 5.5 cm on a side that are separated by 1.8 mm ofw-2-5ppv 59:e2lq/aq *ugifgvn li6 bkz, yjw paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates7 c* zl-g /jsl5lish 7s8wu)bwma u61p with a radius of 5.0 cm separated by 3.2 mmlbizals7uwpg-sj *sh l7) 5m186/cu w of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. I .mcwetlv3 lc5 -n7m8hl(e /mzf a piece of mica is placed between the plates, how much charge will flow f3lmnvlmec c 5/-t.m(l 87ez whrom the battery?    $ \times10^{ -7}\,C$

  The electric field between9gtkjo4m,pqmy0h 96ea1 ria6+ jn4fk the plates of a paper-separated $(K=3.75)$ capacitor is $ 8.24\times10^{4 }\,V/m$. The plates are 1.95 mm apart, and the charge on each plate is $0.775\mu C$. Determine the capacitance of this capacitor and the area of each plate.
   $ \times10^{--9 }\,F$
   $m^2$

  650 V is applied to a 2200-p ndrqdag6.on+ o5c+efr()0v: dl: fp yF capacitor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beating erratically.*v6wf .nkgj9p A capacitor in this device is charged to 5.0 kV and stores 1200 J of energy. What is its capacitancjpk 6* 9gvn.wfe?    $ \times10^{-5 }\,F$

  How much energy is s2b3.hb/.v 4wy qebos ks8tn h8tored by the electric field between two square plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on the plates are vnq bw. 8he3.s/b2 ko8ht4b syequal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in. pie pans ra o99t7l1)t 8/ ( znoxq)x vam+cyibx5 cm apart and cv +(9caa n/xm7xybto z1)x9 rt8o lq)ionnecting them to the opposite terminals of a 9-V battery. Estimate
(a) the capacitance,    $ \times10^{-12 }\,F$
(b) the charge on each plate,    $ \times10^{-11 }\,C$
(c) the electric field halfway between the plates,    V/m
(d) the work done by the battery to charge the plates.    $ \times10^{ -10}\,J$
(e) Which of the above values change if a dielectric is inserted?

A parallel-plate capacitor has fixed chargm vng7dlt hep;,(5g.4rgb ds8r:rax5es $+Q$ 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 differeovl4no r 2f;g4:ol g0od mx;s;nce is doubled, and (b) ;2vg;l4 0mrlofos gx4o :no d;the charge on each plate is doubled, as the capacitor remains connected to a battery?

  A $2.70-\mu F$ capacitor is charged by a 12.0-V battery. It is disconnected from the battery and then connected to an uncharged $4.00-\mu F$ capacitor (Fig. 17–29). Determine the total stored energy
(a) before the two capacitors are connected,    $ \times10^{-4 }\,J$
(b) after they are connected.    $ \times10^{-5 }\,J$
(c) What is the change in energy?    $ \times10^{-4 }\,J$

  In a given CRT, electrons are accelerated horizontally ilo)0jcc,ff1 k ag d)/by 7.0 kV. They then pass through a uniform electric field E for a distanci)k1lf),dj/f ao ccg0 e 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 and4qe8dy, g9aazk ub *y4 is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizontally deflec *q4d8 zyka,yba 9egu4ting electric field vary to sweep the beam fully across the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from rest3hp y8v(vk4en acquires 6.3 keV of KE in moving from point A to point B. v8(vn e4y ph3k
(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 anw3b iwsgyiov 8+v.h 3 -bc2l(jd 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 E ( o5yl*ous( 7muitop jm,yfcs+;z ;0qarth’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, electrons are accelerated by tho*7hdpl,0 eji eusands of volts through a vacuum. If a television set were laid on its back, would ele7j,i l ep0h*dectrons be able to move upward against the force of gravity? What potential difference, acting over a distance of 3.0 cm, would be needed to balance the downward force of gravity so that an electron would remain stationary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough stored energy to(-j0uiyn7ep f96 srju 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 b/g:h(b2 hvrwv -5qj 3)nnhwri attery until it is fully charged, after which it is disconnected from the battery. A slab of prq rwhn-ib2( )nwj:v g3vh/h5araffin is then inserted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down if the electric field excee+g*aw/qy3se)1 flt- psfd )mc.0l eom ds $3.0 \times10^{6 }\,V/m$. 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 ws /mj rftux 1j)m, /iu2y6)wran equilateral triangle (side L) as shown in Fig. 17–30. Determine the potential at the midpoint of each of the mj/ r/1t xj)w26msuuiy fr),w 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 Pydjpl//+seh ua zl* v-v095dwkrex glass is placed between the plates, how muc/ 9wv0-hvkd l/ pe d*+ls5zjauh charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in,ff5s(*p6 df j mj f*j6ox4yss 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 difference of 250 V (Fig. 17–31). At what aod j6f4ff ,ssp* 5jsy*6fmxj(ngle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capacitaa fgyfk/9 bmkz2/2c 5qnce $C_1$ 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 12 ppee/0 4yhov-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 platesheo04 y /pve2p? Is this practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth thevu7 y fnvo:+.ore 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 laser has a/4*flt rxthu1yv6; 1/9,ca z mbw ;tvdqd0zhy $0.050\mu F$ 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 and the bottom mz1opnxa: -qdii//zaiqls+ +p6 x) v(of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are typiil-)1ai/v +xqqx / pozpn+dasmz: 6( ically 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 t 5n ,*fah/jyxct.or -j j3hx,e5 bs1velectrons 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 e/3ctxh ea-y, x*5tjhrnf 5b o,1j. vsjnough 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 p2 q(ig)8nh wi)ho3yhh laced 36 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-mf /gf6 6dxw3qdm-thick piece of dd xwg/6qf3f6paper $(K=3.7)$ 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 capaci 1jxmih zwm1ib:bc8xxs) k6+;tor 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 luy972dm (06l)j/jx4etptxy u bt -ub apart from each other. 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 bc2 v5 hlw33mg:r5ynsg sjrjd,l*aam (t)/h(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$