If two points are at the same pote/swork iso+qy.z 5 n./ntial, does this mean that no work is done in moving a test charge from oneyiw +/o r.kzsn/5q .so point to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initiallyqr, )gtd fm y:*-1;*eblxh bib at rest in an electric field, will it move toward a region of higher potential or lower potential? What about a positive charge? How does the potential energy of the charge change q*1 g)byr-d ;bm, *exbi tlfh:in each instance?

State clearly the difference (a) between elect9(+ k:zeyjlot50wpxz3n z.hp ric potential and electric field, (b) between electric potential and electric p 3(.yx:t0 e5+ phzljkzonz9wpotential energy.

An electron is accelerated by a potential dify. p bton,vz w-lw717k-ts7, so tffw/ference of, say, 0.10 V. How much greater would its final speed be if it is accelerated with four times as much , fl7zwks7ywf7bnsot/1 v,po-t w.-t voltage? Explain.

Is there a point along the line joining two equal positive chargce,70 j 3uklzues where the electric field is zero? Wherezj03, ue7l cku the electric potential is zero? Explain.

Can a particle ever move from a regifdk6d hti 9i11on of low electric potential to one of high potential and yet have its electric potential energy decreaseih 1i9d61tf kd? Explain.

Compare the kinetic energy gained by a protonaep1(ctl( , eh $(q=+e)$ 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 g16*qnep rumaf .pf,i-qx5ie ocd *1 -lines cross? Explain.

Draw in a few equipotential c qovh8v8k(3k-bu0 a/xxhood c /:r m2lines in Fig. 16 – 31b.

What can you say about the electric field in a region of spacep81ofagp pa d6w; i.i/ that has the same potential throughout?8 owi a;ag6fd.ip1 /pp

A satellite orbits the Earth along a gravitationacvvnya6 .8/zl l equipotential line. What shape must the orbit ./cnl8y vav6zbe?

When dealing with practical device dhdqe ;/d-099e cbeeqs, we often take the ground (the Earth) to be 0 V. If, instead, we said the ground was how would-h 0d bde/ee; 9eqd9qc this affect (a) the potential V, and (b) the electric field E, at other points?

When a battery is connected to a capacitor, why do the two k4ufg + t/f7prplates acquire charges of the same magnitude? Will this be true if the two conductors are different siz/u f7tfprg+4 kes or shapes?

We have seen that the capacitance C depends on the size, shape, and positio cd ( 3jg6d;fn:zaqx2dn of the two conductors, as well as on the dielectric constant K. What then did we mean when we said thadjg;dc:2azd 6x n3 (fqt C is a constant in Eq. 17 – 7?

  How much work does thes4u8fw5dtmskdcx - ;;k k*d7o electric 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 elect2/ba.xg4ex h7 biys mp;- eh+aric field do in moving a proton from a point with a potentia+h7h.bbe yaeam/xsp - ;xig4 2l 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 a;ygwk6ch 3 2sgb, zqh 5q7twdyfhx 8:uq)l: u5ccelerates through a potential differenq5;qwwbhkcqxz6ts 2y5g ):, uhfhldy73: 8 ugce of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquiresrpagu-tnr + ,t xl1th8e3)*qp $7.45 \times10^{ -16}\,J$ 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 m5voiwd)h ; e0/,xgndvm apart if the potential difference between them i)wgo v0; h,n5di/xev ds 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of kqbc8h ;9;kr-nam (hh $640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two parallel pladea jh+ebd4 nzc :(1c*tes connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field betwei2vfvc vmg 9rl 6wx93nf1;k9een two parallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to gflk.- 4+:k pedkmk g l 1x-yvc/:v(irzive 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 separ)xxc 17wcyb bq1w09ko2mvoko nv +4)nated by an air gap. How small can +mwo0q1y1knk)v)n49v o wx2bccox7bthe 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 fop or *.fdcut9h1r1:3ucyay kh ,b1 b6irce to move a $-8.50\mu C$ charge from point a to point b is $15.0 \times10^{ -4}\;J$. If the charge was started from rest and had $ 4.82\times10^{ -4}\;J$ of kinetic energy when it reached point b, what must be the potential difference between a and b?    V

  What is the speed of an electron with kinetic e ez jtx+.x5yyww;0 d4qnergy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whose kinetic energy is 3.2 keahx *b;9yj5 1 )vt nfx2wu+nmsbwk8p 4V?    $ \times10^{5}\,m/s$

  An alpha particle (which is a hq+w fy (y/,mcrelium nucleus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric potential 15.0 cm from5id;8qqjfi (ctn)f qe92pmm 6jty/5a a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electio*pe/:iuhcs4yq1w 4 kh 9hc:ric 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 sovqea01kf ke*( yax 09hape of a football. This conductor carries a net negatikfeeax 1y9aq(0o v* 0kve charge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electj7 ar u rnck)z84ecb2;pr r9qygtj115ric potential 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 side L as sho q5 fyr+w7sc3 )bpoil,wn in Fig. 17–25.i fl5q 7,rb+3s)oypwc 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 frmj/d8+ ,7mptopr-l *(i +6p jhnlr vuwp 7c3koom 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 electrofte,*g.pu npl ,(bt8l l kj/c(ns from a great distance apart to lc (8p/ekf p tg.nt,l,b *u(lj$1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm north wd1 xr4l2n 85drwxi.pc33)mgpo4oi qof 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 (raddg)+a d 2ph3hmius $1.2 \times10^{-15 }\,m$) 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 chol c(hho g )agc5.-eq9arges are separated by a distance d, as shown in Fig. 17–27. Determine a formula f qhgc(o9 h.l)goea5 c-or $V_{BA}\,=\,V_B-V_A$ for points B and A on the line between the charges.

  In the Bohr model of the hydrogen atom, an electron orbits a phwwzu , m5l(g-/hz71bco*+p8n purg xroton (the nucleus) in a cirw*n ugr1hzp /bm8+uw,lx -(zpgc o5h 7cular 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 pro ,78-zz w6pfoltc qsd0ton 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 dipolexlcaj2 w0,cdy9q yt zb;84w o0 cd2i.v 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 g z vi/(.1) jvmsmkt;ypositive charge. The water molecule, Fig. 17–2. g1vjy(izv; m)/sk mt8, 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 capacitor hcm h7*fj 1a) tkfd05iel(tn/oold $+2500\mu C$ 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 ct9o0nervvt8 + apacitor 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 minus chargr.:kng inh )ys8-cxr(wd(yx+es of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of parau) d s6o+xagqcui)- i6llel wire in air is 120 V. They carryiq 6 ox+si-dgu uca)6) equal and opposite charge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from exwd+ :2 k:pb93vq6)ciqvhod hach terminal of a 12.0-V battery when it is connectedh6: k3xdho2qviwq d 9)p+v:bc to a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plate4z .tbza(:* 1do;8 yruoovedps have if they are to be separated byvyo8te . a op4dz;(1uob:rzd* a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increasrremb (c1*x,j:le kzb;v cx v6ma+2j0es 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.uo/2x i im ylw o8gtcw6; oo1u)ua7h2 $8.5 \times10^{ 5}\,V/m$ 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 opposi;.qmnpz j :t)fcz h3)hte $5.2\mu C$ 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 betweendgnao2 )uaa 6qg/ya +8.vmz/j 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 by a 125-V battery (Fig.+kx maultj(+r (uqb /; 17–29a) and then is disconnected from the ba jau xm;rt+qb/(+l(kuttery. 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 sr4iq8vp (: lead2ucfuc4 j8 (lide that are separated e 8 j84i2rl( (qfu:du4v pcaclby 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a radius of 5.0m: -0sfh1o1rt:k. fpexu ljb9 cm separated b :jmk10l h:t xp9fs1u.r-eofby 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is 8 z oa/h8hy;vd7/l gwoconnected to a 22-V battery. If a piece of mica is placed between the pla aowh7y /;gl8vdoh8/ ztes, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a papemx1 ) :2kbqktdr-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 casu3q 0o f4hr(zpacitor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used tw-kkca2,jz3a3v s8h * wuvj)4;hsold o shock a heart that is beating erratically. A capacitov )u48lw3v* j3ahaskzjs -2c;wdo hk,r in 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 electric field between two square puhzd,ozdtnw y.064 ,hsw 0z+j2oc* wh*x ;eutlates, 8.0 cm onh,stodowz *w6.z2uc0d* h;4+0h uztw jy,xen a side, separated by a 1.5-mm air gap? The charges on the plates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in. pie pans 5 c o **mp4t-nmc4 7ombv ulrp;tn.;4qimm apart and connecting them to the opposite terminals of a 9-V batte q.4p *ub7-t;ornmmm;c4pom4i nt*v l ry. 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 capacitorcdhue* dna-f) z -1j;g 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 differenca0b+cru h/+ejy4l4,ec6 f + z 3fnvu3soe de6te is doubled, and (b) e3n+eybel34zrc,uj sf euf +40vc+dat h6o/ 6the 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;1 rpbj ey0dwu:6fv14 z, pass pass through a uniform electric field E for a distance of 2.8 cm, which deflects them upward so they reach the screen top 22 cm away, 11 cm above the cer0 11f wpeb;v ,yja 6s:4udszpnter. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a CRT. The screen is 302z ogn( 6rcauvv80t 4p cm wide and is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizontally deflecting electric field vary toz6 coanrvg2ut4 v80( p sweep the beam fully across the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting fr2ohsdr4cr ,h;om rest acquires 6.3 keV of KE in moving from point A to poi rrh;4ohd2 ,scnt 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 2wdp q6 9 nrxoc(1y- bidkw*.rMJ 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 electric5jpc:khcq1 +s(r;b kb h4d/wn field 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 accelerated by tho0kn,8lk0 uwwetn7ek 5usands of volts through a vacuum. If a television set were laid on its back, would electrons be able to move upward against th kew ek78ut ,5nw0n0kle 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 stored energy to heat 2.5 kg of water from ggs u2p9.phl121$^{\circ}\,C$ to 95$^{\circ}\,C$. What is the potential difference across the plates?    V

  An uncharged capacitor is connec,;fua06n p wwg as9yx-ag (a2qted to a 24.0-V battery until it is fully charged, after which it is discon w0n, 26fysx-gqaa(aua;9pgwnected from 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 e, hv 0nhn.kfw5lectric 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 sze/ y f,8sllg +ua)e2l*e7ghan equilateral triangle (side L) as shown in Fig. 17–30. eae ,2sg lu) *yg hsl8fz+e/l7Determine 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 battery. If a pie c05h * /l;irbsse,* )zjohcjxce of Pyrex glass is pla/ e lxj5sbsr)icch*h0;* oj,zced between the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated ho/ (mb6mgsfz l.yd0w-vrizontally 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 dm0 b fvmg-(/lsyzw.6 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 capacitav (.r6+o,us tk xnz1lznce $C_1$ 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 wanz/k pbri/3c;g2ec-g q t 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 thez c/k3c2q-g/pbr ige; gap have to be between the plates? Is this practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Emn mrtw+32e6( a fv0jaarth there is 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 a pulj( unf-wj6vtb5,j-pya8w+ dw/rxrni w f;19 xsed 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 t4 *o5vs olvsrw 2u-be6he Earth and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are te6 bow*vu5osr-sl4 v2ypically 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 cpi 15shj1yhf.1h: lqenough energy to some electrons in barium metal to eject them from a surface at high speed. See Fig. 17–33. To measure the maximum energy of the electrons, another plate above the barium surface is kept at a negative enough potential that the emitted electrons are slowed down and stopped, and return to the barium surface. If f.pq 5:li h yjsh11h1cthe 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 idg4lv)m s6(4k4 ez*g2oor au)bi pgsl)entical $+33\mu C$ 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 fz bii uh txb::x2+v/1gsx:1hu9a6d sr rom two 1.1-cm-diameter coins separated by a 0.15-mm-thick piece of9us+ 6bh 1di :vuz1/haxxbsir: 2:gtx 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 capac7fmi,g p.b ppbmhse+c7*: e;bitor 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 each other. Their charges aree sgw7g 5x91ogr1 (4h+dimw9pj 8fajo $Q_1$=$Q_2$=$5.0\mu C$, 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 showngdz)sancm btt1s+y8e v 6/68s in Fig. 17–35 with $q_1$=$1.5\mu C$ and $q_2$=$-3.3\mu C$ Find the potential difference between points A and B.    $ \times10^{ 5}\,V$