If two points are at the same potential, does this mvg9:ntqpk d ,8to/ .*uer:xe mean that no work is done in moving a test charge from one point to the other? Does this imply that no force need *d:,qknpg. tvm8:9rut/ exeo be exerted? Explain.

If a negative charge is initially a1t: .z ksp6ucrenlc)5l2c.7ufbs q.o t rest in an electric field, will it move toward a region of higher potential or lower potential? What about a positive charge? How does the poten6sl 7q z r :cs2be1.c.fcolup.n)tku5tial energy of the charge change in each instance?

State clearly the difference (a) bigh5n * hzu7lz6mq )22cen7ueetween electric potential and electric field, (b) between electrh 752 izen*umlzehqn )7g2cu6 ic potential and electric potential energy.

An electron is accelerated by a potential difference of, say, 0.1ke b-37wp9abowo d ,w*0 V. How much greater would its final speed be if it is accelede *kwa-3 ob7,9wopbw rated with four times as much voltage? Explain.

Is there a point along the line joining two equal positive charges where m2f/ m.s.8w p6 fjafpnthe electric field is zero? Where the electric potential is zerfamjfw.s /fpn 82mp6 .o? Explain.

Can a particle ever move from a region of low electric o)f5: z-u se i6c)(urg.paw glpotential to one of high potential and yet h(u6puiow 5 s g r-flz).c)eg:aave its electric potential energy decrease? Explain.

Compare the kinetic energy gained by a qk u sbc2,i:x;8 xkel,dg .yf7proton $(q=+e)$ 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 linej nu1u0jtdv+ (s cross? Explain.

Draw in a few equipotential lines in Fig. 16 –jndci5i- 5z,yct(svf 7 :5pg t 31b.

What can you say about the electri /qle v(yv1ojb.e0qa,6lpxk . fk -kbi )dnf4;c field in a region of space that has the same potentia, 1xk.k(jyeklfi 0/v)qla .fdpb64eb onq-v; l throughout?

A satellite orbits the Earth along a gravitational equipotential line. What s81rr6dkm m-45otweq 5p, sk kbhape must the orbit bdqr,1ob4 6ks kk5wm8etm5-r p e?

When dealing with practical devices, we often take the ground (tvg; l6bcrn+: yhe Earth) to be 0 V. If, instead, we said the ground was how would this affect (a) the potential V, and (b) the ele;:cl+gv 6bnry ctric field E, at other points?

When a battery is connectep+a;ia67 zn b+e jov;rd to a capacitor, why do the two plates acquire charges of the same magnitude? Will this be true if the two conductors are different sizes or sha 6bn;+oa ev7zirp;aj+pes?

We have seen that the capacitanl3bv1fvon ;op 8 *u/rsr0 o:tice C depends on the size, shape, and position of the two conductv tr/p ;ov1ri 8*3o:sn 0oubflors, 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 movlbu j3,nt x(u50fyv r1ing 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 fieldc aryh3ifc(x0f 6:q q1 do in moving a proton from a point with a potential oqr610 (if xafhc:c3y qf $+125V$ 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) if it ecn 6n9;,/e boy)f 3 w 8i,bj1mkenprhaccelerates thn,n8;1e c93/o, 6n)ybfpeb k j whrmeirough a potential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires 7 0 evhlkg t;rwch:v21$7.45 \times10^{ -16}\,J$ 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 5.8grks 8;3imczl( qxs qn(n9f+7 mm apart if the potential difference begc8r+7nsk3qs9nf x(i;lz(m qtween them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of.ob* m9u0c+ptv1icl cxx mo.vjv: z 01 $640V/m$ 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 batt9acy hyvsrqx,qy2*, : ery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected to a 45-V batteryp 1t9mdgb c z+ria4*8f is $1500V/m$ How far apart are the plates?    m

  What potential difference oyff*y3e yl .: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 power supply, are s +o9-fj kdj0idr4+pfbeparated by an air gdfr o++ 0pj9idkb4jf-ap. How small can the gap be if the air is not to become conducting by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external wp*o-; j-c/dfvyf,k uljuc9 )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 kinewx0y/oi)h/xd.ht8 xal9 / ihktic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of rm,35 .,nyxkf/)cvk ru)kd p dh/enw3a proton whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which 1+x*quqd1sqgi n uh++ is a helium nucleus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric potentialrp ixyfp0k+2 2g kd)z: 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric potenn/a zcnd1v -df+kz8d 8tial 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.w*sfo9e7 h 16mspkevz of/. k- This conductor carries a net negative charg9 hk/.*s1e- 6w7mz osekpovff e, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the eleclv 4: ,r511d/hgg4vtg* il h4smvsyvztric 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 7, hceh bv+jbijb)g(ziq / 2xaosg9)4arranged at the corners of a square of side L as shown in Fig. 17–25. What is bogv eh/9, 7xg 4zj))bq h(i a+js2ibcthe potential at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a +cuu2nu s(0 4qzo+r,e/jg( ud1dc tzofixed point charge with $Q\,=\,-0.125\mu C$. How fast will the electron be moving when it is very far away?    $ \times10^{7 }\,m/s$

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

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

  How much work must be done to bring three electrons from a gre /d +n16ekiiv) fmnv;mat distance apart t1vv)+i6/; dnkfn mi emo $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm north of ,pf*r u2)n bpn08 o h(:tizbipa $-3.8\mu C$ 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 t whv1roslyn l8g. 00.0pgev6xo 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 separated by a distance d, as shown in-7ouki gx tij01.l 2p+i0w 2/fu xxagi Fig. 17–27. Determine a f2i-kpfo +u./jii107 x0uxg xwi a2lt gormula 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 atomf8*ss6c phutwses;+ / , an electron orbits a proton (the nucleus) i+ s c;th6fs8 upsse*w/n a circular orbit of radius $ 0.53\times10^{-10 }\,m$.
(a) What is the electric potential at the electron’s orbit due to the proton?    V(Round to the nearest integer)
(b) What is the kinetic energy of the electron?
   $ \times10^{ -18}\,J$
   eV
(c) What is the total energy of the electron in its orbit?    $ \times10^{-18 }\,J$ $\approx$    eV(Round to the nearest integer)
(d) What is the ionization energy — that is, the energy required to remove the electron from the atom and take it to $r\,=\,\propto$, at rest? Express the results of parts b, c and d in joules and eV.   $ \times10^{-18 }\,J$    eV(Round to the nearest integer)

  An electron and a proton azkb8 +,0+c9 uhqpyhr2 7k bj9hu(rztrre $ 0.53\times10^{ -10}\,m$. apart. What is their dipole moment if they are at rest?    $ \times10^{-30 }\,C\cdot\,m$

  Calculate the electric potential due to a dipole whose dipoticu .dk4gf:0pi4p4 8nt: enkle moment is $ 4.8\times10^{-30 }\,C\cdot m$ at a point $1.1 \times10^{ -9}\,m$ away if this point is
(a) along the axis of the dipole nearer the positive charge;    V
(b) 45° above the axis but nearer the positive charge;    V
(c) $45^{\circ}\,$ above the axis but nearer the negative charge.    V

  The dipole moment, considered as a vector, points from the gupydhb+o u./*u2tpbz 6*e3gnegative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can6 .h tgyu3bbd/2**gep uz+pu o 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 ;+a96-fv ig- vcltoal capacitor 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 capacit us1zl:y)uw :si3)mfvcx zd2(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$

  A 9500-pF capacitor holds plus and me.ldo(mi. 5x vinus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections os..ux obbr;rxs;s4p;f parallel wire in air is 120 V. They carry equsxob; r. r;xpus; b.s4al 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 a 12.0-V battery when it is connecteq.+,p fkg nfa)d .n k,ff)gpa +qto a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must thdp( tk y8vyf-o ;3;4ah cf0gy xdt*,fae plates have if they are to be separa-fday f,8hp(3govfatx;t;4 * kc0ydyted by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor e-(tc dkhhem+nidt) a66k0s/ h8q(ax5xda 0tincreases 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 ofhk(v x /f5e5mo6(nd xzi ltm1; $8.5 \times10^{ 5}\,V/m$ 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 opposite u k)pq588 btn ukax)b/$5.2\mu C$ 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 a c8sus h, k mgp8i7a35x9xrq) enve8.x $0.80-\mu F$ 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 i1*3w7kx 7irs;s8 :j/nr gogwf d,qlm125-V battery (Fig. 17–29a) and then is disconnected from the battery. Wh:7s;78 rw fkqs,i/wgim *n3l1rdoj xgen 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 sqa3x)qo(as i* s r()u 2auccu1gx)ii u2uare parallel plates 5.5 cm on a side that are separated by 1.8 mm of paraffr uag)ucu(i* i1sa2x( u)3x)a cqo2siin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plat4:bn 61uivxzappo.3l- v2 sbnes with a radius of 5.0 cm sepa: bin.bvuo-v2ppzl 4nsx16 a3rated by 3.2 mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor p7vu.5o-v0q -)ajlq; wjcy td is connected to a 22-V battery. If a piece of mica is placed between the plates, how much charge will flow froc qvu- 5w7.-al; jpyqv)0odt jm the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a paper-separatedo g4z v2-3zjgm $(K=3.75)$ 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 much7 4zekbfkwf// energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beating erraticalle14 l dmz*vldiv5 n41. .oehaky. A capacitor in this device is charged to 5d1. i .ahon1k5zlvedl4*4mve .0 kV and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric fielea3mv h l:.o:ed between two square plates, 8.0 cm on a side, separated by a vl 3e a::e.mho1.5-mm air gap? The charges on the plates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitorck563 hz5kiep5k gx0kwwf 2:n is assembled by placing two 9-in. pie pans 5 cm apart and connecting them to thi5k p6:nf2k0x5zkk w cwg 5e3he 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 charqco2pf(*bh k(2 , sylbru2 )jsges $+Q$ 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 cj 2e9auy +2q4(5nlztsymo . yif (a) the potential difference is doubled, and (b) the charge 5+(o2neqs.4umyljat9z2cy y 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 hz)gdv 5q+i3h uorizontally by 7.0 kV. They then pass through a unifgi qvu 3dzh)5+orm 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 value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a CRT. The screen is 30 cm widp 4dvw ilwj54jmp *,0ae and is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizontally deflec4pj*0lv mwi, w45ajpdting 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 acquires 6.3 keV of KE in moving (,acj 2jcw71kw1x vwxfrom point A to point B.1 1 w2jw(a c7j,vwxcxk
(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 Ea*b f52mh1ed berth.
(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 surds ty qsmq,210face 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, elecmq 2 ofd4)r8u3 (3oazmrg. lfqtrons 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, wou.aoq4mzr3frqo8g mfd 2lu3( )ld be needed to balance the downward force of gravity so that an electron would remain stationary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough stored energy to heat 2.5 kg of water fromo 9ks5mjr*-ib 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 unti ,1ccxn4w nka7i5zdrs )r9q4p l it is fully charged, after which it is disconnected from the battery. A slab of paraffin is then ins49i4axq)wp 5c 1ns,7rnr kzcd erted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down if the electric field rkkhq.a1b;0 p;cuad /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 ;jlgixgv c 3f-u +/,ayvk/ 2pgcorners of an equilateral triangle (side L) as shown in Fig. 17–30. Detea2g+guj- v lf3xk;i pv/c y,g/rmine 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 to a 9.0-V battery. If a piece o rk2k rkj,okx3,1ky;of Pyrex glass is placed between the plates, how much charge will then flow frxkko 3ojy,k 2 ;,1rrkkom the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally froghz u8 qriki c350cn b;9jfa/-h qhupk7+ ;mv:m 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 anc7qfkc gh z:biqjhu h3; au/0p9+mrk-i ;5v 8 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 capacita;49wa+n c .mmg o nw17yq,f m.dwipx/xnce $C_1$ 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 )o2npfl .v0jv farad is, suppose you want to make a 1-F air-filled parallel-plate capacitor for a circuit you are building. To make it a reasonable size, suppose you limit the plate area to What would the gap havjnv .02)lvpfo e 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 ,ot*v(t1x(g(el)tjgw dz8x se-o7 baof 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 laser5ji69bdv s s5*:r(cjb9 e poige*f-ou 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 Earte8 -m6.am ;)sqzw z nmrwtu0p:h and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are typically 1500 m above the Earth, and can have an : u06m);mw es pm8-nrz.aw ztqarea 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 enmj92z5r8pnd g h5iin;ergy to some electrons in barium metal to eject them from a surface at high speed. See Fig. 17–33. To measure the maximum energy of the electrons, another plate above the barium surfar25 g8jp;9z dnm5iihn ce 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 placysd q ,kf: fvhr-n, sqlw)im2uo)9.;o 3rng l9ed 36 cm from an identical $+33\mu C$ charge. A $-1.5\mu C$ charge is moved from point a to point b in Fig. 17–34. What is the change in potential energy? $\approx$    J (round to one decimal place)

  A capacitor is made qy72v g *p1prxfrom two 1.1-cm-diameter coins separated by a 0.15-mm-thick piece of paper vpq r*p7y 12gx$(K=3.7)$ 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 with7x4vp( k0gqnwtkfl ,m79vbeab 13 -jf 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,63tdby t n)dt 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 as show gh, -g1cepu -s2fiz)pn 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$