If two points are at the same potential,k(rc *1yskgh qc2q +ewjvi m.)5( 0l+j-ns ulh does this mean that no work is done in moving a test charge from one point to the other? Does this imply that no force need be exerted? E1)uyl2c (-ikgrkhe5v 0*s q l+cns(jj+h q .wmxplain.

If a negative charge is initially at rest iuwok/;0.c o.*kq j onin an electric field, will it move toward a region of higher potential or lower potentii oqjc kw*/0uo.;kn o.al? What about a positive charge? How does the potential energy of the charge change in each instance?

State clearly the difference (a) betweenwss5cp/abxh6moy)z/ l -p1 o4 electric potential and electric field, (b) between electric potential and electric potential bp1c sx/oya 5/zls6phw-4) moenergy.

An electron is accelerated by a potential difference of, sayow jga9fcb 8q1ndm4 0., 0.10 V. How much greater would its final speed be if it is accelerated with four times as much 4. qnojwdg f8b0cma19voltage? Explain.

Is there a point along the line joiningkzib11v2 rmd o 1rt/k, two equal positive charges where the electric field is zero? Where the electric poten mor/ v2k1 ,1trz1bikdtial is zero? Explain.

Can a particle ever move from a region of low electrzj1xc qp8 qpdy;-i *r2 7njus4a,-mlxic potential to one of high potential and yet have its electric potential energy decrease? Explain dlq1x2np7yp-qu8 zmjicsja;- r*,4x.

Compare the kinetic ener) p8irw50axxqr4e 9kggy 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? t0fk mo uh3h y3l drh4)q9;;axExplain.

Draw in a few equipotential lines in Fig. 16 – 3th w0 :cp*lh 4* jsg her4am32tzpw5;b1b.

What can you say about the electric field in a region of space thamp i4i l ql 1t a.sidlj4q5o5nm8g5e/;t has the same potential throughout?ma pleldi qsg in5it ql48./41;oj5 5m

A satellite orbits the Earth along a 3fo w, rp2*gnut,c,msgravitational equipotential line. What shape must the orbit be?,ngfm,s c2turwp * 3,o

When dealing with practical de875e gx wi78tl6d.rbzo o)oxgvices, we often take the ground (the Earth) to be 0 V. If, instead, we said thdzlt ox)obex67885 o igrw.7g e ground was how would 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 2+* gpbze h*g-(i5nkh:zd wx utwo plates acquire charges of the:i5-+ w*hzgx g *n2ke(pu zdhb same magnitude? Will this be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on the size, shape, and position outo5nds g25lfv/ru-u; seg, 9f nro5/s tlvue gu ;,-2 s5ugf9dthe two conductors, as well as on the dielectric 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 fielf24 o/ l-id-vm,(mgurt)elipti f w+aeu- + 7jd 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 th y)dgps1r-/ece electric field do in moving a proton from a point with a pote)/ c-rdps yge1ntial 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 ylp 6p+*dta 2dkd(e8 x(in joules and eV) if it accelerates through pdd*xye2t+ pakld(8 6 a potential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquiresjz sjt9 +/tj2 ayw5ut9 $7.45 \times10^{ -16}\,J$ 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 betw fmnq mv;ew-d-+ ly(ubrj 5)*reen two parallel plates 5.8 mm apart if the potentiajqfe -nrw +*vm-b;5lr ud) (myl difference between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of lort;7f z/t 1n)vxt x1$640V/m$ 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 ax9f, ctmp t0:lye26aj 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field betweenrpaag3c y2 x)9 two parallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference +x8 vh0f8 asnhis 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 a9l)xvn4 l/,rdsz0x)jmj of;ogu6 +y hir gap. How small can the gap be rh,xlgj f4+o)o/vmn9d)yu6szlj x ;0 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 2rx)ic cmgfuru95w4)e 7 mlg *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 withd4qjwye( b1c )l:qq:b kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a protowf v ylgo,sq,8qz+wb)ig53l( n whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a heliumk3*xlyq7 wd y ,v1i/fi 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 qra*,h7-h)zn w ady-dpotential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates a4u+e2 uhb/wa avp- x91kvt+kun 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 ofnyo 05 e,(b0oa:xxyrk a football. This conductor carries a net negative bay 5kn,r 0yox:o(0excharge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electri 2afmk cb 4i2s 32-g:qs1zgdyhc 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 cornersyw( l :nrs9b*lf,5hj dzt.u 6d of a square of side L as shown in Fig. 17–25. What is the potential at the fourth corner (point .nsj tlwd*rzy96 b fu,d5(:hlA), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixe7w j z:rkga,cto o25(n*m da2xd 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 fro:q.1lytqdz0sly ( qtm,0-pk-x pvi s5m a great distance apart to q-ds qzykp xmspqt0 ivtl-., 0:y(51 l$1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which i0jpd j,(.n d )ghkia6os 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 proton (radijf j7v6od4f0v us $1.2 \times10^{-15 }\,m$) 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 separateolw+;hi 1k e6/o) tafud by a distance d, as shown in Fig. 17–27.fu6olh+ ok)/ a1e;itw 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 hydrogen atom,vw i7xe0:*y0; amswxp an electron orbits a proton (the nucleus) in a circular orbit p xwvse 0mxi*:w7ya;0of 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 proton alo7 x/b1(innmiq2epsqp4 qn5d84t o 0re $ 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 dipolaqhc(:lk02nn b5 ,e c wij9hm/kvf4 8ye 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 vea/0*c,s,nw ncrdhqa f1ro u6( ctor, points from the negative to the positive char(*r/ 6h,fcsqrn, a cd0oun aw1ge. The water molecule, Fig. 17–28, has a dipole moment which can be considered as the vector sum of the two dipole moments, $\vec{P}_1$ and $\vec{P}_2$as shown. The distance between each H and the O is about $ 0.96\times10^{ -10}\,m$. The lines joining the center of the O atom with each H atom make an angle of $104^{\circ}\,$, as shown, and the net dipole moment has been measured to be $p\,=\,6.1 \times10^{-30 }\,C\cdot m$ Determine the charge q on each H atom.    $ \times10^{ -20}\,C$

  The two plates of a capacitor 7ogv,0tumlh 0 s/cwlxzc9t9c)u j7z+ 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 holdin c-; vm5bw31d8t xoufw/z)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 and minus charges ofc 5ft x.h22rrb $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference bx9wt 6)g n4kadetween two short sections of parallel wire in air is 120 V. They car4xtg )nd wa9k6ry 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 of a 12.0-V battery whct-s*n6(z do len it is connected too (ln*-c d6tsz a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What4)e;lr f1k- g3cxfk mt area must the plates have if they are to be separated by a 2.2--me3 1; lk c)ktr4ffxgmm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitordn xdeo: 8 d;pv-zuje23z 9:sg 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 of n *g58fsd(4e:e vnrnv$8.5 \times10^{ 5}\,V/m$ 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 oppositb +g hubdua 9u5ozyf,tij39,6,; vbafe $5.2\mu C$ 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 betweezm0xq j3 y**7ze:aq jn*qmf 4tn 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 char.q k br1wmvp28 kxc*y;ged by a 125-V battery (Fig. 17–29a) and then is disconnected from the byc rvkmw ;1*2b 8qpkx.attery. 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 t7bbp2w)tttv :0 m9.0 a 8ipy*bmdhc ccm on a side that are sepabttcbm ctt .2v p)hi07bawpy: 89* dm0rated by 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates wi dshf z w:8aktt2ryvs6p)./(uth a radius of 5.0 cm separated by 3.2 mm of mica? w/kr.8p 2t)(yszfv utd s6ah:   $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V batteryfe8esduli1 3sb a*h3:fb (y w-. If a piece of mica is placed between the plaw s:3f(db 8*lybesu 1a ief3-htes, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a 0w4ac0,qr mo qpov *e*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-pFmb3 qpsw4+l/lc0 x )av capacitor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beating erratically0w2w. si;grad j krq0-. A capacitor in thii0;. wkw-qa2sr 0rdgjs 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 plates, 8.0 iecog; uwd1pd-5-/j acz*b5vcm on a si 5o g-dejzc;daiwb*up/ -c5 v1de, 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-..+w isfma-g :tce 8suin. pie pans 5 cm apart and connecting them to the opposit cw+sg i-.e8.uta :fmse 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 capacitor s ed()cd:+dr l0(y vdmhas 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 differela d2/-iphfo-nce is doubled, and (b) the charge on each plate is doubled, as the capacitor remains cap/f ido 2-h-lonnected 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, elect 8cbyg7n1cf3rcem- 8 trons are accelerated horizontally by 7.0 kV. They then pass through a uniform electric field E for a distance of 2.8 cm, whfrm n8g7y t38ec-cbc1 ich 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 ansmka26h+ /mii o-,yppd is 34 cm from the 2.6-cm-long defp2p yk /om-,im6i+ ahslection plates. 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 fr-jz /s, tc3fcnom rest acquires 6.3 keV of KE in moving from point A to poin/z-j, 3cf tscnt 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 energy to the 2dcitw4 vp hg l.a3;;bEarth.
(a) Across what potential difference did it travel?    $ \times10^{ 6}\,V$
(b) How much water could this boil and vaporize, starting from room temperature?    kg

  There is an electric field near the Earth’s surface whose maglawnr ;;p. 4d5hv-hgvag 4km:nitude 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, elecez 7qfw 0zt 8d:f3vb7qtrons 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 gra qtzdzf q7 ebv07fw83:vity? 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 egsj+v v6kvw o/r-lh ,0nergy to heat 2.5 kg of water from 21$^{\circ}\,C$ to 95$^{\circ}\,C$. What is the potential difference across the plates?    V

  An uncharged capacitor( v wefstjkq0au 2gvz225h/c x- l.mli-8w;sp is connected to a 24.0-V battery until it is fully chargedl- ;w 0w ljf.-gviha ssvc82xup22/( ekqt m5z, after which it is disconnected 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 no(*s dc(i 4g.vld 9opthe 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 atkvdve:m*y/q,wsjl.e x 1-0 b f the corners of an equilateral triangle (side L) as shown in Fig. 17–30. Determine the potential at the midpointv0-mxsl/beydv: .f ,kj ewq*1 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 cg.*lzgdz7 7lgrs.be6onnected to a 9.0-V battery. If a piece of Pyrex glass is placed between the plates, how much charge will7. 7drsg6gbl*lzg ez. then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in a television ,wk b-ngso3q7 picture tube bo gn3qkwsb7- ,y 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 (Fig. 17–31). At what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capacitanc, 2rq mdju+zzkq1 )kf1e $C_1$ 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-,l1 / i,sj p4o gcc;7shlhcao+filled parallel-plate capacitor for a circuit you are building. To make it a reasonable sizecsgh o,;llj/op41+ ,ca 7shci, 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 thers zk5qqh.(kio8kbyjx,2z wj:2)e h n3e 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 pulsed nitrogen laser has e v +w;22zshsju b-,b)ottic 9 xb3 d0cn8ab4ra $0.050\mu F$ 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 betweeee:6ctp -rf97bgw-h mn the Earth and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are typically :e76 9thf- gpre cmbw-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) lig1*ao m ihzql0 pk8ag1;xlr eu :bf1w-8ht provides enough 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 surface18q 1-;m z*xh1k8ipfuw0:ao br allge 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 fi jhn 1v.3one1 mte12placed 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 1.1-cm-diaf8 cwc/1q frv.meter coins separated by a 0.15-mm-thick piece of pap/ fccwf.vrq18 er $(K=3.7)$ 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 capacitor with plate ap 8*fq3 ea: +cpw,gseurea $2.0cm^2$ 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 frlqk:n3v,lh q / db x*o ,w;8vtq*rw0vlom 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. 7: 0kiyzeqk4r17–35 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$