If two points are at the same potential, do bkg3bs7r0 ah.es this mean that no work is done in moving a test charge from on.3s gar0b7khb e point to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at rest in an electric fielzg(;wk8 n4e k +bdv;lhd, will it move toward a region of higher potential or lower potential? What aboutbdgwhkn +ek4;8 vz( ;l a positive charge? How does the potential energy of the charge change in each instance?

State clearly the difference (a) between electric*o ca/j6jyc3b sa7r(t potential and electric field, (b) between electric potential and electric potb7a(c 6aorjcts /yj3* ential energy.

An electron is accelerated by a pob cb/k6yqa5xmo* gon-p8*m5 c 0)-hn yiraur 8tential difference of, say, 0.10 V. How much greater would its final spe bc*6*/0ruickmo - y 5abnmq p)x5r8ya8 hnog-ed be if it is accelerated with four times as much voltage? Explain.

Is there a point along the line joiningros93czge6et 8f hd9 5 two equal positive charges where the electric field is zero? Where h 68e9zg9ce35 r stdofthe electric potential is zero? Explain.

Can a particle ever move from a region of l)mb1ty blgf is 2b/l1uis4h25ow electric potential to one of high p4ilfly1) stbsbg52m h2 1/ibuotential and yet have its electric potential energy decrease? Explain.

Compare the kinetic eneri(enhhl;r tc et35 0:( nmy7vugy gained by a proton $(q=+e)$ to the energy gained by an alpha particle $(q=+2e)$ accelerated by the same voltage $V$.

If $V\,=\,0$ at a point in space, must $\vec{E}\,=0$ there? If $\vec{E}\,=0$ at some point, must $V\,=\,0$ at that point? Explain. Give examples for each.

Can two equipotential lines cross? Explainw6hb/jv+f9fmfy o3s:m oq/0 9 ntw4bw.

Draw in a few equipotential lines in Fig. 16 qx:7lgtooq(0 – 31b.

What can you say about the electric field in a region of space that has the /+rc* r kgyf t:tpr4h3same potential through:tt+pr chkyfr *r3 g4/out?

A satellite orbits the Earth along a gravitational equipotential li6a icrljvv vc/iw; :(1ne. What shape must the orbii6 aw/r;:ci cv lv1(vjt be?

When dealing with practical devices, we often take the ground (the Earth) gzzng) phuq.5/tzj 3zkb-ah.t, cb): to be 0-u h/z)n.ap35jb bc ttzhz ), .q:zggk V. If, instead, we said the ground was how would this affect (a) the potential V, and (b) the electric field E, at other points?

When a battery is connected to a capacitor, why do the two plates acquirsmtq0iqs;st9s i+9 0ge charges of the same magnitude? Will this be trqsts9 g0i+;q9 sim0stue if the two conductors are different sizes or shapes?

We have seen that the capacitant cf)i kecvc*92;a;qbdv 8f /zce C depends on 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 constantk;e;2v) b8f*ccdif q/ ac9 vtz in Eq. 17 – 7?

  How much work does the electric field e3rxax alc f6pa59-8pxmf -l7do 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 mov8dbnuf csn5t:k8k)uhl t.- v3 ing a proton from a point with a potential of t5v3b) snlfd. -:un k8h8utkc $+125V$ 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 joul7sm ,p3zogsb1 es and eV) if it accelerates p,o7 z13bmsgsthrough a potential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires *ayn)-k9 4ds4vwf 7vfur ,kko$7.45 \times10^{ -16}\,J$ 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 elrlio yz u 84z8q23 )rf4x*mnktectric field between two parallel plates 5.8 mm apart if the potential difference between them i *uzztn8qk8f43r)2 y4irx m ols 220 V?    $ \times10^{ 4}\,V/m$

  An electric field ofz3sin c ydxm ,0g y3g4l(jpo;7 $640V/m$ 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 connecvhq-2wl ms1 5lted to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field betw -sxjv+uf zt(;een 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 6b9odh p)vf* fjed*c-a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 2ofxth*oi.zd/y3 3int+e ga dt1m(5cv+; c 7nv00-V power supply, are separated by an air gap. How.c +dm1n+xciv 7*t ooahiztt3n;gyedv 5(/ 3 f small can the gap be 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 fih a*s da8q9a8:*. wto;fyq h/j.q 0flye6poyorce 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 enexl5e2d-+q;y ;mayp7l aicx vdb2*k 3brgy
(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 3.2 keV?i0j/, x/d,uzlpb-g j a/u/n xq    $ \times10^{5}\,m/s$

  An alpha particle (which is a h7tqah;ugh 3 x0.s of.felium 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 sml/gb;(2k zf27qj5fdqry /wa);i ihcm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric potent4xjc)o8lts 3av6hv -dtk cqf2yn. c 61ial 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 footbtbm wptfoiti mbwa0: 0 /2.,p// ,jejfall. This conductor carries a net negati/ft ,p, 0 i meot0f.b:p ibm/ja/wwtj2ve charge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potentialg(da 6njotb8y0a. ul3)u 0enn 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 corners of a square of uz+p1csnl08 z8r5 imjside L as shown in Fig. 17–25s+51czp 8i unzlj 80mr. 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 fixed point charge wt02/bibv pam/wyr( *o(.gzk uith $Q\,=\,-0.125\mu C$. 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 great1 0ry5b/i34vk q qkzng distance apart ton0g1rky 5iq /b43k qvz $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is g hc3a5cwfe(* 72 cm north of a $-3.8\mu C$ point charge, and point b which is 88 cm west of the charge (Fig. 17–26). Determine
(a) $V_{ba}=V_b-V_a$    V
(b) $\vec{E}_b-\vec{E}_a$ (magnitude and direction).
   V/m
   $^{\circ}\,$

  How much voltage must be used to acceler,zw4w5a(+i)we ,wlby 7jz gsmate 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 separated by a distance d, as shown injk9+d/-bxoj0w/f, : hr5jezlyllq .p Fig. 17–27. Determine a formula fo.5 jk/qdje /wlo -l,0+jxhzf p9r :ylbr $V_{BA}\,=\,V_B-V_A$ for points B and A on the line between the charges.

  In the Bohr model of the hydrogen atom, an electrot1 etj/qw/ xz4w,qn)vn orbits a proton (the nucleus) in a cxe/),w1/ vt4nq jwt qzircular 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 proton are wmc1 sp8b77oq8j ll7g$ 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 du+rsxv2ogf r3 hqq-8,se to a 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 negw ov6(ptk-x41lu+ n/v 6 7wsozc7u r uscok0u5ative to the positive charge. The water molecule, Fig. 17–28, h76p4cwvou k6ucou5vs (u xr+ 01os-lt7/nz w kas 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 capacitorcv f+,2pd)k b 4:uuyxj 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 capacit*to (q lvugb94or 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 7 u8epoir sj*j.2ezc8xz4/txand minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sect9r08jey;es1trg +jih ions of parallel wire in air is 120 V. They carry equal and opposite charge of mag9siey8+ej t h0j rr;1gnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows ph8d*gj. c oiy- 68rwcfrom each terminal of a 12.0-V battery when it is connected toiyoc 8rp8c6 -j.*hw dg a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must0f gv. lb-y8r-ysxq;rgo;fj8 the plates have if they are to be separated by a 2.r s-fyoyq vrf-;bj 8 ;.8gglx02-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increases i( 1z9rx5uu qz*bz 6zkby $18\mu C$ 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 wj;0 /qz/ kupe$8.5 \times10^{ 5}\,V/m$ 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 o-wco- dnk v49:; hhnxipposite $5.2\mu C$ 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 kk0o7 9*i:ag18zqekq30ld-nk byda h 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. 17–29a) and then is dis qlipo t/3sv -po8w( gju4.q+tconnect43pvo/(8o q qguipj l t+s.-wted from 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 two square parallel plates 5.5 cm oc7l tce)p 4vgfp/b*iy bjt-.)n a side that are separated by 1.8 mm of pa)) t 7ylcjgcbbvip4ptf* -e/.raffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates s:5 vhsmrtlzgl*q ;cr ar4g 9s+k)75 awith a radius of 5.0 cm separated by 3.2s459klgr zc+57 r ;al qg*)tamshrv:s mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. If a piechknm,br6b4 n5 e of mica is placed between the plates,4bhrmn6,k 5 nb how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a paper-separd:y135btr ks1 qw jk3gf2nzo4ated $(K=3.75)$ 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 energy iy f./6he(r hw0k3otl5a muh -ds stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a(fqaf8 ;l,ey9qhk3t r8e,cg9d3tln t heart that is beating erratically. A capacitor in this device is charged to 5.0 kV and stores 1200 J of energy. What is its capacitaf39 tqkg a;8e tr(t38felydq,n,9h clnce?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between two square plates,sltlv+xq a u93fa:j7p7*vu0a 8.0 cm on a aus3vt9j q7alx 7+0f:uv pal*side, separated by a 1.5-mm air gap? The charges on the plates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembl(v*9tr iof yg-u.z9g yed by placing two 9-in. pie pans 5 cm apart and connecting them to the opposite 9o*f.ztgivgr(y -9 uy 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 fia +w(k vfoy2;fxed 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 /t4lzp7bldz 4orl 4k 0a capacitor change if (a) the potential difference is doubled, and (b) th7/dz ob z4k4pr0l l4lte 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 are accelerated horizontally by 7.0 kV. They then pass*4is 2use6esl through a uniform electric field E for a distance *les46 ss2eui 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 v,.h -qp:9 hz 2tfotha1mg-mpa CRT. The screen is 30 cm wide and is 34 cm from the 2.6-cm-long deflection plates. Ov-qgm1,t9 . z -phhav:m fp2htoer 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 keVnl lx cv,pe86 (0ei:nv of KE in moving from point A to point ne6i:ln0(vxvlp ,ec8 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 4.2lthq e/hf:;sc 3g)6h i0 6;zvl,1buo1 baqngg 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 fiaot-/6wg+u1lc;z 7fihg8 femeld 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, electroc,vk y.fvbn 4;bwxux113w;gnrb 0 ,amns are accelerated by thousands of volts through a vacuum. If a television set were laid on its back, would electrons be able to move upward against the force of 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 elecyx w4vf,w0,ca; vk1;nm nbbux3 b1.rgtric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough storepnv,a ;-l;t 5toj*pknd 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 t sk n -r xofq4-lg29o59xuytz-o a 24.0-V battery until it is fully charged, after which it is disconnected from the battery. A slab of paraffin is then inserted between the plates. Whatqzo nsxkfg5u-2 tx oy4-99l-r will now be the voltage between the plates?    V

  Dry air will break down if tpb/qlxd h4 f+:7-grn(nv0d bshe 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 L) as showz 7e11x+e pr1+p m h:hccp1dmmn in Fig. 17–30. Determine the potential at the midpoint of each of the side:ehm7 pz +pc+remphdmc1x1 11s.

  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 conaqut p6dftrop5s14.mzq v-nll8 / -8 mnected to a 9.0-V battery. If a piece of Pyrex glass is placed between the p1ulfd-- 4p t v 8/anqomlmrtq.5z86splates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is acceleri+5:kyh 9x5t zsxh7r jated 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 and 1.3 cm apart that have a potential difference of 250 V i+9t7 5:x rysh5h xkjz(Fig. 17–31). At what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capach3o8jw 1dz9vy m/tj6b itance $C_1$ 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 ag-5b7dk y z4/q0tgmb s farad is, suppose you want to make a 1-F air-filled parallel-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 tgy 5gbz7ktqs0/-bm4 dhe plates? Is this practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there is an electric f+ag j2tu 3gowbd*m1 s/ield of about $150\,V/m$ which points downward. Two identical balls with mass $m\,=\,0.540kg$ are dropped from a height of 2.00 m, but one of the balls is positively charged with $q_1$ = $650\mu C$ ,and the second is negatively charged with $q_2$ = $-650\mu C$. Use conservation of energy to determine the difference in the speed of the two balls when they hit the ground. (Neglect air resistance.)    m/s

  The power supply for a pulsed nitrogen laser h;doxca yw:l *b ,ldpy/ (jc).pas 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 Euwg jh4q(y3h 7arth and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are typically7 w4hy(uh gjq3 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 elt+sg)k jd/i0drlv+ i0ectrons in barium metal to eject them from a surface at high speed. See Fig. 17–33. To measure the maximum energy of the electrons, anotdvir0td/ 0gl+k)j+i sher 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 placedpdeam3y;q7 j 3kx2 :lm 36 cm from an identical $+33\mu C$ charge. A $-1.5\mu C$ charge is moved from point a to point b in Fig. 17–34. What is the change in potential energy? $\approx$    J (round to one decimal place)

  A capacitor is made from two 1.1-cm-diameter coins separated by j b6-xq4yy 1wea 0.15-mm-thick piece of1qx jbyy46- ew 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 capacitor with plate a o;cda +.1twu*c(8smwo+fal i rea $2.0cm^2$ 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 ovkn75g/ yi c9other. 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 F ,92 klus7wvatig. 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$