If two points are at the sa*zxkw4e y+y0pyc zuz (0-i 0ryme potential, does this mean that no work is done in moving a test charge from one point to the other? Does this imply that no force need be exerted? Explzx0+ *y 0iwke0 zpyy(ruyz-4c ain.

If a negative charge is initially at rest in an electric field, wilby9e: m+6yzk nl it move toward a region of higher potential or lower potential? What about a9y mne b:6z+yk positive charge? How does the potential energy of the charge change in each instance?

State clearly the difference (a) between electric potentd :bdi2rwat 9.ial and electric field, (b) between electw9.i db2:tard ric potential and electric potential energy.

An electron is accelerated by a potential difference of, say, 0.10 V. df .t p(2/re rgkkel7/How much greater would iet( /rgpk7fler /d k2.ts final speed be if it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining two e-bmlt28sl4y- un( c h*bn1kh xqual positive charges where the electric fiel1h ( n2xtb8u--k m4lbycnls*hd is zero? Where the electric potential is zero? Explain.

Can a particle ever jkwxln 9q-((rmove from a region of low electric potential to one of high potential and yet have its electric potential energy decrease?- kj nxwq9r((l Explain.

Compare the kinetic energy gained by a0rhu r:mdt: cldwt1 0+ 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 cross? Expc-1b6 0sbc /mb7sej(wi, ljb flain.

Draw in a few equipotential lines in Fig. 16 – 31b3h:4ky 1opf 5ne4ij xd.

What can you say about the elecpc7am r n(dp5)(z n/ymtric field in a region of space that has the same potential througho(/zpn 7a (nrdm) 5ypcmut?

A satellite orbits the Earth along a gravitational equipotential line.ri)4;l k: lolh What shape must the orbi l;4 ki:)lohlrt be?

When dealing with practical devices, we often take the ground (the Earth) phzzu).4kh9 u,bcgd 6 to be 0 V. If, instead, we sa k6 4gdzuzb9.hu)hp c,id the ground was how would this affect (a) the potential V, and (b) the electric field E, at other points?

When a battery is connected to nltw2z 8j2jab zq852r a capacitor, why do the two plates acquire charges of the same magnitude? Will this n85z a j2lb82zjrq2wt be true if the two conductors are different sizes or shapes?

We have seen that the capac7qvch:59 zyrwy*3ndy3u ud q va02 *huitance C depends on the size, shape, and position of the tw5u*dz*3uvqh v q0:2 auy9w3cy7hrnydo 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 electric n khy:8qd+p)sm4c2 f/m cd(rh 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 electo s8pt d46q o *xp*noco+5ej)oric field do in moving a proton from a point with a potentialootsdp8 *54 x*q)no+op6coej 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 gaicj tj gvuk//4:(a jp-fn (in joules and eV) if it accelerates through a potential difference of 23,0/j(:/ jg-vfcpukj a t400 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires sk8n-xrgm / gvw9b2 n;$7.45 \times10^{ -16}\,J$ 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 plates 5.8 m o/wtd+3c fr*zm apart if the potential difference betw cd*+ow t3z/freen them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field ofu/i yox1 (ezj+/k quz8 $640V/m$ 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 conmfk.9t4/xsld+ c..xxyw x p c2nected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two paraluc3 p;a+-jfw7pc9 w culel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is nee9u(5m yqg co.mded to give a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to h(wv;,g,ro y ia 200-V power supply, are separated by an air gap. How small can the gap be if the air is not to become conducting by exceeding its brv;gi y,wr(ho,eakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force to qh,vwr)wg +tsl0 *f,tmove 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 energ 6t 5kuxog79-xprg; aay
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whose kinetic e4qjv(biqt 3 +ynergy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nucldagwnj/( kv4f/y 56+qcq86(yuhb wazeus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) 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 froczdcp 7bsd sv/ c*z8+1m a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric potentia vnmk,o kpm,ns)(ie 2y8c2y9y))bmusl 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 footbal g 7(zihxzfx 6+jmb7u1l. This conductor carries a net negative char7m1z(jh+xgfb i7 u 6xzge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electri1 salrw3s+5 if0x s ree7 yf+p5ccw87mc 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 :h)ncc 2fbej8 the corners of a square of side L as shown in Fig. 17–25. What is the potential at the 2jn :h8fbce)c fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed point chapcn/klxb w*g3 hii8 .ktti6(/rge 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 th znit: ux**85k. urjum+1k7;x pdlekzree electrons from a great distance apart ;.znrk: *txp 1* d8 5emukzklxu7iju +to $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm norx r kg9zwn8o*jry, a871*crh/:qxlq uth 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 bead-mze61/k27(c skg z irq2ij used to accelerate a proton (radius $1.2 \times10^{-15 }\,m$) so that it has sufficient energy to just penetrate a silicon nucleus? A silicon nucleus has a charge of $+14e$, and its radius is about $ 3.6\times10^{-15 }\,m$. Assume the potential is that for point charges.    $ \times10^{6 }\,V$

Two equal but oppositeojl);4pt80x4murnd d charges are separated by a distance d, as shown in Fig. 17–27. Determine a formul40d; jolup x)t r8md4na 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 nucleu0r jpep*5 pd.cs .,s p;fgr z3c-:amsys) in a circular orbit of radiuz..fs;p, pm g3p:c5sdac*0jpre s y r-s $ 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.zguvx6qu; t.-scg csg*g -7s 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 whose dipole moment8sz)bbe k7s2p pnb :hk4h*/mo 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 t9q r yvu/h,u4negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which can be cons uh9t4,yu rq/videred 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 capacitxqr g 3l42lnt7or 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 )pi8l p m-bc1ayrk7g-b ;cq 0di vo2(mhold $+2500\mu C$ 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 )jk/e2cvr, pn ;dlj 2zcharges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of parpmv.o ,..:x*:eefbq,h yooopallel wire in air is 120 V. They carry : .,fov.o he.eomqb * yxpop,:equal and opposite charge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from 5gr .)+p+5 wwu-ke:z g.mruedecmup:each terminal of a 12.0-V battery when it is connected e+k:zgupgw 5.e. w: mmcue d-u)rr+5p to a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. Whatpzc -f)8.zp. ynfzafy .*zc3b area must the plates have if they are to be separated by a 2.3b -z p)z*.zca8pyncy ..fffz2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increasq mb -8fhc3)hj+ 8bnyses 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 7,cfg8nw qe o7n*hk1b $8.5 \times10^{ 5}\,V/m$ 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 opposite v;,uqgk/ nw vyau 7(q zcawrv*n:x). ;$5.2\mu C$ 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 t,:ldn(uz +vad63sse ahe 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 (F,p ldk- 9aw+xyqd;w-j3 nx 2wgig. 17–29a) and then is disconnected from the battery. When th- xd+ d2- wpagyx3n;kq ,9jwwlis 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(fxb gk um-56j 5.5 cm on a side that are separated by 1.8 mm of parafg 6 mb(xujf-5kfin?    $ \times10^{-11 }\,F$

  What is the capacitance of cjcm48/ive0vd4i )bbn(tp 6wk st 8h6a pair of circular plates with a radius of 5.0 cm separated by 3.2 mm o4/t vvdpn)wc4s6i i8m6(0tbbe8 hjkcf mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is conlq-ktiz6q2 tj:9b: xz nected to a 22-V battery. If a piece of mica is placed between the plates, how much charge will floz j2:z9- itlt kxqqb:6w from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a paper-sep*wt5ji,fx+bzzja s 4x8j 6p;uarated $(K=3.75)$ 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 isafb;x5x03 q rs stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillat 6a;g 3h7ahotbor is used to shock a heart that is beating erratically. A capacitor in this device is charged to 5.0 kV and stores 1200 J of enh;oa6ghb3t 7 aergy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between two square plates, 8.0 czd9)y6o2h er95s gnl*zb rx1mm on a hy1mlz xn5rg)z2 se9r 9b* o6dside, 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 is assembled by placing two 9-in. pie-sja/lxpxm-e hy c,r-0*o hc( pans 5 cm apart and connecting them to the oppositxx * rapm-jsh- y/oc,he-0l(ce terminals of a 9-V battery. Estimate
(a) the capacitance,    $ \times10^{-12 }\,F$
(b) the charge on each plate,    $ \times10^{-11 }\,C$
(c) the electric field halfway between the plates,    V/m
(d) the work done by the battery to charge the plates.    $ \times10^{ -10}\,J$
(e) Which of the above values change if a dielectric is inserted?

A parallel-plate capacitor has fixed charges 0mkmr9d rll/($+Q$ 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 s6l5v/ 7xsomm capacitor change if (a) the potential difference is doubled, and (b) the charge on each plmv sx 7ls56om/ate 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 acceleratedx3n3+l) i 0vl-st*rvw eyfr p7 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. Estimate the value of E l3rfp)3v xw*iy+t n0v7-resl.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in knejx5yzx 4( wuq*3iv4 rj,i -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 across theze iux,3yw j( 5qvn-kx 44r*ij screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from rest acquires 6.3 v-opqb:vb q i6p2, ot:*+nc zikeV of KE in moving from point A to point B. 6+b ,zt:vopc q:iivpnobq-* 2
(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 d b*5tr 9xhrxe9 cd78l:.crtjC 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 Earth’s surface whose magnitur8i-o3v- iz7am) g 6x,t tonfide is about $150\,V/m$ How much energy is stored per cubic meter in this field?    $ \times10^{-7 }\,J/m^3$

  In a television picture tube, electrons are accelerated by thousands of ao tk1e-rde1- 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 o1e-a - 1ertkodf 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 stored c .7o:ph+c xedfv)j7kenergy 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 conneqcil7c-1*)) xv;)jkdwcpqd v cted to a 24.0-V battery until it is fully charged, after which it is disconnected from the battery. A slab of paraffin is tcx)di7cqc)1 ql;p v djk*wv -)hen inserted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down if js:(d st.lth5 -q fppbps7k +: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 equiuyisa+kkch:oy/u s80 .2,8eso 5mh wvlateral triangle (side L) as shown in Fig. 17–30.ykahuiu82 y8+o/es.svh ck s:5wm 0o, Determine the potential 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 conne2mcz 4am/ jd(svfc6p4z *wy ;tcted to a 9.0-V battery. If a piece of Pyrex glass is placed between the plates, how much charge will zvydc tsw6m 4z/pm4 afc(j2*;then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated j 4sfckeih,33eap6z ;0 l3whghorizontally from rest in a television picture tube by a potential difference of 556 lezsea ,ck f0p w;3jh34i3gh00 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 capacita 9*xxt6ekcwdm/ix :o0j 87h q6 obgly)nce $C_1$ 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 make a 1-F air-filled c+u,es :le b6xparallel-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 prac: usc el,+6xbetically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there is an electric fiel dj/ql:0tz 1eg3p zkun6r4n9 qd 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 l2;pr nct4v dq.aser 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 diffe39xh; iwwp 3bbrence between the Earth and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunph9i3 bxb3w w;derclouds 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 enough energ6abkbo4.p. n) ox f(uvy to some electrons in barium metal to eject them from a surface at high speed. u 4p. o.kfbo6 x)n(vbaSee 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 fry9z4pkbv/ar:zp 7 5uh/yq)bo om 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-diameter coins separck8bhhx+r2ble;g4+ x)k) px -5anp gtated by a 0.15-mm-thick piece of gh+pc) bx+tap;nbl4x)h8kg25xk r e - 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 capaci n4aj)7 une8*l b6;yhe*zmpsf4- sq uptor with 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).3ur wv(lago hjm)6i 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 placeduc, jr))i/v)ajx owiw w.9a**o/ cvsx 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$