If two points are at the same potential, does this mean that no work is 82srb56 +qqa)omh flp done in moving a test charge from one po)ap8 2bqo5qsfh rm 6+lint 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, wil4cotmfsy f 4:i6r,zm:l it move toward a region of higher potential or lower potential? What about a positive charge? How does the potential energorm::s f6t, 4y ic4mfzy of the charge change in each instance?

State clearly the difference (a) between elec-(kwj5h7nw 9pv) vvf8me b+p ytric potential and electric field, (b) between electric potential and electric ) epb(8mk+ v-ww9v7hnjv5ypf potential energy.

An electron is acceleraj0ov,nf o1u3 r4ht05)el xxcpted by a potential difference of, say, 0.10 V. How much greater would its final speed be if in1u4 trpo0xjx0h) v,of5 ecl3t is accelerated with four times as much voltage? Explain.

Is there a point along the line joining 4k6 f142ri ct-kxnoznk udgnq 6a3(5ktwo equal positive charges where the elecicnf4 k 6qkx n5ug64kr z(ak3nodt-21tric field is zero? Where the electric potential is zero? Explain.

Can a particle ever move from a region of low electrigcal 9 aw7kcdc:z0c9w7h0;g qc potential to one of high p07;h a:c9w7lk0 gccawzg c 9qdotential and yet have its electric potential energy decrease? Explain.

Compare the kinetic enerrs e+9f; hh dnp4rps4lu; z 9bbk-2jv*gy gained by a proton $(q=+e)$ to the energy gained by an alpha particle $(q=+2e)$ accelerated by the same voltage $V$.

If $V\,=\,0$ at a point in space, must $\vec{E}\,=0$ there? If $\vec{E}\,=0$ at some point, must $V\,=\,0$ at that point? Explain. Give examples for each.

Can two equipotential lines cross? Explainiijt5hin ;+ 3cao.l5;t lnh o-.

Draw in a few equipotential lines in Fig. 16 – 3 sv*pztlq,j-wxs06 :e1b.

What can you say about the electric field in a region of space that has the sameuymenu7p g-duvv mi,5 k 76j*m21xkl* potential throughou1* 5ji-6 umkguy mve7uldmpk7 v*x n,2t?

A satellite orbits the Earth along a grav)7la3b fn,q y8,bwe3*j+pmd w voazk +2iiwe/ itational equipotential line. What shapn oj7w+,bw+vqwl*ebzep ,f8 a3 mka/i32y)d ie must the orbit be?

When dealing with practical devices, uy+3m41 hbf 9sbc zv)vwe often take the ground (the Earth) to be 0 V. If, instead, we said the ground was how w49bmvb)v 1fu+3yh cszould this affect (a) the potential V, and (b) the electric field E, at other points?

When a battery is connected to a c)okirggv9c1 4 apacitor, why do the two plates acquire charges of the same magnitude? Will this be true if the tw go9c krg)iv41o conductors are different sizes or shapes?

We have seen that the capacitance C depends on the size, shapi6 s e6t,gu5/gq q9ozpe, and position of the two conductors, as well as on the dielec g6ut/qg e,9zo 5q6isptric constant K. What then did we mean when we said that C is a constant in Eq. 17 – 7?

  How much work does the electric field do in movin s*,8xz0x vj3n ju4ql uths.h8g 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 poinw.khgvc(l 3x,+i 3wsbt with a po c3,vsil(b.gk3w hx+wtential 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 gain0 64c 2mkcx hwger9i85vjp+h y (in joules and eV) if it accelerates through a potential difference of 23,000 Vcg w265hrex+mk9 8jciy0p4v h in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires )des(3+nmnw3;n1k skv*od p9x,com w$7.45 \times10^{ -16}\,J$ 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 elect;ud xw 9clg6ox.e-:7okl+ pe xric field between two parallel plates 5.8 mm apart if the potential difference betwu o 7lx+ g9oe.xk:cxpd-;lew6een them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of vb9na3m z .ir*a:sbh*$640V/m$ 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-Vux287in0cym c battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected to a5w wgoa 6 6k(vxm 5m4h skcw*sq6(pn0r -vslu8 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a helium nucc ic u(u6 h.gkl/uzx41leus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V pe jrdq;q+*w: r; 1ontoower supply, are separated by an air gap. How small can jr:q ;1;d+ten rqoow*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 external force to move78gsv8 3u zpif 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 electron - ,lzf/jjb33oj1 pm:p ltjx)cwith 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 kinetpn7k7vbchhxu*; +mwj m-/ gi1ic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nucleus,r)26 hbtm oxq.8 fsye, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) 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 onarl4q7+* r r i7h(e) pxe0racm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q create-ywy7 1xuyu ez439qz)vfht g )s 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 footballtyvg+nf ch hu9on+ kjz2, +(fm++ a)xa. This conductor carries a net negative ch++f2hn)tca9kxa(+f,g j+ onyzvmh+uarge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a distancejpmr-1 pk;dm-p:o q30wp y1lv 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 sqi. 5zno5pas;a(zn dh6 uare of side L as shown in Fig. 17–25. What is the potential azz;a5in (nohda6s 5p .t the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from restx5e hj 7eiq3q4rc8h4h 32.5 cm from a fixed 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 dis cp7a.uf2 ctp(tance apart toc c puf72a(p.t $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm2c;-yn dhwya( 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 proton (radi,(fm 4-vzgulq b z+cd8us $1.2 \times10^{-15 }\,m$) 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 areq(xp1kawnj*w 6:fat , separated by a distance d, as shown in Fig. 1,6 pk(1qjwanaf :xt*w7–27. 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 f, x2el 9q*vb b6ksou wf8sf70hydrogen atom, an electron orbits a proton (the nucleus) 6kxefb9s ul fv*qwo,2 f708sbin a circular 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 proto qa:nrg7r +3:cys e1ubll dv4: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 wh 9h,ldzg,ys n5f.:f o;fjnu-sose 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 vectorwv-vps 2i(p8 2j igkpd4-rdo3, points from the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be considered as the vector sum of the two dipole m23vk( wdo4d8pjps2--vri igpoments, $\vec{P}_1$ 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 cap/q9amu3o kmwsa/ :;c )ta-pt ):ixx yxacitor 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 fo+;*/ aaqfiocapacitor 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 minu f.tnab4d0* fgs charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two 1qw1q 36y vcoxshort sections of parallel wire in air is 120 V. Theywoy1q1qv c3x 6 carry equal and opposite charge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal ol8fum.yw5(3( v0 j92z/te fibt kk wtyf a 12.0-V battery when it is connected to ai ( .lf3ywj5tub20k8ek9vyfwz t/m t( $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What+jy;3/cvom ;pahypr 9 area must the plates have if they are to be separated by a 2.3j; +m;op/payc rhv y92-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor p9mkgr/n*j3pewl :c -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 offtnl (6tzgn41tlg f07 $8.5 \times10^{ 5}\,V/m$ 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 oppositewjwj9bqm+ (y) (gei2t23tcj t wl :jq8 $5.2\mu C$ 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 of a yo;.sgg y8bq: $0.80-\mu F$ 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 battery (Fig. 17–29ar nox l0;:4p nnr*h;qr) and then is disconnected from the battery. When thinp*;4 ; xr 0:rhnronlqs 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 para2a x8xe9gxg28r wi1f cllel plates 5.5 cm on a side that are separated by 1.2xi8 w f1axrgg8ce9x28 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circuln c((sua2t8ze ar plates with a radius of 5.0 cm separated by 3.2 mm of mica? ztec un8(as2(   $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. If a piece ofdp-e*o ybo:xjr eqi9zu,5.. v mica is placed j.oy-z.9od qxrpev i bue:*5 ,between the plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a i3ugm4iv iv v11.zw 5shh)gjb x79f:7rbohu 5paper-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+2cssl dlg k9-enuj+3 is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrilla/ x7khe)+e3 szomj* eltor is used to shock a heart that is beating erratically. A capacitor in this device is charged to 5.0 k/e +oskez*hem3)l j7x V and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between two dw* +am9uo+pmsquare plates, 8.0 cm on a side, separated by a 1.5-mm air gap? Tw ou+9adm *m+phe charges on 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 cmx cpkg;4uvoo;a*(:j f apart and connecting them to the opposite terminals of a 9-V battavxjop:4cou ( ;g*;fk ery. 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 fixefp7:mub3zz 1/lufx .d d 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 (jlgcqvjavn 3uf+ m(eb)-qz*f 0,g 46j a) the potential difference is doubled, and (b) the charge on each plate is doubled, as the capacitor remains connected to a battbg)zfgq6e* vmnjju 34j0lav,f (q+ c-ery?

  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 5oxg)z+- vpod 9/ kili*ntt )eare accelerated horizontally by 7.0 kV. They then pass through a uniform electric field E for a distance of 2.8 cm, which deflects them upward so they reach the screen top n5-))lekz/ +9v* tipx o iotdg22 cm away, 11 cm above the center. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are acceleb z 44bq/ekt sg,lprp(9uk0jkj64 l)z0nxyx2 rated by 6.0 kV in a CRT. The screen is 30 cm wide and is 34 cm from the 2.6-cm-long deflection plates. Over what z br(ukqxkn204 409sjgl4bzy )x/ltpj , p6 ekrange 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 r4 ckjf6+uj,b 0y iwf6yest acquires 6.3 keV of KE in moving from point A to poinc4ki + u,wf 6j0jyf6byt 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 oqh; :rsi-yw6ixi d+wf *cwv ; )asr56rf 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 sur6pryo3c+c jw+i66zj rl.ep eqy)+w +yface 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, eleclca*o+xm7uh886 hs vp.upds1 trons 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 over a distance of 3.0 cm, would be needed to balance the downward force of gravity so that an elem6vh 7l1p hso*xp88s ua+ ud.cctron would remain stationary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacito6/s) hojkq md9q *-poiq8oht ;onc*2prdra8-r 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 capacithdc5: 7 qek lahid.5y8or 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 th 7ylqdd58he:ch iak5.e plates. What will now be the voltage between the plates?    V

  Dry air will break do 0zf9 j1msztu3 dmq3g,wn 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 equilateral triaa/ ;;y+yqhoy mbv 89gefe 5f1ba0al ,gngle (side L) as shown in Fig. 17–30. Determine the poteg;bfaq8lbf,1ee5ay 9 vhy ya/ 0 m;+ogntial 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 vs 2w 2nbmzu6r59gfq*connected to a 9.0-V battery. If a piece of Pyrex glass is plac m*bv2wz9gn2qrf5s 6 ued between the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in a television pictui-a2-6k 7/mjl 1bgp2 nbsirv ire tube by a potential difference of 5500 V. It then passes between two horizontal plates 6.5 cm long and 1.3 cm apart tha 67/1i2bi ksrm2 lvng --paijbt 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 capacb(jyp .t/:tjsm*z 1wkitance $C_1$ 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 air-filled par-vn0 ihk,ez 5 swhz:l ++t:kgnyy/ma3allel-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 yht0il/ny::e5m-,kns zazv+hgw 3 +k practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there jr8f mjh,6ua1is an electric 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 ajwi7q hl,p09j pulsed nitrogen laser has a $0.050\mu F$ capacitor with a maximum voltage rating of 30 kV.
(a) Estimate how much energy could be stored in this capacitor.    J
(b) If 12% of this stored electrical energy is converted to light energy in a pulse that is 8.0 microseconds long, what is the power of the laser pulse?    $ \times10^{5 }\,W$

  In lightning storms, the potential difference between the Earth and the bott 0cso)6hnbv8u om of the thunderclouds can be as high as 35,000,000 V. The bot60h8vbo) cs untoms 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 9 xfo5)n,w ukbmegx 6-enough energy to some electrons in barium metal to eject thxeb9 kmx ,) 6n-uwogf5em 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 from5),rtufe opo;0un -hjgs,q 1m an identical $+33\mu C$ charge. A $-1.5\mu C$ charge is moved from point a to point b in Fig. 17–34. What is the change in potential energy? $\approx$    J (round to one decimal place)

  A capacitor is made from two 1.1-cm-diame4:p6zh,c/uj 6 crho8qlgn )(xm)qqmm ter coins separated by a 0.15-mm-thick piecemo(mq)/cpcxjh)864q:nuz grhq m 6l, 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 capa;fwj xo / q8)tzh:rfv *3*, ;gzdtnfbtcitor 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 from /b3t)gwv me3weach 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. 17–35 with 3 tbyna rafp4t*4 js**n3ie6o $q_1$=$1.5\mu C$ and $q_2$=$-3.3\mu C$ Find the potential difference between points A and B.    $ \times10^{ 5}\,V$