If two points are at the same potential, does this mean that no work is don .+de r/o0rmawe in moving a tem o.rw+ r0ade/st charge from one point to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at rest in an electric field, will it move toc 4ovkic; ezfgrv rt.o 2)hw 06;klm/1ward a region of higher potential or lower potential? What about a positive charge? How does the potential energy/ 1ekorc r);fgowh .60k l; i2vv4mztc of the charge change in each instance?

State clearly the difference (a) between electric potential and elet(lz 0n8,kl/m -n9x6 ocrko3txf kkq: ctric field, (0 t-zkm(l flo/ xkoqkcr39 :xt nn,6k8b) between electric potential and electric potential energy.

An electron is accelerated by a potential difference of, say, 4q50+b)o j2iuwe az ul0.10 V. How much greater would its final speuobuwi52e4 )lqa0z +jed be if it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining two equal positive charges where the e6wn1m/dg: (sihvz:uu lectric field is zero? Wher 6/wg:h i:nzd(uums1ve the electric potential is zero? Explain.

Can a particle ever move from a re5:;k :6ixwlarvu ) hovgion of low electric potential to one of high potential and yet have its electric potential energy decrease? Expv ::o;uvr hka x5lw6i)lain.

Compare the kinetic energy gainy *,(qu/hork*ej9t uned 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 $\vec{E}\,=0$ there? If $\vec{E}\,=0$ at some point, must $V\,=\,0$ at that point? Explain. Give examples for each.

Can two equipotential lines z uiwy1l :ov.+g5*mbf cross? Explain.

Draw in a few equipotential linx* /ow9l /ppaaes in Fig. 16 – 31b.

What can you say about the electric field in a region of spr.htm px+5fk:;c08xm :cn h waace that has the same potential f pm+0:n;c. r xxka8ht5mh w:cthroughout?

A satellite orbits the Earth along a gravitational ebd 3vucsbhi/ ,;oa0p0quipotential line. What shape must the orbi 3,bpid/bvusah 0;c o0t be?

When dealing with practical devices, we often q*2b+khhy3 ;.ulrfhvtake the ground (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 q+.hf2 rk;h 3*vhluybE, at other points?

When a battery is connected toadvs*5mzy q+a :*jdcl( nj6 e3 a capacitor, why do the two plates acquire charges of the same magnitude? Will this be true if the two conductors are different v nl(sq z3jem+:d6yj*5daa* csizes or shapes?

We have seen that the capacitance C 5ei3zc6iabd,9 qlba2depends on the size, shape, and position of the two conductors, as well as on the dielectric constant K. What then did we zdb i,92acaq eil5b36 mean when we said that C is a constant in Eq. 17 – 7?

  How much work does the electrwh*h5wa+ow8 h ic field do 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 the electric fi7sq-utb rl/)a kq 5(mpeld do in moving a proton from a point with a potenti s/b(u)qa-plr5k tq7 mal 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) if it acch.su( w3 *t 3 3t/kgmusmagh3ielerates through a potential difference of 23,000 V in a TV picture tubeiuu/sw 3.3mggtmtk3 (s3 ahh *?
   $ \times10^{-15 }\,J$
   eV

  An electron acquiresffw8nez bbg72 -a +.qh $7.45 \times10^{ -16}\,J$ 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 parall9 :x/ukcwg-fz el plates 5.8 mm apart if the potential difference between them is 220kgwf- 9:x/u zc V?    $ \times10^{ 4}\,V/m$

  An electric field of oubd ww2xxo(-n)t l ;wyb4 fn,2mfe3 *$640V/m$ 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 xu 16pw nx hq-;vt;mddz3r7+cbattery is $1500V/m$ How far apart are the plates?    m

  The electric field between two f( eq-7n* 9xtg e9kba*5ivsup7zu0 uh yl1)lh 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 h l8myc;a53hcqakclc 00kw v8r18 s;ot elium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 20 n s7zx7jc*.uj0-V power supply, are separated by an air gap. How small can the gap be if the air is not to become conduct zsc*ujx.7n7j ing by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force to m3ox8swf gu(d9 ove 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 electrokltc;k8 1/edsyt7 0o edkg h09n 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 ustj x;ts 5len c.0:.: wzmos*energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nucf:-*zv y d;6prpis1n n( sed)ileus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric potential ; a ,)bnrf1rai s,e0op15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electri gs:0tss7 qa-uc 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 a football. This conductor carries a net negat1ksr ( ahbdopzv 1g;2+ive chah kp11;dzs+(2b g rvoarge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a distance 2xa b 2zanw0p-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 i; y hxa/r8l+xat the corners of a square of side L as shown in Fig. 17–25. What is the potential at the fou+ hi;axy x/r8lrth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed pqrzlyz4y d n/hikd;s2+fx1d n9: zd /1oint 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 donesm d1v4(8w u:1urozm g to bring three electrons from a great distance apart t: 1rd 8vwozmu 4ugm1(so $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which iu/o iai op:*2o-hpo2 hs 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 accelerat 45e:wr*lqzgt z8t wo0e a proton (radius $1.2 \times10^{-15 }\,m$) so that it has sufficient energy to just penetrate a silicon nucleus? A silicon nucleus has a charge of $+14e$, and its radius is about $ 3.6\times10^{-15 }\,m$. Assume the potential is that for point charges.    $ \times10^{6 }\,V$

Two equal but opposite charges are separated (b)vwyq/b g+o8xr i(lby a distance d, as shown in Fig. 17–27. Determine a formulay/ir(bw xgb8l q vo(+) 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 proton (.za(7ck fncr/ the nucleus) in a circular orbit of radiusf.7/caz (kncr $ 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 protod7bn ot1l*m,r n 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 dipole whosg :jcyba4 z*58q)zdk)nmn2 q/j ca;fk e 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 to the po ibxdt// 1 uok*xx 2htnv 4a(,w+kv*cnsitive charge. The water molecule, Fig/x*hk4w1 vtk/nn xvob,ui tca2 x*(d+ . 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 cavelw9r qfvm*j( 6j4 /ypacitor 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 capacit7slz5oq pz 0 edc+36xpd+f(lgor 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 plc - kb/mod9wd;jw/ wbr0 ees(9us and minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of pa d49fyj 2vmu+nrallel wire in air is 120 V.9jfmn 2v+4dy u They carry equal and opposite charge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows vyevwv8u .m)0l:kxs *dmp 2b .from each terminal of a 12.0-V battery when it is connected 0sb*2.vdk:euv)xm m8 pl.yvwto a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What are zcrzcum 9d460:zga ,za must the plates have if they are to be separated by a 2.2-mm air gap9 6uc0azd rzzg,:4zcm?    $ \times10^{ 7}\,m^2$

  The charge on a capa .n e 7v7iin,pu.s-l3dmt/ hhqcitor increases by $18\mu C$ when the voltage across it increases from 97 V to 121 V. What is the capacitance of the capacitor?    $ \times10^{ -7}\,F$

  An electric field offrnupy1 8q3)r $8.5 \times10^{ 5}\,V/m$ 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 opposil3edr;+ bz v*v )e95 pluqm*idte $5.2\mu C$ 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 platjagva;n 0 9;zbes 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 b)+ rzxi/ tptzmjk5/m, attery (Fig. 17–29a) and then is disconnected from the batterxtm+ prk,j/ 5t )i/zzmy. 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 side tht(c qqc w40t e tkzsojc+q:ah)c019 *lat are separated by 1.8 mm of pa(e t+1*cqsh0j9q az k to:4clwcqt0)craffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a radiulzeq n x)89e. 8* qojbz:uy yfx+b:5fjs of 5.0 cm separated by88*bye j: x5yl +e bqf 9x).qzfuoj:zn 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connec,dwe/ct)0p wk ted to a 22-V battery. If a piece of mica is placed between the plates, how much charge will fl/kw wpd0 ),tceow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates l94dg rbmau4 aa.e1;c 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. Hz 185(vmb;c+uqe9-jtt 8ljo00 *mb tvbzve twow much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is m5,achi. g mdfe aweq+1:l l2.v- /kxpbeating erratically. A capacitor in this device is charged to 5.0 kV and 5a2mx l iq.l,khmf. /acpw+ve1gde:-stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric fie4q+ 4l;m gz,zzzplvd0k, ul 5sld between two square plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on z5;,ls+u zlk4 mz pg4lv,d0zq the plates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in. pie pans 5 cm ap;m8a1s3( vrz ae vw-jbart and connecting them to the opposite terminals of a 9-V-swzm8a1e vab; 3v(rj 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 cap c7ao,zujerc-dy9k(nxuf6 9 1acitor 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 (a) the potential e,laeygv 0y0lle+c) r,kv) c7j q;h,v difference is doubled, v0jy+,e rv)vge)ylkeh,cq0; ,a l7lc and (b) the charge on each plate is doubled, as the capacitor remains connected to a battery?

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

  In a given CRT, electrons are accelerated horizontally by 7.0 kV. They then pas) zs-e bo-5embo,jm r naj)c59s through a unij 5 )rmm9ban e-oec-sjob,z5 )form 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 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 wkv nw.6ul06 ji .pc+mride and is 34 cm from the 2.6-cm-long deflection plates6m0 vr6. +nuiwjckp .l. Over what range must the horizontally deflecting electric field vary 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 of KE in moving fpib42 hz;nl6- ; ao jpi-hwci:rom point A to point Blhcwp;zinjobi4h2 6p ;ia--: .
(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 trans;4)h7kv :l yb,gr* p*zpib75miv+qndv. c segfers 4.0 C of charge and 4.2 MJ of energy to the Earth.
(a) Across what potential difference did it travel?    $ \times10^{ 6}\,V$
(b) How much water could this boil and vaporize, starting from room temperature?    kg

  There is an electric field near the Earth’s surface whose/l/7dpi0r c 0tc fgbye49ge z0 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, electyuh0w lw-;mg- rons are accelerated by thousands of volts through a vacuum. If a television set were laid on its back, would electrons be able to move upwar0m; yu--g hlwwd 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 stw;z i0s l+ebn/,tg 8wnored 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 is connected t xvrx.cvx z -x3t p72gp.,zxwi do*5-yo a 24.0-V battery until it is fully charged, after which it is disconnected from the battery. x x*vc2xprwp iox7vy5 gz tzx-,3 ..-dA 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 elecz* udkzlj s6*1:2r, xoki: irdex*vg7tric field exceeds $3.0 \times10^{6 }\,V/m$. What amount of charge can be placed on a parallel-plate capacitor if the area of each plate is $56cm^2$?    $ \times10^{-7 }\,C$

Three charges are at the corners of an equilateral triangle (side L) as shown g )e hm8hin:lj))4y,kdxuj3r in Fig. 17–30. Determiner, x :8ey3h)jilk)d 4)ujghn m 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 connected to a 9.0-V batta e5r ot2dmgnn ,iz3fb2k*0z((qlfe5ery. If a piece of Pyrex glass is placed between the plates, how much charge will thenagen qr 2 , (ze3ti0(lf2kf oz*5b5nmd flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accel 7-uk wy.vb/mverated horizontally from rest in 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 apak-/wb um .vvy7rt 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 capacitance0j kh ps.*yelb-anb6+anea/; $C_1$ 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 youbg0kw8*gk-5op 3z 2 d fkhcdc9 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 between the plates? Is this pr9 c0d5bg*2fwhzgc kk k8d-po 3actically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there is an electric field of about*q6e ic4 u /r 58e9jw5zwsisdq $150\,V/m$ 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 la/3b7tor8k*nrqfgjn* wy j se )wz6)d(ser 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 between the Earth and the bottoe)wb+e5*cpt dp9r x)it t b455gdd0 fnm of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are typw 5*b)pnbxd r09deei4 5tgt+dtf)5pcically 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 lv4e/ vc38k d cf5:ntuelectrons in barium metal to eject them fe vn v4cl85d/3ktu:c 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 the plate voltage is $-3.02V$ (compared to the barium) when the fastest electrons are stopped, what was the speed of these electrons when they were emitted?    $ \times10^{6 }\,m/s$

  A point charge is placed 36 cm from an idenzra9xndxej 2xem268m 3a0 3 zotical $+33\mu C$ 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-diyv 2+*0eckn fl-hu*kqameter coins separated by a 0.15-mm-thick pieuc0 *ykq 2v*en-k hlf+ce 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 capzm1mmq8y t r.;acitor 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 k (qt1 glu4z0y4.0 cm 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 as shown in Fig. 1z pqyfb,nzo-q/;xf7y1: 3gww 7–35 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$