If two points are at the same potential, does this mean that no w2 3cq:f 0ksf: xuli7e0o2agx jork is done in moving a teac k2:j7lgiu 2x0s:0qo3x ff est charge from one point to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at reutrx ;g 4c6k )yll+;mhst 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 ch46 r;;c)llxt g yku+mharge change in each instance?

State clearly the difference (a) between electric potential and electric fieldakxh1p 2g0yb,evs 2q3z rt(6a, (b) between electric potential and electrice6 qg12 3py 0ahzb(,ar vxst2k potential energy.

An electron is accelerated by a potential difference of, say, 0.10 V. How much*wu8stc gdk /- greater would its final speed be if it is accelerated with four times as muk*cu w -g8/sdtch voltage? Explain.

Is there a point along the line joining two equal positive charges where th.(r7lujh4xu 30cf 1wbk j rk6f s3;fiue electric field is zero? Where the electric poten3sk ik1 7bjfu4 (crfjx6hu;lu3r.0 fw tial is zero? Explain.

Can a particle ever move from a*9tlenb llep+v3(d; a region of low electric potential to one of high potential and yet have its electric potential energy decreeb n(lv 9dla te*;pl3+ase? Explain.

Compare the kinetic energy gained by a prot.e ikd5; yae*(vp+(nhne0t alon $(q=+e)$ 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 crr b0 w/mwe;+l.s/xwfqoss? Explain.

Draw in a few equipotential lines in0o4x go smwcwnmsyqc-0 a.6 84 Fig. 16 – 31b.

What can you say about the electri 4,6ljy4ols3 lgzg8sjnv;nz ,c field in a region of space that has the same potential thjg8l oss 4;l4l,gy ,63nnvz zjroughout?

A satellite orbits the Earth along a gravitational equipotential lin1kd; z5 mxst 76f6cjr 4f4fujbe. What shape must the orbit be;jkx brff6ts 76fmd4z4 c1 5ju?

When dealing with practical devices, we often take the ground (te(c -6evv tyl:)nme kzj,3v,p he 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, at other,z e(nmvc)jyve p3l6ek :vt,- points?

When a battery is connected to a capacitor, why do the two plates acquire ;c/iolh fc8.pxhq4f2 charges of tlf 84c;oqh x h.i/2cfphe same magnitude? 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, an: ncjkibd4 ,c1t:rj -td 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 in Eq. 17 – rk,jb 1:d tj: n-t4icc7?

  How much work does the electric field do in movmdby -ar0w u 7k98k)rping a $-7.7\mu C$ charge from ground to a point whose potential is $+55V$ higher?    $ \times10^{-4 }\,J$

  How much work does the electric field do (/j alxrmlzk awpu.z3+q: / b)in moving a proton from a point with a potentialx pq+.rb(a/)j3azzl :mul w/k 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 eV4dryrtq797,l 2 yn;pq1i a leh) if it accelerates through a potential diff yq21 pltnhyq7l9 red;a4,ri7erence of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires -dco 380x ugh jr 1rbf).me;ve$7.45 \times10^{ -16}\,J$ of kinetic energy when it is accelerated by an electric field from plate A to plate B. What is the potential difference between the plates, and which plate is at the higher potential?
   V
plate ----待选择----AB 

  How strong is the electric field between two parallel plates 5.8 mm apart it-/mt,pmv5reb1+ (v-so m1 n xwmk st*f the potential diff,*5v tttro-m/1vp +m(me 1 kssxmbnw -erence between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of ;5w,.p7 occ62puap s ru bg,ta$640V/m$ 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 ) 77edw/ngcbnr+ dnz,cjs5gvl.(a6s-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallells25 ta(qda;/m 7iqwi plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed ;cwe/7b2)4d*prvuc epyj5 b7 w2w obhto give a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to *u3 s +ytt3yblwrb8/bb rc5a,a 200-V power supply, are separated by an air gap. 8wbbs rycl35t/tu*,abb r +y3How 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 e.gx04 y (a+bbqqsyrs 4xternal 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 el3zh t,9h4rojzectron with 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 9w7dr)ht )zt cdcui l, s6.mxb2.h pu)3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium yd5ec d;lfw2 *nucleus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric potq ) kywcl12vn5 u;l0hvential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q cre9 -ve zl9x(rlom si:jhxr9t2z4ggo9k 9v *7 hyates an electric 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 of/ 6xu*j gcm4qrq+u+ ru a football. This conductor carries a net negative charge,+qcuxrugmq64 u*rj+ / $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potentu zkwev6xqf1f( ar )cr*d*6,fial 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 squar4m1tgbk qvim;b 2kn /el1p6 7se of side L as shown in Fig. 17–25. What is the potential at the fourth corneqk1 el6m1n4p vki/t72bsmg ;br (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a (ed jr6a rrp s8(wpb;xw-f3p6. (hsylfixed 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 d2rqis :jk3dm733 xp keistance apart es 27irq: xd 3j3kpk3mto $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a whiyhv-.,3dd ku1 *gqdp4hye.wzch 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 used to accelerate yy3j,a9snr,d.k9h .e(1 sm crjj6fy ja 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 separated by*l v.vb (epm/tvo-9zj/xvr ;. cuuci7 a distance d, as shown in Fig. 17–27. Dete9vvtx/l(c.zr7/buiem*uv p v. ;o-j crmine 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 pro rwa) tn m8)aj/-8vibrton (the nucleus) in a circular orbit of radiunjtrv)8-iwab m a)r 8/s $ 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 are xnbx,yv (xhu z4j+bq,a:g )s* $ 0.53\times10^{ -10}\,m$. apart. What is their dipole moment if they are at rest?    $ \times10^{-30 }\,C\cdot\,m$

  Calculate the electric potenq5pqw+ey+t6 yj)jt l1tial 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, points from the negati0 qq,m3 e. skbo,,f wg8iujp3rve to the positive charge. The water molecule, Fig,0 qrg,mu pb3 3q,isf. eojw8k. 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 capacitzk, g gw.4odnglr -m)0or 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 6yk(it popv8--v/7 yo6 yki0hoq o/szcapacitor 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 h;kwc5i)u)d mg ; unbi*olds plus and minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two shortj4qoa :bgc( sfcmx-,-j.y (xp sections of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is the ca .o-( c(p4jfj : sgxqm-baycx,pacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of a w th0)2w ve4t9rrn2igtzho *(12.0-V battery when it is connecte2h*thowv40e t n29grwi()z r td 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 1l x / c1/bre-dmy bz22f7udfrto be separac12b uddr /zf2xmr l7f-1by e/ted by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increasegdkh0ocxw 53i1ny- - ps 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 ofjpqxs oetj:pmf 1 03h/553cdbc 1)q hl $8.5 \times10^{ 5}\,V/m$ 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 oppositm4i5x-cozi a hub/* d8e $5.2\mu C$ 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 the7 dygtyvx67fq,fa,v 6 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 chargw6 jwggi20h 5ced by a 125-V battery (Fig. 17–29a) and then is disconnected from the b50 jwwc2gh6gi attery. 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 cm on a sio p;):y0jwaro de that are separated by 1r0j pyo:) oa;w.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of cir8z ui bznpb+)7z zkm*/cular plates with a radius of 5.0 cm separated by 3.2 kmzp)n / zzi8 zbb7u+*mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is cobtq8xc7w8:jh nnected to a 22-V battery. If a piece of mica is placed be:7jqt 8hx cb8wtween the plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field b:y9rr3bbli 4 27tsdd7*iqyndetween 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 ex+1)4pxes t1yvkn m3 a 2200-pF capacitor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is bi65ec 5j y)amaeating erratically. A capacitor in this device is charged to 5.0 kV and stores 1200 J of energy. What is its capacitance? e5iacm 6)5j ay   $ \times10^{-5 }\,F$

  How much energy is stored bye83rj+6oo kffb: oa8z the electric field between two square plates, 8.0 cm on a side, separated by afa 8e r+8ozo bj3o6:fk 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 mhee:;jbn 1l): 2raes+ o.xt 6;drxln9-in. pie pans 5 cm apart and con jmel ;16r2ns:a )ex h bo;lnrx.t:ed+necting 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 cb52rqq;ez- mckf*o8 d harges $+Q$ 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 capacis94o tx:lqxk uzh )77htor change if (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as the capacitor remains co zkq7)x4ulhht s9o x7:nnected 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 by 7.0 wmb:7bls5bwz n0 ao +:g +9mggkV. 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 22 cm away, 11 cm above the cen7 o5 la9+bngw gbsm+ :g0mbz:wter. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 ktaj+t .9 s9yydV 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 varyta9 9d y+js.yt to sweep the beam fully across the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from rest acquires 6.3 keV ofu :q(-tleb i.xzji5j/ KE in moving from point A to point B. :lz u ( ib/itxjq-ej.5
(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 4aw +ft qlpg ) (a:uapiq+dsw*8s4i-sthe 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 fiel*j+ ws 8ybled7d near the Earth’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 accele36q scn,mf6w q/hd 7b 6oqzww8rated by thousands of volts through a vacuum. If a television set were laid on its back, would electrons be able to move upward against the force of gravity? What potential difference, acting over no/wfbh 78dwqwsmcqz q66 36,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 hascxu.i yb 5f(h( enough 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 capacitore. qzc wf:u*+ mb5ut;j9(wtaz is connected to a 24.0-V battery until it is fully charged, 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 5j; bz:cu9e+muw.at f(z *qwt?    V

  Dry air will break down if the electric fiez1 :zpfdx 3x:n; itj8nld 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 ofiz qr+6 (gw).zwr;exz an equilateral triangle (side L) as shown in Fig. 1z .zierr;+6)wg(w qzx 7–30. 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 capacitor is con9 iw(;qyhi1zr)gu:aa nected to a 9.0-V battery. If a piece of Pyrex glass is placed between the plates, how much charge will then flow from the baui;:9z1wigr) y ( aqhattery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in a television picture tu+i.8 ddvc qob0be by a potential difference of 5500 V. It then passes between two horizontal plates 6.5 cm l8c+b. dv0idqo ong 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 capacita knjo9my+r9q8nce $C_1$ 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 a ; dlg t+wglm1h 2cgnird,-:5giz-gq0 ir-filled parallel-plate capacii w,g+ lmzq5ril- dnhg- d2ggc 1t0:g;tor for a circuit you are building. To make it a reasonable size, suppose you limit the plate area to What would the gap have to be between the plates? Is this practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there is an electrxa(,y(vub2u) fs ti(qrp i s-1ic 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 lase5hq6c4 g- eekg9.flklr 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 potential difference betweiq8v( fsco88 een the Earth and the bottom of the thunderclouds can be as high as 35,000,000 V. Tc 8(ove 88sqifhe 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, ultraviolet (UV) light providesyv: 25uq9ys fg 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 emitted electrons are slowed down and stopped, and return to the barium surface. If thgs qv2:5 uf9yye 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 36llqljq)0vdls4 t3 svc: (w78 d 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( 31f vcbntrjsm.*.a ke 7c;xx two 1.1-cm-diameter coins separated by a 0.15-mm-thick piece(7rb.ca1csk vxef 3t;xnj *.m of paper $(K=3.7)$ A 12-V battery is connected to the capacitor. How much charge is on each coin?    $ \times10^{-10 }\,C$

  A $+4.5\mu C$ charge is 23 cm to the right of a $-8.2\mu C$ charge. At the midpoint between the two charges,
(a) what are the potential    $ \times10^{ 5}\,V$
(b) the electric field?    $ \times10^{6 }\,V/m$  ----待选择----leftright 

  A parallel-plate capacitor wjk 6 mm0s u4x8zbwy-3rith 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 fro z::bz t7/wnyqm 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 placedrb)t+ onrwkm(f 48pk4 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$