If two points are at the same potential, does this mean that fq(,akyp36e cz ija ;d.di5a1 no work is done in moving a test charge from one poinikjy3 efzdi q( 1 5a6dc.pa;a,t to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially a;+iqfepbsjd3;xs:w .t rest in an electric field, will it move toward a region of higher potential or lower potential? What about a positive charge? H d3iqsjpbwe.+ ;; xfs:ow does the potential energy of the charge change in each instance?

State clearly the differens )expewe6h2ymjgp30 jji 3 3*ce (a) between electric potential and electric field, (b) between electric potential s6ixj3m)wp 2pjhj e0e3g*ye 3and electric potential energy.

An electron is accelerated by a pw ot (d)jf+5eovik1v3 otential difference of, say, 0.10 V. How much greater would its final speed be if it is accelerated with fo )v 5(1oo3 kfwvtijde+ur times as much voltage? Explain.

Is there a point along the line joining two equal 0)q::qfp8mdto y d p qcm1+4svpositive charges where the electric field is zero? W1c:+y) q mmqdpdvqt:0p 8os4fhere the electric potential is zero? Explain.

Can a particle ever move from a region of low electric potzbs ri 8 (+d wx *mnewuos2e- pbij25-n7e7bg9ential to one of high potential and yet have its electric potential enn-5 sip*2w+7n bgo9e mew 8bje(sxzb7 iu2-drergy decrease? Explain.

Compare the kinetic energy gained by a protonidi o9he :pi(:vb1c,t $(q=+e)$ 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 lv4qnyx c5gs*ta k0*.mwx -bc0 ines cross? Explain.

Draw in a few equipotential lines in Fig. 16 – 31;s0l;-u)mil aa ar.ecb.

What can you say about the electric field in a region ofqhw z0zc 5+4xd space that has the same potential throughoutz50w4z q+ch dx?

A satellite orbits the Earth along a gravitational equipotential line,d- tg3 -z 8ezs yc+lbtgl+85p3ftxhs. What shape must the ortz3b8 eh3dstzsplt+ -c ,yl-x5+ 8fggbit be?

When dealing with practical devices, we often take t0.xgxz -ywt9bhe ground (the Earth) to be 0 V. If, instead, we said the ground was how would this affect (at gxx-90.b ywz) the potential V, and (b) the electric field E, at other points?

When a battery is connectednce5tn;c * edu y8h5p8op(q 1f to a capacitor, why do the two plates acquire charges ot5c dcon*ef8(8n ypup h51;eqf 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 size, shape, and pos4 ha:okcd-g g- zt)q)a az;jt-ition of the two conductors, as well as on the dielectric constant K. What thaq ;-azt--hg z)jg4da:) ktocen did we mean when we said that C is a constant in Eq. 17 – 7?

  How much work does the ep.xp* e. jly.4oowpy*y9.rlxlectric field do in moving a $-7.7\mu C$ charge from ground to a point whose potential is $+55V$ higher?    $ \times10^{-4 }\,J$

  How much work does the electric field do in moving a proton bkv+ljmzp3) 2)u sizp6eb54afrom a point with a pot ms5ai bje4zbu)6zpvp 2k+l3)ential 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 ansy / ,w((rg ivh/kr tvd-9*dcfd eV) if it accelerates through a potential difference of 23,000 V in a TV pi ,(ri(w s gf-9k/t/v*c yrhddvcture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires,n;to zqr3 vb. $7.45 \times10^{ -16}\,J$ 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 betwe6 xwpbe,4 a)a nfc1x:oen two parallel plates 5.8 mm apart if the potential difference between 6:wx)cpnfxa o e,b4a1 them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of ony2 ode7xixtdsw*q0i; w0+ 5$640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field betj3/tt x11r7lrh z)lg uween two parallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel platespw fl40c-k:po connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is neqyu.,b b3tlc )d7evk.eded 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 separated by an :t1q45 b p(t5wwxueg/wc en2pair gap. How small can the gap be if the air is not to become conducting by exceeding itbeqg/42txp5enw(5ptu 1 :wwcs breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an u5(x b0np 0iga uz:()vo4scsuexternal 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 ksy617bq1bsrgu wh00v inetic 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 w8jytnmu;jhr2a1h; + is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (whz0w a1ii d54o,q10buldaav 0xich 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 p;,sv9 rre.p-ehlkeku h+ (t,x otential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric povzr7lh f*vn (o u8)1xhtential 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. Thisjdht 4rmjp i01b /p7.h conductor carries a net negativr1d.p4m jh0bpih tj7/e charge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potentejxf fsdlv bnmhi v;c a+8z:ac 870244ial a distance of $ 2.5\times10^{-15 }\,m$ away from a proton?    $ \times10^{ 5}\,V$
(b) What is the electric potential energy of a system that consists of two protons $2.5 \times10^{-15 }\,m$ apart — as might occur inside a typical nucleus?    $ \times10^{ -14}\,J$

Three point charges are arranged at the corners of a square of side Lo;( qtz7z d,qp sc*h*m as shown in Fig. 17qcp d7*moqz,*(t z;hs–25. What is the potential at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from r; vee jng09hl llp.vx/l4 r6/rest 32.5 cm 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 electrons from a great distancrb:wsh 06 r)*,uesy efe apart rby0rh*fu ,ee6 :ss )wto $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm ;+wbys3- qia pklxa,-o8guq: north of a $-3.8\mu C$ point charge, and point b which is 88 cm west of the charge (Fig. 17–26). Determine
(a) $V_{ba}=V_b-V_a$    V
(b) $\vec{E}_b-\vec{E}_a$ (magnitude and direction).
   V/m
   $^{\circ}\,$

  How much voltage must be used to accelerate 9k: fbbt2 ae2wa 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 92zgw4t35k6vftfokd a distance d, as shown in Fig. 17–27. Determine gtwfo6 2dk4 vfzt539ka formula for $V_{BA}\,=\,V_B-V_A$ for points B and A on the line between the charges.

  In the Bohr model of the hydrogen atom, an electron orbits a proton (thez6 rf9g:o:u*whq .dmgmf(;0i. uoot i nucleus) in a circuladz:g ou; .hg0*m uro(offi.wt 6:qim 9r 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 pr)r,i hzhou-me-nf fm*7:3uqooton 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 a dipole who6+xk emkpp66/ 9ai0( axvkld.t og5yf se dipole moment is $ 4.8\times10^{-30 }\,C\cdot m$ at a point $1.1 \times10^{ -9}\,m$ away if this point is
(a) along the axis of the dipole nearer the positive charge;    V
(b) 45° above the axis but nearer the positive charge;    V
(c) $45^{\circ}\,$ above the axis but nearer the negative charge.    V

  The dipole moment, considered as a vector, points from the negativ;,.s42 wra a)okuz hone to the positive char k4,hz). ornua ;o2wsage. The water molecule, Fig. 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+g:kydxd3xxc+1 (kz b 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 4b t,lw 5yv8w ,*wxjqcg0x 6xau0 zt,hcapacitor 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 charges of .rw,4c t:8r qsukc 6ma$ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two sho s(mq7-h9ybh brt sections of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is the capacitance of the two wih sy- (qbbh97mres?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of a 12ailxz) gk-j:4 vz;aida 1 sl;w49 bsw9.0-V battery when it is connected t49lv9-: ; ;dwaljzgws1kza)sia4 bxio a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates have if 5sapr jnxo/3 )they are to be separated by )xp nro/3ajs5 a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capa6w b-m4)(;asyat(t 7bewlku i citor 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 ofpd)v.4 fki+oed qv)c.9 mjr3f $8.5 \times10^{ 5}\,V/m$ 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 opposi 8m(yps:w* ojite $5.2\mu C$ charges on the plates, and an electric field of 2.0 $2.0\,kV/mm$ is desired between the plates, what must each plate’s area be?   $m^2$

  How strong is the electric field between the pla 7 xej vce 2tc.-)o*qspe28byrtes 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/ b0v6 lx z0vffet2b:x then is disconnect l60t:e20bz /vbxvff xed from the 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 square pad- czgy 4v) am5+exoc6rallel plates 5.5 cm on a side that are separated by 1.8 mm-yaxm6) 5c4oe cgv+dz of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plaj6nskv/ ;vt6 z0 rz- fvg-6x4jgnp:zmtes with a radius of 5.0 cm separ;x k-z -p6 vn/n6t 4frsv6mgjvgz:z 0jated 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 micamgm f/z;9qmrd/ z+x n/ga43 fc is pxzr3+/gd/ ;mq9z gnfm4mf /ac laced between the plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between wz a.u*r*i(k0*b,wf1jcaezythe plates of a paper-separated $(K=3.75)$ capacitor is $ 8.24\times10^{4 }\,V/m$. The plates are 1.95 mm apart, and the charge on each plate is $0.775\mu C$. Determine the capacitance of this capacitor and the area of each plate.
   $ \times10^{--9 }\,F$
   $m^2$

  650 V is applied to a 2200-p,rf6:yf8tnir 8 1wktkj 9t50rhwt4wgF capacitor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a kcgq 8w1jdwwp,v:g o 4i,i u38 ejua,4heart that is beating erratically. A capac4qpwda8ce4 ovj8wu:gk, ,ji13,i gwuitor 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 electro)gr8 :ax8ya mmg a,7lic field between two square plates, 8.0 cm on,8a g m):xgloaa8rym7 a side, separated by a 1.5-mm air gap? The charges on the plates are equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor if m,) 4w+ ub6wn/azyuns assembled by placing two 9-in. pie pans 5 cm apart and connecting them to the opposite terminals of a 9-V batmww6zuub/a4 y)+nn ,ftery. 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 cw4kc c8d8 sb+1dchu a8harges $+Q$ 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 chujwlm* cz+5+gange if (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as the capacitor rc z+jwumg+*5lemains 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 arlcpx5hn :p4 j9m-kc.ee accelerated horizontally by 7.0 kV. They then pass through a uniform 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. Estihxnp 5jl ce.c4-m kp:9mate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by uu,ut0q)b 90l5eo q8swszn9 de l4zx76.0 kV 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 to sweep the beam fully ac9zo8su0 tse479l ulqdw0 ,e )xbuzn5qross the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting uyid)hezuf 2 ;8jnh1*from rest acquires 6.3 keV of KE in moving from point A to ph e j8 uu*hnz2;f1y)idoint 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 C of charge and 4.2 MJln* z3of7q,od 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 Eartvbz;9 5ct47 rp)sjly-pr qs9sh’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 acce/chb ; e7gbm hp*j87aulerated 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 the electrm8pj e*7 ghc7a ;hbu/bic field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough m9g *my9aeyf5r.f1 feuzto56stored energy to heat 2.5 kg of water from 21$^{\circ}\,C$ to 95$^{\circ}\,C$. What is the potential difference across the plates?    V

  An uncharged capacitor is connected to a 24frrfnh 5vp 62vhsp bg:o;op)q3- qqk7x8n* )y.0-V battery until it is fully charged, after which it is disconnected from the battery. A slab of paraffin is then inserted between the plates. What will now be the voltage between the plates? gnpvbpfq os2v))nxkhqo*-pr 7 6; 58q3 hf: ry   V

  Dry air will break down if the x jvbu4q5/t, ptk4 +kwelectric field exceeds $3.0 \times10^{6 }\,V/m$. What amount of charge can be placed on a parallel-plate capacitor if the area of each plate is $56cm^2$?    $ \times10^{-7 }\,C$

Three charges are at the corners7hen+xq,*;qk s0is pgg+) xro of an equilateral triangle (side L) as shown in Fig. 17–30. Determine the qe;x0x)* + po+s qgsn7ihr, kgpotential 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 h,limr qdqt658 +h4cypj : -ewof Pyrex glass is placed between the plat8l yhi: we+d-4ptj rc6q5m,hqes, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from resc jslu wklc;w8 8b:*j;t in a television picture tube by a potential difference s8kujl*w cw;8;c: lbjof 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 capacitancm x- 7e/,(5dn(e 9juifdzgyvke $C_1$ 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 br; c.w y4b.vjmake a 1-F air-filled parallel-plate capacitor for a circuit you are building. To make it a reasonable sbv; cb 4ryj..wize, 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 Earthonl,u+ 0obc*j+ tkmw, 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 pulsed nitrogen laser ha,q*7w dl a3h z-tr ij96o7on.je5r ners 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 betppweb:- 0 8jv 8x1ajrhween the Earth 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 cvxpj jpweh -ar8:1b 08an 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 some7 ccc84z- o j71cvqpev electrons in barium metal to eject them from z18oc-7 pqvc7e 4vccj 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 fro:*h)tzptcj o9q(t* /u* njcwwm 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 1.1-cm-di:oe 3k0y*xq 0fze 3oevaft,c,ameter coins separated by a 0.15-mm-thick piece of paqve ,*f0otaye3z3cx 0, keo:fper $(K=3.7)$ 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 aru 2ugs)v u6ce5ea $2.0cm^2$ 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 arekvv046xr utho+q 6-ut fixed 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 shown iil/ ;epgrup :x qa/u7o)*gm/mn 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$