If two points are at the same potential, does this mean that no wvxj+ n4j l xr 9yfp,t-x6/+tvbork is done in moving a test charge from one point to the other? Does this imx 4/vtpjtx6j x-9+fv, lrbyn+ply that no force need be exerted? Explain.

If a negative charge 99b/a hwjs*vbis initially at rest in an electric field, will it move towabhv j 9as*9/bwrd a region of higher potential 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 and electric fiel, 9by .d7atp1 jvp nhzg/94wzatil7v *d, (b) between electric potenz lhb vt1 / g7.np 94zt9j7idvpaay*,wtial and electric potential energy.

An electron is accelerated by am ug;)5usknk* potential difference of, say, 0.10 V. How much greater would its final speed be if it is accelerated with four times as much vol*ksk)5 mnu;ugtage? Explain.

Is there a point along the line joini p d0h,zmgyp4:ng two equal positive charges where the electric field is zero? Where the electric potential is zero? Explainhgdzy p0p m4,:.

Can a particle ever move from a re tnktmh 9/2mj4gion of low electric potential to one of high potential and yet have its electric potential energy decreammn t 4/h9tk2jse? Explain.

Compare the kinetic enmoce/rifxr97 6yc.5 b ergy gained 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 c/obl 4qc/./tgf abx0cross? Explain.

Draw in a few equipotential lines in Fig. 16 – 31b. q,lmrr t: zpbdcr,::7

What can you say about the e zg:g e-g:5swhlectric field in a region of space that has the same-hzg eswg5 g:: potential throughout?

A satellite orbits the Earth k hyc4 ier:et42l 0s:falong a gravitational equipotential line. What shape must te0c2 4ti:hrs :flyke4he orbit be?

When dealing with practical devices, we often take the ground (the Earth) t+pu.;0kj h 8 dmfbuqtuh 46uo9o be 0 V. If, instead, we said the ground was how would this affect (a) the potentialj0b;9hdu hqmo6u u.p4kf +8ut V, and (b) the electric field E, at other points?

When a battery is connected to a capacitor, why do the two pcd4h cifcg9*9p :m)oj lates acquire charges of the same magnitudec4:o ) p9c9ifmgdhc* j? Will this be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends o(xykw* r: u;rxw2wy+kg q27 xonu65yan the size, shape, and position of the two conductors, as well as on the dielectric constant K. What then did we mean when we said that C is a cr* 72yx;xky+2u 6a oyu5w w(:kgnxw qronstant in Eq. 17 – 7?

  How much work does the electric field do in mon6,hn1ybcqss a nt05ok,t 24 uving a $-7.7\mu C$ charge from ground to a point whose potential is $+55V$ higher?    $ \times10^{-4 }\,J$

  How much work does the 4lc z7:zfvizr 04l,hf64uxfv electric field do in moving a proton from a point with a potel fz4vz,cr 4ul60v4:fhfzx 7i ntial 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 elec9h/kxba y*mqui/ :a hbg(f5+s ou1)evtron gain (in joules and eV) if it accelerates through qyg(b i) e m:/vfu1ko/x9*sah+b5ahu a potential difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquiresy1 pxp/figj )2)2dy-j1 pm svr $7.45 \times10^{ -16}\,J$ 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 betrppv52hn5amt0/ 3cr dween two parallel plates 5.8 mm apart if the potential difference between tra2vpmcrth 0n 55pd3 /hem is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of k8hcfq qc.2* e$640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two paralleli9p scy* :6p3owdsya- plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connecteq+s(7b4b, bin n3f1 o0jdgcusd to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a helnvty3ki h 7cj ae5,r,pfxm*6 0ium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, are separated by an ,q ai:p et8-d l4lb*yk ,k.yohouol:7air gap. How small can the gap be if the air is not to become conducting by exceeding its breakdown, q,y:.yuea*lt - oko hoi 8bl4p:k7dl value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an extl ,4iz; a6j5yxkpriy+ernal force to move a $-8.50\mu C$ charge from point a to point b is $15.0 \times10^{ -4}\;J$. If the charge was started from rest and had $ 4.82\times10^{ -4}\;J$ of kinetic energy when it reached point b, what must be the potential difference between a and b?    V

  What is the speed of an m7n1g) ber- v9:gnfwnu5s ; raelectron with kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a z84.gc0cf-:v-r rhc3fahis uproton whose kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which isvq*ri(.f 0a (nm4wor s(4eeky 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 potential 15.0 cm fo fydmii5y9a j5dz:5(gnq+ 0 erom a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electric pote2 w5ui6vvw2qt4; loxyntial 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 caxrk2k s/hl-h;rries a net negative charge, l 2k;kr-/xshh$-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potentia.)u d(pui :d z20tcauwl a distance of $ 2.5\times10^{-15 }\,m$ away from a proton?    $ \times10^{ 5}\,V$
(b) What is the electric potential energy of a system that consists of two protons $2.5 \times10^{-15 }\,m$ apart — as might occur inside a typical nucleus?    $ \times10^{ -14}\,J$

Three point charges are arranged at the corners of a square of side L a sbw 98g3:a(:bqzqmbxz +y)qd s shown in Fig. 17–25. What is the potential at the z yxgqz 8a bbs3dqb:q)+(m9w:fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed point charge wiy8x/sz cac13e le d+ qh5br8m)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 apaqd 3r,+uu;agm rt toauur;g,+mq3 d $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is q(fcd5o3 m wex,od7 *8nvg*cqo-qh0n 72 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 4,,zs wpf56h 5ykspvt 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 opposite charges are 4zu 7ny1 9 pncoz;d*vfseparated by a distance d, as shown in Fig. 17–27. Determine a formulp71 zcnvnu y*;ozf d94a 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 orbif8z4i0 h2ntcfts a proton (the nucleus) in a circul0zf8ncft i42har 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 o ,l, vg) klbz)7/prg/gveb9p 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 y,gmhg7o 3gm* - qka-ddipole moment is $ 4.8\times10^{-30 }\,C\cdot m$ at a point $1.1 \times10^{ -9}\,m$ away if this point is
(a) along the axis of the dipole nearer the positive charge;    V
(b) 45° above the axis but nearer the positive charge;    V
(c) $45^{\circ}\,$ above the axis but nearer the negative charge.    V

  The dipole moment, considered as a vectg(o ntsg/9 z0oor, points from the negative to the positive charge. The wg(0 o9n /sztogater molecule, Fig. 17–28, has a dipole moment which can be considered as the vector sum of the two dipole moments, $\vec{P}_1$ and $\vec{P}_2$as shown. The distance between each H and the O is about $ 0.96\times10^{ -10}\,m$. The lines joining the center of the O atom with each H atom make an angle of $104^{\circ}\,$, as shown, and the net dipole moment has been measured to be $p\,=\,6.1 \times10^{-30 }\,C\cdot m$ Determine the charge q on each H atom.    $ \times10^{ -20}\,C$

  The two plates of a 6/pnfwda/9ue+d q c,vcapacitor 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 cap+/w kf) mkgx 5qmsc/p,acitor 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 charcrim o6( 6 fkxw+.rr;gges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between tq32 bkl63n9ryky7am86jai z owo short sections of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is the capacitancear3ybq2y n 3kj6o mia87 9lzk6 of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each t,4 /2iwt;*sa todlne herminal of a 12.0-V battery when it is connected ts*2eat,;lwh o i/n4td o a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is z 8e b:bkll sp-k7ou2*desired. What area must the plates have if they are to be separated by a 2.2-mm a7-lp ks eblub2 8*o:kzir gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increases/il qv2io ybz0;iv:n j32s:vj 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 tz) dyb6d9js+q0r- uu la2i 7f$8.5 \times10^{ 5}\,V/m$ 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 94sk7r fmjc jma(eb/hv:3c9h $5.2\mu C$ 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 fjykx8m1j:zc4 j 0-noo l7:lhg z;oolw 7iu-:vield 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) a5xg6k k vcpx99nd then is disconnected 69xv9gxc5pkk from the battery. When this capacitor $(C_1)$ is then connected (Fig. 17–29b) to a second (initially uncharged) capacitor, $C_2$, the final voltage on each capacitor is 15 V. What is the value of $C_2$? [Hint: charge is conserved.]    $ \times10^{ -5}\,F$

  A $2.50-\mu F$ capacitor is charged to 857 V and a $6.8-\mu F$ capacitor is charged to 652 V. These capacitors are then disconnected from their batteries. Next the positive plates are connected to each other and the negative plates are connected to each other. What will be the potential difference across each and the charge on each? [Hint: charge is conserved.]
$V_{final}$ $\approx$   V(Round to the nearest integer)
$\begin{array}{l}
Q_{1}\\
\text { initial }
\end{array}$   $ \times10^{-3 }\,C$
$\begin{array}{l}
Q_{2}\\
\text { initial }
\end{array}$   $ \times10^{-3 }\,C$

  What is the capacitance of two square parallel plates 5.5 cm on hxt:gk5 4,0 g,vkkfrq( /vdbia side that are separated by5khf k,bv4q: vxi 0gdk(gt/ r, 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circgdt*1; ;ldnjzular plates with a radius of 5.0 cm separated by 3.2 mm of mica?*d; lz 1;ntgdj    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is conne/ix6o o;jk3u (aiyl5 k2e mym9cted to a 22-V battery. If a piece of mica is placed between the plates, how much charge will flow fym a/km;oiyuexjo56k( 9i l3 2rom the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a pks;d3p(sr8 yr asoa+eo-i3 )0b*i vpjaper-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 cap 5 b klccut:+m)qtt30cacitor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is be yk;ax :u;27 kkja/o 4g;;y,w rozrqoeating erratically. A capacitor in this device is charged to 5.0 kV and stores;o/uq;aagkk7w4eo y,;yjz2 : rxo; k r 1200 J of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is stored by the electric field between twoi x iw*07oykvao1 wo31 square plates, 8.0 cm on a side,1io13 w0 yo*o7wav ikx 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 assemble:qmuwc, kj,- 3xzkda.d by placing two 9-in. pie pans 5 cm apart and connecting them to the opposite termina,k a jd:ukwzc3,qm.- xls 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 sjnx 72 7(,ofzrg/yficharges $+Q$ 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 capa3pke j6+c;e3kr ubsaojt2/9hq bi5a 7citor change if (a) the potential difference is doubled, and (b) the charge on each pcb+q3 are3 jt97/5poua kks ; ijbh2e6late 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 accenfv7 .qtvuq9r)nx w9 3lerated horizontally by 7.0 kV. They then pass through a uniform electric field E for a distance v).qnv 9run3t9w fq7xof 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 kV in a CRT. The screen is 30 cm wide and is q.p ri *pmn9n(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 the screen? (p9*nmpi . nrq    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from rest acquirei0zg lfwvs73qz tsmwm.v8(r ,rp+yc7 .4pf3ks 6.3 keV of KE in moving from point A to poir mrfv7 pkw s.38f,0si(q3z+ytmplgw7z v4 c.nt B.
(a) How much KE would a proton acquire, starting from rest at B and moving to point A?    keV
(b) Determine the ratio of their speeds at the end of their respective trajectories.   

  A lightning flash transfers 4.0 C ofck0i mpe +4qf38u4zmf 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 qtsv l:cufn 3o q215k1y(d ;pqmagnitude 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 thousan;v /w)0sc vjmods of volts through a vacuum. If a television set were laid on its back, would electrons be able to move upward against the force of gravity? What potential difference, acting over a distance of 3.0 cm, would be needed to balance the downward force of gravity so that an electron would; m0j vvwco)/s remain stationary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough 4i wxs69gpff* stored 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 it is fully char.h60k1 0+yhiss 4co 6eplew bjged, after which it is disconnected from the battery. A slab of paraffin is 1o40kys 6ehw+cb.pj0ei l 6 hsthen inserted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down if the/fuwu06b9ra u:6cjqj 4nt n 7l 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 /ci0v9-hg+t8vsu ky6 8ha 5lonwl,hmequilateral triangle (side L) as shown in Fig. 17–30. Detea htol80cmh9h ,vv8l 6kn suy/w -5gi+rmine 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 connected t ukjym4t/ /0 8ccspn2so a 9.0-V battery. If a piece of Pyrex glass is placed between the plates, how much charge will then flow from u cyj4stn kc2m//p0 s8the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizont1w -ckjtr6ni6 ally from rest in a television picture tube by a potential difference of 5500 V. It then passes between two horizontal plates 6.5 cm long and 1.3 cm apart that have a potential di1- c j6irwtnk6fference 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 capacitancfg 0mo9coy-z -e $C_1$ 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-k./h ykb vgq5;F air-filled parallel-pla/ .5;kvhkqy gbte 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 thevk pmar-2:b-gsg:px 8/c fsh 2 l5atc8 Earth there is an electric field of about $150\,V/m$ which points downward. Two identical balls with mass $m\,=\,0.540kg$ are dropped from a height of 2.00 m, but one of the balls is positively charged with $q_1$ = $650\mu C$ ,and the second is negatively charged with $q_2$ = $-650\mu C$. Use conservation of energy to determine the difference in the speed of the two balls when they hit the ground. (Neglect air resistance.)    m/s

  The power supply for a pulse,)s1 gd nyykp/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 potentwh-- -wxml m(iial 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 typical i l(mw-hw-xm-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) ligrp6bd -+ 81q cy2xkvpe,j z8xtht provides enough 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 potentia,d8bprv6c+8xz2 xy pk-qt1ejl 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 -*;wln,hz:h 6rh rf tt36 cm from 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 fbw2(l,nj al0coins separated by a 0.15-mm-thick piece of papebal(2n0jw, f lr $(K=3.7)$ 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 p lj+8ne qrz,m83.kco noda;)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.cs(mw. xr9 w8z0 cm apart from each other. Their charges are $Q_1$=$Q_2$=$5.0\mu C$, and their masses are $m_1=1.5mg$ and $m_2=2.5mg$
(a) If $Q_1$ is released from rest, what will be its speed after a very long time?    m/s
(b) If both charges are released from rest at the same time, what will be the speed of $Q_1$ after a very long time?    m/s

  Two charges are placed as shown in ez gp3d.b(wl dypudc 6x:197uFig. 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$