If two points are at the same potential, does this mean thc :bl+8v1xj 5l)p r6 o6l i wal9m:1q-qrtksumat no work is done in moving a test charge from one poiqt+rlo p sqx61abi)1mmrklwlu 6:9:c-lj8v 5 nt to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at rest adzu/q o -dmfn0fvj0q:bi)2 .j7/urnin an electric 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 chargij7d0jubdq /ou -fnfv r z/qm.0a:)n2e change in each instance?

State clearly the difference (a) 6qt 12 uloyb48klx,; ju6whz tbetween electric potential and electric field, (b) between electric potentiujl46q u1x ott ybz wk6hl2;,8al and electric potential energy.

An electron is accelerated by a potential difference of, say, 0.10 V.5p 4ktuu h.j bb-x5l:v How much greater would its final speed b v-bbx.5 ultu: 5hjp4ke if it is accelerated with four times as much voltage? Explain.

Is there a point along the lin,d;n 4(z e/.zvwqvmdvqq 0inm5s m/v/e joining two equal positive charges where the electric fie.md /q vqdws0emz54(;n/z,iv/v nqm v ld is zero? Where the electric potential is zero? Explain.

Can a particle ever move from a region of low electric potential to one of hig x,6he nr4)m 62hhvqexf-(hb nh potential and yet have its 2m)h 6(xrxhfv bq4neh6h,- neelectric potential energy decrease? Explain.

Compare the kinetic energy gained bykjn t:(c5 fmgc d45;hq39mm3st gf6di 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? Exp gs//hw3a;4t,t jxdchlain.

Draw in a few equipotential lines in Fig. 16 – 3w;cy-4tp e.gycd. p4 n1b.

What can you say about the electric field in a region of space that has the pht gy.w7 e;vr ,,dv-.b7etotsame po v,-t7t.vp7.t br,degeywh ;otential throughout?

A satellite orbits the Earth along a gravitational equipotenti avgm+u5 .6tm w ++xlky+-xjiqal line. What shape must the orbij-5ymgmkv.iu + +t +wxxa 6lq+t be?

When dealing with practie/tjf 5,a ue0 ei htqzcd;zm e 5+r5q6lflz30*cal 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,e,l0 l/ ztem5qze05 ;6q tcu ef+fd3*iar5hjz at other points?

When a battery is connected to a capacitor, wh3q/:45c2 kjl2hjqr r*x n wwnuy do the two plates acquire charges of the same magnitude? Will this be true iq/254xk3c q jrrl w:2huwn*jn f the two conductors are different sizes or shapes?

We have seen that the 2ym2 vkdepfpfa1xs3:9fj- k )t:y sm7capacitance C depends on the size, shape, and position of the two conductors, kvf2j xm3 y:p1ypea-dkm7f2s:)fs9t as well as on the dielectric 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 moving:dr/u/ b(/ k )tb utcdg*l8vii a $-7.7\mu C$ charge from ground to a point whose potential is $+55V$ higher?    $ \times10^{-4 }\,J$

  How much work does the electric field do in moving a proton from nburtb brjyp 5ox9wt,(583 .q ,c:inaa point with a poten,q5p8r 5o:(u jt3ab b.bnyc xn,r9wittial 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 acceql8-d9mewpcff(- wo : lerates through a potentiaw-9:( w -o qfcf8mpedll difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires 4 y+r/w6 fmv:pj-ezij$7.45 \times10^{ -16}\,J$ 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 b6yv8b fmdeh)fk.i,d5 .nf lw5 etween two parallel plates 5.8 mm apart if the potential difference between5w. fv,myknfd6 )85bfh di.el them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of d/36++oe bpaknmdw u4 $640V/m$ 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 bate 1zrj:m,9shqv + h4dttery is $1500V/m$ How far apart are the plates?    m

  The electric field between tg9p cmh7bq,+40 x lghvwo 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 heli.wzkebvqu l /;lq6.g+um nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, are sep w n70m1e:ae*umjx; tuarated by an air gap. How small can the uu* 0mx;t eae 7:1nwjmgap 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 force to7 /.rlxa n5s;myb9ea4vlqls-(d2 god 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 energvd:x n1b5jk(ly
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a protonby6k o1+hv( se whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nuclou,;j4)uy2 jy(dkdfgeus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric potential 15.14vcd +st-kxewh0 ad p yx2p8;0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an elecb.qy6 jga7s6v2j.sl um 2 t2a)tc0osatric 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 shaph ,6xx h:yh:6pg,xtjbe of a football. This conductor carries a net negative char:,: 6x gh x,6tjhphxybge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electrio/p6z)v:w i phru w,/dc potential a distance of $ 2.5\times10^{-15 }\,m$ away from a proton?    $ \times10^{ 5}\,V$
(b) What is the electric potential energy of a system that consists of two protons $2.5 \times10^{-15 }\,m$ apart — as might occur inside a typical nucleus?    $ \times10^{ -14}\,J$

Three point charges are arranged at the cor1 1k2+qat2aioazk:0)d k f9 u4r wijezners of a square of side L as shown in Fig. 17–25. What is the potential at the fourth corner (point A), takingi2owfj1t9 0+e kraiak1k:q4zz ua2d) $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed2kx6vw0ar;- y l0gk bo 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 bp-njaxb) r h w1/gpn40ring three electrons from a great distance apart t wb-n a )1jprgpn/4xh0o $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which isninx/76dzo x , 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 accelerate a protfa 9/m-i-gic xon (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 in Fig.nru;py.u(za ; 17–27. Detu(a;.un rp; yzermine 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 v* r-e.gr -e74h:r 72xrzunbns t3kppa proton (the nucleus) in a circulpk-7:3sr htgne7u*rz x .bn2r4e-pr v 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 proton arkq i 6v1d0h.resl1 *ilhi3lf4 e $ 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 dipocv bs/ orl2bboy(i;6+ z 5udg3le 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 yu jqh3d/)skiqi:0r/j ))us*dlkdm 0the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole momendj:0 /)i us*l)d dryki03/qm juqkhs)t 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 capzi tb 52esold1g/s8i7acitor 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 capacitor holnd64iarlwc. 3/9vj po d $+2500\mu C$ 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 * xc i:6*fjgeysh9/lpx0g7t.xus(acof $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of parallel wire iyk; f(;d)/ 04bqblc6xyedm bln air is 120 V. They carry equal and opposite xdyq;bm;fb0)(4bd lk yc/6el charge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each ter5ldvf5y ll/8e;vb7 heminal of a 12.0-V battery when it is connected to/75 hv ld5f8ybelle ;v a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. Whatyua* b- i bj2s6uz:rb8 area must the plates have if they are to be separateu2abbu-:* r6i jyzbs8 d by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increas wder96n g;d)6emmx (px7ukxa1cv+-oes 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 tbb2ke1 *1jao l,kjv/ j,:qvb$8.5 \times10^{ 5}\,V/m$ 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 oppicw6,+mixj2 q.az..td4 bjy gosite $5.2\mu C$ 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 ;zatq2f 5-n ;ie:b 0q7jdgr;4qnjclva $0.80-\mu F$ 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 )khud x+6i w b.vuuzndk:/ie +gt7+p7b*rq.n is disconnected from the bake ui .+twnz nu7v)u 6q*b.xb /r:+h+pdkd gi7ttery. 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 on a side that 2*ahc+ i0;xl1fvqm j/ l1moh ware separated by 1.8 mm a2h0l o/lqm* imc1fvxw+1 j;hof paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a radiuspt vah/q4i0b- of 5.0 cm sepqi/0thavp - b4arated by 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 2 39ah1hjsi (vem6z. bj2-V battery. If a piece of mica is placed between the plates, howambzjv1 e.i3 (hs96 hj much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a pap.jkr j9.gzdd/er-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 much energy io ,+vu mge)q0es stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used l- 5gw5y4bok9b7 qix dto shock a heart that is beating erratically. A capacitor in this device is charged to 5.0 kV and stores 1200 J of energy. w b -7gdlbx9oiy54k5q What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric fie 2 b9alotso1c,cp:iq1ld between two square plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on the p,2qi9:p o soctlcb1a1lates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assj wj2h*-srq0sembled by placing two 9-in. pie pans 5 cm apart and connecting them to the opposi q- sjs0j2w*rhte 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 fix g75py ri 2jmsj4v/t0l8hu(leed 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 sto6(hmr i) v/, iivi;xwvmn4 0aared in a capacitor change if (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as the capac(w; mv)haiivaixi6 r,40nm /vitor 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 pa:z3 4st3ezwn6 i,ix (l rry1shss through a uniform electric field E for a distance of 2.8 cm, which deflects them upward so they reti3xr: ,l wnzrsy 14(z h6is3each 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 2anzw/vx:p k(uk,9 3ft6d-osnt ts4e 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 acrotws,/-k9op6k 4ed:fv3(n uaznt2xts ss the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from rest acquires 6.3 keV of KE in ljl/ ke y1-8d cu9w-xpmoving from point A to poij c9d--lp yek8/ lw1uxnt 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 and0:6 22 uupk,j7zit.x1dftv9tl wy zti 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 magnituj0lpf2/40w fg w4cmjyde 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 accelerated by thousands of voltsg u;v 7q z8yp0ej7sl.t 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 z.l0 ;8 vuejg tqsyp77would remain stationary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough 9w,)wl2vc.bktwtz x5; xuzp frsv: 5m.q b 3(ostored 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 to a 24.j7+unwau o* +g0-V battery until it is fully chargedg7 wj u+u*n+oa, after which it is disconnected from the battery. A slab of paraffin is then inserted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down if the electric fieldk8l;vidt,z :qraw6i5o; cyp5 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 1mciv9, kxy q+qk-mzb3:rv0v shown in Fig. 17–30. Determine the potential at the midpoint ofz bq:vv q-, 30m9mx1ikkcyv +r 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. If a piece of Pyr sm.6uj 9py8yiu 4w8 tml2z6leex glass is placed between the plates, how msy9yjltmz . 6w2 u6up8e 8li4much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in a :cgu)zxx+u n.j t,pcfa*2j 2tgt c-8 ctelevision 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 25g gcucz-p)t t.jfx,xn caj*t+:c u8220 V (Fig. 17–31). At what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capacnvbiecir:f0(( xv 7 +0 6gzlh:ja/igvitance $C_1$ 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 faraf gho th02(zyk04ih0td 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, suppos20(zhgih0h ytf4otk0 e 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 electrmp/0 p7lic-rrfc* 2 e(lmlnd7ic 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 pq/+a qk+ 95nytfi st. q 3j*z/ipp w:8uq:lpbxulsed 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/o y mwyz4+v1a the Earth and the bottom of the thundercloud+/wzva1my4o ys 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, ultravdb;n3u,58uo.jzojg n( e- ugeiolet (UV) light provides enough energy to some electrons in barium metal to eject them froun8 oe, .nb gou(ezuj-gj5 d3;m 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 p26 ce2nn;zyran 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-m9qujwl9 4b :ucm-diameter coins separated by a 0.15-mm-thick piecbwlu: 9q 49ujme 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 capacitor wfo1w4ju* gm- )uz ,gxtith 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 chargwpuuyxw3x y,j *j;; 2qqxi1 hl ft*.2xes 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 u3osmn7yh3f+7d hmy(ig. 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$