If two points are at the same potential, does this mean that no w :2s0lgrfv.d(6c mqvjork is done in moving a test charge vmqvjd .gcs6rf(:l02 from one point to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at rest in an eleco*lx -dia2dncn i/g 7*tric field, will it move toward a region of higher potential or lower potential? What about a positive charge? How does the potential energy of the charge chann*ad2l gdi c/x ni*-o7ge in each instance?

State clearly the difference (a) between electric poem ewl6/r; 9xxvc 0tg8tential and electric field, gtlexmr980 6 xw/c; ve(b) between electric potential and electric potential energy.

An electron is accelerated- f+zh 5enaqxrwpq:4; by a potential difference of, say, 0.10 V. How much greater would its final speed be if it is accelerated with four times as xhz qqa+p4nw:r ef5;- much voltage? Explain.

Is there a point along the line joining two eqxka xzyi7c1/dcm -p(n lo i7e9 fh142pual positive charges where the electrkeacn4/ xm11 x(p dz9i7-oic2pfh y7lic field is zero? Where the electric potential is zero? Explain.

Can a particle ever move from a region d3x7(a fkyxv7 of low electric potential to one of high potential and yet have its electric potential energy d(f3 x kyv7ad7xecrease? Explain.

Compare the kinetic energy gained by acf0qw ;st;ffr ;wjh /l61 ul7a 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 equipotentialmx) v2zb 2ti4t uv0r3m lines cross? Explain.

Draw in a few equipo7e5lq 9)jqk lytential lines in Fig. 16 – 31b.

What can you say about the electref 2*ve98 rk/o*mcbhaic field in a region of space that has the same potential throughev e*9bohf8*k r/cm2aout?

A satellite orbits the Earth along a gravitational equipotential line. What shap2n twh-udil 6q9qd :d3e must the orbd6i9ld2d-:hw t nu3qqit be?

When dealing with practical devices, we often take the groa 8a+u.v-qw)3 )zxl8bw pisco und (the Earth) to be 0 V. If, instead, we said the ground was how would this affect (a) the potential V, and (b) the eqawpa.8z3) sl+ cxv u-i8)bo wlectric field E, at other points?

When a battery is connected to a capacitor, why do the two pljvey 3a3 vt23kates acquire charges of the same magnitude? Will this jve t23 3vya3kbe true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on thejl-h ddl z1x +pyg0;r7391w1gloc vxn size, shape, and position of the two conductors, as well as on the dieleploy1w0j 9c;xx-+ lggrdz nhl13v 1 7dctric constant K. What then did we mean when we said that C is a constant in Eq. 17 – 7?

  How much work does the electric field do in mou/mdz1 (nh+llving 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 more4gd .o.+b ,iu ebmj26cj;-y6f lswu ving a proton from a point with a pofb;6j4uw-,6dy2mc goe. j+ule b i.s rtential 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 joule(f7 )t4s/cdn z ilvu5gs and eV) if it accelerates through a potential difference of 23,000 V (zl fngcs)ud7v54 /i tin a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires qmid5eb tg-5rq3sqg 765y w0f$7.45 \times10^{ -16}\,J$ 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 tw z6.yq7* bmdxmo parallel plates 5.8 mm apart if the potential difference betw6m dx mzq.*yb7een them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of zfh dt64/se ;lcuy/(i 0- nsgv$640V/m$ 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 bat+/a6mcb2gtlt g( ,q h(cp;iq ntery is $1500V/m$ How far apart are the plates?    m

  The electric field between coq(g m bso4 5z7wefuso82*h wux6(7xtwo 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 helium nucleusq/v2 /lhiu hc qgccf.7dv; 9p3 $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, are separ13a5qg7. wm eh4dh g77vb svsxated by an air gap. How small can the gap be if the air is not to become conducting by exceeding its breakdown value odvav w g5g x4 7.bh7ms3q1he7sf $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force eim4hk6a .b7jq y;f7za8xqy: 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 kin0 j- sw*syea--o;dtvu)be5esetic 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 3.2 kenp 4 q::j/l r a(dti-xs4nav*mV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a 2/m mm:)d-w9 rqssqxxhelium 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 cmd d-5j yxfijs 7(2ae71sd r*wc from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electo2 p4mqyz0+ kvric potential of $+125V$ at a distance of 15 cm. What is Q?    $ \times10^{-9 }\,C$

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

Draw a conductor in the shape of a football. This c s md h7z9wq mssut;;gr:e/j7*onductor carries a net negatitw*:rzmse jgsm7;d 7/h suq;9ve charge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a distance ofozh 8 ydwpc0iz1y4 lh/0 zl,y3 $ 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 side7pd+)w 2e9 1 x5cnlurcq3; ixnbhlv4 p L as shown in Fig1picrxhvn9 3u cp2n ; 7lbdl+x5eqw4 ). 17–25. 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 frokf3l4izdj- 8um 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 a great distaniu 1q5(6a fbsx/ gy3oace apart to g/o3bufa sa xq61y5 i($1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which 8x7yf3ifhh2)yp)6 ek n 5xbvp5mmv(qis 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 ba3d;d9l )qfu pe used to accelerate 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 sepat2f ao+img;.7smvlqp8m -ia) v*div-rated by a distance d, as shown in Fig. 17–27.*m gqv)v7m l-2 ;-aif voids.imt8a +p 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 orbits a proton (the ++w9 dl 1.*jc nxjigvl.(c l:qftv+h gnucleus) in a circular orbit of radiufcxv+.:n. ci(jwtg1v +lg*q+hj d 9 lls $ 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 prvb*l ch/z,*z)nm ds 1pfdd7(t+4k 6lnxeqai4oton 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 dipole m59 bqfd(mxrb1s:8 mn 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 vecteco.xh dv/z) 8rud+rw7p-iy85m r rwloiy208or, 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 soyw+d)yw88rid/ux58 mr 7hro2cz0- .i rvle pum 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 capacitoev22qb7ofrk 8 tb0n+xr 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 capacl:p12cnyzdqx/x;y5 qq1mz6sitor 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 l3lnv /:lr am8minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two sr6;hh/4njwt/9+c qt vol 2 sephort sections of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is the capacitance of the two +n c4wevsrtl/ phh t9 ;qjo62/wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of a 12.0-V battery when i qumpo1x hyo/ 4u604tx udeep*25kt+ot is connected to dk21pqu *eho5 0464m+ut xto p uexyo/a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desirea6t9tfg ib.9 1q9bbb sd. What area must the plates have if they are to be separatet 9ab 1b.9 sbtfqbg6i9d by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacita ;+le+r uqu,for 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 nee 9 2bjyqv70$8.5 \times10^{ 5}\,V/m$ 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 oppositnej * tc:-;soa m+ n5t*et9mnee $5.2\mu C$ 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 n/8(oa 2pjauqa $0.80-\mu F$ 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- hu9 9/f w.v8uyrc7+wxp8xkn cV battery (Fig. 17–29a) and then is disconnected from the battery. When this capaci +8xwwruck yn997 v/f.chp8uxtor $(C_1)$ 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 tworhjxslo/mi(;mt i9 z g3/) k9kn x5o:y square parallel plates 5.5 cm on a side that are separated by 1.8 mm of paraffin? ir9xni5g/)khm j/oklty 9x: o3(m sz;   $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a rarjem4+o9qr 2f5 ely q6dius of 5.0 cm separated by 3.2 mm oq5 l qjry 269r+oe4fmef mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap ca+/u: 4.ylj, dvum;bd i0 tivzcpacitor is connected to a 22-V battery. If a piece of mica is placed between the plates, how muchuvtdc/i.4iulm :b,z ; +vj0dy charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a paper-seps 5aso19dhg skp,4ke4arated $(K=3.75)$ 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 e wm9 t*ss:z)grnergy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heat yeud6l; z1 qw+vo-ipqzl+13r/lv;srt that is beating erratically. A capacitor in this device is charged to 5.0 kV and stores 1200 J of energyovzuq/-li z ;6 1r1 +w+t;pe v3ylslqd. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between te+g6-gjbnu lk.c ;itp fc/i b:1tb4z7wo square plates, 8.0 cm on a side,c6/7kzln t+bu : gtfebij4i-.;gp1cb 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 assemblezh7qg;p dcpcl:mht )p vo(,- ie0ci7/ya0p1 c d by placing two 9-in. pie pans 5 cm apart and coi0i cp/7 pe(7l;h0q)tmy:, cdv oh1gp pzcc-annecting them to the 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 capacito- pc iq8q3a vr*fk-3-lltbj6jr has 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 changzpipwh u.3l3lc,,c: 6x/ sigfa2apx 5e if (a) the potential difference is doubled, and (b)s35ulx3a:z,/fch . p xwgi p ,pal62ic 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 are accelerated horizontally by 7.0 )v /9*-pqh0cavdtps vkV. They then pass tc*vq vt-0p/ ahpv) ds9hrough 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. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 30v nvu3*,iiegsb x* b6.0 kV in a CRT. The screen is 30 cm wide and is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizontally deflecting electric field vary to sweep the beam fully vv *i0*e3 3bxiungbs,across the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from rest acquires 6.3 keV of KE in (rgej 5lz/+l zojr6 zs00w /yvvpq7y5 moving from point A to point 50z /pej/y z+l60gz(oq ryw57srvjlv 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 transfersvq .mleuhq6iy ) k:mv5- /np(u 4.0 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’s surface whose magne fk, xaw9-ce;i. (; z;njowfaitude 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 acce ivjf97)a) ji2j3bjeo lerated 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 remafii3b7oj)) je j9v2jain stationary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough stored energyz+lt.tt0l g- ms73o.nuhta e9 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 bapy0:ugfna/t;oe )( sxrd qcbd- :72stttery until it is fully charged, after which it is disconnected from the battery. A slab of paru 7; deqsb (adopn-sgcfrtx::t2)/0y affin is then inserted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down i 2gi.cyt izt*z1 bw)6ef 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 ax o,(car 8w7vhiou 6p6n equilateral triangle (side L) as shown in Fig.o v66u(,xipa 78or chw 17–30. Determine 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 battery. ele ci8h*9pdkgn4x ))If a piece of Pyrex glass is placed between the plates, how much charge will then flow from the* hk p)8ce)4dil eg9xn battery?    $ \times10^{-8 }\,C$

  An electron is accelerated hor:7qhm1ujlrzrg f (t jsu;7nl5jt6, 3 nizontally 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 dit 7nuq :rs;lzg nul(,3m1 5h7j6fj jrtfference 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 capacit d*xpg(trtpoptm4 (j,z1 2k )9az op9tance $C_1$ 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 you want to mak :k47gpzh:3rjbjt ),u:.lr ecbj) yb ke a 1-F air-filled parallel-plate capacitor for a circuit you are bjb.jc rz ph4:,b))uy7reg : :klk t3bjuilding. 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 th 8o0.c,v8wg) iu oscrbere 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 t* ui ,rco(,u k+xvk0*zcm0a opulsed 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 between the Earta0bhmkb raa4 6wpo;kg2s+r10h and the bottom of the thunderclouob0a+6mk sha10rp r2b4kw;g ads can be as 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 pi7iktlvfejhurdo6onfs 8, k8) 8)q4.rovides enough energy to some electrons in barium7hu6 st )vi .fqkf kol)8ioj,e8drn4 8 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 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 as4d1fpopf( v9n 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-a+b 5on 7os4as t/;mt(s)hilxcm-diameter coins separated by a 0.15-mm-thick piece of sbila/ sox4osh7(n+m5 tt)a;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 plaob:is5tlsf, i-ec z/xdx2,a -te 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 charge-ip1sj 0vn f1es 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 ahavg3 nq;+tt ,dii.5js 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$