If two points are at the same potential, r*us79ksqy+d3 o )l h gx,pis8does 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 exert3losr ikq8dgs7p )xuy9+h,* sed? Explain.

If a negative charge is initially at rest in an ele+sa n)7hgr6goft 6z j(ctric field, will it move toward a regjnggzf+ s)t6 (oa h6r7ion of higher potential or lower potential? What about a positive charge? How does the potential energy of the charge change in each instance?

State clearly the difference (a) between electric potential and ct0jt*u2*rtys4 lm*kelectric field, (b) between electric potential tl k0uy4*ctj*tr* m2s and electric potential energy.

An electron is accelij(+c (0tg gzzerated by a potential difference of, say, 0.10 V. How much greater would its final speed be if it izg(gc0(j zi +ts accelerated with four times as much voltage? Explain.

Is there a point along the line joining two equal positive charges where the ele6szslbic s, d, ,8f;nictric field is zero? Where the electric potenti ,,s ,s6l bcizi;d8sfnal is zero? Explain.

Can a particle ever move from a region o nig9(i9lb.jsf low electric potential to one of high potential and yet have its electric potential energy decreas(bn9i jilgs9. e? Explain.

Compare the kinetic energy gained by a protonajlbc(u j94u7nl 8h9t $(q=+e)$ 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 0r/ p,19duy5l su sp )r5yj 8a1wqzklpcross? Explain.

Draw in a few equipotential lines in Fig. 16 – 3/igp/83qd ybz l wz e-+juo2f,1b.

What can you say about the elect189*f2 nknvpcryjc,qu5lk ztni- vqt/r+ d57 ric field in a region of space that has the same potential t1nl,dnqv*5 kfryt u/cn5j2 + 8qr79zptvcik- hroughout?

A satellite orbits the Earth along a +d0w/ an(9oj scbjbt heap/9 ;a/ru5egravitational equipotential line. What shape must the orbit be? ; 0/5(dehptjawnoe +ra c jbau9b9//s

When dealing with prac2p.) akarf i;ktical devices, we often take the ground (the Earth) to be 0 V. If, instead, we said the ground was how would this ak)a fr2ka;i.pffect (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 placifd bs ryl 43k87v8w;,/olbntes acquire charges of the same magnitude? Will this be true if the two conductor yi8lc;lkso7df/4nvb 3w 8r,b s are different sizes or shapes?

We have seen that the capacitantdl1o/ 7qie qh4u51y4 rlqnk1ce C depends on the size, shape, and position of the two conductors, as well as on the dielectric consu1/d1 lte q44inko hq75yr1lq tant K. What then did we mean when we said that C is a constant in Eq. 17 – 7?

  How much work does tn qtdi*0h :)mnhe 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 electric field do in moving a proton from a point with 2ibw9ld.plvg:-6rs 3 7qgdat a potential osa- : .ggwt 6l3dr29bq7 vdlpif $+125V$ 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 hn/ i(2ke tdj*joules and eV) if it accelerates through a pothid2j *t( k/enential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires k.l,j+ y eoi:(axhwvpz6m2 )rof,u1e $7.45 \times10^{ -16}\,J$ 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 paral9dh+vivme3e9 jg5wz 1lel plates 5.8 mm apart if the potential difz9vjeg wh3m5d +i19e vference between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of(p5 o n8,cfqm2 yv98 am)f5iwrufmih/ $640V/m$ 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 batter t453u6x6zsq rwyom:z y is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel pl+lme z04yxp+ l.w.6 su:ywoodates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed sduwj*q n)r:.r) a u4rto 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 by2 ju4;y 0v ikqii7 ekn/7lr9mn an air gap. How small can the gap be if the air is not to beco9ik0url;y7j 4k2 invi 7 emqn/me conducting by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external t48 fwqq f-nf*force 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 wihx59z85 q,mkyf4d jnq th kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whose kinetic energy is 3. 8bi5 yyg:1ib0+hygg;leb5b +mqge x6 2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which iy0lgurj v .k,ip(x**p s 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 potential 15.0 cm from2x y icpsf(e;ym+t7 h4 a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an elecl g ,8otre9mg0tric 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 condume0 ss;n9gs +vctor carries a net negative charge9 sgns +0svme;, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electr4,*njtxk )id/wh 35tqw)7( u 9/mi witkimxbric 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 p* m*q9nn:2kieby8pj bp( (*kxcq*(w) scztu corners of a square of side L as shown in Fig. 17–25. What is the potep pw*im:)c8tu( (pqencs2 bzkyx* * qkn(bj9*ntial at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts frjx :wq2 f eh(ypgl64y s;d+b1oom rest 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 asn*m1y,kh 97 ):b3jtl g- nhckri9r gr great distance apart to g9chg)1tj 3krn -mk*9:i,lb7hsynrr $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm rselaa bb562tsb1,- hnorth 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 accelerak.3op 4zz/d r x6x2hbzte 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 charges are sepa cl318zkal 0yarated by a distance d, as shown in Fig. 17–27. Determine a form31z k lala08ycula 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, an electron orbits a 1k0nl0rne be; proton (the nucleus) in a circular orbit of re;0 b1 nekrl0nadius $ 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 protono6rxd:pf a;. rh8/9fw z8cpjn 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 i u9s0h ene*:-nfgl* fmt2u1bdipole 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 th. ;k3jg4w(o/hr xub bbe positive charge. The water molecule, Fig. 17–28, has bubkoj bx (;.4r/wh3 ga 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 holdw8g:.8+gd0 n;fmqgbn *1z (wzrya pos $+2500\mu C$ 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 capaci :;w , nzxv3wuqfgu)cbk0h47ator 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 r hu89e 82q1w r2hhwgcholds plus and minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two sho m7hsu1c ej9bs r:gg2+rt sections of parallel wire in air is 120 V. They carry equal and opposite chargeg7gs1 cb s2meju+9r:h of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each18q* wgm1iy:ek bf 2ur terminal of a 12.0-V battery when it is connected to ae : 8bry1u21fqmk*igw $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plot5hjp1oj -c rx; fmu8 dh8 qs4-+x4mnates have if they are to be separat fpu 8- o1xj4hso 5 jmqrxd+tcm8h4;-ned by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increases by +9m 58g,v yjz8:x*kon vsczld$18\mu C$ 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 ofy3w .*( zxi.piawal3h $8.5 \times10^{ 5}\,V/m$ 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 oppos e)o ap fb6yxiju)7uxf u7:0d-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 the plates of adjfu0p:;ubs(s u ;:xa py12xc $0.80-\mu F$ 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 qcoc 6zd3(*yg 125-V battery (Fig. 17–29a) and then is disconnected c y3zgd o6(c*qfrom the battery. 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 (xr. e- /)m tolxjgsms wd1p/*two square parallel plates 5.5 cm on a side that are separated by 1.8 mm of paraffx.wp /ml(xsd)e -1jsot/mr*g in?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a radiymtaeoqu71 k:es.20 ius of 5.0 cm separated b u7ma ye12q:sk.0eioty 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is vc*a ifjh+n 9;connected to a 22-V battery. If a piece of mica is placed between the plates, how much charge will flow *h+n jiafc;9v from the battery?    $ \times10^{ -7}\,C$

  The electric field between (pp;o h x-7drnp(nfkr9f8me- the plates of a paper-separated $(K=3.75)$ capacitor is $ 8.24\times10^{4 }\,V/m$. The plates are 1.95 mm apart, and the charge on each plate is $0.775\mu C$. Determine the capacitance of this capacitor and the area of each plate.
   $ \times10^{--9 }\,F$
   $m^2$

  650 V is applied to a 2200- o+4e93 laqsprpF capacitor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used tob7e equl9q* h+ shock a heart that is beating erratically. A capacitor in this device is charged to 5.0 kV and stores 1200 J of eneqlb*qu 9e 7+ehrgy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between t 5)i4+ 3ibaik 5r gyzff9zh*9z.wxuztwo square plates, 8.0 cm on a side, separated by a 1.5-mm air * y 95urt iz.9azigzxff3ibw)h4k 5+zgap? 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 pa2xy.wz8mq j/fs woj29 *wlo 5hre*bp+ns 5 cm apart and connecting them to the ljqz2o8rxmj* h/ wsp ebw5y.2 ofw+9*opposite 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 has fixe )p 1cw*7- tdwu x,xzojso,dh8d 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 difference x;o0epss/wh1nr +yqv9lesuid . +9x/ is doubl .l 9urew dxvoyn+1+s0 i;phsx s/9/qeed, and (b) the 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 a a dbf4.h07d ggiv6 k2 xgd5m:jowxm61re 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 t61vg56gko4jm. mxfd ba:dxw 02 7higdop 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 and ist3( ny;vttjmoizuv adr 7rhw1n *,nf9.9( nl5 34 cm from the 2.6-cm-long dnvh mw5 n 73(tf;,9 vr1( *aizojdnt.t9 yulrneflection 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 from rest acquires 6.3 keV of KE in moving from point A thcje gonq.1. 5o poih5 c1e.nj.qg ont 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-lhf. q- j;elx,kh6 ybwiz9: i.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 surfacedl:eiy /v1d/ t 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 accelerati3t7h 6r;won qx;5xsbed 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 electron q;xt7 6nsi rx ;w3hb5owould remain stationary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough stored energy to hgvm cc)7aa fc+29 zv0leat 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-V battery uhy+mpaa4m:c7: n1l0runv;nnql )t 8mntil it is fully charged, after which it is disconnected from the battery. A slab of paraffin is then inserted between the plates. What will now be the volt4a;1r0qlnp:ah n+mytlm )mvu c:n 87nage between the plates?    V

  Dry air will break down i, qx2*nf9cvq o ubi(,yf 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 triangle (side ,ysz2sb6*v;x*v v cp8 lzx xk3L) as shown in Fig. 17–30. Deterc ;x vk8 xp*szv2*,lvsb6yzx3mine 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 bat8 sh b9 .o3sec(8:be.sk sitwbtery. If a piece of Pyrex glass is placed be9wb .e3.ksot sb 8ecb:(i8sshtween the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerate + 36rcfhcvuwc9 )evc/d horizontally 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 aw3u9vhvccrcf/) 6e +cnd 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 capac; qlu)oxt+o+witance $C_1$ 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 youna 65sh9e;jpn want to make a 1-F air-filled parallel-6;jh5epn sn9a 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 practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there is an electric fi +t8ki2;lgytf.e4 jok eld 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 nit ugr vnx7*8j /py55elzrogen 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 betwee e;4 yl wxu)wpeb1sc7tp25r. . js8nmen the Earth and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are typmnycs;erwp 8 )xws j 75b.2ep4l 1u.teically 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 vk8zea y-5ue +xt). jzprovides 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, anott.zyae- zkxev+)ju58 her 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 from an identica f7f/ r*g-symnv(k bo*bhv) w-l $+33\mu C$ 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 by a 0.15mo0 ho+ ),r,o ax)tbuq-mm-thick piece of paper),o,q+t buxm0ho )r oa $(K=3.7)$ 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 platep95e y)2km fsh 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 apty 66 dfx(4j-umvon5part 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 placedim20lqd2g 3rvol2ke 6ruf2d( as shown 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$