If two points are at the same potenti5i4p-ns fa:sp al, 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 nssa-p4 f 5pin:eed be exerted? Explain.

If a negative charge is initially at rest in an electric field, will it move tjh4 hv .w-qe9poward a region ohwh-e9 4. jvqpf 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 anj j 0-ypmzo(,fd electric field, (b) between elecy (jpof ,m0jz-tric potential and electric potential energy.

An electron is accelerated z(n0+;o5fotv qmo yo3 z8tzsv t 8g p:85fbs8yby a potential difference of, say, 0.10 V. How much greater wz(vytof g; obsotzo +5 m8 p5n3:t08qvszfy88ould its final speed be if it is accelerated with four times as much voltage? Explain.

Is there a point along the l7b ln: phzs297/iv0ht5aar5u sd av,oine joining two equal positive charges where the electric field is zero? Wher5,7lvz7tdr 9so2/a5p0:bn ahiv sha u e the electric potential is zero? Explain.

Can a particle ever move n(uvjq2 e9 a0tfrom a region of low electric potential to one of high potential and yet have its electric potential energy decr2q v(ju9na0 etease? Explain.

Compare the kinetic energy gained by d/lkt v3;y5j 4cvm-cua 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 linisq-jg ta /lh (w.fv9.es cross? Explain.

Draw in a few equipotential lines in Fig.ssma4 c gtc ug4;ps,k.twt-l:*m/2 it 16 – 31b.

What can you say about the electric field in a region of space that o*cz/jldjf m6qeq7 6:has the same potential tj67j6ecq fd om/ql*z :hroughout?

A satellite orbits the Earth alo7gvu,e ud us*0ng a gravitational equipotential line. What shape mu u us,g7uv0d*est the orbit be?

When dealing with practical devices, we often take the ground (the Earth) to a2x2z in.nea8 be 02aexi zna8.n2 V. If, instead, we said 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 a capacitor, why do the twoax7( d 26lquo3gxajbmgao+- * plates acquire charges of the same magnitude? Will this be true if the tw 37jg glao+* ob6ua dm(aqx-2xo conductors are different sizes or shapes?

We have seen that the capaig8:s:.buwl jim hi: z4tpvi //xj, u/citance C depends on the size, shape, and position of the two conductors, a w mhv/ijl8/:u:xi. tugbsi/:i, jz4ps 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 elevm0,-q b)r hkgctric 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 movin nto 4t;fstc+/s3leguj7ps: -r k /tn;g a proton from a point with a pottl3-/;/ nefgtcjo;ss4p+ks r7:un ttential 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 ab(dqk(y/) hzln electron gain (in joules and eV) if it accelerates through a potential d/kzlbh(y)d (q ifference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires l(uw /fo29 r)pb dqa/c$7.45 \times10^{ -16}\,J$ 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 elec8):v fs c3juiutric field between two parallel plates 5.8 mm apart if the potential difference be8:j3vi usc)u ftween them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of dz6, w pu6:)iioedh 4vg- i:zx$640V/m$ 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 connec -qgnl+n;h0vilmg : b0.thc84odef y: ted to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates cdb+)1jyz :k t w*ff;mxonnected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference idkc+ 3kg:mu*ens 3cc :c1+ht8 bwf*ku s needed to give a helium nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to bd)h m z5to(h,a 200-V power supply, are separated by an air gap. How small can the gap be if the air is not to become conducting bybm5th)zd h(o, exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external foxp4ih,/l/6 eoo 8dskorce 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 kinevh;tc6t,pp f0m b, dq*tic 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 energ ) 5bkiu9x:kiry is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (wfgtb*;2 p/jzs t7h0rvhich 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 potential 15.0n,2lcy m(h. jv cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q createoa02d 27zma1 cotsoi.6n - yfbs 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 conductor carries a net ne 67 lca8sr j1h-scczf1 frn+0ndcx b+x 9o/l,egative jc n f7 a1,++ z 1c9bc-0sodefxclslxr6/r8nhcharge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a dby,j (m jshi*7m*jv d0istance 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 th/tb hpkb(l.gh6 +br-je corners of a square of side L as shown in Fig. 17–25. What is the potential at the + jrb6p b gh.lbkh-/t(fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 a78t-a:hi2i bq+7 ;iqa wlv tocm from a fixed point charge with $Q\,=\,-0.125\mu C$. How fast will the electron be moving when it is very far away?    $ \times10^{7 }\,m/s$

  Two identical $+9.5\mu C$ point charges are initially 3.5 cm from each other. If they are released at the same instant from rest, how fast will each be moving when they are very far away from each other? Assume they have identical masses of 1.0 mg.    m/s

  Two point charges, $3.0\mu C$ and $-2.0\mu C$ are placed 5.0 cm apart on the x axis. At what points along the x axis is
(a) the electric field zero    cm leftof $q_2$
(b) the potential zero? Let $V\,=\,0$ at $r\,=\,\propto$.

  How much work must be done to bring three electrons from a great fwl-6u 4o7mrf pm0j-odistance apart tomo6 -7 fr0mpu4 w-jlfo $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm norinj6dzhzll5, q46o .ath 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 accele* .)ko/vxw ahcrate 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 c t.8* x)ltai 7+viaydseparated by a distance d, as shown in Fig. 17–27. Deteaxti.la*7i t +vy )8dcrmine 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 t t fq4wvxw /vf37e0c0ihe hydrogen atom, an electron orbits a proton (the nucleus) in a circular orbit of v/ffq0 0wc37xw ei vt4radius $ 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 (- +keac )jjzcare $ 0.53\times10^{ -10}\,m$. apart. What is their dipole moment if they are at rest?    $ \times10^{-30 }\,C\cdot\,m$

  Calculate the electricpx *-bt8o g6ep 8jxtu( potential due to a dipole whose dipole moment is $ 4.8\times10^{-30 }\,C\cdot m$ at a point $1.1 \times10^{ -9}\,m$ away if this point is
(a) along the axis of the dipole nearer the positive charge;    V
(b) 45° above the axis but nearer the positive charge;    V
(c) $45^{\circ}\,$ above the axis but nearer the negative charge.    V

  The dipole moment, considered as a vector, poi/hrpo+ ybm)sj5zm-5y:(o l ctnts from the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole moment which -y 5 rms(m:/ot+5 o pbjh)czylcan 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 caa d,ev:mwx(98/sc1upddy r+f pacitor 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 capac/ x eg:+pfkqw)th;s)z itor 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 chargeaq)e-fomn*( n s of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sections of par3j/,zgm 9n bvkallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What i93vm /zkj,g bns the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from ea68d-+poaejt7(veh.t xyl7dlch terminal of a 12.0-V battery when it is connected to 6+t-he8lxot 7( pl7ydjad . vea $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates have if they au+hbyvvrr. +-vo) i. 3 /kt jusbo51jtzy; ;zyre to be separated by a 2.+ o3;vv r.s;t)b.5 vouz yhiy zyub1 jkjtr/+-2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increasesqijm7q -k pwz 8sml204 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 of5b id *ojqvf :(1jh8 r5(ysaqs $8.5 \times10^{ 5}\,V/m$ 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 e) cn(uj .6bnyiwzn; :$5.2\mu C$ 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+ir2-bkov5yf/2p5 g uy a6n dr plates of a $0.80-\mu F$ air-gap capacitor if they are 2.0 mm apart and each has a charge of $72\mu C$ ?    $ \times10^{4 }\,V/m$

  A capacitor is charged by a 125-V battery (Fig. 17–29a) and then is discontb6c2um 1lhryel 8;8c ch cv(2+ mgeq:nected from the battery. When this capacicmcbyqv:1 h8um2(8;c+ lreg6hc2 e lt tor $(C_1)$ 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 5.544cblow (y p9 fn)bbv5 cm on a side that are sepa )c(4bbp4flo9n byw5vrated by 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circullk.e8sno3;375urib vt on, nuar plates with a radius of 5.0 cm separated by 3.2 mm of si n ,l5ubn t.ru3n8oekov7; 3mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to a 2 t+jbd u19)gnn:ft2)uyggqc5 2-V battery. If a piece of mica is placed betweengj f9+ y u)12u gnd)b5tgnq:tc the plates, how much charge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of aey9 re 60oau;o 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 capaci-5ej d+tadg e/tor. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beatinp)-zgbb be6gu,j/ n./o*jp gzg erratically. A capacitob -/pjo,u *znejgp6gzgb/) .br in this device 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 field between two square plates, 8.0w. a2txf x/yov- u8n8a cm on a side, separated by a 1.5-mm air gap? The charges on the plates ar 8xtna82o/ u-.awxvfy e equal and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing tw a(wt. ;8cgsgfe 9*s-de*.nof+whmnr o 9-in. pie pans 5 cm apart and connecting them to the opposite terminals of a 9-V batteryg s w. fec8r*mn.wg*-nest;fa(9+o hd. 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 capaci2f)*no;rdxjdc3) v yn 8ll b2ator 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 capaciy 024vg sw8wf ujx5ne6tor change if (a) the potential difference is doubled, and (b) the charge on each we u8 2y0nj5sv46x wfgplate 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 acceleratedfrn iloal7 e -a)8)h+y horizontally by 7.0 kV. They then pass through a ) lanf8i+7l)a-heoyr 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 kV in a Ca0io2mfe - w1pRT. The screen is 30 cm wide and is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizontally deflectinp-m02io e 1fwag 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 moving from poin-p: cj xq:,r ukm,j1ez( )6x/esmfnyot A to point px1c:,6/ymjo)j x-rsz f,:eukn e q(m 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 transfersiwqw )/ja3 7zn 4.0 C of charge and 4.2 MJ of energy to the Earth.
(a) Across what potential difference did it travel?    $ \times10^{ 6}\,V$
(b) How much water could this boil and vaporize, starting from room temperature?    kg

  There is an electric field near the Earth’s surface whose magnitude is )doniqmwgf lr - k-n(jk6*w 0g )c/jf/f 6u6nvabout $150\,V/m$ 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 thousanw ,5hz;pe1pm +plxp:l ds of volts through a vacuum. If a television set wl1 pmxh5;z p, w:el+ppere 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 hasjk)g;s5 4uqmg enough 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 i2vtq7 6bte)d fs fully charged, after which it is disconnected from the battery. A slab of paraffin is then ivt2)t7qe6bd fnserted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down if t6sephgqku 0+t-h3qs (he 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 e0 n 5-0hac eeg/hqdsa2 zq.9:jcf3ddiquilateral triangle (side L) as shown in Fig. 17–30. Determine the potential at the midpoint of each of thqd3f/.eagj-2d9 hcq e 5 a0i0zds c:nhe 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 7 uvh-v b (t;wvb.vmh1is connected to a 9.0-V battery. If a piece of Pyrex glass is placed betwe bhw7buv(v;t.m-v1v h en the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in a tel4.6s uez e8ftjpj-s,zevision picture tube by a potential difference of 5500 V. It then passes between two horizontal plates 6.5 cm long and 1.3 6fu,p j.s -jte z4ez8scm 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 capacibv1 z*ke*y 2eitance $C_1$ 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, suppr:ajvi8wb(exul6h*ey 1/sr j* e 6mv/ ose you want to make a 1-F air-filled parallel-plate capacitor for a circuit you are building. To make it a uwrsebjma/x:lj816vi*r6 (h *y/ee v 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 +(q, oxxatu p+d.yiz/ 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 nitror ,5sm,kd )ctigen 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 difference between thw r0es )4mxeu3e Earth and the bottom of the thundercloudsswemex4 u3)r0 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 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 energy to somehguz6 4g6de 05narhn) electrons in barium metal to eject them from a surface at high speed. See Fig. 17–33. To measure the maximum energy of the u)g r6 aehg4z5 nhdn06electrons, 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 froq g(vjz +la uq4.3z8bxm 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 sd kr;o.d/ 3nxn02mx h)n.f9pilwny ,reparated by a 0.15-mm-thick rk2)0d rfi/o;nhn xnpx,.dm3y 9wln.piece of 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 btn,v8rh 1b -3ezdr+i 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 cha- ggi)(e st p;qmq+bf9rges 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 show i y2wcyi-r/a;a sc,v:n 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$