If two points are at the same potential, does this mean thao vonmq mfa5w:;lk+5+ t no work is done in moving a test charge from one point to the other? Does this imply that no :okn5mo l; +5f+wmavqforce need be exerted? Explain.

If a negative charge is initially at rest in an electric field2,byb y7dv/xx9 e bvw 9jlu83i, will it move toward a region of higher potential or lower potential? What about a positive charge? bubxj98 ,lwxy d e72vv9yi/3bHow does the potential energy of the charge change in each instance?

State clearly the difference (a) betwenm g4 qv3i41gyla +d6s-q/jwzen electric potential and electric field, (b) between electric potential and electric potent/a1z4gd4w gjiy 6l-s mqvq3 +nial energy.

An electron is acceleqj2 ubcf*yu* fa-(q7vrated by a potential difference of, say, 0.10 V. How much greater would its final speed be if it is accelerated with four times as much voltage7(2c*fqfvy -jqu ua*b? Explain.

Is there a point along the line joining two equal positive charges wh(sp of*k-qs-gkm8lpz5 ic*.q ere the electric field is zero? W i(zs.-8k 5k* l c*m-qfpgsqophere the electric potential is zero? Explain.

Can a particle ever move from a region of low electric potentiiqcrb*zs / a74al to one of high poten/7br*i q sacz4tial and yet have its electric potential energy decrease? Explain.

Compare the kinetic energy *mw y0cm )z*2j6pohffgained 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 cross? Expla5zl y6, yo)qviz6k5v fin.

Draw in a few equipotential lines in Fmha,l :8dt8t(xx aj u 9228flkesym w.ig. 16 – 31b.

What can you say about the electric field in kuv) 7/5 mn1:lanlm ora region of space that has the same po 1ln5al on7uk)/rmv:mtential throughout?

A satellite orbits the Earth along a gravitational equipotentisv sx jnpjn4hq6b, ch,k9r147 al line. What shape must,1hkv4psnr7,s jncbj9qx 4h 6 the orbit be?

When dealing with practical devices, we often take the ground lf-lv/b9fupj mah t p222n.o((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, at other pomf o(nlf9./2puvalb thj 2 -p2ints?

When a battery is convk2u m)5,(f.l,yd qhu lhat;mnected to a capacitor, why do the two plates acquire charges of the same magnitude? Will this be true if the two conductors are different sizes or sha v,q (2 mu.mhhluy ;alt5),kfdpes?

We have seen that the capacitance C dk; en9xdghd4.epends on the size, shape, 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 .kdx4ndh ge9; in Eq. 17 – 7?

  How much work does the electric field do in --b a/qy;29/ vk 9c vg,fdnb cc4gueckbx -d+hmoving 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 in moving a proton from a mi(is7zfj0o : point with a i jio:7fmz(s 0potential 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 gaic(x 9fmyjpf+/cru m3;n (in joules and eV) if it accelerates through a potential dc rmup/3jy+;cf9fx(m ifference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquirestp q8d 7w8g dw))tfp0l $7.45 \times10^{ -16}\,J$ 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 -,gy- q f6d*ggsyk-t;nuin2u parallel plates 5.8 mm apart if the potential difference bety6-uguis;fn -g2,*-ykndg q tween them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of s.8 xn8 ffk)te$640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field b1 clibiv n+8i8etween two parallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected to a 45-V bu(*:xmx :qb qhattery is $1500V/m$ How far apart are the plates?    m

  What potential difference is neednswqmhixcx 9me5/gd+b4-4d 0 ed to give a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, arl/u,5 v9 br pdf.tvus8 o,rpl4e separated by an air gap. How small can the gap be if the air is not to become conducting by exceeding its breakdown value/ tf.95br l8uv4d,porvups l, of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force .s,bo;dtc( v6ycq-nu bc,iiz/o; qa 0 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 ofg8x0j t1; bka1d ncz4r an electron with kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a protone ( 0pft sgp.p5z02ii8ttm5n d whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nuctg -6a.-iqhk9ex7 fw gleus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) 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 cpfuc :t e0+a0(m mk+bwzr; zww+;8cs vm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q createsljxp2 ud.tbo7il)c n7 ihonav3194a- 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 a football. This conductor m wphm eh0(v3j 8jgng(m.7 +hqf;cml-carries a net negative charge, v h0pl(.8 gmj7n w+-e;fmq(mh cm3jgh $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric poten2jh:) n6d . +wtxlwykwxi(6qi tial 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 sides).vn e co w)uns l76/ddpe10ym5yhn( L as shown in Fig. 17–25. What is the potential at tdvenc0sd5oe .1 hs (yu7)wmyn/)6 plnhe fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed point z+8z +oc1z.umh:ji.k q k7pxm 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 thr9vj1w/zsk hcm7kk pc ):x3q2lee electrons from a great distance apart toc 3vhks)m q/z x97wpcl21j:kk $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a whichwrfq; ky6g,xp1;dk cu d0ldnon .u)7qq 17.df 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 a goh.jjoo b8;v57; rim2s9f wa 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 separatet x+qi(ane 6n1gnio+8d mg6;t d by a distance d, as shown in Fig. 17–27. Determine a formuld+(t +6q xnii g;8omg 1ate6nna for $V_{BA}\,=\,V_B-V_A$ for points B and A on the line between the charges.

  In the Bohr model of the hydro c/cgsg*aa;ow0m4 k3nssgh 87vg 9g;cgen atom, an electron orbits a proton (the nucleus) in a circular orbit of radiua;g mw *gs9h8 gv/s3ckcn;7cgs 4a0gos $ 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 8a t dzn tn)h+z d;tfv+j4t/9dare $ 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 d;th/zyzo0eekt 6/i,p eejg7+ue 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 negative to the fo4+wppq ze2* o:x j(upositive charge. The water molecule, Fig. 17–28, has a dipole moment which can be considered as the vector sum pozu2f +4w(:xepqj o*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 capacitor hold ;dco b,at2l)9 fc+vk: q lqt2e$+2500\mu C$ 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 capa-3cemhhgvdzzq; kdi o3le(0rb-;g3 :citor hold $+2500\mu C$ and $-2500\mu C$ of charge, respectively, when the potential difference is 850 V. What is the capacitance?    $ \times10^{-6 }\,F$

  A 9500-pF capacitor holds plus and w jbn:c g.69t+0a d)kfm 3vkjtminus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two shorf58p;vp-q a6h pm/ux 5gak9m0) mowhct sections of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95pmv5)pmcf08w m5x q-a/k9pghhau ;6o pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each ;eq tr9v5ktnvg0lu 5jm2u29l2w gs : iterminal of a 12.0-V battery when it is connected to a wtvnm si g:vu;0t2959 2lr gqu5jel2k $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates have if theygfof;fn 9 90 lay+g7sh:9 dhae are to be separatens 9ygf9;fl0e ah+dg9foh:7a d by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor inck.vtf4z kje7c7er:w z.r q+5m reases by $18\mu C$ when the voltage across it increases from 97 V to 121 V. What is the capacitance of the capacitor?    $ \times10^{ -7}\,F$

  An electric field of f3b .sdy4lqn*xxq2 ,wf in)7w$8.5 \times10^{ 5}\,V/m$ 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 oppodf.t8fp8b,fdk3 il b-site $5.2\mu C$ 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 ele vp6 oyt2lf*5// l2unk1co rayctric field between the plates of a $0.80-\mu F$ air-gap capacitor if they are 2.0 mm apart and each has a charge of $72\mu C$ ?    $ \times10^{4 }\,V/m$

  A capacitor is charged )6l6h zamoy9d by a 125-V battery (Fig. 17–29a) and then is disconnected from the battery. When y96lmaho6z d )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 sf smhk1l 0k.1di2a a0h4sn4 (xmu.etof two square parallel plates 5.5 cm on a side that are separated by 1.8 mm of .h1ti2a h4 d00k. ms41fxn ulamsk(esparaffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular i5f 6vl5odkpqfv3c 3+plates with a radius of 5.0 cm separated by 3.dvl+536 5cifq pokv3 f2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor t5 xylia1o-0 nis connected to a 22-V battery. If a piece of mica is placed between the platt -oi 0an5xy1les, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the nsq5zmdiut1xlyy50 -7uj ,( jplates 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 2200o;. )wc3whoic -pF capacitor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beati2c9 ,nbusbk*wxigk2s kg q.+)ng erratically. A capacitor in this device is charged to 5.0 ksk2* sg+n9.) qwbukxk2bc g,iV and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between two square platkmpbfy9j3th9 1zal ,hv a x75/es, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on tha17hybl ha3xp99m,t v/z j5fk e plates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in. pie panzfvw *xpqv*ez)j2- *fs 5 cm apart and connecting them to the evwz*-x*vz* ) ffqj2p 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 capacc6onxpl*t l 776vmm t0itor 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 cha13my9ot ,wo y0.ay l4 nw13gejc /wejinge if (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as the capacitor re 413j9wtcj 1o/lny,. a0we3iwmyy og emains 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 accelerated9zzh( rf9j+eut,d1f-o ni4oyf ne9h* horizontally by 7.0 kV. They then pass through a unihtd i*foj h ezf9,uo- 9zr(n9e+1yfn4form 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/wuur. 2b zs:iz0)qxy in a CRT. The screen is 30 cm wide and is 34 cm from the 2.6-cm-long deflection plates. Over what r2izwzu :bysqu0/r).xange 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 movdrz0t:.v/ghq 3i 7cjcing from point A to point B. .qdc 37cj:r/itgh0 vz
(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 Eh ki3hitp.32wikyx oyz v8*+.arth.
(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 whosey .gq3a9jp/hf 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 t0e qww6t(hv( uh0mz*zz3+nkkube, electrons are accelerated 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 k+(zzu *twv6hqk 0 h(ne0zw 3mover a distance of 3.0 cm, would be needed to balance the downward force of gravity so that an electron would remain stationary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough stored energy toe,akoyqjl94cp-r +xx21 0fts heat 2.5 kg of water from 21$^{\circ}\,C$ to 95$^{\circ}\,C$. What is the potential difference across the plates?    V

  An uncharged capacitor is connected to a 24.0-V battery until it is fulpn-5 lujgn pnty4c. 6q / 5;fcbvmku4,ly charged, after which it is disconnected from the battery. A slab of paraffin is then inserted between the plates. What will now be 4l5tnjcn4,pcp .5nb k; u fqv6u-ymg/the voltage between the plates?    V

  Dry air will break down,-me3yv lq*dnz f7xb ( if the electric 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 (ky7q k2o*tx0lttu ,jequilateral triangle (side L) as shown in Fig. 17–30. Dto* u 7jt,l( k02ktyxqetermine 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 cs h /so u;ap 8c(zmci,;cb.ar3zsl.6qonnected to a 9.0-V battery. If a piece of Pyrex glass is placed between the plates, how much charipszls q.c;hr;m. oa,s3 c8ac bz6u(/ge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is acceleraqiw -o fem:4f ) nchfaeq-7qvph-5pag o:562j ted horizontally from rest in a television picture tube by a potential difference of 5500 V. It then passes between two horiqw eivfn h5pag)-f7:qo6oa f52c-: jmpq-h4e zontal plates 6.5 cm long 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 capacitance ))q5:w c9gpz xjtx 6qc$C_1$ 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 wc5ys*y8i4h eis, suppose you want to make a 1-F air-filled parallel-plate caw8siyc4 * eh5ypacitor 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 electric fielditvta la*v 9u8mnn22+ of about $150\,V/m$ which points downward. Two identical balls with mass $m\,=\,0.540kg$ are dropped from a height of 2.00 m, but one of the balls is positively charged with $q_1$ = $650\mu C$ ,and the second is negatively charged with $q_2$ = $-650\mu C$. Use conservation of energy to determine the difference in the speed of the two balls when they hit the ground. (Neglect air resistance.)    m/s

  The power supply for a pulsed nitrogen laser has a6v07bloysr+ qr+yy e 8 $0.050\mu F$ capacitor with a maximum voltage rating of 30 kV.
(a) Estimate how much energy could be stored in this capacitor.    J
(b) If 12% of this stored electrical energy is converted to light energy in a pulse that is 8.0 microseconds long, what is the power of the laser pulse?    $ \times10^{5 }\,W$

  In lightning storms, the potential difference between the Earth and the bottom oh o8/*qv8qxplv 7ulbj6dj. db64 lci;f the thun.h u/ qo vj7;b lpj4*d di8x8clblqv66derclouds 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 $110km^2$ 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 som( aa7wq 9 vgyj8w2yta6e electrons in barium metal to ejv( 9 2t aag6q7j8ywawyect 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 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 av1e.b.lfj5, twl ucfbay 4 xam0ly),1n identical $+33\mu C$ charge. A $-1.5\mu C$ charge is moved from point a to point b in Fig. 17–34. What is the change in potential energy? $\approx$    J (round to one decimal place)

  A capacitor is made from two 1.1-cm-diameter coins separated by a 0.1pgk kb.aq+.p :9) aajl5-mm-thick pieca+kajqgl )a.:kp .9 bpe 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 capaci ey*z 8kt+*zsktor with plate area $2.0cm^2$ and air-gap separation 0.50 mm is connected to a 12-V battery, and fully charged. The battery is then disconnected.
(a) What is the charge on the capacitor?    $ \times10^{ -11}\,C$
(b) The plates are now pulled to a separation of 0.75 mm. What is the charge on the capacitor now?    $ \times10^{ -11}\,C$
(c) What is the potential difference across the plates now?    V
(d) How much work was required to pull the plates to their new separation?    $ \times10^{-10 }\,J$

  A $2.5-\mu F$ capacitor is fully charged by a 6.0-V battery. The battery is then disconnected. The capacitor is not ideal and the charge slowly leaks out from the plates. The next day, the capacitor has lost half its stored energy. Calculate the amount of charge lost.    $ \times10^{-6 }\,C$

  Two point charges are fixed 4.0 cm apart frq8/7*jt*kee:/uv-s w k o mm70jlio iwom 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. 1xitb;gp*s2 ys6ks22y 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$