If two points are atp7hv5,3pa qny the same potential, 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 ne 3q y7pp,5vanhed be exerted? Explain.

If a negative charge is initially at t8fidbrz vnh: ;; o0i;rest in an electric field, will it move toward a region of higher potential or lower potential? What about a positive charge? How does the potential energy of the charge change in ea:tfnhbvizio; ;0 r8 d;ch instance?

State clearly the difference (a) between electric potejsq; g )v)cl.vfpt*6 fntial and electric field, (b) between electric potential and electric potential energ6cfpf)s;*lt)vg v.jqy.

An electron is accelerated by a4fn6 dyp ,ws5d potential difference of, say, 0.10 V. How much greater would its final speed be if w4np fsy6dd5,it is accelerated with four times as much voltage? Explain.

Is there a point along the liw) iqh1g2o xnxp* 7,ijzm8a x5ne joining two equal positive charges where the electric field is zero? Where the electric poten7w,oxmxq) x2gaipzi85 jh* n1tial is zero? Explain.

Can a particle ever move from a region offp(n278zn: qaed s*dl low electric potential to one of high potential and yet have its electric potential energy 28s:dnnzq a7p*(led fdecrease? Explain.

Compare the kinetic e h(dn2(fla uz8nergy gained by 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 $\overrightarrow{E}=0$ there? If $\overrightarrow{E}=0$ at some point, must $V=0$ at that point? Explain. Give examples for each.

Can two equipotential lines )az;)yzoxj.f*0jbzgcross? Explain.

Draw in a few equipotential lines in Fig.a :/1zzi whtc fmxl1g(* i(tppp+4;hl 16 – 31b.

What can you say about the elec)k2:sb h0/: v utoppxztric field in a region of space that has the same potv:b hpso:2) p0 ut/kzxential throughout?

A satellite orbits the Earth along a gravitational equipotential line. What ce/h*nz5*npd shape must thc/ *np*nhdez 5e orbit be?

When dealing with practical devices, we often take the g 7wvstf( tlp:-it0tm.u0gh kh2 /s )tvround (the Earth) to be 0 V. If, instead, we said the ground was how would this affect (a) the potential V, and (b) the electric field E, 2vkfi0mt: gt v0hut()s .t st-h/wp7l at other points?

When a battery is conm vzr +nk:9es:j+i.cnnected to a capacitor, why do the two plates acquire charges of the same magnitude? Will this be true if the two conductors are different sizen.j 9cvzek+:is+nrm:s or shapes?

We have seen that the capacitance C d5+9165gj;v, hi c*ewxyhodzt,b,qe y hfyk( pepends on the size, shape, and position of the two conductors, a,eq (f,y v whxgyj d6bke *,+5ho;5ziyh9pt1 cs well as on 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 do z6hbr17 qwc3oc -1;sdcfx qsp z .m.,iin moving a $-7.7\mu C$ charge from ground to a point whose potential is $+55V$ higher?    $\times {10}^{-4}J$

  How much work does the electric lct2d,1p yueh4v ,z)v p mtz-f,hmx2shb84f-field do in moving a proton from a point with a pot,-8u l m2h 2,mezpftpdvsh,v4x4 f1 c)hyzb-tential of $+125V$ to a point where it is $-55V$ Express your answer both in joules and electron volts.
   $\times {10}^{-17}J$
   eV

  How much kinetic energy will an electronx+gm47ud5ro/sm+bl4m m oq e / gain (in joules and eV) if it acceleratesm7/44xum /me+qsood + m grl5b through a potential difference of 23,000 V in a TV picture tube?
   $\times {10}^{-15}J$
   eV

  An electron acquireste,ksi,bs* 1i )vx il2 $7.45\times {10}^{-16}J$ 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 plagrbe fy*ef46(7yia pu, 35xnhtes 5.8 mm apart if the potential differen,bfy5p egh 6fxa(ein u4r3 y*7ce between them is 220 V?    $\times {10}^{4}V/m$

  An electric field ofp*jzjfw /2u:zw. 3,cs6 ks*smz4dvcp $640V/m$ 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 bf: d9a 8kp+a*8gmf76wl l wjlzattery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected to a 45-V battery i9b1z un:aq0d,n/d ,lo+tir xcnr*m4ks $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a helium nuu2izxv9y g)q/b riu2 3cleus $(Q=2e)$ 65.0 keV of kinetic energy?    $\times {10}^{4}V$

  Two parallel plates, connected to a 200+j 2547idonc0dvg 4 2zhemxkq-V power supply, are separated by an air gap. How small can the gap be if the air is not to become conducting by exceeding its5vhq7znxi 4mc2dg42ed kj0o+ breakdown value of $E=3\times {10}^{6}V/m$?   $\times {10}^{-5}m$

  The work done by an external force to p(62c + /mn0qlsn(k a0elqkfkmove a $-8.50\mu C$ charge from point a to point b is $15.0\times {10}^{-4}J$. If the charge was started from rest and had $4.82\times {10}^{-4}J$ 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 eleiw(b(ax)oqp , ctron with kinetic energy
(a) 750-eV,    $\times {10}^{7}m/s$
(b) 3.2-keV?    $\times {10}^{7}m/s$

  What is the speed of a proton whose kinetic energy is 3.2 keV?+cp,ocvjo e-4 w7j5/ibg/n*wjp( yb n    $\times {10}^{5}m/s$

  An alpha particle (whichl,u;q2lmggjl-d, t5 :dty k 1z is a helium nucleus, $Q=+2e$, $m=6.64\times {10}^{-27}kg$) is emitted in a radioactive decay with ${}_{KE}$ = $5.53MeV$ What is its speed?    $\times {10}^{7}m/s$

  What is the electric 4lvqc8k)sv rh0unbk*s w7ax722p - gue2.ajipotential 15.0 cm from a $4.00\mu C$ point charge?    $\times {10}^{5}V$

  A point charge Q creates an elect l d9pwb6;nn(h+* d0rrkc9mqpric potential of $+125V$ at a distance of 15 cm. What is Q?    $\times {10}^{-9}C$

  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 of a football. This conductor carries a nczokl*6a2n2tif.5h 8 cngl(a et negative cha lga*26lh ct i.5 coknfa(2z8nrge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a/gr)es *upfn0j76 7zh9ka/ a h5gxaj u distance of $2.5\times {10}^{-15}m$ away from a proton?    $\times {10}^{5}V$
(b) What is the electric potential energy of a system that consists of two protons $2.5\times {10}^{-15}m$ apart — as might occur inside a typical nucleus?    $\times {10}^{-14}J$

Three point charges are arranged at the corners of ah:eb. hc8na3xeo q h:) square of side L as shown in Fig. 17–25. What is the potential at 8naqb. c3eh:: hx)eoh the fourth corner (point A), taking $V=0$ at a great distance?

  An electron starts from rest 32.5 cm from a n 1jlklf.xeho; z l71,fixed point charge with $Q=-0.125\mu C$. How fast will the electron be moving when it is very far away?    $\times {10}^{7}m/s$

  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 frf9y,di-j vd1z ew68zaom a great distance apart td6ef,vaw- 1 9yzi8z jdo $1.0\times {10}^{-10}m$ from one another (at the corners of an equilateral triangle)?    $\times {10}^{-18}J$

  Consider point a which is 72 cvsm11f 5:x8m rp 84 :ps 8+iqoz0q borqhkazg6m 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) ${\overrightarrow{E}}_b-{\overrightarrow{E}}_a$ (magnitude and direction).
   V/m
   ${}^{\circ }$

  How much voltage must be use*a4pzy5 bze;n d to accelerate a proton (radius $1.2\times {10}^{-15}m$) 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 $3.6\times {10}^{-15}m$. Assume the potential is that for point charges.    $\times {10}^{6}V$

Two equal but opposite charges are separated by a distance dxfuavue.wc-7j ( m1dfs,r9/r, as shown in Fig. 17–27. Determine a form,(rer1 -.7fv /m9sxaw c udfujula 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 piajhvn43ns7 t.45 p ijroton (the nucleuspnj45t3 ivs a4nh7.ij) in a circular orbit of radius $0.53\times {10}^{-10}m$.
(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?
   $\times {10}^{-18}J$
   eV
(c) What is the total energy of the electron in its orbit?    $\times {10}^{-18}J$ $\approx$    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.   $\times {10}^{-18}J$    eV(Round to the nearest integer)

  An electron and a proton ar3 x/ybd-wmjhho oc;g1dd 8p,4hw( hd.e $0.53\times {10}^{-10}m$. apart. What is their dipole moment if they are at rest?    $\times {10}^{-30}C\cdot m$

  Calculate the electric po+wtd - 1q.tlzqbzx5nii*j5 ) xtential due to a dipole whose dipole moment is $4.8\times {10}^{-30}C\cdot m$ at a point $1.1\times {10}^{-9}m$ 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 negk:8fixz d2kr3 p edoov 3i/*/iative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be co3*3ik v i:rxdp/d/ ezf8k io2onsidered as the vector sum of the two dipole moments, ${\overrightarrow{P}}_1$ and ${\overrightarrow{P}}_2$as shown. The distance between each H and the O is about $0.96\times {10}^{-10}m$. 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 $p=6.1\times {10}^{-30}C\cdot m$ Determine the charge q on each H atom.    $\times {10}^{-20}C$

  The two plates of a capacitor ya kfd*3n l:-ghold $+2500\mu C$ and $-2500\mu C$ of charge, respectively, when the potential difference is 850 V. What is the capacitance?    $\times {10}^{-6}F$

  The two plates of a capaci/rfos 5e1*4usyy rr/9 ufo.sltor hold $+2500\mu C$ and $-2500\mu C$ of charge, respectively, when the potential difference is 850 V. What is the capacitance?    $\times {10}^{-6}F$

  A 9500-pF capacitor holds plus andemm03sy1gqe(qd 3o kwoih8 / 3 minus charges of $16.5\times {10}^{-8}C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of parallel wireb(slpk4v;0f*y n0y9s b3cq xs in air is 120 V. They carry equaclx*by9n;yq ss04 3vkb0s pf(l and opposite charge of magnitude 95 pC. What is the capacitance of the two wires?    $\times {10}^{13}F$

  How much charge flows from each terminal of a 12.0-V batt.vgkh6poc;8nm 0bbt wp xnb f.8g39n5ery when it is connected ghp05bnn.fcbwm8k o;vn9xb 3.t8 g6pto a $7.00-\mu F$ capacitor?    $\times {10}^{-5}C$

  A 0.20-F capacitor is desired.x2 ;1t6cj*p -quryhg0e sqqr* What area must the plates have if they are to be separat j6q1x*r p;qug *q2y0 c-ehtsred by a 2.2-mm air gap?    $\times {10}^7{m}^2$

  The charge on a capacitor incgjt4mc.m,in/bg7lb).k8 w)i v :k fcbreases by $18\mu C$ when the voltage across it increases from 97 V to 121 V. What is the capacitance of the capacitor?    $\times {10}^{-7}F$

  An electric field off2 xffa+i6+hfp vf7 qml773rm $8.5\times {10}^{5}V/m$ is desired between two parallel plates, each of area $35c{m}^2$ and separated by 2.45 mm of air. What charge must be on each plate?    $\times {10}^{-8}C$

  If a capacitor has oppositeq 9ei /zotuf1),+ qq9lsv+cg f $5.2\mu C$ charges on the plates, and an electric field of 2.0 $2.0kV/mm$ is desired between the plates, what must each plate’s area be?   $m^2$

  How strong is the electric field between the plates of :5ql 7sa-hozs6;cs jx a $0.80-\mu F$ air-gap capacitor if they are 2.0 mm apart and each has a charge of $72\mu C$ ?    $\times {10}^{4}V/m$

  A capacitor is charged by a 125-V battery (Fig. 17–29a)x3 9y.x a1enz(n,amroh8m yq (wx05s t and then is disconnected from the bayorm(,8qyx5 at93ze.1 x(0 xmn wna shttery. 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.]    $\times {10}^{-5}F$

  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)
$\begin{array}{l}{Q}_1\\ \text{ initial }\end{array}$   $\times {10}^{-3}C$
$\begin{array}{l}{Q}_2\\ \text{ initial }\end{array}$   $\times {10}^{-3}C$

  What is the capacitance of two square parallel plate. dw5v rym:*f3x c/*fotoxwj/s 5.5 cm on a side that are separatx :w3rd*wf m.j/f*/ ocytx5ov ed by 1.8 mm of paraffin?    $\times {10}^{-11}F$

  What is the capacitance of a pair of circular plat0z9t,p k4obmoes with a radius of 5.0 cm separated by 3.2 mm of mica?p0otz,94mb ok    $\times {10}^{-10}F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. If a piece of mickx.gi kz9dg 2(a is placed between the plates, how much charge wz(2 k9.gd gixkill flow from the battery?    $\times {10}^{-7}C$

  The electric field between the plates o m)eq9f0 x*5rznc2g2; p yslhgf a paper-separated $(K=3.75)$ capacitor is $8.24\times {10}^{4}V/m$. 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.
   $\times {10}^{--9}F$
   $m^2$

  650 V is applied to a 2200-pF capacitor. na2n(ge mvsdl9;b*dv q58.az How much energy is stored?    $\times {10}^{-4}J$

  A cardiac defibrillator is used to shock a heart that is beatin3 93 kca r;5+ jt bu kxoq)al-j1rm;ftf)wd4bbg erratically. A capacitor in this device is at);lokc-qj4bf d b 9wr5 +muxka31 j b;)f3rtcharged to 5.0 kV and stores 1200 J of energy. What is its capacitance?    $\times {10}^{-5}F$

  How much energy is stored by the electric field between two squaree 8jw1az;g 0bw plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on the plates are equal and opposite and of magnitud8 ;gwb1ej0azw e $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in. pie pans 5 cm apart and zy/)dk;h jo *wr*+ dtfconnecting them to the opposite terminals of a 9-V bawk ;*ft*r)+oyd djh/z ttery. Estimate
(a) the capacitance,    $\times {10}^{-12}F$
(b) the charge on each plate,    $\times {10}^{-11}C$
(c) the electric field halfway between the plates,    V/m
(d) the work done by the battery to charge the plates.    $\times {10}^{-10}J$
(e) Which of the above values change if a dielectric is inserted?

A parallel-plate capacitor (q 9 uqu/y2i) * iu9odswhdvy.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 stored in a capacitor change if r/jv*au5tzucxzce(x5i6*a 6(a) the potential difference is doubled, and (b) the charge on each plate is doubled, as the capacitor remains connected to a bax(*c6uie/6ja xv cz a*rt5z u5ttery?

  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,    $\times {10}^{-4}J$
(b) after they are connected.    $\times {10}^{-5}J$
(c) What is the change in energy?    $\times {10}^{-4}J$

  In a given CRT, electrons are acceleratecj5 eetd sv1 bnv /:+m+fir*-id 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 r nvd: -e m/r++ *ite1jfi5vcbseach the screen top 22 cm away, 11 cm above the center. Estimate the value of E.    $\times {10}^{5}V/m$

  Electrons are accelerated by 6f/zqt7 u .a)d, zn4ci*pcm(cg.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 electrip ,c. i aczu)tzc d7nm(/gfq*4c field vary to sweep the beam fully across the screen?    $\times {10}^{5}V/m$ to    $\times {10}^{5}V/m$

  An electron starting from rep8kl4(ev mo3 ebp1 em,st acquires 6.3 keV of KE in moving from point A to point Bl, 1km(m 8eeo4b pvp3e.
(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-y)a6ks(kh+v,kerkxb 4 ,f af.2 MJ of energy to the Earth.
(a) Across what potential difference did it travel?    $\times {10}^{6}V$
(b) How much water could this boil and vaporize, starting from room temperature?    kg

  There is an electric fielb ez80l- ezb)uj(pf 3ld near the Earth’s surface whose magnitude is about $150V/m$ How much energy is stored per cubic meter in this field?    $\times {10}^{-7}J/m^3$

  In a television picture tube, electrons are accelerated pun0,-r ngu )uby thousands of volts through a vacuum. If a televisn n0g ur,u-up)ion set were laid 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.    $\times {10}^{-12}V$

  A huge 4.0-F capacitor has enough stored energy to hea+vfc ;lya(-0fwn ,e vjt 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 24.0n1ptf,eo;;20 ot6qq wnq5 hii-V battery until it is fully chargedq wqo6q,htp ;n t51f;no02iie , after which it is disconnected from the battery. A slab of paraffin is then inserted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down if the ewfxi.ptg*mpvu(v n 32b 8)l /rlectric field exceeds $3.0\times {10}^{6}V/m$. What amount of charge can be placed on a parallel-plate capacitor if the area of each plate is $56c{m}^2$?    $\times {10}^{-7}C$

Three charges are at the corners of an equilateral triangle (side L) as3 0aonv-:sqxew(*6h wt ic -za shown in Fig. 17–30. Determine the potential at the midpoint of each of nevq -ti-*sz awh6( 3w0ocxa: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 congk/ eu-yz ultktu(l ,)z1r.c7nected to a 9.0-V battery. If a piece of Pyrex glass is placed between the plates, how much-tg luru7e,u zty .)ck1z(l/k charge will then flow from the battery?    $\times {10}^{-8}C$

  An electron is accelerated horizontally from rest in a television picture tnlt9sjc qg4 8 hj2i,owt*f:,6ywp6h w ube by a potential difference of 5500 V. It then passes between two horizontal plates 6.5 cm long , w j,hj64 9o2cht 8snlqp6 :wfwyi*tgand 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 capacitance js2kt.5wdqu4y nn*(a $C_1$ 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,tlouug 3n 21 pp(gcf1* vyd 0eep*yr4 you want to make a 1-F air-filled parallel-plate capacitor for a circuit you are building. To make it a reasonable size, suppose you limit the plate area to What would the gap have to be betru g*v yg1p c(2f n t*epe0o,4py3l1udween the plates? Is this practically achievable?    $\times {10}^{-16}m$  ----待选择----YesNo 

  Near the surface of the Earth there is an etdbjf) dzpm 8+. ila0-lectric field of about $150V/m$ 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 fk9 v(rc v7r3zl1jiq4:z8zkycw3 0w ppulsed nitrogen laser 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?    $\times {10}^{5}W$

  In lightning storms, the potential difference between the Earth and ther f 5h6qm9h 1l-zyiok: bottom of the thunderclouofm:z6y19 h kirq5h-lds 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 of $110k{m}^2$ Modeling the Earth–cloud system as a huge capacitor, calculate
(a) the capacitance of the Earth–cloud system,    $\times {10}^{-7}F$
(b) the charge stored in the “capacitor,”    C(Round to the nearest integer)
(c) the energy stored in the “capacitor.”    $\times {10}^{8}J$

  In a photocell, ultraviolet (UV) light provides enough energy + t8;rxq(pbj lto 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 poten8tr ;jlxqb(+p tial 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?    $\times {10}^{6}m/s$

  A point charge is placed 36 5+9 s 2rqc :l /pbh.pvr,iyrhncm 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 v1di gzk/6l)* (hsa7wggxhs7 .1-cm-diameter coins separated by a 0.15-mm-thick p1ihzd(7kas lg7s)6x * g hvgw/iece of paper $(K=3.7)$ A 12-V battery is connected to the capacitor. How much charge is on each coin?    $\times {10}^{-10}C$

  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    $\times {10}^{5}V$
(b) the electric field?    $\times {10}^{6}V/m$  ----待选择----leftright 

  A parallel-plate capacitor with plateb:a4 dhcyj z k /0mxvyf7je2-ryd;f)6 area $2.0c{m}^2$ 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?    $\times {10}^{-11}C$
(b) The plates are now pulled to a separation of 0.75 mm. What is the charge on the capacitor now?    $\times {10}^{-11}C$
(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?    $\times {10}^{-10}J$

  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.    $\times {10}^{-6}C$

  Two point charges are fixed 4.0 cm apart from each other. Their chargedh)8v1iz8m 7j mu (yzes 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 ay x ;ez.( tumkmpyp du71.(v,rs 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.    $\times {10}^{5}V$