If two points are at the same potential, does this mean that no work is done jpm-l7 i1w t wp8t759 )uxmwa3 ikxlj3in moving a test charge from one point to the ompm5 x7 3wi78)t k1wx-tliwpuj j39 alther? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at rest in an electric field, wis(g kcgsw/zz/cka/ xb+26x1y 05kg cdll it move toward a region of higher potential or lower potential? What about a positive charge? How does the potential energy of the charge chan5ggk xkxczcs+z/gak s02 c6/b 1(/ dywge in each instance?

State clearly the difference (a) between electric potential and electric f h1*wd;1j)jq6 0kor8ahaj s,dx 8b1y9xemocfield, (b) between electricsea jo9168*)k0o wchx1qrhfmd;j ya ,8 b1jxd potential and electric potential energy.

An electron is accelerated by a potential difference of, a f6xd+r +i hwo)9bq-usay, 0.10 V. How much greater would its finu-hw 9o d bqa)+rfx6i+al speed be if it is accelerated with four times as much voltage? Explain.

Is there a point along the lyi*z; g*3oj )u gdv5 govs-3i qz,y6tgine joining two equal positive charges where the electric field is zero? Where the electric potential is zero? Ext g zi3so*3 6*5zq)oj,-ygygud vivg; plain.

Can a particle ever move from a reib(sn*i h7 p(9rtx0mngion of low electric potential to one of high potential and yet have its electric potential energy decrease? E ir0 i97 xhsb*n(tp(mnxplain.

Compare the kinetic energy gained by a proton 85yyx09ode )m7 emdv )mk(hkt qdarl s+7*zd5$(q=+e)$ 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 lin q-,7 /6m16 ngqx0zvpje6 prue ojb5toes cross? Explain.

Draw in a few equipotential lines inexv k787q ya*t9bnj pk/n) h/q Fig. 16 – 31b.

What can you say abouna yw3n (23r/.jbhehf t the electric field in a region of space that has the samejye .f/hbn (ran3w32h potential throughout?

A satellite orbits the Earth aj96 oor*,ymwalong a gravitational equipotential line. What shape myj9w o6 *r,amoust the orbit be?

When dealing with practical devices, we often take tumhtyi/m 0 *sqp9i23k+ w4d+u8hz iip he ground (the Earth) to be 0 V. If, instead, we said the ground was how would thip4iiwt/ 3pq980+hhi*us+u mid z 2 mkys affect (a) the potential V, and (b) the electric field E, at other points?

When a battery is connected to a capacitor,kfplo t0w45,iyq1m)g +t gy1 v why do the two plates acquire charges of the same magnitude? Will this be true if the two conductors are difwl4y ,pi0gt)mqot+ vf 5 1y1kgferent sizes or shapes?

We have seen that the capacitance C depends on the size, shape, and p539 a,gvrdwkhk6 q (wposition of the two conductors, as well as on the dielectric constant K. What then did we mean whehk5a k ,(w9v3qdp6wgr n we said that C is a constant in Eq. 17 – 7?

  How much work does the eu2*ai4, + unkkcz8no/dm,cz flectric 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 field do in moving a proton from a po+po-m8to q0 jaoa1(8 crg+vvxint with a potenm01qo(ca +jvp arog- 88t +xvotial 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 (ie3wbpk7i)4d,hn4ih kn joules and eV) if it accelerates through a potential difference of 23nehdi h 3kbi4p7kw,4),000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquirescf l06dvo tp;t52yw c3 $7.45 \times10^{ -16}\,J$ 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 mmy )5gdk, nqx 4+p*1my hf)d zbt6q0mis apart if the potential difference between them is 220 yzt d5pfm0i4 6qg),x sh*) m+ kqd1nybV?    $ \times10^{ 4}\,V/m$

  An electric field of l(3ei u93uqd uhnpg6jaq*55y u.c2r6bt3 ibx $640V/m$ 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 brwc+rp()v q -dattery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected to a 45-V battery i,1mpx+ (wbcu cs $1500V/m$ How far apart are the plates?    m

  What potential differ;).1ihpdu frrence is needed 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, are separated by an afsr/(yos7c y 3ir gap. How small can the gap be if the air is not to become conducting by exceeding its breakdown vs 7yc/o3r y(sfalue of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force toz9ovcmxv.z5 f; (c cv.om m..n 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 elec uda qq )26h :vnh,oztahon(*:tron 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 iq 01p3go xdn)ul3u59s qwnro554fnots 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nucleuqse ;)ofoy 8k9q,b) ngs, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric potential 15.0 cm fromp ur ohp:emv) s3,jc(/ a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric pote9nn(jdhmx+6l ntial 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 conductoty1 wxn+7v:n qr carries a net negative charge, :nt17 yqv+xnw $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a distance of dsod(4pse 7 +zz::fmg$ 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 sq(gl 06m3ul3o4ln0ftzo hno6kuare of side L as shown in Fig. 17tl(l3g40z 3u o o6fl6hkn o0mn–25. What is the potential at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed point c u 4vfu;,w-5x2iy ;sti(rwpcf harge 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 k58h3xjf8a q+.j nq cjpbw0+atif 9/ythree electrons from a great distance apart to b5 30tnpkq +faa8. 8jc yjwjq +/fhxi9$1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm ;bwf i:q)fhpef +9 3tknorth 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 acceleratuk );s1/kj 2frgyoh o)e 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 cj qg5/ je7ed0eh:(qovharges are separated by a distance d, as shown in Fig. 17v/ ogq:0hqj57e e(jd e–27. Determine 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 hydrogecz sb rlpiup39l51)5ln atom, an electron orbits a proton (the nucleus) in a ciplpsr3ubc 55)9 1 lzlircular orbit of radius $ 0.53\times10^{-10 }\,m$.
(a) What is the electric potential at the electron’s orbit due to the proton?    V(Round to the nearest integer)
(b) What is the kinetic energy of the electron?
   $ \times10^{ -18}\,J$
   eV
(c) What is the total energy of the electron in its orbit?    $ \times10^{-18 }\,J$ $\approx$    eV(Round to the nearest integer)
(d) What is the ionization energy — that is, the energy required to remove the electron from the atom and take it to $r\,=\,\propto$, at rest? Express the results of parts b, c and d in joules and eV.   $ \times10^{-18 }\,J$    eV(Round to the nearest integer)

  An electron and a proto1t y fh7:8bi v-p rqvaz*zn8i.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 v zat(5.w c)wamvz8b/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, consid zfy 7+z)h-jeoered as a vector, points from the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole -ezo hj7z f)+ymoment 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 capac 5.xw(hg8gcif itor hold $+2500\mu C$ and $-2500\mu C$ of charge, respectively, when the potential difference is 850 V. What is the capacitance?    $ \times10^{-6 }\,F$

  The two plates of a capacitor holc7 )ek znerqqc0 ge6(.d $+2500\mu C$ 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 and5qlmx3ls w- , +zpxax, minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of parallel wire int e4 7/ yfayy79fx8pxkf s(kb0 air is 120 V. They carry equal and opposite c0 pbksxy 7fxe7 48y /ya(ftk9fharge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of a 12.0-V battery when it9 yshkf5l9f+qv 83 4l ohv)pey is connected thf yq3 hkpvlv+) 8y99eo5fl4 so a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates have if they d.co 72gndk3cn+ g og0are to be separagd2cg.n3ck 0+ o7odgn ted by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increasepqy7)yt 6m 3hmw1tkls)gy;/n s 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 ofrjd7(jt :ru73, hnb tc $8.5 \times10^{ 5}\,V/m$ 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 opp y lap)y yovc7/pccohp7(u8*; osite $5.2\mu C$ 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 plates v6lq f+eg6 d8yof 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 1255n81 +pn d.xwqxnutn5b t dqb2; x/wk,-V battery (Fig. 17–29a) and then is disconnected from the battery. When thixbb q;/w, 1nun .wpx8ttd5xdn5 +n2qks 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 :u ngy4ga *ei4plates 5.5 cm on a side that are separated by 1.8 mm of paraffin*4g:ygi e anu4?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a radius of 5.xk*df*lz d 89r+rzb 6c0 cm separated by 3.2 mk z*9+*l 8czx6drr bfdm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. If a piece of mica c au t8)b2,rz l2 vlob4fp cx2uc3p2s1is placed between the plates, how much charge will flow from the batte2 3pxba2cvfczp2lo1b sc2luu8,rt)4ry?    $ \times10^{ -7}\,C$

  The electric field between the0 /yp u1qf3faf:bzs9f 7;(cnd,b xvpt 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 a 2200-pF capacitor. How much energy isw ,ts9o9pycz o (mp/c8 stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heartw no9bgdyj 5j: f 9l25.c4tyqn that is beating erratically. A capacitor infn 54.wnyl2jb:go cqdjt5y 9 9 this device is charged to 5.0 kV and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the elec:od:bgpm c+y :ozeu.2 h1o (dhtric field between two square 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 z edy:do bh :c:ou1.g+2om h(pof magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in. pie pans )ovfh::i. r ix-uwha(5 cm apart and connecting them to the opposite termina)u wix::a ho .(i-hfrvls 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 qwu0w ;5ty c6;ctwjt 0charges $+Q$ 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 storevb+f nlb i5;fz2ubn4 kid, w)5xcex+2d in a capacitor change if (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as txcz5ni4 5;i,fdbu2f2lwb + v n)bk e+xhe 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 thenqr zuk65eu -./fhm6 .pecqow / pass through a uniform electric field E for a distance of 2.8 cm, wh qf/u.mre /6k6wc5-puqeo.z hich 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 wide anf 1 r7x7c-mpxud is 34 cm from the 2.6-cm-long deflection plap x7u71 rfcmx-tes. 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 mois/r1:ivw;m f ving from point A to point;/rwfv 1s:iim B.
(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 exq k1 :3hw1 *h0c7;byocqoo z +5zsfegw ylc:;nergy 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 fieldw0wrz w6khxv610y q66amcir9 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 accelerate9 .. (l:rezljuio 2mmbd 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 a distance of 3.0 cm, would be needed to balance the downwj(l.lmbui2o mz.e :r9ard 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 capacitxb:lzh 9s09 .2ms.ann- km cisor has 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 capacite:yrt sd*3 f.gor is connected to a 24.0-V battery until it is fully charged, after which it is disconnected fromgy:fr *s dte3. 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 electric field exceedxdvb c1x-ve q*l*(km7dz 1gb7s $3.0 \times10^{6 }\,V/m$. 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 y x g:akwgr9tvht a+*:r *4b/rshown in Fig. 17–30. Determine the potential at the midpoint of r4gx y:9 *ar:hrwa*/ gb +ttkveach 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 cpbx7 grx)acwz -+ y,x7onnected 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 battery?a+ygzxb x r,c)7- p7xw    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in a television piv.(ai s-57t 4ay ribm ,a(pow+ dn0fepcture tube by a potential difference of 5500 V. It then passes between two horizontal plates 6.5 cm long and 1.3 cm apart that have a potential difference of 250 V (F,- m((rftv0a+a4o 7deay5. piisnpbw ig. 17–31). At what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capaciar.3 r1xm pkyddgw-73 tance $C_1$ 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 tf zmn9q5ytgf;q b*h/sewlp /k 70s(4farad is, suppose you want to make a 1-F air-filled parallel-plate capacitor for a circuit yotqb07pe4ys/lkn *zt h;fs f9(g q/w5mu 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 field of abaus4o.wp4m;r8 p qf1/ /zlo pbjq/ni+ out $150\,V/m$ 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 nft4i )v7s) te,hht+od itrogen 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?    $ \times10^{5 }\,W$

  In lightning storms, the potential difference bes8 )ig c)k x,tetu+ge)tween the Earth and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottg8ie))t ksg tx ,)+eucoms 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 s x4kk:c*tpz d0ome 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 the plate voltage isc :d 4*p0zkxkt $-3.02V$ (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 place3ah) 19 indde g+2lmuod 36 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 two 1d0h 6 n9j+xo3qw ryp9g.1-cm-diameter coins separated by a 0.15-mm-thick piec9 j0px 36+q r9gdwhynoe 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 capacitor097bvurfbal * 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 fi tnw12 lhekyxb,m)1vg.;hde o8 v,fr(xed 4.0 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 )/u.ys( mm+1eunsmur 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$