If two points are at the same potential, does thiszg-w1gw/ x it5 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 exertedwgwz-x/g1 5ti ? Explain.

If a negative charge is initially at re5 vt 3lt6i bh3xk(cy ox2,xr5cst in an electric field, will it move toward a region of higher p r(,62cvh x5bt3ct5oxxiy kl 3otential or lower potential? What about a positive charge? How does the potential energy of the charge change in each instance?

State clearly the difference (a) bes1 e)pls,6 qr8s +uopb0pdhx+tween electric potential and electric field, (b) between electric potentia6qp)oes+x 0lpd1sr hu,pb+8s l and electric potential energy.

An electron is accelerated by a potenti 8f*:ce c8- djeopof(8b izu, zw3wh5rudn-7pal difference of, say, 0.10 V. How much greater would its final speed be i8pouuc5 jfbc7izd(zhdfo e88:w*r-e3p, - wnf it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining two eq0yqa awg37,fmi f+n/l ual positive charges where the electric field is zero?,q/f+iyf30am l 7ganw Where the electric potential is zero? Explain.

Can a particle ever move from a region of low electric potential toui4pmz)e( 0 hu one of high potential and yet have it0z upimue( h)4s electric potential energy decrease? Explain.

Compare the kinetic energy gained by a protonw )/xzv)x6/vmp9a*f h kgjcc3 $(q=+e)$ 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 3dzoso,-+sc *hy 6qyplines cross? Explain.

Draw in a few equipotential lines in Fig. 16 kkg1p4 nwlw /)– 31b.

What can you say about the electric fiern)6 (mk t3qaqld in a region of space that has the same potential throug ra(tq kn)q3m6hout?

A satellite orbits the Earth along a gravitational equip.e6 6ybv5puyk otential line. What shape must the okey.vu yp6b56rbit be?

When dealing with practical devices, we often takex:k bys81nhec7) /az-(uav rm 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, at other m)uk a1hcz:r8xby(-7 /vsa nepoints?

When a battery is connected to a capaciteaq,3dzd;p1 v rl2 1fdor, why do the two plates acquire charges of the same magnit32lqfvp1, d1 dz;dearude? Will this be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on the size,jr n.zl4eac)sr wh. 19brlb *1 shape, and position of the two conductors, as well as on the dielectric constant K.) 14 1snbreabw j*.r9rlzlch. 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 ch 0u k gjztut0fgxxb.*0v2by9222i omoving a $-7.7\mu C$ charge from ground to a point whose potential is $+55V$ higher?    $ \times10^{-4 }\,J$

  How much work does the ele, :cgcphpsq z/,wu,lqq/ i*:tctric field do in moving a proton from a point with a potentiauq:*pp t,gcq/,s h/iw c,zl:q l 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 3 x4xzv8q: vr ah(tiohl;vz)3and eV) if it accelerates tv ;(tzq 3vvxzrx:8 ah ihlo4)3hrough a potential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires 58kql)dl t0rg2) wao b$7.45 \times10^{ -16}\,J$ 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 /gzga5bpi( 4 +.qk aqutwo parallel plates 5.8 mm apart if the pouq/.( pqzkb i+gag 54atential difference between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of cay*mn 5:o qx.$640V/m$ 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*jkahgfd, 58c-: 4ro(q ypkgp battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plalrbso) ,n4 72en) lbyioing1 (tes connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a helium nu.jh4kk5 6ks .kuo rvq;ax(rs 2cleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 202w,*dx8gnp kl0-V power supply, are separated by an air gap. How small can the gap be ilp,g8d*n 2 xwkf 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 extern4t,y ;;yflvrkn 6*rvsal 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 electron with kinetic energ t0xc8qg .afb1j*ouc -y
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a pr)w9f7 yd i0sk(tg f;zeoton whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nu0s*86lpuwm ml :zk1m5kupp m1cleus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) 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 ajg j a)5;zzdpot4wb j2n3r 24s $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q crei9pgc5hn+ uq8x4 3bj uates an electric 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 footb o*s afc2n;+lpt2ch r1all. This conductor carries a net negative charge,c*r2csfa+;plho 12t n $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a di5 qh: )tqhbe:35q1 hvjtmktl8stance 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 (ox.;,8tb;n othkjn )ac( harL as shown in r 8o nhxjn,b(;)ah;oa(ct .tk Fig. 17–25. What is the potential at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed point chau0;xp v(kqrz 0gb ja2+6tlw3 srge 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 f(c 7pjez ;mdmr2h/ bi ; rh7nf)v20ikirom a great distance apart c2mhf7p; r)jik v7eh(mb2 i ;dn/ izr0to $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm north of*un +nlq8z0zj 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 usd5 tg+. rx-ypazsq8+hed to accelerate a proton (radius $1.2 \times10^{-15 }\,m$) so that it has sufficient energy to just penetrate a silicon nucleus? A silicon nucleus has a charge of $+14e$, and its radius is about $ 3.6\times10^{-15 }\,m$. Assume the potential is that for point charges.    $ \times10^{6 }\,V$

Two equal but opposite charges are sepaek *-pnjx4fgr.c*g -av9 n1airated by a distance d, as shown in Fig. 17–27. Determine a g*c1j -nen a9xiprga *v-fk4. formula for $V_{BA}\,=\,V_B-V_A$ for points B and A on the line between the charges.

  In the Bohr model of 3z rbcvibfr+r 20, jcgz h))(mthe hydrogen atom, an electron orbits a proton (the nucleus) in a circular orbit of radius+c( f,3)0 zgbcri m2brzhvr j) $ 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 proton9 y+mkf:c/iai2 x 8jjd 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 qnb.k4 j, 0/q *rrd8o( bfiswupotential 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 /))2l ys,dxa3w+bbdc oc gd8das a vector, points from the negative to the positive charge. The water molecule, F,bx/ d8g)o3dsdy wlcd)+cba 2ig. 17–28, has 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 capacitor horby,5ih 5-6 edhllk 7tld $+2500\mu C$ 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 caikx qwo:3 ;ts5n d2w8ipacitor hold $+2500\mu C$ and $-2500\mu C$ of charge, respectively, when the potential difference is 850 V. What is the capacitance?    $ \times10^{-6 }\,F$

  A 9500-pF capacitor holds plus and mr;;j28 o1z xddau2p6uw,d pihinus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between 4fsijwg ml3-d/j5 j- h lsg*,ltwo short sections of parallel wire in air is 120 V. They -/s5ljs gj* h ljl d43iw-m,gfcarry equal and opposite charge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each ter7qo;rbql:s7 l minal of a 12.0-V battery when it is connected to a 7ob;r :sqll7q $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is des himm8/cu (*vkjzm2 +uhd,3enired. What area must the plates have if they are to be separated hzmn h2(je38 * kmu,ivcd+um/by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increases b6bzv )eghtqvta86e :8p +6-xc74yj qsp+aag h y $18\mu C$ 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 uasmm17o g7exg-jb 2vues4- /$8.5 \times10^{ 5}\,V/m$ 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 opposf,cw e-s0x*m bite $5.2\mu C$ 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 betweeav7/r ol*luik1r /b h5n the 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) and the;duryc: zfv r m83i vl)90tz4ci 10xajn is disconnected from the batte3v 9i0zt0 az;cr ur ifxlmjd81y4v)c: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 ploa j5g03pr g.th6y 4ycates 5.5 cm on a side that are separated 53r 0t j.gyaypc o46hgby 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circu w9 uzwy13wds*eq7ub3lar plates with a radius of 5.0 cm separated by 3.2 mm of m*73ubdw 3qw y1u9zwseica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. If a piece oo/s9ehj olu9 k)1,x kxf mica is placed between the plates, 9lo1/skj)x hu, 9eoxkhow much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a paper-sei 2vt.suyxkey lxd *n240y:/zparated $(K=3.75)$ 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 stored? n1 *wzn(j vln+   $ \times10^{-4 }\,J$

  A cardiac defibrillator is usq6 nmewi8 dag6 ffn6;0bt9fo3 ed to shock a heart that is beating erratically. A capacitor in this device is charged to 5.0 kV and stores 1200 J of energy. Whaf6f3nnet df09w; g6q8 mbi6a ot is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between two squ . 6x ucsu5x2rknzz1ghitc4kh3m( )h7are 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 m)mr(h.s6 4 z z7h uk3hc1x nxtc5i2ugkagnitude $420\mu C$.    J

  A homemade capacitor is assemu /z4yp2dd )x5zj e(prbled by placing two 9-in. pie pans 5 cm apart and connecting them tdpyz2d(e5)/r jz u4x po 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 fixed charges 4rt.j6k):(7q m v yzg5 icbuqh$+Q$ 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 p ga :9rspi t)ui8 hlqk9pj9m99otential difference is doubled, and (b) the charge ms99raup9i)hg q:8j99t plki 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, elec; dgb+.s9mz. 2fwfyvs trons are accelerated horizontally by 7.0 kV. They then pass through a uniform electric field E for a distance of 2.8 cm, which deflects t 9fv+. s;.dmz2wsg byfhem 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 qan9iqiy+q97 4( f 7ptyyenf* 2sng*jkV 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 taqyq**y7f2gqife 4ny(7i jn npt+9s 9o 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 nt l1, fwj/luqu d1 4l.njac-4from point A to point B. l 4fcuula wqd t,n1/1-.lj 4nj
(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 transff.o+ix gpdwa d+b7 vf;s bz,0*ns /q3pers 4.0 C of charge and 4.2 MJ of energy to the Earth.
(a) Across what potential difference did it travel?    $ \times10^{ 6}\,V$
(b) How much water could this boil and vaporize, starting from room temperature?    kg

  There is an electric field near the Earth’s surface whose magnitude is about*i ouo otn. 45uk+yw+lyn 8v)rspli34 $150\,V/m$ 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 )pb3gav/w z6u of volts through a vacuum. If a television set were laid on its back, would electrons be able to move upward against bv p/u 6wazg3)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 enou.;vmwza w l;cc,1umi+gh stored 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 capacitond3 .8b n+ :h aox,034qlsxwvr +dvztkr is connected to a 24.0-V battery until it is fully charged, after which it is disco d 3,x+vnq3db 4a:8kh.zo0slv+wn xrtnnected 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 fie/,ifs 5lv qo9ny wws:8;m*smo ld 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 equ6dv8jo5q o1c hilateral triangle (side L) as shown in Fig. 17–30. Determine the potential at the midpoint of each of t qv8hod1 6c5johe 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 1s4 syx/s ,1dvvt0wdscj6 1fe Pyrex glass is placed between the plates, how much charge will then flow from thyd1,0s cj6dse1f4/vs wx 1vste battery?    $ \times10^{-8 }\,C$

  An electron is accelerated )v ng42iu8q sahorizontally from rest in a television picture tube by a potential difference o2 ) u84giqanvsf 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 angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capacitancl)2bzb bji: 1me $C_1$ 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 rll15ah, 1jlce kw,s 2you want to make a 1-F air-filled parallel-plate capacitor for a circuit you are sl1,ekl2l 15 jarwh,c 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 practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth tu3g7l7g )zpb8 7y qzmi1 kdh;ahere is an electric field of about $150\,V/m$ which points downward. Two identical balls with mass $m\,=\,0.540kg$ are dropped from a height of 2.00 m, but one of the balls is positively charged with $q_1$ = $650\mu C$ ,and the second is negatively charged with $q_2$ = $-650\mu C$. Use conservation of energy to determine the difference in the speed of the two balls when they hit the ground. (Neglect air resistance.)    m/s

  The power supply for a pulsed nitrogen laser has ay:vjreh y9,( y $0.050\mu F$ 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 and trg jt*/k-( xc.d-ub hphe bottom of the thunderclouds can be as high as 35,000/t*xhgp -rkcdju .-( b,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 provides enough energy to somey 2c1zy+8ala c electrons in barium metal to eject them from a surface at high speed. See Ficcaaylz1y8 + 2g. 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 2sjjz*i gvf7iig-*)r 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 two 1.1-cm-diameter coins sep 9c*4ta3+r xhkkx*fe,x cf5sm arated by a 0.15-mm-thick piece of p 4fxt fx9shx+3mrk*kca ,e*5caper $(K=3.7)$ 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 capaci06q9y46mep +aa8kc rbrfu;cytor 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 from each other. Tdk brt v+5hjl1hin1u) +sq00jheir 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 Fig. 17–35 wi )zj oirv*tfof67vms940 z+doth $q_1$=$1.5\mu C$ and $q_2$=$-3.3\mu C$ Find the potential difference between points A and B.    $ \times10^{ 5}\,V$