If two points are at the sa6 v dsm-;5ntochb)z++a)il2j g wmxl6 me potential, does this mean that no work is done in moving a test charge from one point to the other? Does this imply that no force need be ei6m;6nxsvjmgw+a l -o)z5hclb+d2t) xerted? Explain.

If a negative charge is initially at rest in an electric field, will jlve27wvl 0 h,8yx3iax-d2f i it move toward a region of higher potential or llvw2, 7jei-h2fx a0 vi ly8xd3ower potential? What about a positive charge? How does the potential energy of the charge change in each instance?

State clearly the difference (ab3eqgh4jny,l3 c;9d v) between electric potential and electric field, (b) between electric potential and electric potential ener3c4j e39db,lyg; vnhqgy.

An electron is accelerated by a potential difference of, say, 0.10 w4 5 brxuim )zw,.0acqV. How much greater would its final speed be if ia. r 45xcw)bu,iwqm0z t is accelerated with four times as much voltage? Explain.

Is there a point along :27u/ 6y iemlptwjg epf5dh: (:g.kyz4ioq k5the line joining two equal positive charges where the electric field is zero? W.: m(7yjdyhikg 5kqoe pu 6zl/f5t 2g:pw4:eihere the electric potential is zero? Explain.

Can a particle ever move from a region ld2ik26zo vc;:a-cneof low electric potential to one of high potential and yet have its eledc-i2co en62l z:;k avctric potential energy decrease? Explain.

Compare the kinetic energy gair 5;ggdaw-oesa(mh /o8n(zr52*h; xc1hiex o ned 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 line(.szv5x s53+y2j7jl-ble :iqfq 1k o ok-ckz ls cross? Explain.

Draw in a few equipotential lines in Fig. 16 – xjs6dqa r:q7dt2 -l,ske)t0f 31b.

What can you say about tq3a 3c( eomj9qhe electric field in a region of space that has the same potential t 3c(q mo93ejaqhroughout?

A satellite orbits the Earth along a gravitational equipotentia/fn m fnug0d581othkcdu: k ps1-d(4h5z v7etl line. What shape mc/fp4 hz5 0g-1enntfok1u v78d(5u :skt mdhdust the orbit be?

When dealing with practical devhk st, )c htyv5w6q+s+ices, we often take the ground (the Earth) to be 0 V. 6 w)s,5hctvk h+tqs y+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 plat2 vinr2 th on3gbs8(6zes acquire charges of the same magnitude? Will this be true if thevsb823tonrn2(6iz g h two conductors are different sizes or shapes?

We have seen that the m:rq:se mm-a*( mz8 tecapacitance 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 tha setm:m:q zm*e( 8mr-at C is a constant in Eq. 17 – 7?

  How much work does the electric field do in movig lm1cnp/7*wlng 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 di 13 qj4z;dzuw9x 9nr;7 y dd(.pfjqwjo in moving a proton from a point with a potentialqzn 3 dw 1 ;dp.f9jdjwx(qj7u;r9 iz4y 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 electyv k** 5hpezg 1-yjij;ron gain (in joules and eV) if it accelerates through a potenykj1- e5y pzij h;v**gtial difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquiresnk9ui/siqz-e 3br w4 u ges445 (fs4,b;ryemy $7.45 \times10^{ -16}\,J$ 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 plc+l1d uwy4+a49dcp qv ates 5.8 mm apart if the potential difd9l+ pcy4a du1qv4w+c ference between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field ofqj+t, , mgqp ;w-j;vnd $640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field bet1 j-ug;y41efx9kpa ae ween two parallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates coq,j6m ki9 k*ze )phrs/nnected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference ioq 6zy 4(6mato8nx /jce7bdp1 s needed to give 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 separatl9:y2-(; ccmvh9*-ktp fv0 u ybcsjdped by an air gap. How small can the gap be if the air is not to become conducting by exceeding its breakdown value oy- 9t*jlcvphm c( pb2uv9c0k - :y;fdsf $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an externa*,x t nj/;ny1t4mwlgav;c gs( l force 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 elect1dm+ zw :;syhpl8yom8 xys1e3ron with kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whose d jc+ ,4ogkxk:kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nucleus: z v)f(qz2mt(j2 sqxi, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) 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 cm from a y t7;8e,)9g rw xtg;o q-bokmm$4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric-t54 k59rhk)et.0eh ( v ehk xe3wcmjl 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 conductor carries a net negjme rbbn-f7y68l f72yative fr n7yyfjbm7l-be28 6charge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a dista gxis wgfkpi2::8/ 8v w:xsz)hnce 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 arranmp2kqnni 7 56+b o+swpged at the corners of a square of side L as shown in Fig. 17–25. What is the potential at the fourtmpi+pn6+n 5 72qsbwkoh corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fiknkr: p1f1i0nd;z0o n/ t1dbnxed 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 bringtcy7y k-bd+ogq *z c-*ty(bb uoo ;9o8 three electrons from a great distance apart to o9ktq(ccz8y+d7go;b-b* - ooy uy * bt$1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm north of)hhozoj0agf( +rly :b,*sy(k 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 pfma;d) i s*vac3m,go /roton (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 Figb5k )p8-zpwhk . 17–27. Determ 8 w)zhk5ppb-kine 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 electnl6z,nv.ul k )ron orbits a proton (the nucleus) in a circular orbitz6un, l. nkvl) 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 b jj9djjk6 oeeh8j8a ;r06 ax3uw z8t0are $ 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 dnn7k5sxfn.sp b*zdri8s f2 + 4ue 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, consid oqbrx)jze*z cv/*o7g:r;90osft+bf ered as a vector, points from the negative to the positive charge. The water molecule, Fig. 17–28, haqx*)broz+fgsc/ 9 v7:b*fr0t;o ze ojs 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 capacil 3w a* gs)/d ly1d8kqi/vwgg7tor 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 8:w * /aawfbzohold $+2500\mu C$ 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 chargq1rjk39;tfj w vrsi35u pn /hwv )p-+ees of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of paralc5+g2bwr 3lj tlel wire in air is 120 V. They carry equal andcgwt5bl j+23 r opposite charge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows fr,6)vy 2fv bw+x1slnlp om each terminal of a 12.0-V battery when it is connected to b+w vlxny2 )s,lf6 pv1a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates have if they 0pkc; b1gzh5)7xjt gqare to be separated byg chk75 gq1p0xt);jz b a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increa dt0wq (ts)a 7j-.(mtsjr-ayco jm7u*ses 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 d )dk+ ed/5 oh.ufg2ztphym7 g*u(6yz$8.5 \times10^{ 5}\,V/m$ 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 oppo .np st.g(4i ob(o3gwlsite $5.2\mu C$ 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 u 2fpdmd0x5xka(( *r ba $0.80-\mu F$ 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 8 rqv0 6nm*f 6u.*pkt14;cvwtr pqng pthen is disconnected from the battk1p*fp rv*4wqpqg;6nc t.m6 ut 8vnr0ery. 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 sik s+mbsj/y mo+ *k4hi-de that are separated by 1.8 mm++*/s- hojkm kbs 4miy of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance ofoq i7-x(xuozrh ao/7h862 nuc a pair of circular plates with a radius of 5.0 cm separated by 3.2 mm of mi67nxio-ahxzo (u /uhr2 8o7qcca?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V bat wzzq.wd1y kxub3st9y :( 4*ghtery. If a piece of mica is placed between the plates, how much charge will fyy w:9uz 1bk.hz3(4 twx*d sqglow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a paper- o1 lzm+t gg- /,z2czm0wapcd/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 x.bq/4gltvy ;te f/cgm o.3e8a 2200-pF capacitor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is usede35 kqzdm f-pcjqa* 4zo9ow.8ws).va to shock a heart that is beating erratically. A capacitor in this device is charged to 5.0 kV and stores 1200 J of enerqzz awe34 o5m)fos*pc8j.a- .kdwvq9gy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between two sq 9 m4+ejsasvvg, i(+jeuare plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The chmvves(jea, 4 gj +si+9arges on the plates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in. pie pans trd3yv5q:6 dd 5 cm apart and connecting them ty:dv t 63rd5dqo 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 capacitor has fil e p*n me/tu6r*9x0jexed 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 pot-o:h7tu i+ usico0 nxl7p3qu -ential difference is doubled,0iuhos77nlct -o3-+iu qp :xu and (b) 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 accelerateda6/lj 979 ;1qq qkw.xvvk jfwov gt::e horizontally by 7.0 kV. They then pass through a uniform electric field E for a distance of 2.8 cm, which deflects them upward so they reach the screen top 22 cm away, 11 cm above the center. Estimate the valu1. 9t;ekxwv9 qa/ 7gj wv::lk6qfqvjo e of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a CRT. The screen is 30 cm wid62ml blmm to.ppe m euko:;p1z5ea2b2nur.1 3 e and is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizontally deflecting electricpzm e 5k2omb.m3 n p2olu1u:mte;62p .ea1brl 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 keV of KE in moving from poinpspzh xh:5hdoa 9 +v;3-qqap 9t A to point Bhqa+hd q9 v 5 ops;3:zph-apx9.
(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 4.2 MJ of energy to the Eart64p x7nod8vd f,so/ gvh.
(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 surfac+sr;sk x+ d0uwe 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, electr xk7 4-f0bz*r8wpp gugons are accelerated by thousands of volts through a vacuum. If a television set were laid on its baf g70r - bkugpw8xz*p4ck, 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 electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough stored energy to hea* qos/gqsn/ 0xt3( ff-qc ; 8bhzfc)jlt 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 cody:*k:5ap e aunnected to a 24.0-V battery until it is fully charged, af eakudy5p*: a:ter 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 s4/ph/ ng o3jw9 o wydf:gwcq9g*7z4jthe 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)nh-eegxxnfu) l uojh8m;v)+a y 7x/x/1/h(bj as shown in Fig. 17–30. Determine the potential at the midpoint of each of nb/y lu hf )h/;gxu1em8 n()v oj- xja+7xx/ehthe 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 P :kg:zmjg4ip:tw;e, cs 0e fa6yrex glass is placed betwekwp :gst:e6 gi,;czjf0ae4 m:en the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally froj:i dp- 3dxof6m 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 (Fig. 17–xf63di j-p :do31). At what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capacitanxs6 1klx(h *nrl g/ea d7pt97ece $C_1$ 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 make a 1-Fj7ip1v7 t 2kuv 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 7 k7vtupvj21i be between the plates? Is this practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there is an electric fielfxpa; w)+1ga bd 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 has aojdc1j2vl) j )mdd;(dwe,f0 t $0.050\mu F$ 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 Earth* cuec)* ;gj47xkxm xy and the bottom of the tk7mc;x ux xyge4c*)*jhunderclouds 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 prov-n:jyw c ru+u8.ep -ddides enough energy to some electrons in barium metal .we 8 cp uynu-d:rd-j+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 an identical .x::6xwr ; :lbgumpp4h 0-/cdg yqrym$+33\mu C$ 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 co8 un: 7e7 ;hnsi*x0p qs*tf zcwzj4nr7ins separated by a 0.15-mm-thick p7c:8r 7e;p4siw7s* 0*nnqjxnzhfztu iece 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(hl )z5y: bpyg 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 charge 0w l-i i (z5nbv95m7ghhi5xxrs 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 Fig. ho)sydaw c;wow+81j 5rp2 z,g 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$