If two points are at the same potential, does this meae/b xhtsi p9w r1brn-n:9m6r5n that no work is done in moving a test charge from one point to the other? Does this imply that no force need be exerte9b6- :hnw it/mxr9pbrn 51rsed? Explain.

If a negative charge is initially at rest in an electric fieldrys kv20, oof24o/dd .om3rbbduxj *p8 +y wc+, will it move toward a region of higher potential or lower potential? What about a positive2row b +oyyx4roj., dpbu8sf+2m3c kd0 od*v/ charge? How does the potential energy of the charge change in each instance?

State clearly the difference (a) between electric potential and electri k/9ega r:9hzb /gnjx1c field, (b) betwzgj n/bh x1/kear:g99een electric potential and electric potential energy.

An electron is accelerated by a potent6p*8i 8tlrqy nial difference of, say, 0.10 V. How much greater would its final speed be if it is accelerated with four times as much vtril 68p8 *yqnoltage? Explain.

Is there a point along the line joining two equala:s zf2fvq w.-h-p 0fr(vdvjt/8(dzq positive charges where the electric field is zero? Where the electric potential is zea- zvz :-d.wf(vf/r hst0q2 vd8(qj fpro? Explain.

Can a particle ever move from a region of low electric potential 3yc,yl ygn3vkoo96 vo:2plyz rwnntr7935 +nto one of high potential and yet have92+yyv, tlrwo y:3olp3onn7znkv 9r3 6yg5nc its electric potential energy decrease? Explain.

Compare the kinetic energy gained by a proton)f/xfx * dm*de $(q=+e)$ 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 bz3hv0 jaq4l4z;gml:v6ysmaj *(uh 7 cross? Explain.

Draw in a few equipotential lines in Fig. 16 – 9ey5dyyl mu6) 31b.

What can you say about the electric fin/vi6uzem6i , eld in a region of space that has the same potentialm6 iiev 6/nuz, throughout?

A satellite orbits the Earth along a gravitational e anwd-l s .*q.1t+lmha sae/4gquipotential line. What shape must the orbit ben+ g 4aaq*- wal/.mesd.s hlt1?

When dealing with practical devices, we often take the ground (thd w z2khuv p,ytol9o,z:dl-5:e Earth) to be 0 V. If, instead, we said the ground was how -oz,:o92ydvw ldz5khul , :tp would this affect (a) the potential V, and (b) the electric field E, at other points?

When a battery is connected to a capab nbk-sn5;f3yw3f .. 4otbtgbjtwz3 7citor, why do the two plates acquire charges of the same magnitude? Will this be3yb3f7s.- w tf bwz4tjn5;.b3to bn gk true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on p c,aa 25,4mrx0zkggyr4k;tz the size, shape, and position of the t2,kr4gz;4x5m,ayc gazr0 k p two conductors, as well as on the dielectric constant K. What then did we mean when we said that C is a constant in Eq. 17 – 7?

  How much work does the ele t xt/4i0c5jaictric 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;a) t)lj 2hfcl proton from a point with a pot )l jl2c;thaf)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 joul(;m +ciku hks+es and eV) if it accelerates through a potential difference of 23,000 V in a m;+hc ks(u+ik TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquiresh wj060ta55.gg gpb j(9apupn $7.45 \times10^{ -16}\,J$ 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 paralz bqj+b.a4+m alel plates 5.8 mm apart if the potential difference be4qbjab +mz. a+tween them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of ;c-k-j oyzq1cdkm* c /$640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two para,15l jot 9sbtt b-gqd.f;; ppallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two pak *c)tlqs-2o r v:rqqo4/xzw +rallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a helium nucvq e*fh2ycr3*b1 kgl ;o7u*s7d0ntrfleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, are separated ww+nvv5 f( 6dzby an air gap. How small cvvfd5+ z 6nw(wan the gap be if the air is not to become conducting by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force toxm c:ikc-v4ull )79ao; m6yor 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 kinds86c- yd4qo:n 1wwksetic 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 ksg:ux ijr 2i-.eV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a dn(xbq077e z/n:fkm4xg v l/ lhelium 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 frn3dve; 80 vqbzom a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates zlbb,z r*a cl pob)c 4k*.d3+9peuoy, an electric 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 conw vdx 1 d:mf;b5m*f5zry 6qj4gductor carries a net negative chargj mzqdr*wm56yvbfx:4f; d51 g e, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric pot bwe24y cm l;(urduakt3/.o4 pential 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 c:p .b6a065 zpkv nvzyoorners of a square of side L as shown in Fig. 17–2a0 :p5.yz6vzv kb6p on5. 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 from a fixen1tikfg3was/;cx1 a 0d 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 dis o 039hufkl4wymzot /y d(9wr-tance apart yw/or - 0m w3hydout(99lzk f4to $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm north of a 48uejj0z -xuc$-3.8\mu C$ 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 toy9nd5d8xw+dk qy+0 6d/lu bproton (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 separafjb ft-q 6(r4q-b7u opq8a l5ated by a distance d, as shown in Fig. 1 qqqf--t(uojb f54al p8br7 6a7–27. Determine 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, an ele/ p.xb/xi sk9qctron orbits a proton (the nucleus) in a circular xx.b/ ik/ps9q orbit of radius $ 0.53\times10^{-10 }\,m$.
(a) What is the electric potential at the electron’s orbit due to the proton?    V(Round to the nearest integer)
(b) What is the kinetic energy of the electron?
   $ \times10^{ -18}\,J$
   eV
(c) What is the total energy of the electron in its orbit?    $ \times10^{-18 }\,J$ $\approx$    eV(Round to the nearest integer)
(d) What is the ionization energy — that is, the energy required to remove the electron from the atom and take it to $r\,=\,\propto$, at rest? Express the results of parts b, c and d in joules and eV.   $ \times10^{-18 }\,J$    eV(Round to the nearest integer)

  An electron and a proton aremch;r5i3hek lx kg/80 $ 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 8l l o28lzgr-na 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, consid+/c lolkyrd/d-3 c/ozered as a vector, points from the negative to the positive charge. The water molecule, Fig. 17–28, has a/y+kdd/oc/ol rlz- 3c 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 capw2:qkvv+4 k yaacitor 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 hold j4 wj8mnxad(xi -65dg$+2500\mu C$ 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 plumb2c1 -ld njv-s and minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two shb;gfh0) jf0r1 d;ss0mtkrs,port 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 01srstr hmgf ,b0df) pkj s;;0two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminaeaj1isc. bk,6wv 1b v(l of a 12.0-V battery when it is connected ai6wv1e(.v k ,b csjb1to a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates hav kwst;)n9uz cwo:* qx4e if they are to be separated by a 2.2tokxuc :;swzq 94n) w*-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor incrof4+wi9n(, nqapdlqbp6: p 8eeases 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 of2pcs;f 8tzjq nt/.o5 - 1jezml $8.5 \times10^{ 5}\,V/m$ 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 opposite3t hc0ot23p w ezn-xn1 $5.2\mu C$ 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 ofqw9p pq8 w ;uaqp ck (ss4/x/,)ve0gta 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 (nc2lj6u gfz*h*p/ 3s nFig. 17–29a) and then is disconnected from the battery. When this capan6hsc*3 /2flg*n jz upcitor $(C_1)$ 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 on a side that are fsb h788vas-r separated by 1.8 msfv 8r8s7h b-am of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance 8uwm) j;xano3cnp5h* j:7e2b.kpyg tof a pair of circular plates with a radius of 5.0 cm separated by 3.2 mm of mica? ;:kcj 3xpw5phm*gnj 82o. n)b7ytuea   $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 22-V battqt lr95(ie 7haery. If a piece of mica is placed between the plates, how much charge will fl rh7a l5ieq(t9ow from the battery?    $ \times10^{ -7}\,C$

  The electric field between mz :o4hhqi3:q,mpm1p 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 muco 0xkd1nu ;w *yon+q0jh energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beating erratically/bmh*p.q8d; w08r6w ex ikiaq. A capacitor in this device is charged to 5.0 kabqpwk* r/0 8 wxmii;eh8q. 6dV and stores 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the ev7ho ra*4kv/rlb5t)jlwe5 y 1lectric field between two square plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on the plates are equao1twa j4e)vklb 5y 7lr*vrh/5l and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assvnm m9.p m.wc:embled by placing two 9-in. pie pans 5 cm apart and connw m:m.p vn9m.cecting 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 capacitob7,vz)ldtmv 8g .* 6q,npg)zpahvl ) mr has 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 poten+,f d eymvwz4bu+tk +) ruu-t+tial difference is dou+ d4u-tw++m+v)bkefy,zu rut bled, and (b) the charge on each plate is doubled, as the capacitor remains connected to a battery?

  A $2.70-\mu F$ capacitor is charged by a 12.0-V battery. It is disconnected from the battery and then connected to an uncharged $4.00-\mu F$ capacitor (Fig. 17–29). Determine the total stored energy
(a) before the two capacitors are connected,    $ \times10^{-4 }\,J$
(b) after they are connected.    $ \times10^{-5 }\,J$
(c) What is the change in energy?    $ \times10^{-4 }\,J$

  In a given CRT, electr +t x8ay iw10yn516c.qwpz dvqons are accelerated horizontally by 7.0 kV. They then pass thr 1dzywc.0 vpny iaqt1w685+x qough 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 the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kVsn pd 0,h4f+jg 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 defle+4 p,jd hn0sfgcting 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 moviok7g78uld d,u98 gagzq m:d ;ing from point A to point :qkgiz lua;md, d o8g79ug d78B.
(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 anrh53t 1 w;cdil)hr5xud 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 Earth’s surface whose mag q1w/61xrgia/ kop2rt nitude 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 kmf /5.ipw/zt are accelerated by thousands of volts thz kifwm .p/t5/rough 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 electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough storpkd; k7k2im br.0y6aued 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 24.0-V battery until*w0mjy : h ogpa55n uy8,i)sfb it is fully charged, after which it is disconnected from the battery. A slab of paraffin is tm8boa* yf u:h,p5y n5jg0)siwhen inserted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down if the electric field1welo7l 4 d:ha 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 thetr-4ci9nbe/n t/*f fn corners of an equilateral triangle (side L) as shown in Fig. 17–30. Determine the potential at the midpoint of each of the rne 4f9/ i ttf-*bncn/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 capx,6 xfja9dnjsk7 h 7;eacitor is connected to a 9.0-V battery. If a piece of Pyrex glass is placed between the plates, how much charge will then fl 6e,d 7aknjx7sx;fj9h ow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in a te8jx;y( fw+)rha -dqgx levision picture tube by a potential difference of 5500 V. It then passes between two horizontal plates 6.5 cm lo yhqg(dxaw8-r+ )jxf ;ng 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 capacitance v 5ktfzg)n(w -$C_1$ 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, shnxo +*1r-qo(unos )d1d defihj5.r7uppose you want to make a 1-F air-filled parallel-plate capacitor for a circuit you are building. To make it a reasonable size, suppose you limit the plate area to What would the gap have to be between the plates? Io+se7o- 5.nd1i *ro 1 hn (xhrjdudq)fs this practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there is an electric field of3g zbh0v)td/ ,ag9ys p 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 pulse9(edxvhmf6l 9 c6l aq4n u+wr/d 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 potential differenl 0 7y/tedc:ifce between the Earth and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are typical/itf:07cyde l ly 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 j41o0sxnb 1znx *wk 8qenough energy to some electrons i4x nbnkj1zxo18s* 0wqn 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 placed 36 cm from an ide1a8 t 7ual( d an;ey 05bfmydls33:mtzntical $+33\mu C$ 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-diameterl7x/ 4xjbn:gi coins separated by a 0.15-mm-thick piece x7/b:j ign4x lof 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*yug+i jh+ fvfq7* ,cusjidosnu7-4+ 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 are uk tuute o)0y /*0oh3k$Q_1$=$Q_2$=$5.0\mu C$, 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 witab,12b*ua o*o 5o;m dv 0dh4wkquz7jeh $q_1$=$1.5\mu C$ and $q_2$=$-3.3\mu C$ Find the potential difference between points A and B.    $ \times10^{ 5}\,V$