If two points are at the same potential, does this mean that ng5lbk+.ik+f9zy 2gnso work is done in moving a test charge from one point to the other? +9gynk5z bs gk +il2f.Does this imply that no force need be exerted? Explain.

If a negative charge is initially at rest in an electric field, will it movoi2wmb 86crm++rbgmr 05wtj; e toward a region of higher potential or lower potential? What about a positive charge? How does the potentia;tr6+r5bg+wi8jowr2m m0 b cml energy of the charge change in each instance?

State clearly the differvnq t8z c-.uw)ence (a) between electric potential and electric field, (b) bu q- .wcv)8tnzetween electric potential and electric potential energy.

An electron is accelerated by a potential difference of, say, 0.10 c*qrp7frc (f1V. How much greater would its final speed be if it is accel*r71frcqf p (cerated with four times as much voltage? Explain.

Is there a point along the line joining two equal posi oa+gr6emu,xq3kx 5c;nks; f,tive charges where the electric field is zero? Where the electric potenxe6ak,rqf ksu,mnx c ;o;+ 3g5tial is zero? Explain.

Can a particle ever move from a region of low elez8q,ja+w cl4jctric potential to one of high potential and yet have its electric potential q, j8lz+wja4cenergy decrease? Explain.

Compare the kinetic energy gaine:lbmbk(7l l9 .u)uu xbj4u5* 8 wyisesd 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 equipotentia m8b,ozqb+0shp-e 5xml lines cross? Explain.

Draw in a few equipotentia) c-)bhvm:ef wpeo2/hl lines in Fig. 16 – 31b.

What can you say abo7 aprvapnh.18nt)jl54hl + 3 a ygmh,put the electric field in a region of space that has the same.mpn+n a47,3lh 1vyj 5hp)ahlarg pt8 potential throughout?

A satellite orbits thevcn)1i yfz 4b* Earth along a gravitational equipotential line. What shapei1zbvy4 f cn*) must the orbit be?

When dealing with practical devices, we often taam9kkvzvfck,6 c :u e289y e4hke the ground (the Earth) to be 0 V. If, instead, we said the ground was how would this affe :ecvhyk,ekmuk6a8924 f c9vzct (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 plates acquireuna orgw1 :14/3 grixp charges of the same magnitude? Will this be true if the two conductors are differen gpogi 131uw4rr/n:xat sizes or shapes?

We have seen that the capacitance C depends o-;c 1i m*ov9pzmfe ( b:pkyfh-n the size, shape, and position of the two conductors, as well as on the dielectric constant K. What then did we mean when we said that C is a constant in1phme*pf -ybfio -(vk m :9zc; Eq. 17 – 7?

  How much work does the electric fibc(2p4w ba, gneld 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 p5nciq.o 4-y, iqfc-pzxk o,4do in moving a proton from a point with a potentxp4c4 i fkq. q ,5c-opnyzio,-ial 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 accele l.g7jqjro)z 8i2pm-wer ;dp*:cs8ij rates through a :;8*iogjr )cmq pz2-7wse l.jijr pd8potential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires d3yvqmc6.:i 0j fi(y:wckrm6or5;lz$7.45 \times10^{ -16}\,J$ 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 firgfh.9o 0t 8mveld between two parallel plates 5.8 mm apart if the potential difference between them isogmr t9 v.hf80 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of hp0(g(q,x s ma$640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two paral2yrwzmh; t8akjcp42(6p c-erlel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected to a 45-V b ol;k pwf 6.xiegdq570attery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to g*ohf-) z9ta1*dx mzlgive a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 20w+fq fa4a:+h26fj qhb 0-V power supply, are separated by an air gap. How small can the gap be if the air is not to become conducting by exceea+2 fq bhhjf 4+a:fw6qding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external weyk *3sgm: 1pforce to move a $-8.50\mu C$ charge from point a to point b is $15.0 \times10^{ -4}\;J$. If the charge was started from rest and had $ 4.82\times10^{ -4}\;J$ of kinetic energy when it reached point b, what must be the potential difference between a and b?    V

  What is the speed of an electron with kinetic energy,jha.r3z/: brxs zna g-cyr4;
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whose kinetic energ6ljh2e 0meeddc d f*41y is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helia q:rpy s r fe19rmn6vm14vk*sbv*+m,um 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)u0rz azufk-g ,27x,kymo+ps potential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an ele/g n(w2+jz mf;ulza o4ctric 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 fooa* ; vrvch*ig1tball. This conductor carries a net negative ;va *hrig 1v*ccharge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential ahb0sp 4l*3c0qhg gj tcg18hu0 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 arrcyit86 box8p0xga;iq./k8i canged at the corners of a square of side L as shown in Fig. 17–25. What is the potential at the fourth corner (point A), takqgx i.i60xb88 tkyc ci/8o ap;ing $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed point 9 rq(co*7f 6eztv v(sg(vdsij .g/gv 6charge 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 dongu zza(4zd4 f rt*p73oe to bring three electrons from a great distance apart to a p3*o4( tzdr7g4fuz z$1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm north ofrox0 -p kh7qy**+zi *g++5nvxtzfwgw 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 (rn5jr-7x s d8a5 srf(gqadius $1.2 \times10^{-15 }\,m$) 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;(ejq cs74ohr separated by a distance d, as shown in Fig. 17–27. Determine a formula forsj; h rce7o(4q $V_{BA}\,=\,V_B-V_A$ for points B and A on the line between the charges.

  In the Bohr model of kf1 nl5 +tmhjof:r90b the hydrogen atom, an electron orbits a proton (the nucleus) in a circulnh9m 0rb1 fok5l f+tj:ar orbit of radius $ 0.53\times10^{-10 }\,m$.
(a) What is the electric potential at the electron’s orbit due to the proton?    V(Round to the nearest integer)
(b) What is the kinetic energy of the electron?
   $ \times10^{ -18}\,J$
   eV
(c) What is the total energy of the electron in its orbit?    $ \times10^{-18 }\,J$ $\approx$    eV(Round to the nearest integer)
(d) What is the ionization energy — that is, the energy required to remove the electron from the atom and take it to $r\,=\,\propto$, at rest? Express the results of parts b, c and d in joules and eV.   $ \times10^{-18 }\,J$    eV(Round to the nearest integer)

  An electron and a prbeph/w;i*z8 b w9o6k+ir ).csi/v3h se xj;smoton 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 dipole whose o8u.bh5 2e(gmd;b cp dg*2pu j*4 wxyn4gb+itdipole 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 a8 zvq.l 9zoin)r0 54upe n7zct vector, points from the 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 i90tqp8)uevlo znz r4z7 c.n 5dipole 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 he7r +v hkpnkk.9 mrgu5 2u:o,eold $+2500\mu C$ 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 .a6 dknum/4bb 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 charges ofalqm *ntj nt8+tj 6i37 $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sectiw6 tbmw h)zsj)0pl5 e3ons of parallel wire in air is 120 V. They carry equal and opposite charge of magni6zw)j0 3hlt mspwe5b)tude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each tuzaaaf464i0 p erminal of a 12.0-V battery when it is connected to a 4zaafa60pui 4$7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates have if they are t r1h:+xi +59nprzh cnto be separated by nh5:czthix1 +rrn+9p a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitorf 6 y4jn6ka0hf3xze2u92 t gb0(t uyqs 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 2+ +kpigqs+3sv hovlq;e 2v8n$8.5 \times10^{ 5}\,V/m$ 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 opposite lqssr+y9sh3-ts*-n j$5.2\mu C$ 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 o3a(saam ku/m(l 0xpv;sfi,*tf 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 batt;v*ia4pqgrlz (we x9 4ery (Fig. 17–29a) and then is disconnected from the b4e *vpwla q;g(9z4rixattery. 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 pnm20 ap ete:9marallel plates 5.5 cm on a side that are separated by 1.8 mm of paraffip9m2:ane met 0n?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates wh,,(0rzjm tav -)gcmp ith a radius of 5.0 cm separated ,(t ch)mzvgjmrp0-a,by 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. If a piece of mick jpubh r1c:,3 5h3l3 8lctzasa is placed between the plates, how much charge will flow fru3h3t srp: 1chjz8kc3 lb,l5aom the battery?    $ \times10^{ -7}\,C$

  The electric field betweep02y)km 6 pi q3zc,vkdn 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-pF capacitor. Hodihc+ f 60okw5.f.zyyw much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillatobna5jk8 ;qot8y/ ht +vr is used to shock a heart that is beating erratically. A capacit; tnv 8ok5a y+8tbh/qjor in this device is charged to 5.0 kV and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is storehn k x,-gfl4e4 2*25jr tak*ak xqh-awnzd1: xd by the 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*z54gfx : kje4nkaaq,kt2an dxlx1h*2wh-r- equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in. pie pans 5 cm aparut-vuo /xl4 :y:9llv zt and connecting them to the opposite terminals of a 9-V battery vvo:uyz lut/9-x4:ll. 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 fixwt2 5aekaq17x ed 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 dimqpb:sp .f6qa d4w,vl e,p15 sfference is doubled, and (b) the charge on eachq:d pf1 4psalpq56 ,sw, e.bmv plate is doubled, as the capacitor remains connected to a battery?

  A $2.70-\mu F$ capacitor is charged by a 12.0-V battery. It is disconnected from the battery and then connected to an uncharged $4.00-\mu F$ capacitor (Fig. 17–29). Determine the total stored energy
(a) before the two capacitors are connected,    $ \times10^{-4 }\,J$
(b) after they are connected.    $ \times10^{-5 }\,J$
(c) What is the change in energy?    $ \times10^{-4 }\,J$

  In a given CRT, electrons are accelerated horizontpzghuf fx+. .rm*lm,(ally 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, 11 cm above the center. Estimat ,*mrfu(lgf+.x.hzm pe the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a CRT. The sqy i74in51q vmh e1.nsy5eoc7creen is 30 cm wide and is 34 cm from the 2.6-cm-long d.c1yeq 4h n5m7 evnosyiq 715ieflection 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 acquir 3qk/qlc5ksf 5ryx -tyr7/nn+es 6.3 keV of KE in moving from point A to point B.r fn/tl+55r-yyqxk/q 3ks7cn
(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 chargejr. b.o) :m)6txagihe 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 f j1rsuuxnc+b-s p 7(4zr4hxl*ield near the Earth’s surface whose magnitude is about $150\,V/m$ How much energy is stored per cubic meter in this field?    $ \times10^{-7 }\,J/m^3$

  In a television picture tube, electrons are accelerateumhg:q kpj/***y1m za9zeu i7d 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 potentialhg zuu7qp m*9/ji me:1za* *yk difference, acting over a distance of 3.0 cm, would be needed to balance the downward force of gravity so that an electron would remain stationary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough stored energy to heat 2.5 kg of watern30jl 7j-* o ynpi7rdl 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 fullyi8 m t9m)*p)fd, g 4yinxttn:m charged, after which it is disconnected from the battery. A slab of paraffin is then inserted between the plates. 9*mgm,t:4nnt)iy8)fit d mpx What will now be the voltage between the plates?    V

  Dry air will break downsviw7)d35 fy -y n cux;;oux4z9m .www if 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 equilateraljb-+0 7utws rl5ram uq( .6dri triangle (side L) as shown in Fig. 17–30. Determine the potential at the midpoint of eachr5u(6 dum7lt+q.bi sar0w-rj of the sides.

  A $3.4\mu C$ and a $-2.6\mu C$ charge are placed 1.6 cm apart. At what points along the line joining them is
(a) the electric field zero,    cm left of $q_2$
(b) the electric potential zero?

  A 2600-pF air-gap capacitor is connected to a 9.0-V battery. If 0*-j en)kat)o jmdpf i 2ffl.(a piece of Pyrex glasfpa mf0df*j )li)k2-nt e(o.js is placed between the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizouu1i7;w +qcdk:bg5if ntally 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 and 1.3 cm aparu; g5q:ikw1 i+fbc 7udt 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 capacitance 1/3ip pzhj3hy$C_1$ 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 1w:l; yh dgi:5swaa vh o3:z;yyou want to make a 1-F air-filled parallel-plate capacitor for a circuit you are building. To make it a r1i3so v alw::;zgawhhy d5 :y;easonable 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 elect1r jb*-xk o:to1 u-:tgqnff455 hlnvgric 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 pu9ax9vvc hh2y6c 23mzk lsed nitrogen laser has a $0.050\mu F$ capacitor with a maximum voltage rating of 30 kV.
(a) Estimate how much energy could be stored in this capacitor.    J
(b) If 12% of this stored electrical energy is converted to light energy in a pulse that is 8.0 microseconds long, what is the power of the laser pulse?    $ \times10^{5 }\,W$

  In lightning storms, the potential difference b )t sb:mbu 5xv,w8td:me- sc338qhzsretween the Earth and the bottom of the thunderclouds can be ss3c wx:eqm-,tbs3:rdh8 tb mz8 v)u5as high 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, ultraviolet (UV) light provides enough energy to some electrons :xo 6vw:1sntct8 mvj/.z9 mxjzva x1 /in barium metal to eject them from a surface at high speed. See Fig. 17–33. To measure the maximum energy of the electrons, another plate above the barium surface is kept at a negative enough potential that the emitted electrons are slowed down and sto16x vv:t8:av/xnmmws 1j zo / jtcz.9xpped, 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 otudjv 98/ 3mv( 4lzhflsn qz,o1o n2f2 k8t3q36 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-diameter coins separated by a 0.15-mm3f vd kltn5 .broj;0d4-thick piece4rbfon 5d. t3k;0ljv d 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 capaciteo 7/rlm, ,a/nrft3i gor with plate area $2.0cm^2$ and air-gap separation 0.50 mm is connected to a 12-V battery, and fully charged. The battery is then disconnected.
(a) What is the charge on the capacitor?    $ \times10^{ -11}\,C$
(b) The plates are now pulled to a separation of 0.75 mm. What is the charge on the capacitor now?    $ \times10^{ -11}\,C$
(c) What is the potential difference across the plates now?    V
(d) How much work was required to pull the plates to their new separation?    $ \times10^{-10 }\,J$

  A $2.5-\mu F$ capacitor is fully charged by a 6.0-V battery. The battery is then disconnected. The capacitor is not ideal and the charge slowly leaks out from the plates. The next day, the capacitor has lost half its stored energy. Calculate the amount of charge lost.    $ \times10^{-6 }\,C$

  Two point charges are fixed 4.0 cm apart from each other. Their charges arx, 9+g/lh+ dok zxlhcd30xlg (ov7gq*e $Q_1$=$Q_2$=$5.0\mu C$, 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 showkey1 78ev6mp fn 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$