If two points are at the same pote7g es3mo(m+0 z j f0slk/9wvtontial, does this mean that no work is done in moving a test charge fromomsf3kl t0 v wo/zej+(0s7mg9 one point to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at rest vbpq;0 y;/w4/jot kyb in an electric field, will it move toward /pb0vot q; b yk4wyj/;a region of higher potential 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) betsk;n,tofpd+dv:s xv;l+0 u l)o0as. ay-pts,ween electric potential and electric field, (b) between electric potential and electric l,+f ao apn0t ;-,x0sl+ ;y ds).psvs:ou tkdvpotential energy.

An electron is accelerated by a potential difference of, say, 0.3)q+)o 9bjz ic nzzph;10 V. How much greater would its final speed be if it is accelerated with four times as much volh biz j)q+;pzzn)9o c3tage? Explain.

Is there a point along the line joining two;j1 ekxnht)v( equal positive charges where the electric field is zero? Where the electric potential is zero? Explv( hk;)nte1xj ain.

Can a particle ever c mlbi56qc :5b( hdb0pmove from a region of low electric potential to one of high potential and yet have its electric poten mb b5d5c:l0c(ipqh6b tial energy decrease? Explain.

Compare the kinetic enkas/8i6)li ,;lryxv iri/5ahergy gained 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 qwlb)emjtil r hbz46 3kp 29+)*)j cjqlines cross? Explain.

Draw in a few equipotential lines uz5m3-,j yxd-mvnh9 l in Fig. 16 – 31b.

What can you say about the electric field in a region of space ,i,.il)tesw *et :gwrh-o * owthat has the same porl w,)i:et g*es-.othw wo*, itential throughout?

A satellite orbits the Earth along a gravitational equipot gp xb f,,;v8tdsaqy (03ki9yaential line. What shape must the orbit be?sf89, g3 iabdk0p (,taq;yvyx

When dealing with practical deviec)cv/fqu x 8tsv/ ofxfj4a rxhs 27:(re).h9ces, we often take the ground (the Earth) to be 0 V. If, 8xf4e/cx 7hfcavtsersj9fr) (:x)q /.2 uvoh instead, we said the ground was how would this affect (a) the potential V, and (b) the electric field E, at other points?

When a battery is connected to a capacitor, why do tha0 jeu(krf*q4e two plates acquire charges of the same magnitude? Will this be true if the two conductors are di r(*fe4 j0aqkufferent sizes or shapes?

We have seen that the capacitance C depends on the size, shape, and pos( 3ium f y4a8y dmcbjk4kg37)aition of the two conductors, as well8ma(c dk4a)7u3kbjy 4i3mg yf 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 moving e/(eql*bug4lwsi)lgbqh7./h,vsq6wgd3 m7 a $-7.7\mu C$ charge from ground to a point whose potential is $+55V$ higher?    $ \times10^{-4 }\,J$

  How much work does the jr,rt1xib7 1 s1daci/electric field do in moving a proton from a point with a potential of /sd,tr7ria i1c1 b1jx $+125V$ 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 x)6 y ,c/fq4l:qgj spzjoules and eV) if it accelerates through a potential difference q/zq fpgx: 6s)yjc,4lof 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquiressztbdc9u6 m p lv8q/-6z jfr*. $7.45 \times10^{ -16}\,J$ 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 px3 4 *5h: j5 mlumedzn;cymkm(arallel plates 5.8 mm apart if the potential differencceuh x* ml:55d;kyz m3 m4nm(je between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of x1f7q0wgx d.o$640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two d7duiyi747 zfl y.jl5hux+ o; 9 hxwa3parallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel i xvyc +950fs6sre(v eplates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a hentjg: :p/)jqx lium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a d yv 54p;i3hvo*zjw/6.ezlft 200-V power supply, are separated by an air gap. How small can the gap beoyh 6. izpt/d5vv3 wez*4jfl; 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 force to movb+cfl f:dv;2ce 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 electrd,hy v.3i:/hp.rrh faon with kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whose kinetic energy is 3.2 xdgwjvcw e xt29qqyagk+.t m;-(322l keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a heliuh,/z1r jst 5auan(s,um 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 from aa dnvk29g, v+d $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric potentiaok*ekzy ,3un 4an-(r /wot8wrl 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 th/i/1 hhss ( o )aatxqf0b, dkoa*oo 6/hehlk.7e shape of a football. This conductor carries a net negati 1ah,o/hltk(a b .7) qso dofxk/hiseh/6*0a ove charge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric p3qj4k go-ep e;otential 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 sq mwat31qrv(my/r /)k muare of side L as shown in Fig. 17/wr m/) 1yakvrm(t3mq–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;4 thhpv c,xve p+yd23 from a fixed 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 e589icqb17jlefbrxg )fu 1qr +2liq)electrons from a great distance apart tobqlrre9i luije)x c1f5gf1q 2 b8+)q7 $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm north ofiy,, lzk k:p2y 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 t2/ ab:avqvyn;: 0 jktll lfuqv;0v2,oo 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 separat )wc,gex ew4+bed by a distance d, as shown in Fig. 17–27. Determigxe)4ec b+ww ,ne 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, 2c1(ztroz v/f +a g7/f5yp tavan electron orbits a proton (the nucleuspa 1 +5yz/fct(v7zr t/vgfoa 2) in 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 prot qpa2 u9cif5vxq1 +l4:2zaar c9xawy )on 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 potential due to 1w9w q( wnq*kta 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 asxgb2vn y ji78zy 6ad 7wr+1q5v a vector, points from the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be consi7vviydy7 j+56wgzr x2ban1q8 dered 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 8)ad3x 4uqkuvw x/oz) 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 holl-q0k (rn+pc x+j nk3es yx::ld $+2500\mu C$ 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 ch uf61vgwl h(c sve)5n7arges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of parallel wire in air ixc aqvx7vq9x */xvx 10s 120 V. They carry equcv1 xx/9x 0v7axq vx*qal 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-Vcp 4 tcz6or3dh6qt1w. battery when it is connected to a .wcr1o3cq6zpth t4d6$7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates have if they are 4+ b+9uytubxvy168rkea j d1rto be separated by a 2.2-mm air gb4 xu19+dyu+ 6tbr1keryjv 8a ap?    $ \times10^{ 7}\,m^2$

  The charge on a capac- *rkeryc06g6d1z ljo itor 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 mdr*p73hs /hh$8.5 \times10^{ 5}\,V/m$ 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 oppositk.kn nq , yur5(w p7jgu*lp4np4mwv 42e $5.2\mu C$ 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 atyrlp2tpgv2k a,y k-v o,-8c. $0.80-\mu F$ 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 bywyr 3pslb11 1fit7(f y a 125-V battery (Fig. 17–29a) and then is disconnected from tpb 3 ryl711wti1(sf yfhe battery. 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 squarp1xgoi-0 3n i21ha bgwe parallel plates 5.5 cm on a side that are separated byi0gg 1 - w3bna2ohpx1i 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a rad lrk.:- qsz ,b-qsdw+/2jinyd ius of 5.0 cm separated by 3.2 + :d2wbrjq s/-.snqzk l,-d yimm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battery. If a pieceqjbbeh05j fgt 60+dy5/urc(y of mica is placed between the plahj(gfyj 0bq/5try b5e dc+0 u6tes, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a paper-separaten md::g04(r0fia 7rkr-byoec9mql 1fd $(K=3.75)$ 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 capacitord53 n*uun f3r/u 97h0ms*n jb.oxsmzs . How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beating errko9k wu vl8u/,ljy:p7j8i-eh3 ise8a4 (skog atically. A capacitor in this device is charged to 5.0 kV and stores 1200 J of energy. What is it e h ei83sk8j gp:ko8ausyi- ,o7vu 4l9/(kwjls capacitance?    $ \times10^{-5 }\,F$

  How much energy is stt(/c *rwx:hejored by the electric field between two square plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on the plate*c/ xw: et(hjrs are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing two 9-in. pie pans 5 cm aparo,;hb 9ok,psye yo.a3t and chpo3ao yk.s9y, ,obe;onnecting them to 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 charggkt: iu0ce cu b2 s8.:q342txjyt(0js ka3s rdes $+Q$ 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 capacitonj/zff-njxpi//o )o do 122k+ejrb h-r change if (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as /op+)f j2kj 1/ ho jnr bined/ofx-2z-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 horizontally by 7.0 kV. Tx.hzh2 s5 ,lkchey then pass through a uniform electric field E for a distance of 2.8 cs2xkl h.5hzc,m, 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 CRTgea.z z1l:ny1/ cabfm /y.,jl. The screen is 30 cm wide and is 34 cm from the 2.6-cm-longe:gzfj,c1 ny.a 1lb .m/ y/zal deflection 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 acquires 6.3 keV of KE in pi5oev)/ tf: wmoving from point A to pe vp)o/t5fw: ioint B.
(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 i11e.yt:v/mbw14 yt 4fa llntC 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 fieusv2c:5k) jo dsg 5nv3ld near the Earth’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 tube, electrons are accelerated by thousa+j :3bx02*jkvg qlr atnds 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 electrok3 gjr:t2q +j*blv0x an would remain stationary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough stored ened1rajz bteq1iukm +8q+h z+) +rgy 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 to a 24.0-V battery until it is ful .smni.n8qpa0*;) z d2algydnly charged, after which it is disconnected from the battery. A slab of p;an.*m .0nsiz)a 2 dgyp dln8qaraffin 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 excee i)+sad;w s+0z0 bdzekds $3.0 \times10^{6 }\,V/m$. 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 t j45ao6n6du+d gzjiveao 0y+y .*:aedhe corners of an equilateral triangle (side L) as shown in Fig. 17–30. Determine the potential at the+0eoe*njg 6yaua:4d iay+zd6o d5j. v 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 batzfv4xma)l+-rq)9z yc0)(/m9ktup eghqe7ox tery. If a piece of Pyrex glass is mc)9 )(m94z)-v+ q/zrx fpqlkaxo7h0g t eueyplaced between the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated huf p+hf/b34)cfev5in orizontally from rest in a television picture tube by a potential difference of 5500 V. It then passes between two horizontal plates 6.5 cm long and 1.3 cm apart that have a potential differenccfubh f5e4/i )p+ vf3ne 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 capacitance fotmg3 b f43tb6 wbw7:$C_1$ 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 youb2y m ,;3u3 vnqxcjx)nzxo0ro-2 a 3at 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 h2;3bv-m3z3q,xu t2 yona oj nxax0r)cave 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 fig23ka8vd.rokmd ir l9/2*ya feld 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 nitrogzmbb 2u(un ao4 )bmr0:en 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 Earth )pktk) kidcew) qst021w7wt7and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are typ kt )t wck0p1s )w77eq)itdk2wically 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 enoug5j0 + dlkmz4upg2aq 8vh energy to some electrons 28l04v djq+gaupzk 5 min 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 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 placetna u:+0e u2ndd 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 from two 1z1+r9x-os 6vel * hvdd.1-cm-diameter coins separated by a 0.15-mm-thick piece ofser+ dohzv61* xd9v -l paper $(K=3.7)$ A 12-V battery is connected to the capacitor. How much charge is on each coin?    $ \times10^{-10 }\,C$

  A $+4.5\mu C$ charge is 23 cm to the right of a $-8.2\mu C$ charge. At the midpoint between the two charges,
(a) what are the potential    $ \times10^{ 5}\,V$
(b) the electric field?    $ \times10^{6 }\,V/m$  ----待选择----leftright 

  A parallel-plate capacitor with plate;0uix; li nc56 glxos *uxhq-7 area $2.0cm^2$ and air-gap separation 0.50 mm is connected to a 12-V battery, and fully charged. The battery is then disconnected.
(a) What is the charge on the capacitor?    $ \times10^{ -11}\,C$
(b) The plates are now pulled to a separation of 0.75 mm. What is the charge on the capacitor now?    $ \times10^{ -11}\,C$
(c) What is the potential difference across the plates now?    V
(d) How much work was required to pull the plates to their new separation?    $ \times10^{-10 }\,J$

  A $2.5-\mu F$ capacitor is fully charged by a 6.0-V battery. The battery is then disconnected. The capacitor is not ideal and the charge slowly leaks out from the plates. The next day, the capacitor has lost half its stored energy. Calculate the amount of charge lost.    $ \times10^{-6 }\,C$

  Two point charges are fixed 4.0 cm apart from each other. Their chargese67ke yq9 ,azj 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 withjz--u 4s8ocj d $q_1$=$1.5\mu C$ and $q_2$=$-3.3\mu C$ Find the potential difference between points A and B.    $ \times10^{ 5}\,V$