If two points are at the same potential, does this mean that no work is done i wz0dmdx 6n: z,vu6vh.n moving a test charge from one point to the other? Does this imply that no force need be exerted? Explainzdxvd:6u .w,6 zmvh 0n.

If a negative charge is initially at rest in an ele g ;;.y,2tpiv,txcmp ectric field, will it move toward a region of higher potential or lower potential? What about a positive charge? How does the potential energy of the charge change.2t,iyp ,;epg;xvt c m in each instance?

State clearly the difference (a) betweenp y.l s0mb;q,iii-uw-9bi) rd electric potential and electric field, (b) between electric potential and electric potential energy.qlbd-by ir) ium,9 .p-is0 w;i

An electron is accelerated by a potential differo j kza53lg97tence of, say, 0.10 V. How much greater would its final speed be if it is gloa39z5 jkt7 accelerated with four times as much voltage? Explain.

Is there a point along the line joining two equal positive charges wh:;gc2 ljzgx -cere the electric field is zero? Where the electric potential is zero? Explxc;g c2glj -z:ain.

Can a particle ever move from a region of low electric potenys6 godnn1fb+jpt9) :tial to one of high potential and yet have its electric potential energy decrease? Explatjo nf:pdg 9y n+1)s6bin.

Compare the kinetic energk4xkk2 1z -8zt1i yk;ohl hl-iy 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 $\overrightarrow{E}=0$ there? If $\overrightarrow{E}=0$ at some point, must $V=0$ at that point? Explain. Give examples for each.

Can two equipotential lines crosvg(nhypqal:q57a 8d c1rr,b3s? Explain.

Draw in a few equipotential4 3jilzlo7f1: 6 woscb lines in Fig. 16 – 31b.

What can you say about the electric field in a region of uyy atji.jq 5*wa/)/k space that has the same potential y.ij*/ aw) 5 ytk/uajqthroughout?

A satellite orbits the Earth along a gravitational equipotential line. Wqfh/ k ,tg9y7uhat shape quh/k,y 9tfg7 must the orbit be?

When dealing with practical devices, we often take the ground (the Earth) tonvvd8k5 wnz//)+,excq )uofg be 0 V. If, instead, we said the ground was how /ovd8c +kv e)u) x,5q/gfnznw 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 dmm75xt 0das r) u yivd,0; /kzmq9qq2wo the two plates acquire charges of the same magnitude? Will this be true if the two conductors are different sizes or shkumdzqmqvawi;q7s xr 9)0, /d2mt5 y0 apes?

We have seen that the capacitance Cv :b x b,hyhn,vd0o:/b depends on the size, shape, and position of the two conductors, asohb:bb dn,:v 0,x/ vhy 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 fi8 ffpoe.-dg z7eld do in moving a $-7.7\mu C$ charge from ground to a point whose potential is $+55V$ higher?    $\times {10}^{-4}J$

  How much work does the electric field do in moving a pro vcn ffiq):)t-2m :bloton from a point with a potentfbn:o :2l-)t)fivm c qial of $+125V$ to a point where it is $-55V$ Express your answer both in joules and electron volts.
   $\times {10}^{-17}J$
   eV

  How much kinetic energy will an electron gain (in joules and eV) if it acceleg-/gceza- j (rrates through a potential dig-rzc(- /g eajfference of 23,000 V in a TV picture tube?
   $\times {10}^{-15}J$
   eV

  An electron acquires (au,fneqtriwu4 zf3f/3 z(;a $7.45\times {10}^{-16}J$ 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 pla q x)7uembn izslo-z6fd9,u()b6/*jpv b lf0btes 5.8 mm apart if the potential d6*bbl fd6juvz/(-9 x qp )embib7 nfso)ul0, zifference between them is 220 V?    $\times {10}^{4}V/m$

  An electric field ofn7xhc g1,i;k4js+zab5)wf 2 ykti:a u $640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two parallebrs.+lt,i y2ml8qhk wqgdu 46( 6m/ cml plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between two parallel plates connected to a 45-V bat- smf c/)quw0ytery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a heliumjnfuwxf uad* 2fp4788 j-du 1c nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $\times {10}^{4}V$

  Two parallel plates, connected to a 200-V power supply,d tk,hylt37d lgv): e*,jjl4g are separated by an air gap. How small can the gap be if the air is not to become conducting by exceeding its breakded3g ,ll h d4kl*ty:j7tvg), jown value of $E=3\times {10}^{6}V/m$?   $\times {10}^{-5}m$

  The work done by an l n8frh g6ym qwf4y 35aa8jn:6external force to move a $-8.50\mu C$ charge from point a to point b is $15.0\times {10}^{-4}J$. If the charge was started from rest and had $4.82\times {10}^{-4}J$ 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 energy /, fio4;2+s kpzddjkq
(a) 750-eV,    $\times {10}^{7}m/s$
(b) 3.2-keV?    $\times {10}^{7}m/s$

  What is the speed of a proton whose kineticbo; rcy-0bm 9hn/ 5qt6xyew+p energy is 3.2 keV?    $\times {10}^{5}m/s$

  An alpha particle (which ix2kis v8mr+v6m80 gg ts a helium nucleus, $Q=+2e$, $m=6.64\times {10}^{-27}kg$) is emitted in a radioactive decay with ${}_{KE}$ = $5.53MeV$ What is its speed?    $\times {10}^{7}m/s$

  What is the electric potential 15.0 cm from ,* x0ow-kdnrx a $4.00\mu C$ point charge?    $\times {10}^{5}V$

  A point charge Q creates yg h*g)/evu ,uan electric potential of $+125V$ at a distance of 15 cm. What is Q?    $\times {10}^{-9}C$

  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 car/uiz jins6vf6fc*x)zq b*.x6 8ulq p*ries a net negative chargesp qf*l6) *u6iq*vx n/z cx8z6 jfi.ub, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric m8zlhm4a *cto--fn l,potential a distance of $2.5\times {10}^{-15}m$ away from a proton?    $\times {10}^{5}V$
(b) What is the electric potential energy of a system that consists of two protons $2.5\times {10}^{-15}m$ apart — as might occur inside a typical nucleus?    $\times {10}^{-14}J$

Three point charges are vgt70vy)-8ttw,+8rk e twa ep arranged at the corners of a square of side L as shown in Fig. 17–25. What is the potential at the fourth corner (point A), takinte 8 ,wvek-wp8 rtt+av)7 ty0gg $V=0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixed point char4m4s5p iwagzy +k8fea( z /ms4ge with $Q=-0.125\mu C$. How fast will the electron be moving when it is very far away?    $\times {10}^{7}m/s$

  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 apar 71x /ej9bp0cwn igtwg1r f8x8t to jx/ g 8x1cf087 gtb wewipn91r$1.0\times {10}^{-10}m$ from one another (at the corners of an equilateral triangle)?    $\times {10}^{-18}J$

  Consider point a which is 72 cm noz ydh6-k;g 1be8fsh 8wrth 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) ${\overrightarrow{E}}_b-{\overrightarrow{E}}_a$ (magnitude and direction).
   V/m
   ${}^{\circ }$

  How much voltage must be used to accelerate a ff) mqc75+qdkdjg8 l)(k9zi fv)v ;dtproton (radius $1.2\times {10}^{-15}m$) 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 $3.6\times {10}^{-15}m$. Assume the potential is that for point charges.    $\times {10}^{6}V$

Two equal but opposite charges ar8m6: knjm0o3kd wawa5 e separated by a distance d, as shown in Fig. 17–27. Deterdww0k a8m6 jn3om:ak5mine 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 at+*k(w jbp,r6v r lja.fom, an electron orbits a proton (the nucleus) in ab+ wjjfvkr .6,pl( ra* circular orbit of radius $0.53\times {10}^{-10}m$.
(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?
   $\times {10}^{-18}J$
   eV
(c) What is the total energy of the electron in its orbit?    $\times {10}^{-18}J$ $\approx$    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.   $\times {10}^{-18}J$    eV(Round to the nearest integer)

  An electron and a prlap*q(sxdv47qa4z; 9 gmo vp 3oton are $0.53\times {10}^{-10}m$. apart. What is their dipole moment if they are at rest?    $\times {10}^{-30}C\cdot m$

  Calculate the electric potential due to j (o-v4vzwt;o a dipole whose dipole moment is $4.8\times {10}^{-30}C\cdot m$ at a point $1.1\times {10}^{-9}m$ 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 ft 3ix;daca*vx;bys 63x, p7jfrom the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole m6*dtxavb;yjsx;pf 373a c xi,oment which can be considered as the vector sum of the two dipole moments, ${\overrightarrow{P}}_1$ and ${\overrightarrow{P}}_2$as shown. The distance between each H and the O is about $0.96\times {10}^{-10}m$. 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 $p=6.1\times {10}^{-30}C\cdot m$ Determine the charge q on each H atom.    $\times {10}^{-20}C$

  The two plates of a capacitor hotya)mfuf8 .2ih9by ,pld $+2500\mu C$ and $-2500\mu C$ of charge, respectively, when the potential difference is 850 V. What is the capacitance?    $\times {10}^{-6}F$

  The two plates of a capa xya6l3-st3nv citor hold $+2500\mu C$ and $-2500\mu C$ of charge, respectively, when the potential difference is 850 V. What is the capacitance?    $\times {10}^{-6}F$

  A 9500-pF capacitor holds pa5zxp /m;/q3d5zvt/(ajji u a lus and minus charges of $16.5\times {10}^{-8}C$. What is the voltage across the capacitor?    V

  The potential differen7 fc0:xdr-i:6bs k rjqce between two short sections of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is theq: cbf6 rsi07x-:dkjr capacitance of the two wires?    $\times {10}^{13}F$

  How much charge flows from each terminal of a 12.0-V battery iqhmo;y( r0h)when it is connected thh0)qr o (myi;o a $7.00-\mu F$ capacitor?    $\times {10}^{-5}C$

  A 0.20-F capacitor is desiredbs 8uzb-xeg+c0te .9 c. What area must the plates have if they are to be sepa98tbz+-egce0x .c s burated by a 2.2-mm air gap?    $\times {10}^7{m}^2$

  The charge on a capa) eoxtzpwj m2gc8:1q+ (5opw8x fflb) citor increases by $18\mu C$ when the voltage across it increases from 97 V to 121 V. What is the capacitance of the capacitor?    $\times {10}^{-7}F$

  An electric field of 6 vyhr w:mk-ig6hf;2oae.c afq** dkv7 xh/f8$8.5\times {10}^{5}V/m$ is desired between two parallel plates, each of area $35c{m}^2$ and separated by 2.45 mm of air. What charge must be on each plate?    $\times {10}^{-8}C$

  If a capacitor has opposite el8mx q8 0uw:e$5.2\mu C$ charges on the plates, and an electric field of 2.0 $2.0kV/mm$ is desired between the plates, what must each plate’s area be?   $m^2$

  How strong is the electr )a6g.pzw18j-d k5c8ebvzrv mic field between the plates of a $0.80-\mu F$ air-gap capacitor if they are 2.0 mm apart and each has a charge of $72\mu C$ ?    $\times {10}^{4}V/m$

  A capacitor is charged by a 125-V batu w0)( ;wujxfatery (Fig. 17–29a) and then is disconnected from the wu) ( ;f0awxjubattery. 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.]    $\times {10}^{-5}F$

  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)
$\begin{array}{l}{Q}_1\\ \text{ initial }\end{array}$   $\times {10}^{-3}C$
$\begin{array}{l}{Q}_2\\ \text{ initial }\end{array}$   $\times {10}^{-3}C$

  What is the capacitance of two square parallel plates 5.5 cm on a side that are x*ep4 vwce,4p separated e4x,e4v *pcpw by 1.8 mm of paraffin?    $\times {10}^{-11}F$

  What is the capacitance of a pair of circular pl7w c 8hsrcn4a8rjnq*+d yc:n7 ates with a radius of 5.0 cm separated by 3.2 mm of micr4h +ccywjdnqc*7anrs78 8: n a?    $\times {10}^{-10}F$

  A 3500-pF air-gap capacitor is g6,pk;s(kr hoconnected to a 22-V battery. If a piece of mica is placed h;r k(kg,6 spobetween the plates, how much charge will flow from the battery?    $\times {10}^{-7}C$

  The electric field between the plates of a paper-sep - -e;js9reyjwarated $(K=3.75)$ capacitor is $8.24\times {10}^{4}V/m$. 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.
   $\times {10}^{--9}F$
   $m^2$

  650 V is applied to a 2200-pF capacitor. How much e6h-p.: xjfk j*m*ve,u 7l bnsvnergy is stored?    $\times {10}^{-4}J$

  A cardiac defibrillator is used to shock a heart that is kia r:5w3cw: bbeating erratically. A capacitor in this device is charged to 5.0 kV and stores 1200 Jk5br:ic aw :w3 of energy. What is its capacitance?    $\times {10}^{-5}F$

  How much energy is stored by the electric field between two square b8qh5 eux5vy p-k+-t i0cc 4jb tr3gh;plates, 8.0 cm on a side, x-5;icktcg3-e 4jy8 bvb 5p 0hhuq+trseparated 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-y.ds qx4cui 7r-qu4 g4in. pie pans 5 cm apart and connecting them to the opposite terminals oqg4di4.uq-cy x 4 7surf a 9-V battery. Estimate
(a) the capacitance,    $\times {10}^{-12}F$
(b) the charge on each plate,    $\times {10}^{-11}C$
(c) the electric field halfway between the plates,    V/m
(d) the work done by the battery to charge the plates.    $\times {10}^{-10}J$
(e) Which of the above values change if a dielectric is inserted?

A parallel-plate capacitor has fixvo+gtr r +41vwtj9fq7 ed 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 potentitxf;xi nzwvz7c97lz3,iyjx+n7l 06 dal difference is doubled, and (b) the charge on each plate is doud x+z 97cv3jtx0x 7ifz;6,7nilnylwzbled, 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,    $\times {10}^{-4}J$
(b) after they are connected.    $\times {10}^{-5}J$
(c) What is the change in energy?    $\times {10}^{-4}J$

  In a given CRT, electrong + z* *u;0jpsqees:mzs are accelerated 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. Estimas g 0jzze*s;pu e*+mq:te the value of E.    $\times {10}^{5}V/m$

  Electrons are accelerated by 6.0 kV in a CRT. The screen ism7,gi )8jtmqj+k 6 dkm 30 cm wide and is 34 cm from the 2.6-cm-long deflection plates. Over what range must the horizont8 +q7 dji,6m)gt kjkmmally deflecting electric field vary to sweep the beam fully across the screen?    $\times {10}^{5}V/m$ to    $\times {10}^{5}V/m$

  An electron starting from rest acquires 6.-*i m3h3uk tp2) futkr3 keV of KE in moving from point A to point3)u kpkim2ufthtr-3* 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 of charge and 4.58 2r,2hik2 rkakzogz2 MJ of energy to the Earth.
(a) Across what potential difference did it travel?    $\times {10}^{6}V$
(b) How much water could this boil and vaporize, starting from room temperature?    kg

  There is an electric field near the Earn,toz *u /abi1va5 x1vf;;yssth’s surface whose magnitude is about $150V/m$ How much energy is stored per cubic meter in this field?    $\times {10}^{-7}J/m^3$

  In a television picture tube, electrons arjdgs6)yu)5yn (;ntj ve accelerated by thousands of volts through a vacuum. If a television set were laid on its back, would electrons be able to move upward against the force of gravity? What potential difference, acting over a distance of 3.0 cm, woulgy )jun vnysd;6)t(j 5d be needed to balance the downward force of gravity so that an electron would remain stationary? Assume that the electric field is uniform.    $\times {10}^{-12}V$

  A huge 4.0-F capacitor has enough stored energy to heat 2.5 kg of water fq0.13, -w/-;c isvmgkxk/czsmfm u.jvlg yj , rom 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 chal.v k ;e3g; 0xopnpdk:/vav4 rj/s1rgrged, after which it is disconnected from the battery. A slab of paraffin ps /j;dek14. g:vo;vrx g3 vk/rpaln0is then inserted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down if the electric field exceeds6;ps;q x: oaktva,zbzph7e137 b3ny s $3.0\times {10}^{6}V/m$. What amount of charge can be placed on a parallel-plate capacitor if the area of each plate is $56c{m}^2$?    $\times {10}^{-7}C$

Three charges are at the corners of an equilateral triangle (side L) as sh7pi4 m/h kpnrra +.wc/m/+nsgown in Fig. 17–30. Determine the potent4+cm.wp/7n km/rp s/+hgn iraial 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 iso d 505p +oat8.njmths connected to a 9.0-V battery. If a piece of Pyrex glass is placed between the plates, how much charge will then fsad+o8t o5t0mnj hp.5low from the battery?    $\times {10}^{-8}C$

  An electron is accelerated horizontally from r9m5/z ,pxgv)0bsve1plv v8dsest in a television picture tube by a potential differesv bp)z 51/v0mpvg 9xs,8lvde nce of 5500 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 capacitano;2lu a3;/ xhr; w8ilkj.o exnce $C_1$ 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 ,10y,ukgcs kx to make a 1-F air-filled parallel-plate capacitor for a circuit you are buildingy1xk0k,c sg u,. 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?    $\times {10}^{-16}m$  ----待选择----YesNo 

  Near the surface of the Earth ther9;as ri w0e l(mxfqb5:hhg d16e is an electric field of about $150V/m$ 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 laser qx*2lw la8l;v 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?    $\times {10}^{5}W$

  In lightning storms, the potentia.mb9+c 4n-na,gutbt3mmhal cr6u5t8on - a5x l difference between the Earth and the bottom of the thunderclouds can be as high as 35,000,000 V. The bottoms of the thunderclouds are typically 1500 6tx3ogant u c-.-a9mc4,t lmma hrb85 nbn+ 5um above the Earth, and can have an area of $110k{m}^2$ Modeling the Earth–cloud system as a huge capacitor, calculate
(a) the capacitance of the Earth–cloud system,    $\times {10}^{-7}F$
(b) the charge stored in the “capacitor,”    C(Round to the nearest integer)
(c) the energy stored in the “capacitor.”    $\times {10}^{8}J$

  In a photocell, ultraviolet (UV) light provides enough energy to some ehp,ae42yc1)f/ aw2o0b fyykh lectrons 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 aw yheh/2)2b a40okfp, fy1 acyt 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?    $\times {10}^{6}m/s$

  A point charge is placed 36 cm fro3ekf 5ujm +z;rm 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-dyyx*6 k26ak)shl5ff tiameter coins separated by a 0.15-mm-thick *2 6k5y fylt6xka)hsfpiece of paper $(K=3.7)$ A 12-V battery is connected to the capacitor. How much charge is on each coin?    $\times {10}^{-10}C$

  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    $\times {10}^{5}V$
(b) the electric field?    $\times {10}^{6}V/m$  ----待选择----leftright 

  A parallel-plate capacithab8c ln -eh h2sl jy vo/wc4v4)2ra)4or with plate area $2.0c{m}^2$ 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?    $\times {10}^{-11}C$
(b) The plates are now pulled to a separation of 0.75 mm. What is the charge on the capacitor now?    $\times {10}^{-11}C$
(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?    $\times {10}^{-10}J$

  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.    $\times {10}^{-6}C$

  Two point charges are fixed 4.0 cm zil;qco6kt0 w t(g1 w+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 iknx oqrbblmd6; zoq,61- t-y/,-j a dt)lcz.nn 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.    $\times {10}^{5}V$