If two points are at the s)(i6am fh 6glpame potential, does this mean that no work is done in moving a test charge from one point to the other? Does this imply that 6 f6 g)hlipa(mno force need be exerted? Explain.

If a negative charge is initially at rest in an z85:g b ,f0pcxm 99.yvdneiddelectric field, will it move toward a region of higher potential or lower potential? What about a positive charge? How does the potemp0x,9 g 9dy8dcfn.id:bev5zntial energy of the charge change in each instance?

State clearly the diffe8win;./tho + xob g3zerence (a) between electric potential and electric field, (b) between electric potential and electric +tbgo83n i/x ;w.zeohpotential energy.

An electron is accelerated by a potential dd rgjz nj( 50fs4f1ncy )()ez:.rfywr qrc(7 bifference of, say, 0.10 V. How much greater would its finals z0 fr(4jy n( nc)qewfzrbd 5f1 jgcyr7(:r.) speed be if it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining 9mf skk0au8w, g;p8q jtwo equal positive charges where the electric field is zero? Where the electric potfw8 p,sk q8u 0agmk9;jential is zero? Explain.

Can a particle ever move from a regi9 odpk964z5i ,xq9cj isowf:i on of low electric potential to one of high potential and yet have its electric potential exi49j 5k9q,izdoiw9so cp6 :fnergy decrease? Explain.

Compare the kinetic energy l8s8x+ncyi ci n8mz,/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 7 cr*d9hjgy7e lines cross? Explain.

Draw in a few equipotentia+ggv m-q5q:fqt,o7r r v ofx98l lines in Fig. 16 – 31b.

What can you say about the electric field in a region of space that hasq64r y;n5k o70 xvevgb the same potentiyqroe045 6g ;vkxv 7nbal throughout?

A satellite orbits the Earth along a gravitational euxb s;-y)kth 7z8 1piequipotential line. What shape mus)i-usetx h y7 k8b;1pzt the orbit be?

When dealing with practical devicerh 4)nxxq3c*f3hhc4b0 cu3:zp :ea iq s, we often take the ground (the Earth) to be 0 V. If, instead, we said the ground was how would this affect (a) the potential V, and (b) the electric n f3xu:3)3e biz4 *acqq h0hx4ccr:hpfield E, at other points?

When a battery is connected to a capacitor, why do the two plates acquire chark5hr;u+bgzdx-m(tk /w tf br n fpk++z9( //pnges of the same magnitude? Will this be true if thew;(/t(+5+b kmhpzk/-f9bp+ rrnfkz x ntdgu/ two conductors are different sizes or shapes?

We have seen that the capacitance C depends on the size, shape, an(p/l5qa(+,:guoftxb jw fmvq /1rr /jd position of the two conda(f g(urv:qjo+/wtfq r1p//l jm,b5 x uctors, 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 th5ysm5: ) fhxo-)mie*m qzn81gtn k;mae 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 electsmsvb ava .iym3m ;5r)1az;g.x7io. kric field do in moving a proton from a point with a pot;5mmi7rsvoms.ia yb;a . .a zgvkx1)3 ential 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 i g3 aprhbd:(*b,i; ;kt lm,atp g3 hzu,2e1oalt accelerates through a potentia 1baog,hpap rltm:t ,zbhl(g*3e du3a;, ;ki2l difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires2*l7zyh u;wy uhib23 5px 8ywg $7.45 \times10^{ -16}\,J$ 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 be6wor 46l w:1c, mg3pe;ibspx zl wtq6)tween two parallel plates 5.8 mm apart if the potential difference betwx wp6wlib)t s61p,me;z 63lrc4g w:qoeen them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of h4;9 qh:9 c-dmrybtls $640V/m$ 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 wu bnkor2;.3n battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates co j+upa;eg e)2hnnected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a hel9jg f8nexa2 vb1l2-/lwhh r6 lium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 20*tsgnkx3vo .80-V power supply, are separated by an air gap. How small can the gap be if the air is not to become x. vskgn83t o*conducting by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force to move a gt- oag0k a6hq,/7lwl$-8.50\mu C$ 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 electroa 2yy82*bqzpn n 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 enas(n: m18j*og dial* nergy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (whdr(-mxk .egk vx.g- .h xev*2gich is a helium 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 potentq9iad bj7, r*bial 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an et.bex7e q6 vs0lectric potential of $+125V$ at a distance of 15 cm. What is Q?    $ \times10^{-9 }\,C$

  A $+35\mu C$ point charge is placed 32 cm from an identical $+35\mu C$ charge. How much work would be required to move a $+0.50\mu C$ test charge from a point midway between them to a point 12 cm closer to either of the charges?    J

Draw a conductor in the shape of a football. This c)ccp6 cjh 5q, a-8wcjwonductor carries a net negative cc wqh cjcpwc)5a8,6 j-harge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a distance of 7 1qgyow0emh e8 zp :5t1ovw2d$ 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 square2s *m:+) h ,llousgde rq- iy2vt-h5yq of side L as shown in Fig. 17–25.i)-dgq lm-q+y l shye2 t:5u,*svhro2 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 fi a8m x3j)o 1c4by8tzmcxed 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 distance apart*;blt2:n(v;xcj w mhl l( ;*xh b;:cnml j2tvwto $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cmg usdav a7+r(2qz )4rn 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, td-rginoya23/*q oo 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 chbs-*.( gtf ntha 1ve5oxsdp/ )5iwd4 parges are separated by a distance d, as shown in Fig. 17–27. Dewx.5s opnpvsgd51 -t)t i*bahfd/(4e termine 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 hyd uzj6/ed1 d *g6pr)q0v6*nwgj4u pencrogen atom, an electron orbits a proton (the nucleus) in a circular orbit of r*6vcw *jd6z /pe d eju6 4n)ungg01rpqadius $ 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 protc kx8 z2dw)a k9kt)ru gb3,q/qon 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 c 6t6iowmbx:f lm2ql1*j. xq1a dipole whose dipole moment is $ 4.8\times10^{-30 }\,C\cdot m$ at a point $1.1 \times10^{ -9}\,m$ away if this point is
(a) along the axis of the dipole nearer the positive charge;    V
(b) 45° above the axis but nearer the positive charge;    V
(c) $45^{\circ}\,$ above the axis but nearer the negative charge.    V

  The dipole moment, considered as a vector, points from the negative to ixo7n 5jbe6b8 the positii85 e7nxo6bjbve charge. 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 capacitoj 0 yc q: .vb.8cy5)lykefmr,mr 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 capacycutm *g2u( a;8*oejs 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$

  A 9500-pF capacitor holds p,2pl x t2j 8iqsk*w.pglus and 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 in aiwh)x:w3ylaa945m 4 gczdei- a 1r q.xcr is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is the capacitance of wg 3cl :1 .a4achay5edq-m)i 4x9zwxr the two wires?    $ \times10^{13 }\,F$

  How much charge flows from u480bd:rn0s.ml r bzhf/ q m5seach terminal of a 12.0-V battery when it is connected4 ubbqn 0zrr80d :s.lfm/h5ms to a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area(, ogbyk)xg3 1eiot* s must the plates have if they are to be separated iky,e s o()g3bo 1tx*gby a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increaswg7auj 7j3nt)es 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 pc-irg7/ .6oi z.scpv +fnej+ $8.5 \times10^{ 5}\,V/m$ 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 opposb -m5puyyu;aay. nd,v3qb */w4yxoj/ite $5.2\mu C$ 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 ka p)3h-3db gethe 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. 17–2,y+sopdpm716vv1zlu( m+srs ab)/ ja/weum 8 9a) and then is disconnected from the battery. When this capacipz(+w l 76em)+81s1bpou ys,v a/amsumvj/rdtor $(C_1)$ 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 c u*bj.szgz4: tg 0rn:rm on a side that are separated by 1.8 mm of para0rzgg4j*:us rtz:bn .ffin?    $ \times10^{-11 }\,F$

  What is the capacitance8iqyx cc5 -/nhu-8von:gsp/b of a pair of circular plates with a radius of 5.0 cm sepsg boic/q-v8h npuyn8x-: 5c /arated by 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connecir5ho0*a 2fpo upot/50 nzw.jted to a 22-V battery. If a piece of mica is placed between the plates0phfawu0 p* 52ozi oron/5.tj , how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a pape5 6y*81gywa/sg w:qc.ngl7 snvzn 0zfr-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 en8jcr 3ug7ij:cv9ch 5b ergy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that ism ce2pz )je:,n3cqfe0 beating erratically. A capacitor in this device is charged to 5.0 kV and stores 1 32)0 zf,ne:qejcecmp 200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the h;lsy4lmh4.a4 eqb7 xh 7b)ye electric 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 ah;ab4h4bl4y 7 hey)sq7 xmle.nd of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing t7dysco0;+ie3w( secd wo 9-in. pie pans 5 cm apart and connecting them to the opposite terminals ci( d; oecys70 +ewd3sof 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 u6*rlpe-y)gdy6t bydi7 .z6 fhas 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 cha8l07 cid,p:u ufcj 5qjnge if (a) the potential difference is doubled, and (b) the charge on each plate is doublfl,j8qijcpu cd :7u5 0ed, 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 ne+ en2*sf /clpass through a unn/n*c else2+f iform electric field E for a distance of 2.8 cm, which deflects them upward so they reach the screen top 22 cm away, 11 cm above the center. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a CRT. The screen is 30 cm 4dn e)yqv .+z1cqlbxe1 ;sioke3,p q.wide and is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizontally deflecting elec3 .vkb4ep el1no)ei,1.q+qyxzq ;dc stric field vary to sweep the beam fully across the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting frht(ncz s32vt8zpw5dky 4 +x,y om rest acquires 6.3 keV of KE in moving from point A to point Bp 5zv,hstwcn(324y zx d8+ ytk.
(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 + ;i1vze 8:jt7flm szbto 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 Eart/z h1x faq*h-ah’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 a ulo ve4 y5)lrf;chn4*re 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 potentiuvh4cy; l5rn*4lfoe )al 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 stoqd/8,c bgz- 5 d5wf,drk6zheured 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 capacitor is connected to a 24.0-bbzf9bt +6w8n: 6bh3s+aa(hh 3kbuusV battery until it is fully charged, after which it is disconnected from the battery. A slab of paraffin is then inserted between the platesaba bku ws9 b( :8sz+3b63h+bthnf 6uh. What will now be the voltage between the plates?    V

  Dry air will break down i9 g-y gn z,v/4jfaq9a htj3(rgf 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 5j:*uq z; pwnotriangle (side L) as shown in Fig. 17–30. Determine the potential at the midpoint of each of the sidzj5 n uopq*w:;es.

  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. -dkt( bi olq,*g9,*)hpfkk ,f+ sdndbtl8s;o If a piece of Pyrex glass is placed between the plates, how much charge will then flow fromsl8(*t,o dn)kdp; g, +olfb dbk*q ,hk9 ftsi- the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated hori4swt0q h8n ,aw 8ehd2hzontally from rest in a television picture tube b0ahnds q48 wt ,we2h8hy 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 capaciqdy32r z(9:+0eoj-f yuo it xttance $C_1$ 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, suppvgzat dg;dug-vo3 h zuv.3589ose you want to make a 1-F air-filled parallel-plate capacitor for a circuit you are building. To m.3;u t5d9zgd z-u83vv vha gogake 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 th- vtn 61w0y dfcxff4(ve Earth 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 pulsed nitrogen las gybt2t7. f2bger 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 fr)vn.nb rw.bzu2t; 8v,1)h:tmsxll bottom of the thunderclouds can be as hnxfm2r snr,h)v:;v.w8)l b.ul bz1ttigh as 35,000,000 V. The bottoms of the thunderclouds are typically 1500 m above the Earth, and can have an area of $110km^2$ Modeling the Earth–cloud system as a huge capacitor, calculate
(a) the capacitance of the Earth–cloud system,    $ \times10^{-7 }\,F$
(b) the charge stored in the “capacitor,”    C(Round to the nearest integer)
(c) the energy stored in the “capacitor.”    $ \times10^{8 }\,J$

  In a photocell, ultravioph*c za lsyk2, zv9y(1((fb/ v. qgxwilet (UV) light 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 surface is kept at a negative enough potential that the 2lvsy1/ w.h( 9,ci*zzgq(xkf vpya (bemitted electrons are slowed down and stopped, and return to the barium surface. If the plate voltage is $-3.02V$ (compared to the barium) when the fastest electrons are stopped, what was the speed of these electrons when they were emitted?    $ \times10^{6 }\,m/s$

  A point charge is placed 36 cm from amh-ys; -lcg51h44 fbt ocqji 4n identical $+33\mu C$ charge. A $-1.5\mu C$ charge is moved from point a to point b in Fig. 17–34. What is the change in potential energy? $\approx$    J (round to one decimal place)

  A capacitor is made from two 1.1-cm-diameter coins separated bnanu7:*pqhw4, /r vyw:j )ith y a 0.15-mm-thick piece of papw htw7 j,:u*pyn:rq hnai4v) /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 arey l6s/jsm fnm 8b+1l)sa $2.0cm^2$ 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 4gnl 6;8rjby:to 4w7 nl.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 Fig. 17*29/ownpa )4yur wytm–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$