If two points are at the same potential, does this mean that no work is done in+x orj3g-h z*)dy4thl moving a test charge from one point to the other? Does this imp- rd4ljyt)3xgho *hz+ ly that no force need be exerted? Explain.

If a negative charge is initially at rest ik u(m udtw08(3/u jlltn an electric field, will it move toward a region of higher potential or lower potential? What about a positive charge? How does the potential enerw3u tll/d(t0 8(m kuujgy of the charge change in each instance?

State clearly the difference (a) between electric potential and electrrw)hzks + 5*rmic field, *5 zk+ smhr)rw(b) between electric potential and electric potential energy.

An electron is accelerated by a potential difference of, say, 0.10 V. How muc)+ y) djumbs,pnl,2i2 bnkf x;:akv4ch greater would its final speed be ni:b,b)cmpakun,4ksfj2 yd2+x)l v ; if it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining two equal positivk2e .soos2l/0 w8g3dijed 7zse charges where the electric field is zero? Where the electric potential is zero? Explain.e sdei 0.dsws 8zl2k/ogj32 o7

Can a particle ever move from2(vr4:2jl.cyg ia tt j a region of low electric potential to one of high potential and yet have its electric potential energy decreas4(jty:.tv ij gra2lc 2e? Explain.

Compare the kinetic energy gained by a proasap+3 *1 2vs)iz(*fz49sgj feesra lp)bq)k ton $(q=+e)$ 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 ls4m9 1;jo2c8 )lby9mvc 4cyvd0y yxvvines cross? Explain.

Draw in a few equipotential lines in k d(50n0bp e4 jzjh9bfp r(+vtu4wx9tFig. 16 – 31b.

What can you say about the electric field in a region of space that has the 3. (2um9g rcxnsj cw9tlj,4mc same pot,24g3m j mtsuncj.x 9l(cc9rwential throughout?

A satellite orbits the Earth along a gravitational equipotential line. What shap9nnc3o ilk--k 0kg5tob te+ /fe must k fbg03/- keont 9t +c-ik5nolthe orbit be?

When dealing with practical devices, we oftentofu +qk+ zo wtr.z)9*z7i;he 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,*t q oo9ezzi)t +7+h. ;zfkurw at other points?

When a battery is connected -.(ru-oqwml uh 7wa-uto a capacitor, why do the two plates acquire charges of the same mwu-hq. --(l uur mao7wagnitude? Will this be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C d 7m*t7d+ei. 3 m dh1,ed*z)temssaitnepends 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 *m7 )disn+*se7 .h3e1tmztdid, emat C is a constant in Eq. 17 – 7?

  How much work does the electric field do in moving a ri/* dccb9yj 7$-7.7\mu C$ charge from ground to a point whose potential is $+55V$ higher?    $ \times10^{-4 }\,J$

  How much work does the electmp)9p4p3(7aziw pxgwo *f- 6+yb mcoa ric field do in moving a proton from a point with a potenti- ci6o79fya*p3x)(abp mgzm+op p ww4al 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 rf/7cd8c5o /*yhk p rxa4+v ;3iusd s9gsu2dfjoules and eV) if it accelerates through a potedc97 r8hi4 odf5sf gu3yc2r/p+vu sa*k/;dsx ntial difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires8vg 7rc qt+q68fueck9 $7.45 \times10^{ -16}\,J$ of kinetic energy when it is accelerated by an electric field from plate A to plate B. What is the potential difference between the plates, and which plate is at the higher potential?
   V
plate ----待选择----AB 

  How strong is the electric field between two parallel plates 5.8 mm aparth7lp0 yx5 (bqx7kp sx: if the potential difference betweenppbyh77lxk 50:x(qx s them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of (nn+w;xf g- wz$640V/m$ 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 battery6 ;f oim6hcpw( is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connec9opme0b7hn. j p 6k/ckted to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to giv1n2u yus :(n2aflpa1 ke a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, are separated bw0r6*pwe aftur6r*uwrl s357y an air gap. How small can the gap rwaul s3fe rw*put 0rr* 76w56be 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 toqbx56: ft5qp,l8iqa qv )i zs; 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 kine5*18:nv ytnbo0 in ndxrjn3ofb7. 7 hptic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a protdpa:4h+w 7yle.g/ rq4;t bmtqon whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (whichi;vmf )e1*ywtph 8z*g is a helium 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 electrict5do6cgt.93 p qn zjo y;u7jgy+)vr6a potential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric po/eh;mnu/ 6 igto5 ffmy(o ,d1p q-(mzgtential 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 conductor carries o6,f1 x fq9xlua net negative cuof,xq6xf9 1l harge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electrtg8)h h)*ipft6cnthu xl(1s - ic 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 arraj/hrqi0-ncx v*m+mxd4s k7 l ,nged at the corners of a square of side L as shown in Fig. 17–25. What is the q -hsr*,n+7mxc4iljkvd 0x m/ potential at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rwk1. xxixte42d:(dz:j2x(zwmb/gs eest 32.5 cm from a fixed point charge with $Q\,=\,-0.125\mu C$. How fast will the electron be moving when it is very far away?    $ \times10^{7 }\,m/s$

  Two identical $+9.5\mu C$ point charges are initially 3.5 cm from each other. If they are released at the same instant from rest, how fast will each be moving when they are very far away from each other? Assume they have identical masses of 1.0 mg.    m/s

  Two point charges, $3.0\mu C$ and $-2.0\mu C$ are placed 5.0 cm apart on the x axis. At what points along the x axis is
(a) the electric field zero    cm leftof $q_2$
(b) the potential zero? Let $V\,=\,0$ at $r\,=\,\propto$.

  How much work must be done to bring three electrons from a great d))td67be8m+syfpw3yivh vid s ob ip.0f05h3istance apart toy80is yht bmhw+ .d5) d 60fef3)3vvboi7 psip $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm north pe3s;cr vxvt()o3 :jg 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 prorfd j)yrhr/,(x.c-tu: lk 0:vo q3sm q2;vmivton (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 sho -z8siciofws t, 9xr;6d+):wee -b uecwn in Fig. 17–27. Determiiw fted ier)oc6 +w9,- ;ze 8c:ubss-xne 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, anuhf lx.qcg 7yad l966)i7-m kj electron orbits a proton (the nucleus) in a ciu 6l.yj mkil9d6a7h c7q fx-)grcular 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 protoa6x m3 ,olb2fxn 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 sg f;f:xmbz08 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 thew)bzmd58 pyid 0rp /g/w2 +uivd.+e lq negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be considered as the vector sum of p0 /gyd.+/ilmd p+iu 5wv d)w2bez8rq 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 capa(8 ubxb98y )njjwa.3o7i k vs4y9bgbi citor 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 hold ww b(b/lt2 (wy;z8,jp.con o f$+2500\mu C$ 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 minusb(yj -xggg 4 oem-b io;cq *p*tv1o4e2 charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two u7u,0b. zjwqyn09dv f short sections of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC.w7zu 0. u09vy bdj,qnf What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each termc esmu-r)djlu8 v8v 69s:1ka qinal of a 12.0-V battery when it is connected to a c)lj-veas uk r6uv1q9:8d8s m$7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates have if they +d 0s:8txu plqz* ,zxgare to be separated by a 2.2-mm air gzlxx8 , tu 0zs+qd:p*gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor inddsfn9/qe(f7c8 li rlo3 l;8 vcreases 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 ofbys-io; ./9pys7o pd 8 *xigrjz9x9pp $8.5 \times10^{ 5}\,V/m$ 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 opposit(xfn+8go dt 2 c52ox srzw3o8ee $5.2\mu C$ 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 +ccvvz2 :za g:plates of 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) ai:pw 3bt kukcese :wk*20o, 1cnd then is disconnected from the battery. When this *e2ki:t :cewk uk,bc0s o31pwcapacitor $(C_1)$ 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 pal( +o37zz -5ymfsouns rallel plates 5.5 cm on a side that are separatem5-7ufsz s+oo l3 y(znd by 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plat(v 3ri 9hass8;rk5ui (ou 6(npt/g3+v vbydfnes with a radius of 5.0 cm separated by 3.2 mm o ;fb3vyun8ohvd 6iv/ur(iran+t5k(( sg p39s f mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connectedg.vu0ywh14 tvr fo4tqr +w60g to a 22-V battery. If a piece of mica is placed between the plates, how much charge will flow from the byuwv 0hq.t6 fro g40v4r+gt1wattery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a paper-se nup2r4ho)/z( iz8uu jparated $(K=3.75)$ 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 is store+(hqqtid)sg vsa )+6uhbv, 0 gd?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shoc (uo+ath.c(w)p2k cardgstmo1t) / 6ck a heart that is beating erratically. A capacitor in this device is charged to 5.0 kV and stores 1200 J of eco1atuwr/+sc t.cgo)2 h6 d tp )ak((mnergy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field betweu0p164wjxzk y4f q/ aben two square plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on the plates are equal and opposite and of magniqy /w1a f4x4kpzb 6j0utude $420\mu C$.    J

  A homemade capacitor is assembled by ps;h3oa vg+ a7+t hww3qlacing two 9-in. pie pans 5 cm apart and connecting them to the opposite terminals33 a +h w;otsha7gwq+v 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 hzor u ()s9jb7p55h3vfr tz w (.vzm1gxas fixed charges $+Q$ and $-Q$ The separation of the plates is then doubled.
(a) By what factor does the energy stored in the electric field change?
(b) How much work must be done in doubling the plate separation from d to 2d? The area of each plate is A.

How does the energy stored in a capacitor change if (a) the potenkbv)k 2jss +h3i5 4wzstial difference is doubled, and (b) the charge on each plate is doubled, as the3kvs2 4zsw hj+bis )5k 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 horizontg ro-*j0 i7m+ukboc7s ally by 7.0 kV. They then pass through a uniform electric field E for -imb*go0 +7jc or7suka 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 6.0 p-hhn sz,6 yhhzk;h82 n1c6rq 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 across the scrqp8z2-h1 kc6 znhhyn ,shh6r;een?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from rest acquires 6-ajprb/uvx+, :e : fhc.3 keV of KE in moving from point A to poin:jhbu xfe,:p+va -cr/t 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 Clw0a8exv-f x31gk:-pxv.e g d 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 magnitude is 6g5z 7a sznjq8h9xul6/8nw u sabout $150\,V/m$ How much energy is stored per cubic meter in this field?    $ \times10^{-7 }\,J/m^3$

  In a television picture tuozm3 g,/2mp wmbe, electrons 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 potentm 2omwm/z,3 pgial 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 water from 21g :-hm ejt*s3r8n5hfb/(plop$^{\circ}\,C$ 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 funio. nh+o)a .klly charged, after which it i+o kai.n)ho. ns 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 theud96i(v-xs:y,4y mou demc t, 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 equilatelt w7wr / 23jx qaqmtu* +**bj)6wgvxdral triangle (side L) as shown in Fig. 17wqdwx *j*m/xut37 6jlgt)a2 r qb+ v*w–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 coc59sy7 r z ka6rol09j2 (ubwwhnnected to a 9.0-V battery. If a piece of Pyrex glass is placed between the plates, how much charge will th5 0cw y(2j7uhw 9ro9akls6bzren flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in a television px; .gl5 ncvg+nicture 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 (Fig. 17–31). At what anglx;+cnv .l 5ngge $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capacitand m1u6oxrt+l;(fv- p kce $C_1$ 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 t6 xxa exa2bx3r77: 6aho(ghddo 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 the plates? Is this prab7 d ha:(6de xa 62x3orgxxh7actically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of ty-7+ i vyu6vf ylmc1fi;0wxa/he Earth there 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 forl2 zply/ . 7bwgy1ge* +4thhsr a pulsed 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 betk idd+ic6p-be,n 0xq9ween the Earth and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are typically 1500 m above ,+0 d-pc ibikdn96exqthe 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 enou9nqsd i0zy/d, gh energy to some electrons 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 stopped, and return to the b0, inqsyd/ dz9arium 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 fx qlk5e1n25 e-x b;xmerom 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 fr gkt:. ls(8,wnntk ewd)x2; ylom two 1.1-cm-diameter coins separated by a 0.15-mm-thick pi 8dlngw:e 2(.,wt;n )ktkyxs lece 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 with plateez t4dis mh6w1 9/qwd8:dklh+wu06 1z eh a;io 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. Tpe) g(fae, (olheir 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 mv+s:5 4ey)op l3 7f1gddlasmFig. 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$