If two points are at the same potential, does this mean that no w1tbg, hotkal 4: 3h-vo) vnz d*uo+.dsork is done in moving a test charge from g olv4)vhhk .dtn- :u,t+d*1 oabosz3one point to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at rest in an elt(v. rye3r5 q47f hbtzs8v7ycectric 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 chargt77v8hy 5 crsb(e 3z.qft4 vrye change in each instance?

State clearly the dif9 pv-3sofmmy ;ference (a) between electric potential and electric field, (b) between e39oypf m sm;v-lectric potential and electric potential energy.

An electron is accelerated by a potential difference of, say, 0.10 V. How much 3 yy y6-aqgw*xq u5d)tgreater would its final speed be i)g t6 yd3y-qwx5*aquy f it is accelerated with four times as much voltage? Explain.

Is there a point along the 7ak zxx hm87b1line joining two equal positive charges where the electric fielk 1mha8 7zxx7bd is zero? Where the electric potential is zero? Explain.

Can a particle ever move from a region of low elec0i b+dz me9hp(l:svs/cs 0a-v tric potential to one of high potential and yet have its electric potentiap:+z(mc a dbvls 9e0/hs- is0vl energy decrease? Explain.

Compare the kinetic energy gained by a proton y9u)c0 dd4b q ;vfl8x 1.fieazk+4 xyn$(q=+e)$ 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? Explain.p) 0ob94oy* u4zo 2znt vyfd0j

Draw in a few equipotential jn 0cv)d,kcx* lines in Fig. 16 – 31b.

What can you say abojycr5o sp 6i .awf7a-*ut the electric field in a region of space that has the same potews -ipca67 *5rjy .ofantial throughout?

A satellite orbits the Earth along a gravita zjtv h unnmt 0m 1uhd32jjq.b7;d,omyzt+*,0tional equipotential line. What shapeo7t3uhj* jd jnb,+dhu1n02z, vq 0mzt. m;my t must the orbit be?

When dealing with practicasye 3v5 orwvf,vwhf4 +js1av :du2x -0l devices, we often take the ground (the Earth) to be 0 V. If, instead, we said the ground wa+ - 15ehw jyv vu4ofxvw:srd,32fv0sas 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 plate)*d3-,i5n t pkepiq fos acquire charges of the same magnitude? Wili if ,t3*kepd nop5q-)l this be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends onjfjzz- tp ;*8y the size, shape, and position of the two conducj fzp8j z-t;y*tors, 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 m. 4/ ygpf *5 9qbjaavibiw()saoving 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 a point)/u,ki8e jj shht7t4x with a ph,t4ji xh etu/j87k)s otential 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 ga0orfx gxvwsctjj+ .; ,o,5mr9 in (in joules and eV) if it accelerates through a potential difference of 23,000 V in a TV picture tub jvsr+ ,xr;m.t j 5ofw,cxg9o0e?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires mo )/5nzfnvz km2 k;1f$7.45 \times10^{ -16}\,J$ 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 n vhz* i;qc)egx3i cv7ad5.r-.8 mm apart if the potential differexagncv rez) 53hicdi7-.* ;qvnce between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of g)f(e hk5q*ey;apg3zdo1(qj ,vvey+ $640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two parallelzj*5johsks t tz lmxp ;w6o64p *8,1pn plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field betw9wt- r,3ax0hp aji9/ *tqeexfeen two parallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a hel jb 5hjr bhp)iqdaha 692pim8:s 3d;4dium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 207m repv;yvlrfl9 ,s b+f tk 08buh6;5r0-V power supply, are separated by an air gap. How small can the gap be if the air is not to become conducvrsm8;erl,7 b+klt 5pf9;hbfu60 vr yting by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force to move53mxdu/l uk -d 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 kv;iw j. m7:x73 smssmox:xj9ninetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whose kr zrmi kgylxlry;487vi ;t11ge , lj*,inetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a hel4lrvfx2xd ; s8 sw(20 pml8ixzium 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 cm /3.waxhl fmk6from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric potentiggowkr oexjg +d((1y.5f6* umal 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 tu 3x 5fw8g,vk*w p .0f).eupn;q ocwyqhe shape of a football. This conductor carries a net negative ch ,c.w0yq*pko5;) uqne.uvf8p3f wg wxarge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electri ,3pnibj/,a*w8nsld 7y ypd,n+n ) 3kyr+vdhzc 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 corners of a square of side L asi 3;sh.ta2zv f 4dc6 esvx0o2d shown in Fig. 17–25. What is the pv e2 2azc.x ht3o;ivfds6s4d0otential at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed point charge witiwwnt*q+2: 0cq59 *yvnfhbw r h $Q\,=\,-0.125\mu C$. 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 bre.u.phsb fu 8dm(xse-g3n v29ing three electrons from a great distance apart t sf-xvu9(b2.8 dmgune s3hpe.o $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm nb:99:lb gogtqiz)j 2 iorth 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 proton u;on w,szc0s 4(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 pt3r z:xn y,7care separated by a distance d, as shown in Fig. 17–27. Deter3np:z,c t rxy7mine 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 orb ;40kdd 7li8 bexbjgask2f:zc,n)gn 0 its a proton (the nucleus) in a circular orbit of radius :def7l z gxna;s04 kn8c),2bjbdgi k 0$ 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 ala(.rhhzs726 l g cvv:re $ 0.53\times10^{ -10}\,m$. apart. What is their dipole moment if they are at rest?    $ \times10^{-30 }\,C\cdot\,m$

  Calculate the electric potenb e8cs o*dk: yoj*14ka jryz8,ho 8fb.tial due to a dipole whose dipole moment is $ 4.8\times10^{-30 }\,C\cdot m$ at a point $1.1 \times10^{ -9}\,m$ away if this point is
(a) along the axis of the dipole nearer the positive charge;    V
(b) 45° above the axis but nearer the positive charge;    V
(c) $45^{\circ}\,$ above the axis but nearer the negative charge.    V

  The dipole moment, considered as a vector, points froar5o7ciu4q -5z;( fw efjc l 0irh+i+jm the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be considered as the vector sum of th4f5+ rrhcil ifai(+z 5wjeco u -q07j;e 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 capacitor,dn-e ve*b sbube,5) y 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 ho1yew eerfr7m *:+:cadld $+2500\mu C$ 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 gxarj+ )xlq*0 plus and minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two shoqg:g:c 9gj1a ga7n:g e;po2kprt sections of parallel wire in air is 120 V. They carry equa9 ggn1cg p2o 7gk;a:pge:aj:ql and opposite charge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of v blg0dqdo(- y-v7p/ta 12.0-V battery when it is connected t bd0tdqp/l--ov(y gv7o a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is cmh;z/ 8b2 xus*i f52m ,sgnxtdesired. What area must the plates have if they are to be sepf;x2/b,hmtc2i n8sxs*mg5 zu arated by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capa;z/bg h vnsrh.4 ii*,lh) a)mqcitor 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 :3 nf0q 9pvxwh$8.5 \times10^{ 5}\,V/m$ 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 oppowr0yvl9* g4io,q pb ;wsite $5.2\mu C$ 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 pla;4s za.7nhq q6tn)zb mtes 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. 17–24i f,l(b/6m:nbbahvm91if x a* cn/xy9a) and then is disconnected from the batteb xi*na n6fb(imm l1xcy4vhfb/:,9a/ ry. 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 ty3q0yulbtw6 k,xbops( 4)ga .hat are separated by 1.8 mm of paraffinpb q.sat (u4,l)0bk yy3 w6ogx?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plamh+2. kh wbw7ktes with a radius of 5.0 cm separated bwbkh7m h+k.w2 y 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap cap/ t q k ;a93yb/)uncvphtdc,0jacitor is connected to a 22-V battery. If a piece of mica is placed between the plates, how much char3j0)db,p tnck9qca /tuhv;y / ge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates o5ztwyz;lx ri27qgr4xs;w lxsx 3-9a-f a paper-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 capacilvjps):m-sq h +78ws n-omkc xtk/8* itor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beating /g,;)zxke y3b,5ffc cyl21cwq t2 yoo erratically. A capacitor in this device is charged to 5.0 kV o32;w) cyx q1ec,yl5gz fcko b 2,tf/yand stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between two squ slc ykxm*cy ci: y4*93.hj4fhare plates, 8.0 cm on a siim4*lh: x4*j y3kyyccc.hf 9sde, 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 assembled by placing two 9-mle6qlh4 5j7lin. pie pans 5 cm apart and connecting them to the opposite terminals of a 9-V battery. Ese 4l 7j5qm6hlltimate
(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.vh/mr( -idpj ed 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 capacitqj a8i362xe llor change if (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as the capacitor remains connxl8 3ie2j aql6ected 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 ppn7xf-k i-is2f h*ugc .-f)xlass through a uniform electric field f-h u f)ixnsxc*- 2-lk.ip fg7E 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 6.0 kV in a CRT. The screen is 30 cm wide at pkk* yiz)ng*/s9 s;ond is 34 cm from the 2.6-cm-long dnkzysg)itk*/o9p s;* eflection plates. Over what range must the horizontally deflecting electric field vary to sweep the beam fully across the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from rest ac y0md32hxe,nmquires 6.3 keV of KE in moving from point A to point Bhdy , 0emnx23m.
(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 smezc b7r -pbzn yw/02yn)5s9and 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 mk)j6 0-w d 7pu9 xo/tisqhhk:4l2kc giagnitude 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 tubef35 j/i zj yypt1;4cnimzl*r h0 2z+we, 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 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 statijzzcihn je4/1y3yz02*; pfilm+r 5wtonary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough storn/aqe-szh1 7fta/:by zi* 2zted 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 w,ic4kvic zj*3mh o5d)(b(dl to a 24.0-V battery until it is fully charged, after which it is disconnhwijz 3c,do(k (4 c)5 dvmbli*ected 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 th +) .x fcbzsyjl+-iov;e 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 triangl :znsbv:m+e(spb093iqwnz;j+ 5gtxke (side L) as shown in;e:n+ p sks0xn 9 i5vtz3qmw(zj+gbb : Fig. 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 tol cg+e.t ffijz)szu2 xk1(2l/wy)yp6 a 9.0-V battery. If a piece of Pyrex glass is placed (u)/ltl21f) . s2yg6 yxzj pfi +zekcwbetween the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from re* uelfa mks,sn d-)8h:st 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 Vsa, u*n8lek :dm- hs)f (Fig. 17–31). At what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capacitaww/b; 3oq/) 9jpyk aipnce $C_1$ 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-F.z m; nnx; xvhpl0d3cq*x9ps5 air-filled parallel-plate capacitor for a circuit you are building. To makecnq;hz9*0m l.d5xvx p3x;n sp 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 there is an electric field of abo 0rx1j3:*dvbe:it fqq ut $150\,V/m$ 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 pulsa*ult: bl:18 on 2sos ii6tj6oqgt(h4ed 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 Ea 3gx 6eedrkd( ecm22(xrth and the bottom of the thunderclouds can be as high as 35,000,06g(xrceddx2 e k3e(2m00 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 provides enouo .rl5ej v.6xw*5wsd kxpj1u 7gh energy to some electrons in barium5px*6urjj5 d7l1w vwxos ..ek 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 an iden( 4.uetobpg e 8i04r7nyvut5ps e7d n(tical $+33\mu C$ 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 tqa3mw skhx3 :qm 66q0)v f*dymso:* wwwo 1.1-cm-diameter coins separated by a 0.15-mm-thick piece of6x sw0):mo3qm*f6*wq akyq s 3dwh mv: 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 capac.j d+e6f omf0citor with 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 frodf r (;q/d7ne,e 9nf,n2dqhdzm each other. Their charges are $Q_1$=$Q_2$=$5.0\mu C$, and their masses are $m_1=1.5mg$ and $m_2=2.5mg$
(a) If $Q_1$ is released from rest, what will be its speed after a very long time?    m/s
(b) If both charges are released from rest at the same time, what will be the speed of $Q_1$ after a very long time?    m/s

  Two charges are placed as sq(n( xu8 zfkl4hown 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$