If two points are at the same potential, does this mean w 7 hv-sg0x:,x5 3:giv gxkycf8fm;adthat no work is done in moving a test charge from one point to the other? Does this imply that no force need be exer-v ;xk ,asg08 yw5ixxhgdf73 gm:c f:vted? Explain.

If a negative charge is initially at rest in an el ,qd;ba.k i 6qun6)lsfectric field, will it move toward a region of higher potential or lower potentia a, 6sl6bk;.dqqfiun)l? What about a positive charge? How does the potential energy of the charge change in each instance?

State clearly the difference (a) between electric potential and ele33cb+tu l2-63onj ps zosmy4u ctric field, (b) between electric potential and eletl3jo2yu4+ -s63buzmp con s3 ctric potential energy.

An electron is accelerated by a potential difference of, say, 0.10 yng 6xj9zwsuo59t8cyvo3j3-V. How much greater would its final speed be if it is accelerated with four times as much vo j6ou9yxs-3nwjcgy9zv 38to 5ltage? Explain.

Is there a point along+-)dt5 gshlmoro agg-r6ouo-0(0 tb q the line joining two equal positive charges where the electric field is zero? Where the electric potentims-q -(o0 loguog6) d 0h-o+5agbr rttal is zero? Explain.

Can a particle ever move from a region of low electric0v8 q5ja*uzljz7ev qu2 u3j1- ie6u yw potential to one of high potential and yq7a3 zy*15vu- i 2veq60uj e8juw jlzuet have its electric potential energy decrease? Explain.

Compare the kinetic energy gsvgfvhm) 48a-k q 5/x maek z*/qi-;ecained 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 lines cross? Expl/fw 9-,whfz z) weqqv(ain.

Draw in a few equipotential lines in Fi, bew3;uspvfp1:pp3f g. 16 – 31b.

What can you say about the elec dkqkz-7 u nw il1d31jp9av1a)tric field in a region of space that has the same potential throughoutvwk)zan11a- ui1d kq3j9 pdl7?

A satellite orbits the Earth along a gravitational equipotentii o0tqo7je i:1lt81w kal line. What shape must the orbit be?t 1ol:t7ei1o8jk0wiq

When dealing with practical devices, we often tkus3afo ;x 27b:skz b.ake the ground (the Earth) to be 0 V. If, instead, we said the ground was how would this affect (a) the potentio2:kbf; s 7zsxku.3abal V, and (b) the electric field E, at other points?

When a battery is connected to a capacit18pxtxos6nxygbo 6 .7or, why do the two plates acquire chargesx 8tbx pgs.1x nooy766 of the same magnitude? Will this be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on the s w3j) asf2glz.dt0*s lize, shape, and position of the two conductors, as well as on the dielectric constant K. What then did we mean when we said l2 z)l30st *asgdf .wjthat C is a constant in Eq. 17 – 7?

  How much work does the electric field do in movohm- x:i 1kexhcp,;; iing a $-7.7\mu C$ charge from ground to a point whose potential is $+55V$ higher?    $ \times10^{-4 }\,J$

  How much work does the electeyze *3hh1 l3fric field do in moving a proton from a point with a y1z3h* fe3hlepotential of $+125V$ to a point where it is $-55V$ Express your answer both in joules and electron volts.
   $ \times10^{-17 }\,J$
   eV

  How much kinetic energy will an electron gain (in joules and eV) ip hp8q 5 lp.vk*knh8-lf it accelerates through a p pqnpkpl8.k-*v5h l h8otential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires.f;pi3v j *4qd e7*:srna 0iugc*fojl $7.45 \times10^{ -16}\,J$ 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.s1xsr cze,-)h n g(ht48 mm apart if the potential difference -zrsxh4)( est c, hgn1between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field offz2/o+2 e(kym xe1ebs $640V/m$ 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 connehg .z:)cgslg+ cted to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected to a 4y *fjt 4)lkao45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential differencn1 f2lytx 6oj.,abr 6kaiq1 6se is 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 powppahrg,c)0x 3o :7i6/ ipozu0vqwno:er supply, are separated by an air gap. How small can the gap be if the air is not to become conduct 0)gip6u7/x:vp3w,q oo:h0r zi caonp ing by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force to move a lox q/qv,1mna ik6v/t s.h*0u$-8.50\mu C$ 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 energy ux9hc5bp4r.b mgd9q:
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whose kinett4 n4 g)j*q s:udgc2daic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a fbhgbcgu l)g56;do 2f) vj,+ fhelium 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 potbkeunu1+.,q4 d*fy wbential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electxw9b 2a f8j qcd6zdy.wk 235ykric 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 fpk3h*+:*epi gmf-y juuv1ea* ootball. This conductor carries a net negative ch jyahf*m:uup-kg*p1 e v+ie*3 arge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a ogjp) 6i3 +knb 4td/js xrh9+s r+hdq;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 th--yj/ pth *oyvaw4e)i e corners of a square of side L as shown in Foiaet4 -*yj/w y- h)vpig. 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 charge withm6ne mjw/5(kfdu/ 8p8 lvcvd v9,+cjn $Q\,=\,-0.125\mu C$. 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 dgqi zt409f k,3d7 tndd bnv( xr5b3wd(istance apart to 74xw39b ndbq v(t0 di(kdzr5nt,g fd3$1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm north of k4mk4 /dqu(zp8b isw;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 (radius6 4whg22os rfm $1.2 \times10^{-15 }\,m$) 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 s7ie.l8k03uuz 0gb erahown in Fig. 17–27.uu7 r0zlk 83eeab0i.g Determine a formula for $V_{BA}\,=\,V_B-V_A$ for points B and A on the line between the charges.

  In the Bohr model of6w0 gmyu7 h45,fwijak the hydrogen atom, an electron orbits a proton (the nucleus) in a circular orbit oy4,5mfj 6 70wiuakgwhf 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 ip,c i0mkr.o,7 /ok1 zjhesm 0are $ 0.53\times10^{ -10}\,m$. apart. What is their dipole moment if they are at rest?    $ \times10^{-30 }\,C\cdot\,m$

  Calculate the electric.konefyllwbjs0zofa nx:: s1/, .;8g potential 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, consid3y;k soiubc x:),m 0ihered as a vector, points from the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole mo3 cbuy m0ksh ),oii;x:ment 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 capacitu)gwy :jlsiw552 1fb 4gwe7yf or 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 cabs zr cy400w(wpacitor 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 minus 7nel-i4prl n /charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections y8 zp5de3/p,t0) e-pbtxy: )np kxeaaof parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. 0tx,:pyappx)en/8yte5) pk e3 -dba zWhat is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of a 12.0-V batteryg 9hfj:g/cz 3d when it is connected to a /f3 jz9d:hcg g$7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates have if they are to we87 ule; flcl(-e:q zmi5;ojbe lowei;j 5u8m :e-lf7qce z(;l separated by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increa8yq *kbio-e 5p8pa n s;jzo-+cses 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 lqw8x(riq erv9;:q -j $8.5 \times10^{ 5}\,V/m$ 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 opposito) fo:zk 33s0bxtx w-re $5.2\mu C$ 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 elk 5li 5+dp kv 1i te8auwxww*4o3pf1g/ectric field between 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 byu it+7upmkd()q0q dd;h/ rpy * a 125-V battery (Fig. 17–29a) and then is disconnected from the battery. When this capdkd)it/( uyprd0m q7*;u p+qhacitor $(C_1)$ 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 s 4e5 7wrscfsuc*d j;(yquare parallel plates 5.5 cm on a side that are separated by 1.8 mm udjs *s5 7w;cycfe4 (rof paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a radius of 5.0 c-lkvhxk3* i4l;(op-zb h.il cm separat4hk x3-c*-zlilv o ikb p;(l.hed by 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. If a piece of miaq1 f+h.hx5xvca is placed between the plates, how much charge will flow from the battery? x fx+q 5h.hav1   $ \times10^{ -7}\,C$

  The electric field between the plates of a paper-separlq0 *eslmub.4 3,znqoated $(K=3.75)$ 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 ca4t(p tk8q nv348;rl tcujyebeqs 98 5apacitor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beating erratically. jcxr:,eblmzb9*s ((d A capacitd9z,b:ej*c( lrbxs m(or in this device is charged to 5.0 kV and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field betwevz2;8jg q k4c enbe0;nen 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 magnituejg8bcn nv;4q ;0zek 2de $420\mu C$.    J

  A homemade capacitor is assembled by placin;xf4*4bxany : aihio3g two 9-in. pie pans 5 cm apart and connecting them to the opposite tero344 n;fax *ii yabxh:minals 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 haw j ek/w.am av89-zv5ms 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 store 9ti mf6s)ax+g zmt)5ld in a capacitor change if (a) the potential difference is doubled, and (b x )a)96mg5sltzim +ft) 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 accelerated htp /n y57pb;ds t/hd9zorizontally by 7.0 kV. They then pass through a uniform electric field E for a distance of 2.8 cm, which deflects them upwadnbh/z s7 5 dy9p;p/ttrd 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 eq4 6m +tc tf*.ux:raowide and is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizontally deflecting electric fielte+.oqtc u *rf:6 4axmd 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 moviyaz bs : 4i3h,lf,pgxk:2umb)ng from point A to point 23zif)hp: :k,yl , mb xs4abguB.
(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 Mdc; lpaxt2/9w341p 3xdl hug cJ 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 Earmfx-, rvsr 8ip1inc5 ,th’s surface 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 tu*:z,mvya /c hmfa,t 1gg 16fsraukl:;be, 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 stationary? Assume that,gv1:/ahf g sau,:* lmzcy6ta;rk 1mf the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough stored energy to heat 2.5 kg of water5wotdfu / ejwy84;v7g 1 ynev2 from 21$^{\circ}\,C$ to 95$^{\circ}\,C$. What is the potential difference across the plates?    V

  An uncharged capacitor is connected to a 24.0-V battery until it is fully cyyof9x; kxx9vk t b)lyv pn x98(0,z)tharged, after which it is disconnected from the battery.,k9zt9 ;ly yfnkvpv(xy8 )tbx )x9o0x 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 field e4,ngi srmao1/ xceeds $3.0 \times10^{6 }\,V/m$. What amount of charge can be placed on a parallel-plate capacitor if the area of each plate is $56cm^2$?    $ \times10^{-7 }\,C$

Three charges are at the corners of an equilateral triangle (side L) as sh oqq( :z0jzng32zlyf r-z7wq6fda1w6 own in Fig. 17–30. Determine the potential at the midpoint jzg7: 2qzz(o 61zql-r0f dynfqw a63wof 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 i*s f+ w i++7m3k1wsehik0 ksfhs connected to a 9.0-V battery. If a piece of Pyrex glass +sfw kwm07*f3kek+1hh i+ssiis placed between the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in a television picture tzo09cng t,qk9t2cg nug, 9r;uube 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 g2g 0 ,ncuqrgk999tnouc;,zt 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 capacitanc gv3klh42s bxj8q.k6ve $C_1$ 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 makeh cujt8 8n0pozf l35m- a 1-F air-filled parallel-plate capacitor for a circuit you are building. To make it a reasonable sizt ho830u8cl-m5pjnz f e, 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 Ear)i93ih2io qj gth 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 for a puls iqk ts.f;qk3wqxzp1p v(+0)k ed 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 obc9mv3w9 : pepactg+10zq u5between the Earth and the bottom of the0q9twep:+aumo 5zccb39vg 1 p thunderclouds 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) spfrfgtq9:a1hh,h 2 0light provides enough energy to some electrons in b hsh, f:hptf 0qga91r2arium 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 idel-vm g* .an+wfntical $+33\mu C$ 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 separated by a 0.6j/yz*ymed: w/gzy w015-mm-thick piece of paper y6/z m*/0dyzwe: j gwy$(K=3.7)$ 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 q w:s/ bm f-9xhwjg 5wr7,1agyplate 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 fix*(gy 5yrd(5 jpkis7( azeq-oxed 4.0 cm apart from 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 a9 pz6v mn:2kpe 73 hm3dzqgrz,s shown 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$