If two points are at the same potential, does this mean t4c0j5vnfc kz3y3, ga5 y-iaaqhat no work is done in moving a test charge from one point to t -n35 yjaq 0,g 5kzcvfyc3a4iahe other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at rest in anwo: ,iokp hu9 +c)d8ie electric field, will it move toward a region of higher pote,ice8:d )pk uwi9 +hoontial 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) between electric potential.;y 8imcj v os9 zlh*/yx5jd5q and electric field, (b) betweos;h qji / d8x5ycy5l*zvj9. men electric potential and electric potential energy.

An electron is acceler+l ojzy , 6hg2/ fnzhj9ji86qpated by a potential difference of, say, 0.10 V. How much greater would its final speed be if f/9qjn86 po+,j zj2izh lhg6yit is accelerated with four times as much voltage? Explain.

Is there a point along the line joining two equall2cd5i. y :nmw positive charges where the electric field is zero? Where the electric potential is zemd. 2c w5nyli:ro? Explain.

Can a particle ever move from a region of low electric potential to p(.yd o0:xqn es)5kh n:t eff0one of high potential and yet have its electric potential energd.fphxe5 :s)qety nn0:ofk0 (y decrease? Explain.

Compare the kinetic energy gained by a proton m.jijgvk2h58lp0f*en ( +mmf $(q=+e)$ 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? E) onh5f3 nkq5oxplain.

Draw in a few equipotential lines in Faw.:,sw3y cnnig. 16 – 31b.

What can you say about the electric field in a region of i80/dzr b vv l3kdca()space that has the same potential througvzdc8r0ivdb ) 3k(al/hout?

A satellite orbits the Earth along a gravitational equipotential line. Wd.ixus vb7e; 0a:5asyhat shape must syav b5:.0 d; xa7uisethe orbit be?

When dealing with practical devices, we often take the ground (the;7,d1b2yd szzif lht/ Earth) to be 0 V. If, instead, we said the ground was how would this affect (a) the potential V, and (b) the electric field E, at other idd, z7tb1f/yhlsz2; points?

When a battery is connected to a capacitor, w318hake9+jtnf1n r gb hy do the two plates acquire charges of the same magnitude? Will this be truef 81n na+eh19tb3g rjk if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on the size, shape, and position of z6s3ygq rr ue /:xv/g.the two conductors, as well as on the dielectric constant K. What then di uyg qrre6szxv/3:/g .d we mean when we said that C is a constant in Eq. 17 – 7?

  How much work does the electric field 98svfa 9a s+,qfl*vcg 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 from a pz) mt( f)38v 3i:afli;)eyqj t8)pjxcykzk* point with a potenxt* k(;)iy z:v3y8jkf p 8 pac3iq)lfj)mz)tetial 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 joule6l 6x, 66rf;r e1 iu ghgag:galzm+ri3s and eV) if it accelerates through a potential difference of 23,000 V +u6r 6g 3 izfhr xgrag6 l;:ie,6glm1ain a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquireswj0l/ 5cz3 axu $7.45 \times10^{ -16}\,J$ 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 plate wvkc9di4 t m .0abd;jfa+t6s0s 5.8 mm apart if the potent.d6 a jdiwc4;sak9bmftt+ v00ial difference between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field ofkw0,y zr;lg p9 $640V/m$ 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 battery is ;pi-xaajj10 o 6ijsd8$1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected d2+gkiw: 5yt fto a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a helium nuclt r r-hs-ed./ueus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, are separated by87otp .prxd jq.p mq4i3znx-6 an air gap. How small can the gap be if the air is not to become conducting by exceeding its breakdown value oqmpq ip4d8x - rj.67zt.n3pxof $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force l,r*oca2qh6 9xe/p y0 zccj:-b v4cgv to move a $-8.50\mu C$ charge from point a to point b is $15.0 \times10^{ -4}\;J$. If the charge was started from rest and had $ 4.82\times10^{ -4}\;J$ of kinetic energy when it reached point b, what must be the potential difference between a and b?    V

  What is the speed of an electron with kinetic energy dru 0a*be y5*7 jf ptp9,x0bxh
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a protona7 . p0h2pz.l,vj- kh*f pvlgd whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (whic)p 9 d0bmu*iqm8ow4afh 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 potenk l.50lwlmn2n-w. 6yzae sc:nsu; 6 eutial 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric poten/5dyolm i09:3cdyq44 wz t fhstial 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. This conductor carries a net negati,hy r( k 7v7-g3y* nd2pw 6gknuprley5ve char-gl7,*6hnpgkyn v7(wdp2 ru rye3 5y kge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potentialq:muzjk8 fn 0s0wfj)( 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 h q2p18 fj 3ntvcqwfq-7id 31vcorners of a square of side L as shown in Fig. 17–25. What is th p i v3-cq7qvqj312wt18dfnfhe potential at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5ok9z562+qse.h c 27htp pabn c 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 electrf0fv 7bgvjda0vqfrz3 19n* t0ons from a great distance apart to 70 q*f0n bdvv93f01tafgrvjz $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm na67+a d/rki6;w j 0q cqfhxve3lfr) ,porth 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 a proton (ra5mk 0+iygf7mxdius $1.2 \times10^{-15 }\,m$) 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, afun, pa h )q;ccd nt5uji6:4d)s shown in Fig. 17–27. Determine ai6uc)dupqh )f4n ajdnt ;:,5c 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 (the nucleusfi; zeauz.ebs(p q5f06fj;/l) in a circular orbit of radiuleaq5fs;fu/ zez (.6p;i bfj0s $ 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 protoljmteu 2y d,g bg(*;hat2d3x2n 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 du5mt6hf-tm . tfe 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, consi,plq ytyx2)b) dered as a vector, points from the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be considered as the vectort2plbx ), y)yq 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 qkai 1df:jpa*p-p 4)hqa6a3 ahold $+2500\mu C$ 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 ,wiai3txn0sq efv cvd 73g(bh0pa .)-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$

  A 9500-pF capacitor holds plus and minus charges of3 cqszs.l rq.8 $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference .b41lsk)ds 1y w8jvcd between two short sections of parallel wire in air is 18l1j4 sc)1w.y sdvkdb20 V. They carry equal and opposite charge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of a x / dp2v2cwy-q12.0-V battery when it is connected tox-2d cv/w qp2y a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the platexg j fh z6:rooq ewn9.ly(,*z3s have if they are to be separated b wf3:grz.q*jexo9(y ln ,o6zhy a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increaexn 4 g(1tq cmj:+ah7sses 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)2kv t9al,:qhzunmi.8 y1hjv $8.5 \times10^{ 5}\,V/m$ 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 oppb+e1d-cad)d mosite $5.2\mu C$ 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 elect7k).h a+ y4iwytd+zpu ric 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 by a 125-V battery (Fig. 17–29a) and then is disconnr83 wu4tw,)km:ygaw d+qqe*da/ osea4uc+ k3ected from the baya3k43u 4gwdt)/qw+dqrcuma , o:e * ksew+8attery. 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 9lbp0zbccb7g+r2zg,4jjl d q0mn)h+ square parallel plates 5.5 cm on a side that are separ+0cl jdnjzg)b4cq2gr 0 zm,p7hbbl +9ated by 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates witha(vm z5prnfb k8 .q9z 0i)mq.c a radius of 5.0 cm separated by 3.2 pc9qzaq 0z 5mn8i r.kmf(.vb)mm of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connectqbayd,x8 so :8ed to a 22-V battery. If a piece of mica is placed between the plates, ho,s8o y b8xq:daw much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field ben*im:tkt(v6 jxu6 7*oqjw .p btween the 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-pF capacitor. How much energy is storedqte,c k1dyack j 0h1ti4k.f /5?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beating erraticallg1 n 8q+fd*jyly. A capacitor in this device is charged to 5.0 kV and sj8 +*n1lfq dgytores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field betweu;:;.set/zqd58y+uwrt 8xvy sqi g f+ en 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 an.yirt5 x+;ve tsg uzd:qw8q;+ 8ysf/ud of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by plp+aw8o.9ijleb 4a 2,e dpb 9y65ou vbbacing two 9-in. pie pans 5 cm apart and connecting them to the opposite termi5i l64 ,wy v.d +2bjaboe98uobpbeap9 nals 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 fix+4 p8xj 0 9iqeh,f 5xknebeup-g*u g6ked 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 stored in a capacitor change if (a) the pote)j5;bbvy 2uehl v9* bpntial difference is doubled, and (b) the charge onbye bub *l9pv)2jh;5v 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 horizontally by 7.0 kV. They t0t/ hxw rqm7*aqj:s;zhen 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 ah 7/xqqrwt:m;*a 0zsjway, 11 cm above the center. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a CRT. Tl2du76 ;unhxthe 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 swetx 7dlh6u;u 2nep 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 from pointmffer.lq fva4j. +z0ero :u51 d;leg1 A to poinzrlgv+dum4a5qeo f .1:fe j10 le. ;rft 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 transfww *d/ 0/bqnq4n+ chhfers 4.0 C of charge and 4.2 MJ of energy to the Earth.
(a) Across what potential difference did it travel?    $ \times10^{ 6}\,V$
(b) How much water could this boil and vaporize, starting from room temperature?    kg

  There is an electric finfw;l fsra1*2 l7zce.eld 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, e(xzlyugz3 pyho*.+4do ufuy35:qcm 7 lectrons 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 grau7 :umz3lupzy ygo(o5*xq .3d hyf4+cvity 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 fro)zo d6ynj bt *1bp8y8qm 21$^{\circ}\,C$ to 95$^{\circ}\,C$. What is the potential difference across the plates?    V

  An uncharged capacitor is connected to a , kj).t4p7 v z 4zeggcsecqn2.24.0-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 vocgevs4en.cgz z72),j tpq.k4 ltage between the plates?    V

  Dry air will break d;tzp) ho+ pk)s 8hmg:f- 0stjjown if the electric 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 corners of an equilateral triangle zw9 +dx+h* hg v20cvlf;w c)s9vfh5 ft(side L) as shown in Fig. 17–30. Determine the potential at the midpoint of each ofg+wd sh2 f9f ccwfv x+)t9;0lv *5hhvz 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 of Pyre dk)eg t:2fao(njn38jx glass is placed between the plate:djnea( gk8)nj 3 2otfs, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from res :tn.z:, wtpctt in a television picture tube by a potential difference of 5500 V. It then passes between two horizontal pla:tt:c ,nzpwt.tes 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 capacitancirn :zrbln*2*e wq:d3e $C_1$ 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 z5vgil2e kr px- 0bkft3w+*o3 to make a 1-F air-filled parallel-plate capacitor for a circuit you le02zxokvitg+3- br*fpw35 kare building. To make it a reasonable size, suppose you limit the plate area to What would the gap have to be between the plates? Is this practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there is an electric field of nuxkr6f1 4c 7ubvh u)3about $150\,V/m$ 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 pulsedartzhn+a( az b3*8. +gy;yjui 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 pot.4jvwj - k7. hlv;- noax4vksvential difference between the Earth and the bottom of the thunderclouds can be as high 4.svkkvj a 4o;.-7hxnjl-vv was 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) light provides en3c:fhh ;kz5wuough energy 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 surface is kept at a negative enough potential that the emitted electrons are slowed down and st35:;hfk uc zwhopped, 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 g.v. 4ipu+int3o gm6didentical $+33\mu C$ 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 0.15-mm-thicoir9l :7mu.h64uhu b uk piece of pahb.ru47:uli6 muu oh9per $(K=3.7)$ 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 witfll4 ))cdzjq 1hknpv0iq1 3:ch plate area $2.0cm^2$ and air-gap separation 0.50 mm is connected to a 12-V battery, and fully charged. The battery is then disconnected.
(a) What is the charge on the capacitor?    $ \times10^{ -11}\,C$
(b) The plates are now pulled to a separation of 0.75 mm. What is the charge on the capacitor now?    $ \times10^{ -11}\,C$
(c) What is the potential difference across the plates now?    V
(d) How much work was required to pull the plates to their new separation?    $ \times10^{-10 }\,J$

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

  Two point charges are fixed 4.0 cm apart from each other. Their charges arbq9-zxf -xxlt y4.sn-/su s+n)l3phr e $Q_1$=$Q_2$=$5.0\mu C$, 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. ah: r ebtry/a ,)z+lwxp537s b8hpd,y,vul5 j 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$