If two points are at the same potential, does this mean that no work is done ir5i8ueq arj80n moving a test char58qe8ua rj ri0ge from one point to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at rest in an elea0 nq*nn fv 2i5cvm29ictric field, will it move toward a region of higher potentinvv0m52 a9cq*if n i2nal 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) betq.tsm ujv h-j9,,1ljxween electric potential and electric field, (bv9mthjj-1, xq.u,j ls) between electric potential and electric potential energy.

An electron is accelerated by a potential difference of, say, 9+4y.bhb is0 n(rs f-s aaxb;q0.10 V. How much g ;+sb s9r0yhbq fab-sx4.na i(reater would its final speed be if it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining t3 )+ess3 h3hxcc 3leeu2 4w:iya7ljstwo equal positive charges where the electric field is zero? Where the electric potential ics:33 h4 ix3uh2s 7ew3c lel+ayst)j es zero? Explain.

Can a particle ever move from a region of low electric potential to onvrvs6;- if, fhe of high potential and yet h;,ifrvv-hs f6 ave its electric potential energy decrease? Explain.

Compare the kinetic energy cc v -y4vn-b6ugained by a proton $(q=+e)$ to the energy gained by an alpha particle $(q=+2e)$ accelerated by the same voltage $V$.

If $V\,=\,0$ at a point in space, must $\vec{E}\,=0$ there? If $\vec{E}\,=0$ at some point, must $V\,=\,0$ at that point? Explain. Give examples for each.

Can two equipotential lines cros7ze7,1 s z ozcpedz1.u7/mv bzs? Explain.

Draw in a few equipotential lines in Figk5vh5: xzyo ao2d,rftd207 u7s .g vtf. 16 – 31b.

What can you say about the el:iwf0n x8dzb7j4rrwi1r0 b4 v ectric field in a region of space that has the same potential thrj0 wv1xfi4:biwn4zb8 r0 rr 7doughout?

A satellite orbits the Earth along a gravitational q/m8rv3t.4e0i iqpy1lq. uqzef 1--3kp it ht equipotential line. What shapeiipuzt4li.-tmvpr .q 1k 313ey0qq8etf -/qh must the orbit be?

When dealing with practical devices, we often take the ground (the Earth) to ygquk1mn1 h4 s ic8+nrr 9l0f/be 0 V. If, instead, we said the ground was how would this affect (a) the potential V, rl /hc8knu+mr149 gyisq fn01and (b) the electric field E, at other points?

When a battery is connected to a capacitor, why do e0qcub8- )7 kn 8ayzinthe two plates acquire charges of the same magnitude? Will this be true if the two conductors are different sizes onb8)n7aci-qk0 8yz e ur shapes?

We have seen that the capacitance C depends on the size, shapeoa,26dh2u -auxbpd: t , and position of the two conductors, as well as on the dielectric constant Ka-tbh,u22o u:dd p6 xa. What then did we mean when we said that C is a constant in Eq. 17 – 7?

  How much work does the electric fi,r+a 3uuy+jpt5*dga j eld 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 elec.qim0( lb2j(t. qiptp tric field do in moving a proton from a point with a potential ol p(tq.mqip (t0b2 .jif $+125V$ 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 am *u5q7iuy z0 0qkz1tnnd eV) if it accelerates through a potential diffy7z0u q*n0 5ukt1izmqerence of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires g5zd*(i 6 rl(x vhpj u83tfd9u$7.45 \times10^{ -16}\,J$ 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 bet hro,wkn- p5d1ween two parallel plates 5.8 mm apart if the potential difference between o-,p5nrkdwh 1 them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of *o ay .f7x:(dr7nivyn$640V/m$ 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 mh :)q a zo:rxpz,unp,ui6p54 a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected .e6d uhto;if1 to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a helium p*j r vvsiht)5 p2+v0tnucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-5pi-y w h iz9;o0rtm p;+gdyi(V power supply, are separated by an air gap. How small can the gap be if the air is not to bt0iy w(o9p-ygih+zdm rpi 5;;ecome conducting by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force ipaw9 ;wib :du )r4do)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 k r(q)eypo(xewey(0sm. kx* 4zinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton0wyo(-3 vcxla whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (whij6s r p olr86jvdln4v)y0xg:bw7,wlmam(.g0ch 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 pw0 os6n0+ ec5cu9qlq 3/svxzed3unr5 otential 15.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an elekx 52en ebv;2q( dxrp)ctric potential of $+125V$ at a distance of 15 cm. What is Q?    $ \times10^{-9 }\,C$

  A $+35\mu C$ point charge is placed 32 cm from an identical $+35\mu C$ charge. How much work would be required to move a $+0.50\mu C$ test charge from a point midway between them to a point 12 cm closer to either of the charges?    J

Draw a conductor in the shape of a football. This conductows,05 qwljv )rr carries a net negative charge, wjq50 wv,)l rs$-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the elect t+3to8i k7jdaric 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 arranged at the corners of a squareo+-eae,5j4xegk )ec; ck7 pvf of side L as shown in Fig. 17–25. What is the potential e5+vfxcjekp a-ge4);o 7,cek at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed point charge wi-ree a+tpj5af8+. g5evfv)wa t b.r./ shsle:th $Q\,=\,-0.125\mu C$. 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 distance ape6kxxh-ret 7 ,art ,x6e xhr-et7kto $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 fz3 ls,wkod 6s*4h ;py1hkz o/cm 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 a proton (ravj88 f. hzm)jpdius $1.2 \times10^{-15 }\,m$) 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 ,+ zqt)4m cmtlioe61 jd, as shown in Fig. 17–27. Determinoit emm)z6cl1jq t+4,e 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 hyd5w)(p* vfi v 3ivo-bifst*2 qrrogen atom, an electron orbits a proton (the nucleus) in a circular o*o rv ibf32vqs5 (*ivtpif-) wrbit 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 are4parhp/sx7 w3 $ 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 dipole momeqb ln,.u5wzhw-6kxc 5nt 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, point :egq* ffxbaj)o0(:ids from the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be considerediqbxj 0ea :fg)* o(:df 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 c/sp( h v1guofsu /sd))auj(7mapacitor 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 capacito(o t;sf35rlih sqr g95r 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 minunffb//+)/9l 6rc 5l hmw lcw:jkv1x mas charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two kr2n 7t-d qc8sshort sections of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is the capacitance of tq kc2tsdr8-n7he two wires?    $ \times10^{13 }\,F$

  How much charge flows from each term)7)3lj f cu,*pclstj9tqga7hinal of a 12.0-V battery when it is connecteqjs9 77 tph*a)c ujtc3,)llfgd to a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is dxaffoom.05m0h 9( zu kesired. What area must the plates have if they are to be separated by a 2.2-mm air gz0axf 0 o5m mof.(hk9uap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increohr)rz2f6 t 7oases 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 ofo t5rz:ihd0 m*r qb(zt+4o+cd $8.5 \times10^{ 5}\,V/m$ 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 oppositpnh ;1c -p9ddse $5.2\mu C$ 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 electf 6to l2whg/s1ric 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 ba d7uf7) i.*stqq lb3dyttery (Fig. 17–29a) and then is disconnected from the battery. When thiq y3sq)li tfd.b*7 7uds 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 parallel plates 5.5 cm o a32 -ime(bzufn a side that are separated by 1.8 mm of p -3femu zbia2(araffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates3 v9 tio6zd+/spjip7x with a radius of 5.0 cm septz pixv3di6/ os7pj 9+arated 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 ofw v upgbg9rmu4)y km0(9 h:wp+ mica is plp)mvu9 r( :bh40u +myp9kgwgw aced between the plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the platesxl. vz jd,3 hf)u;htm . rbz5,)xgqle0 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. Howlw(++nv h*+u+k3 wx( ezs m;mmbhgt ;f much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a oav52noelusjzbo );*c 3n-a5 heart that is beating erratically. A capacitor in this devicen 3o ;l-zso5ao e *aj25)vunbc is charged to 5.0 kV and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric f :l(qp57eia uhu:un6k :ka841ya mhdpield between 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 ophy 4aeu5u (a: : kunkphqi8:1md6p7laposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assep30+8 :nwix4yo p2n vajqi u4tmbled by placing two 9-in. pie pans 5 cm apart and connecting them to the opposite ter4nu42a8owy:p i+vq30 t ixnp jminals 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 0e(ei5lst df0qfx24dt)2v m uhas fixed charges $+Q$ and $-Q$ The separation of the plates is then doubled.
(a) By what factor does the energy stored in the electric field change?
(b) How much work must be done in doubling the plate separation from d to 2d? The area of each plate is A.

How does the energy stored in a capacitor change if (a) the p-y5ncr f+c gi8u(.eaaf, * ngm *untg+otential difference is doubled, and (b) the charge on each plate is doubled, as the capacitor remains connected to a tucu 5*na+.mrf gf+*nc-,(any 8igegbattery?

  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 k fws)e 6)0f/gqp8(ehc8xx d,zs gav:eV. 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. Estimate t/)gq ez axhw:cxspgedv 88f)f(e0s6,he value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a CRT. The screen is 30 cm wide and is 3gp0s1jcd0 s0 a4 cm from the 2.6-cm-long deflection plates. Over what range must the horizontally dc0d0as 1gs0jpeflecting 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 kea*hbv+ano 64)c(k7ti j sb gr/7jz3 ljV of KE in moving from point A to po/)j zkr ca(j b*v s4nl +t7g6a3hojb7iint 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 Coeo 5.6z s.5 i/kzq7 bv dvwqst/*)nki 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 field near the Eatw ac4v t.( e:wvy0 8r2(owggarth’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 accelers zwg8jb * /.wa( iue+vhal:(tated 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 t*(g/+zha 8 :j( .batlwvseiuwo 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 energ:ig qyn92k m4-u0m jmry 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 conn 1 tkc 83lzmi2ibd0 yw+lnq,4nected to a 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 p+3ic , 24il1wy8kq bm tlnd0znlates. What will now be the voltage between the plates?    V

  Dry air will break down if the electric field pdw*iciv cvc xq0 9e87.(gu*uexceeds $3.0 \times10^{6 }\,V/m$. 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 equilatera cjzi 6o.htw+4l triangle (side L) as shown in Fig. 17–30. Determine the potenhjcwoz4 6 i+.ttial 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 connectsgaukr))k ( -wed to a 9.0-V battery. If a piece of Pyrex glass is placed between the plates, how much charge will then flow from the batteskr) g-wk(ua )ry?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in a 4x8c6m jg0d8jhcmvx *television picture tube by a potential difference of 5500 V. It then passes betwee80cxmjv dgj8 6cmx4 h*n 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 capacivww+mc mom 3v3m+qb ,n8r 3rm*tance $C_1$ 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, supvrr/ m;h df)1y/)mrdopose you want to make a 1-F air-filled paralmmy/dv or1f))r/h; r dlel-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 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 abds8,s2 9k:cir.p9j(kbt a +cgp 2 zfsvout $150\,V/m$ 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 nitgs 4,0*ujnd-w 6yzkweuu,9uaa vz;l.shm +7nrogen 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 pott9bqc iz0g* qc )hz2e3ential difference between 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 can have an area oiz g0)9 q3e2czqtcbh*f $110km^2$ 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 p6yl go- w.dkd x/j.lx7e-ov )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 stopped, and return to the barium surface. If the pla/v kglwdy.-d7e6x ljpo)x -o.te 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 andivcyiyh8vhz5;9ix3 1r: ;r u 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-diameter coins separated by a 0.15-mm-thik+so 6mw z9m+5fd /y vi9xoi-zck piece of paper zmoy9/k6 sw o++ii-xfv z9m d5$(K=3.7)$ 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 wi/*pq2 jl:k3 ys:q i1anpvia a1th 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 owkz:g6 f/3o,qj w6eytqwa094.0 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 plac h.mj,yd)8cbq ed as shown in Fig. 17–35 with $q_1$=$1.5\mu C$ and $q_2$=$-3.3\mu C$ Find the potential difference between points A and B.    $ \times10^{ 5}\,V$