If two points are at the same potential, dor ms38 76e9h; ub(yudrcwa1soes 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? Explain. 9ud1ym6b3 as(wcoh e;ur7r s8

If a negative charge is initially at rest in an ee(l 3ay:evocm:l1) wt4/m psmlectric field, will it move toward as(apm1/34 e e mmw:llc yto:)v region 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 di k( )0mqj;ibfion-v.0v,ys vgw5t4pe fference (a) between electric potential and electric field, (b) between electric potential and electric potential ener0t-gvbiey vp 4ns;jvo5f,i()w0.kmqgy.

An electron is accelerated by a potential difference ojnj vne.tbefs4; p;8i5e .v(n f, say, 0.10 V. How much greater would its final speenen;.stj4nbv 5(.8ij; f p eved be if it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining two equal positive charges whlh- +uzrjycw551t* xtere the electric field is zero? Where the electric potential is zero? Explain.c -5jtu*l yzt5 hr1xw+

Can a particle ever move from a region of low electric potential t0tsjv-f0 enm+9h 8jolf0 q8d ro one of high potential and yet have its electric potential energy8jtnr 0q9f0lvhef0j8m-+osd decrease? Explain.

Compare the kinetic energy gained by a proton 2 fq825e u, zdd-tlvf a7)zerp$(q=+e)$ 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 cja61(sn r10jz3ujvh c- cp;z eross? Explain.

Draw in a few equipotential lines iavbxl7coxl k )u0. *w1sk6j2hn Fig. 16 – 31b.

What can you say about the electric field in a region or8xon g5 t5ve1f space that has the same potential x eo r15v5g8tnthroughout?

A satellite orbits the Earth along a gravitational equipotential line. What s ak:lu w;agcd4j-x92zdml)s: .6r ifrhape must t.cj42km;9garzi dlf x a ds6)lu:rw:-he orbit be?

When dealing with pracxy ;-p92erccttical devices, 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 field E, prt2yecc9- x;at other points?

When a battery is connecte-/+ qujt*l;mri kt:otd to a capacitor, why do the two plates acquire charges of the same magnitude? Wilt -k r;+tqj:/limuto *l this be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on the size, jurm+u 6cd:w:shape, and position of the two conductors, as well as on the dielectric constant K. What then did we mean when weur jdm u+::6wc said that C is a constant in Eq. 17 – 7?

  How much work does the electric field do ikf*vrlx tw09. 7xnu7fmd oy26n 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 inlrkl ns9 pzu6: p8- eap*rlt-na *4i/f moving a proton from a point with a potenti8 nf- a lrpuz*pk6p/l s4i:lreat-*9nal 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 acceleratt u 8 f-0(n4m.j1sghzxfe edm6es through a potential difference of 23,000 e8f htzf m4ugx1m06e. - sdn(jV in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires8cz riy9t3z/*z:m+9vgaei)r jcf( u v $7.45 \times10^{ -16}\,J$ 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 parallelm 924jlnxw8 v)bn3xcec2:em o plates 5.8 mm apart if the potential die824 xc 9n mwl)ce vjmxnb3:o2fference between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of 60qk g eoxgw-nxgx /u2hu1;4n$640V/m$ 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 t1twx-1jh uw 9ykt4pa5 o a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field bet fu-xajz-+1hj g-w 9;x ygc-qhween 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 give a hrj en *5q4l ehm q:.arw7/t,xjelium 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 airihsi 33f-2 g 9hyxk2fnwzo gm 6a;9f8t gap. How small can the gap b 3is;ik g8gf -f nhawohx6232 9mz9fyte 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 tnb*(b;i+ 73cwdeku2nm( pcn y o 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 anq:dnn ao+8gm6t6h+98b j ievf electron with kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a pr*di(zxlxl4 yfym* 0m+y*k q0moton whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nuc ju9ty,6cb9ki leus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric potiv 1f 08f-r faa)vi44w6ioxeqential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric potentiallu 6po,rjo1;y 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 footb e 0,(k oiw *ca0;1 f7 huwfgly3zxruga/j92kqall. This conductor carries a net negative chyua g fa0hr1oc qw j;3w,k92 (/zu*g7ke0xlfiarge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electrin aviy12s fa7;6 fqmw9ko/sq9 c 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 arrangemp(u iugk fv526 1,nktj.4a fid at the corners of a square of side L as shown in Fig. 17–25. What is the potential at the fourth cornern 4i2au(fgk,56 tkm pj1fi u.v (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from restsw;g9ajver7 8bw) u5o 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 1lff)xv , oqs8to bring three electrons from a great distance apart tf1vo qxs,) l8fo $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm *q, gcb k8n1b+fl,,6dcrkcjynorth of a $-3.8\mu C$ point charge, and point b which is 88 cm west of the charge (Fig. 17–26). Determine
(a) $V_{ba}=V_b-V_a$    V
(b) $\vec{E}_b-\vec{E}_a$ (magnitude and direction).
   V/m
   $^{\circ}\,$

  How much voltage must be used to accelerate a proton (radi.h c(qf*ossn4:hu sw3 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 separated by a distanck cb3x v5q8w7he d, as shown in Fig. 17 x8 hbkqw3vc57–27. Determine a formula for $V_{BA}\,=\,V_B-V_A$ for points B and A on the line between the charges.

  In the Bohr model of the hydrogen atom, an electron or3ql no q6pw+*abits a proton (the nucleus) in a circular orbitpn3oa* 6l+qwq of radius $ 0.53\times10^{-10 }\,m$.
(a) What is the electric potential at the electron’s orbit due to the proton?    V(Round to the nearest integer)
(b) What is the kinetic energy of the electron?
   $ \times10^{ -18}\,J$
   eV
(c) What is the total energy of the electron in its orbit?    $ \times10^{-18 }\,J$ $\approx$    eV(Round to the nearest integer)
(d) What is the ionization energy — that is, the energy required to remove the electron from the atom and take it to $r\,=\,\propto$, at rest? Express the results of parts b, c and d in joules and eV.   $ \times10^{-18 }\,J$    eV(Round to the nearest integer)

  An electron and a proto: nzkfni-2lhyp hkc8f j04l2*r.k ki0n 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 dipqq+vz x- 8d8hsole 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 9 nenp//gt8*mp xa 7 rvtx/hvp23/baithe negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be considered as the vector sum of the two /7vhxprb /ax9mgp 8npei2 * /n/ av3ttdipole 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 capacitoz)c *e3pvul 3. 2n rdoe9ic6qir 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 capaci1g7df 4beyk l,tor 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 2n hg m7+)rdtvder)* bcharges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential differenjlf 5,2b(qh2:utcmw4 /gpl/ ztz tx0uce between two short sections of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is the/2jbtl4c/q mz :ttfuh 2 p,5xlw0z(ug capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of a 12.0-V battery when it is connec4mj1ujn6yb . yted to m j4nuy6.yb j1a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor iscihur9j +cj(g3 /y4mi desired. What area must the plates have if they are to be sep mhrcjygi3(c4u +ji9/ arated by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitorx c8k71h8uujn 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 ofx,/4iqzu sdn*1 zb8zn $8.5 \times10^{ 5}\,V/m$ 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 opposito/le l3j0 hxy.aocuy+ 2ug )-me $5.2\mu C$ 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 offcx.c n-jji r95 ar8)u 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. 1gmppi282pbrh7 *nqsu0ys ;b;m;.ovj7–29a) and then is disconnected from the battery. When this capnum2r;hm20 b.pog s;* b8yp 7qjpi;svacitor $(C_1)$ 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 p a-o zrm(7n4h *kp0ejqlates 5.5 cm on a side that are separated by 1.8 mm of paraffin-k(4ae j n*7 rz0ohmpq?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a radius of 5.0 c * j4d qtzn+,yb:f9hdmk,1afd8 ub:vw m separated by y d z94fv 1b ,q:,8dht*dmf jb:auk+nw3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is co,d:4s9v/m lsjanf cs +nnected to a 22-V battery. If a piece of mica is placed between the plates, how much charge will flow frocl+/4dms,ansf:9s v jm the battery?    $ \times10^{ -7}\,C$

  The electric field between theo l1;pjz ndo2x3vy a*+ 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-pF capacitor. How d1 ah)29otb cdmuch energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is be z )4s)knqcg*ehmdu 7*ating erratically. A capacitor in this device is charged to 5.0 kV and stores 1200 J of energy. What is itc)g *)e4 h qszud7kmn*s capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between two square plates d 1ahb,lvn-m7, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on the plates are equal and opposite and of magnitudnlh, dbv1 7-ame $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in. pieze *+tcrkv 8x3 pans 5 cm apart and connecting them to the opposite tz x+ t*er38cvkerminals 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 h9d(e .sniy2ncagg-:a-d 6v hhas 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 differencet6 h ao:n)ov(gh*7z keid27bq is doubled, and (b) the 6 72hok o7 (bv*inhqe):atzdgcharge 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 acceesj md lqj(uomd5wj:i)m.dl //tc43p7 fx;3i lerated horizontally by 7.0 kV. They then pass through a uniform electric field E for a distance of 2.8 cm, which deflects them upward so they reach the screen top 22 cm away, 113m7sej cp jxmlmiwjilf:t3 d/ ;/.u(d 4doq)5 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 zw5a2 rt pb.(2hxdv2land is 34 cm from the 2.6-cm-long deflea tvhw2.z lp22rxd5b(ction 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 m,pz *rtd zo)wh33vyh4 oving from point A to ptp)hvzdzyo 33 4*r wh,oint 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 bis.q3+0egom34ylk a )p7s cf4.0 C of charge and 4.2 MJ of energy to the Earth.
(a) Across what potential difference did it travel?    $ \times10^{ 6}\,V$
(b) How much water could this boil and vaporize, starting from room temperature?    kg

  There is an electric field near the Earth’scfg/f9 a*sd 6t 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 pictu5mpu1 qeu4gq w/h8a3xre tube, electrons are accelerated by thousands of volts through a vacuum. If a television set were laid on its back, would elep/ 58uqeq 3x wu4mhga1ctrons 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 would remain stationary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough stored e;n* 9 hww/nza1*x 8*lpqiqrmznergy 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-V battery until it is fully chargx(/0ht,mw7 buqb lul+ ed, after which it is disconnected from the battery. A slab of paraffin is then inserted between the plates. What w (qlwb+ml0/7uutbh,x ill now be the voltage between the plates?    V

  Dry air will break down if pg/uf6bp2d: othe 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 equi)qr luo;t5q ) urw+i2slateral triangle (side L) as shown in Fig. 17–30. Deterswr+ )q5t;luoq2r)iu mine 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 conf,s * 1.r/lnvfud3* t 2jsoehpnected to a 9.0-V battery. If a piece of Pyrex glass is placed between the plo1e3rt2fnl*sh/ ,v. pd ujf*sates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally s;b7e6rdrrync(p/ / ipc0ao8 24sihvfrom rest in a television picture tube by a potential difference of 5500 V. It then passes between two horizontal plates 6.5 cm long and 1.3 cm0ovrp isy h( 6ae;2c7dpr/4c/8nr s bi 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 .r.k)fp:s mnxitance $C_1$ 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, sujs1 k9ff,wj pxqaxlcba1c61+)4j c, fppose you want to make a 1-F air-filled parallel-plate capacitor for a circuit you 1fa + k jc6lf9pc,),x1jqxsfca4w1jbare 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 the61/ezikmzp v9re 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 pulse3rho6 /lt1 y ::lolxctd 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 differenrc(+nax-v 5 g 0.c 9)ox9yezeejartc3ce between the Earth and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are gn9rx-ca(yja.3r9xt) 0z+ee5cc oevtypically 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 prot:1iqxwww sozk2fi8wj4j t .9g yigj. f06+*lvides 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 wf0goftw 4j9.k tix8w6s :wj izj2+*liy.g1q energy of the electrons, another plate above the barium surface is kept at a negative enough potential that the emitted electrons are slowed down and stopped, and return to the barium surface. If the plate voltage is $-3.02V$ (compared to the barium) when the fastest electrons are stopped, what was the speed of these electrons when they were emitted?    $ \times10^{6 }\,m/s$

  A point charge is placed 36 cm from an i:(: y+guarq nsdentical $+33\mu C$ 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 n u+9z5ij9 gebfrom two 1.1-cm-diameter coins separated by a 0.15-mm-thick pub+ i9gje9nz5 iece of paper $(K=3.7)$ A 12-V battery is connected to the capacitor. How much charge is on each coin?    $ \times10^{-10 }\,C$

  A $+4.5\mu C$ charge is 23 cm to the right of a $-8.2\mu C$ charge. At the midpoint between the two charges,
(a) what are the potential    $ \times10^{ 5}\,V$
(b) the electric field?    $ \times10^{6 }\,V/m$  ----待选择----leftright 

  A parallel-plate capac ,tu5:8w/y5 goee hbhvpa 6k5citor 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 ccs 2 ;z,)mhx:c dcs* f::siilfixed 4.0 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 - t j5k6sat:feas 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$