If two points are at the same potential, d9d0r/u glkp7zeqh/ yt:u3 * rjoes this mean that no work is done in moving a test charzy k*q /r t9uehl:3u /0rdj7pgge from one point to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at rest ine.u kiudldzn0 .;;)u2nkd1ahmg3lx 8 an electric field, will it move toward a region of higher potential or lower potential? What about a positive charge? How does the pote0um u.3.dg8dhik1z knl ;d )ulx;2naential energy of the charge change in each instance?

State clearly the difference (a) between electric potential and electric fisg1y.hdbf7 i0eld, (b) between electric potential and el fyb7h.1gs 0idectric potential energy.

An electron is accelerated by .te69-dl bu3seo(fcf a potential difference of, say, 0.10 V. How much greater would its finald -6 ut(es o3eff.c9bl speed be if it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining two pee3o eb1pm* ;equal positive charges where the electric field is zero? Where th3emp ee bp*o;1e electric potential is zero? Explain.

Can a particle ever move fr j6x, alpois(ijc7q66 om a region of low electric potential to one of high pp6xq jcs76a,(oii l6 jotential and yet have its electric potential energy decrease? Explain.

Compare the kinetic energy gained b:qs- 7san ed,gy a proton $(q=+e)$ to the energy gained by an alpha particle $(q=+2e)$ accelerated by the same voltage $V$.

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

Can two equipotential lines cross? Ex4cwvvuxsw0*d 4 *-dg tplain.

Draw in a few equipotential lines in +lszsj2 72oura +r dz*Fig. 16 – 31b.

What can you say about the electric field sh k8 qcljaj7,s):zj( iizx*2in a region of space that has the same potential througho7( 8hqil:)jzkzai *ssjxj2 c, ut?

A satellite orbits the Earth along a gravitational equipotential line. What :x1-m 5q-ulc lupgfe:shapee l:c5qmu-:pufg lx -1 must the orbit be?

When dealing with practical devices, we often take the ground (the Earth3m4l2ydb 27mme5rw+(txn ut h ) to be 0 V. If, instead, we said the ground was how would this affect mu2( tlt 4 +2me5db7myxr wn3h(a) the potential V, and (b) the electric field E, at other points?

When a battery is connected to a capacitor,ncxvb + m 0)d))cko9xs why do the two plates acquire charges of the same magnitkd9+ 0cox)msc)bxvn )ude? Will this be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on the size, shape; wkq1f ,0p.hxx px9xzn ahl43n)k)fx , 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 constant xxnnh; 49 z kxl.,wqp a0k)fpfx)1xh3 in Eq. 17 – 7?

  How much work does the electric field d6h qc y1blol6/;pm5b dgs+c5 co 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 the0cyo(s p;.ef k electric field do in moving a proton from a point with a potenti o;(es.ykfc0 pal 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) ikssy1qly4g2 bn / 67h:ts lv-uf it accelerates through a potential difference of 23,000 V in a TV picture tube7-qk 2sn1u 6lstly/v4ygb h :s?
   $ \times10^{-15 }\,J$
   eV

  An electron acquiresdbn73--itl h)g i*vq pbe so;:qj) e0w $7.45 \times10^{ -16}\,J$ 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 bebn77l:vk mif093 dqn4rg 6tmatween two parallel plates 5.8 mm apart if the potential difference between a: ng637tlnrqmfi09 4k bm7vd them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field ofx mana5f)d b1 :0n;hok $640V/m$ 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 batb ;/(:ueonui 3thl8 gktery is $1500V/m$ How far apart are the plates?    m

  The electric field betweeoi5;3+*-oj ug2x dp1l0 ,hzv f oeaoien 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 give a helium nucleus l j.k*vq( 8)ozem:enq$(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, are separatf o:z5 /ld3h*fiwpjajery3 ;(ed by an air gap. How small cao(p 3*5d hjfr;/flzij3yaw:e n 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 externaxoo.0rf; o cabal 4.py s;fr/-l 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 w gabdq6n(1 )gin+orpb/ 0.ap pith 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 energy is 3.2 9(a afhxqg d3qlg)w.*/ h6rw 9pzk0s ukeV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium n+zuvm30ailh /a(f1ob yh9 c,qucleus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) 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 92p28fsfvwhqe+xp o9tcekmc -6 w+d: from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an elec6:rld3w52dx0p z w xqotric 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 sz:fzhu )u v*8njzyl-:o/rik9hape of a football. This conductor carries a net negative charz/krzj9 on-luf):zy h8*u:ivge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric v5qqa c2;l(vw 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 of sjtl0 g-y ,eriq, m:r5-w;q xaside L as shown in Fig. 17–25. What is the -q0:j mwly; xis5,r, ta-qgrepotential at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from restxxa bst.0-r cywgh693 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 ;j1w7;wk 3a)p-p z9pf ljwnk q;ufio0from a great distance apart to fnw9);jquppwaioj 3fz l0;kw71pk -; $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm northbsvg: .ma 7*l.lwj3ms 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 accelerate a proton (rady (4ab.bdc:jl ius $1.2 \times10^{-15 }\,m$) 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 distance d, as shown 0k*s +q jyp8rmin Fig. 17–27. r psqmk0y *j+8Determine 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 hydrogen atom, an electron orbits a po h-/ghxmq 1l vxy0ta ,xqb598roton (the nucleus) ihx85/9g1-xxqho m a0bvy,q ltn 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 proton aruedt, 4yd.i e8e $ 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 xs(it *p2acf6bp4v *j 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 asguu+p5 iad m k309mr+arb)j2r a vector, points from the negative to the positive charge. The + grr+5a3 0mrji ka u)9mbu2dpwater molecule, Fig. 17–28, has a 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 capaciteemz k ./44rtm1ts.llor 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 hol;xn8b 0lqkb0)x:v caud $+2500\mu C$ 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 charges pw5ls)-eap a1 of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of parallel wire pr)zkk/kuw p5 ;b 6bd;in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is theuzrd5 w/b p)6;pkk ;bk capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows frodt*kw0 -5dk0oxclf9 bm each terminal of a 12.0-V battery when it is connectewc9kdf0do *b5 0x-klt d 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 be woda(: fuvzwj4 sf85 9nl9-dvseparated by a 2.4 fd 9ovwsufza -5(n:j9l8w dv2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increases by r(bf,uc4z1ga*mti 7tgglc1ry0 0bs /$18\mu C$ 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 ofidi- g9cvw s.1guc0y) $8.5 \times10^{ 5}\,V/m$ 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 opposieq /xy5 hrs4her;;y3 ste $5.2\mu C$ 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 platet.e ib3hmr(qfacp+h3q .p3.ps 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 (Fia t(rsup5 5ve6g. 17–29a) and then is disconnected fr ea(st65vpu5 rom 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 pvpgv+* h2vk cf; u2rh/ fa+ly7lates 5.5 cm on a side that are separated by 1.8 mf+;*7h2 fav2 ugvpv + ylh/rckm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates wmvmwkvgw:d*8s* tuz 99v3ee(ith a radius of 5.0 cm sepu z 9em**wg(d s3v9v:vek8mwtarated 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 o, 3kwmt64rh xtf mica is placed between the plates, how much charge will flo, t4mk36tw hxrw from the battery?    $ \times10^{ -7}\,C$

  The electric field between the platex4fms2jwouf.2g 7 el:nx,ct mja.5u ; 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 )tzallp umt,b9, p3ogd2; 9lcstored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart th phgbott3i8wgmw1p2;:0hgwf6p5w u- at is beating erratically. A capacitor in this device is charged to 5.0 kV and stores 1200 J of energy. What is its ;5gg2p 8w u6i 0 :31-hwptbfgmpowhtwcapacitance?    $ \times10^{-5 }\,F$

  How much energy is stn4-+ hn5joyout jc9i1ored by the electric field between two square plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The chj91jc -n+uioynth 45o arges on the plates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by plabewlr lq2l 5v3.u;2 rpcing two 9-in. pie pans 5 cm apart and connecting them to the opposite terminals of a 9-V pb3 2e5q;rr.wulv2ll 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 c/(go+ cr;4 xqr nh/xrzharges $+Q$ 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 ,pe-mq.t :)mtwxzik-stored in a capacitor change if (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as t:i-. ,et tpqxk mzwm)-he 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 horizontallgy. x2zhz84yfnju3k qku 2h-/y by 7.0 kV. They then pass through a uniform electric gu n -4hy /2kzj.huxq kz3f82yfield E for a 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(n+an mbs2e o-1bulhnv - +x)p 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 sweep the beam fu -+le1-o 2unna+bvhns() bm pxlly across the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from rest ad:tn) ugp9b(zcquires 6.3 keV of KE in moving from point A to point B. u(td )gp: 9nbz
(a) How much KE would a proton acquire, starting from rest at B and moving to point A?    keV
(b) Determine the ratio of their speeds at the end of their respective trajectories.   

  A lightning flash transfers 4.0 C of charge and 4.2 MJ of energy to the Earth.7b4 oin n92 qrhjso4f.uuept79 cvw)0
(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 t5f pw63p ru:fqeh6-z gkhd,2is 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 thousaq0wqb/cta kwn ,q44uxq 1;r,nnds of volts through a vacuum. If a television set were laidb n nqw,t/a,4; qcqkxw41r qu0 on its back, 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 enoughpez g u4,t. cwh2hc;3 pzzx9y9 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 iu- rx7 evhkwl3*t6c57kcrry 0s connected to a 24.0-V battery until it is fully charged, after which it is disconnected from the battery7 vhk x3ulwe 7y-rrc* t5ckr06. 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 the electrm c,e*p1f9d 8w2 fxs8ahdrfpq ,/b(rkic 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 show *xu5u 4amz10 bmf-ekpn in Fig. 17–3 x5*mu1ez 4ku- 0mbpaf0. Determine the potential at 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 ca4klf. tj9txko q) olx3nu-+d0pacitor is connected to a 9.0-V battery. If a piece of Pyrex glass is placed between the plates, how much charge will then fllx90no tu. x -jqfl3o4+)tkdkow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally fry, dmh( : zkrls;*h 43ez:jvglom rest in a television picture tube by a potential difference of 5500 V. It then passes between two horizontal plates 6.5 cm longgh4,3 hjl sv:lrz;:md* ke(zy 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 capacip g(k3jlk+e0u6d6wuvf d+fq(5 sl-a vtance $C_1$ 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 w ku1csf sir4m7)a/hh)ant to make a 1-F air-filled parallel-plate capacitor for a circuit you are building. To make it a reasonable size,u fcsk)m)/sr7iah h 14 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 elec nx(g+y jbln9+kqzu0 8tric 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 lase7-1oqvdsibq2: n) xnkr 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 qr-h3 fxv*un7 potential 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 m above the Earth, and can have an area of3fhv-qn ux7*r $110km^2$ 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 ehu ri00r c1:go ryx4q0.ic iqhw0q;3bnough energy to some electrons in barium metal to eject them from a surface at high speed. See urbi:hc1rw 0g i0cq hy0x.o4;0q3i qrFig. 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 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 p+yvt btmw67sk: 1 c:wcm 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 fri bnb l7-5cme2ji93puom two 1.1-cm-diameter coins separated by a 0.15-mm-thick piece of papn bjpi3e 7c9 ubilm-25er $(K=3.7)$ 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 a qy5 v47pgl3o* x.tbw:xetty*rea $2.0cm^2$ 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 are m4)aj j5f6gdx $Q_1$=$Q_2$=$5.0\mu C$, 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. 17–35 with 6h5,gcoj fdy+ $q_1$=$1.5\mu C$ and $q_2$=$-3.3\mu C$ Find the potential difference between points A and B.    $ \times10^{ 5}\,V$