If two points are at the same poef+uiuoz/t;x(h r-2rgl riz z 82g-,mtential, does this mean that no work is done in moving a test charge from one point to the ougr+rigmz(f uz/-eoi,-2rl x 2ht z8;ther? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at rest in an electric field, vmyar.mj(p6q 30ta 5bh- i1 +e p.buhjwill it move toward a region of higher potential or lower potential? What about a .h pj-a ar0bq 6yjvi1emm3u ht+b(5p.positive charge? How does the potential energy of the charge change in each instance?

State clearly the difference (a) between electric potential and electrinl54h9+duts i.l9)k tb o0rxsc field, (b) between electric potential and electric poten9nxko5 bh9ti + .rstl4u)s0dltial energy.

An electron is accelerated by a potential diff-m6 h7emndk57f0am 9fqnzh;tle4odq/xg i 65erence of, say, 0.10 V. How much greater would its final speed be if it is accelerated with four times as mucml6;hm 6ntqn7/xd7595e - eqd0i4fkfzmho ag h voltage? Explain.

Is there a point along the line joining two equal2vzygxg xpw;+/,fj6doe u7 w 5 positive charges where the electric field is zero? Where the el fv76w2;zg+xg5,ex/wod p yujectric potential is zero? Explain.

Can a particle ever move from a region of low electric potential to one of highr ef:k0v6tll4 potential and yet have its electric potential enel k64vl:fe 0trrgy decrease? Explain.

Compare the kinetic energy gai+82nfwfs8q:vs4 lr tbned 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 croobmvte wjj2* iyo,.bsi j/+ z2.1wrh(ss? Explain.

Draw in a few equipotential lines in Fig. 16 – 31dkyvv,yt.mf of-, 3n6 b.

What can you say about t7q / w09vz5aj4w.cnuyuu sr3mhe electric field in a region of space that has the same potential throughov myqj739uncr/.a uusw4 0 wz5ut?

A satellite orbits the Earth along a gravitational equipote380 accfmic i3a)rnheh:v v .ed0fz:*ntial line. What shape m3.v0cr:zdim)3 0hcef vfi :ce an*h8aust the orbit be?

When dealing with practical devices, we odsbx.1p4l rv+ ften take the ground (the Earth) to be 0 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?x.b1ld4vs r+ p

When a battery is connected to a capaci/gtrbb84+1s z-zkj iad ;nf: ntor, why do the two plates acquire charges of the same magnitude? Will this be true gi narjk-b+db szn;:/ztf4 18if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on the size, ss,6 ia srkc4rq 51dcj4hape, and position of the two conductors, as well as on the dielectric constant K. What then did we mean4c aq sd1,jsrc5r64ik when we said that C is a constant in Eq. 17 – 7?

  How much work does the electric field do in mfk7c6n*g*xm aoving a $-7.7\mu C$ charge from ground to a point whose potential is $+55V$ higher?    $ \times10^{-4 }\,J$

  How much work does the electric field do in moving a proton from a point with a cqd9 t1y2es;) txw(brsz k 80jpotenti82bxksr czyd9 ttws 1jq(;0) eal of $+125V$ to a point where it is $-55V$ Express your answer both in joules and electron volts.
   $ \times10^{-17 }\,J$
   eV

  How much kinetic energy will an electron gain (in joules and eV) if4 ef*k.zz1cci6q -yn su i-kqx:(e- su it accelerates through a potentia-*-sni qzez16(:ekcy-uq cx.s f 4uik l difference of 23,000 V in a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires0 u r) q4uc7.wvkviq/u $7.45 \times10^{ -16}\,J$ 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-4vvhp-9zl:r8s h aqd between two parallel plates 5.8 mm apart if the potential differenchasr4- zq:v89lh-dp ve between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of n3v*t. +-djk*5umi5ug v kqvo$640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field between two parlsj 8 l6z1s psoc610jto7pg4eallel 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 batte8w6amylo0gr- ry is $1500V/m$ How far apart are the plates?    m

  What potential differergy )z70 sc1qy3luuy6nce is needed to give a helium 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 airc 84 t)mw1xhbw gxc 81bmhw4t w)ap. How small can the gap be if the air is not to become conducting by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external force to move a :fxw20vl 6 kyt zlz::r9grgx+$-8.50\mu C$ 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 uf:nk+f fc(u /1dcu)i 8qrx*y with kinetic energy
(a) 750-eV,    $ \times10^{7 }\;m/s$
(b) 3.2-keV?    $ \times10^{7 }\;m/s$

  What is the speed of a proton whos3t kpn4c8/afve kinetic energy is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nucleus, eb g7.i 5t vmjzv)lk:k /loxk28ab ./c$Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) 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 ho5ilvrem (/; cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creatqvm.pxaka12d-.u n 6ses 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 footbally 1 2 /go0l74w:aq rxz)afx(whoh+wur. This conductor carries a net negative ch0+( /14 :ofhw ragazqyowlu7 rxhx)w 2arge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potentialdq 0y++x,hss j 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 arrange2f u y:y2p:99ay w4gkzqmrpa*d at the corners of a square of side L as shown in Fig. 17–25. What is the potential kzy rf2 4a:pypgqa*ym 2 99uw:at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm frc* tb yzpnr8u4owy (:)om 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 electah6 +blc:gps5rons from a great distance apart t+:al bcpg5 sh6o $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 cm nortj75ply+ cv.e wh 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+(ssv8 ikp h)y 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 separated by a distan((n 7vccaa a6zce d, as shown in Fig. 17–27. Determine a formua 67cazac(n v(la 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 nucsl7zy);mx v 5uleus) in a circular orbit of radius zs yuvx5l;)m7 $ 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 are e8zh fdc*tkdy5012 yt$ 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 dipoloes t; u,e/ p2.o8 vrd*lsxybxq.z80qe 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, points from dggc+;a+;qpz the negative to the positive charge. The water molecule, Fic+;qag d;gz+ pg. 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 capacitor houflf-h bwfa+; e3y1h ;ld $+2500\mu C$ 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 holddr)pp wi,zwn(lyyag.bl +* +- $+2500\mu C$ 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 plbb8 5g9qgy* ugus and minus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference between two short sectionp muy/73vg8 rxs of parallel wire in air is 120 V. They carry equal and opposite charge of magnitude 95 pC. What is the capacitance of the t38gpmv y7 rx/uwo wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal of a 12.0-V battery when it vcnz wj-qd lb 2/)6nb7is connected 6 q-bcd/ vw bzlnn2j7)to a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area must the plates have if they are to1 gys7ent(v. e:ot4rv be separated by a 2vo1( ys4vtren e.tg7 :.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increas8*8 c m khc/p2b8wthbmes 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 g (r28w;dz0s-fk zkuf$8.5 \times10^{ 5}\,V/m$ 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 m y+lt) j*)i ox6lvo-u$5.2\mu C$ 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 electri uo11dcr;s b5yc 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 $72\mu C$ ?    $ \times10^{4 }\,V/m$

  A capacitor is charged by a 125-V battery (Fig. 17–29a) ,owek (iywna0wr7v61jck* 4aand then is disconnected from the battery. When this cn4j6ai(1e,kw7a c* 0wkrwo v yapacitor $(C_1)$ 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 plat4)s(uvs*h9u o/oi *ji5h0n bd )zzcu ges 5.5 cm on a side that are separated by 1.8 mm of pasd(b/ z i )*ooucjnvg*z 4hhu05i)u 9sraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular plates with a +:g n3 rzbpm) v(ujx;dradius of 5.0 cm separated by 3.2 mmz3);m: dv+xb p(grnju of mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to aor d 9dnfz(yq 2jbn33) 22-V battery. If a piece of mica is placed between the plates, how much cha93j b dnryqnfdoz 23()rge will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a paper-separatew25n-jm ijk j,d $(K=3.75)$ 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 is stodlf)w(-cf7iya2+xi n red?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beatin7tqg4u6vt0f jvyeak .x 6kj74g erratically. A capacitor in this device is charged to 5.0 kV and stores 1200 v6yxk4 .ut 6f k7qga7ve0 tj4jJ of energy. What is its capacitance?    $ \times10^{-5 }\,F$

  How much energy is storedwu+h0 i+h7hduoh8 xl q7*ojb 4 by the electric field between two square plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on the plates are equaljuiqxh 4 +h7l uh o*8h+7odw0b and opposite and of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by 5(fqjvk1is0j)bg**o unch w *placing two 9-in. pie pans 5 cm apart and connecting them to the opu5 j 0hvo j)k*i1 c*q(f*bsngwposite 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 7jdg8* a.lfmrfixed 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 pot1dlppk ;p7vu*ential difference is doubled, and (b) the charge on each plate is doubled, as the capacitor remains connected to a b p ;luppdv7*k1attery?

  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 accelerated hori4s7/xeh tg;,xu jhf68,vxoe(w j g fu:w qbc0*zontally 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/getw ,u*(bs:; 0ogw u6ve,jfhq hxxx4jf8c7 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 CR* ltpagxl:hr1tx4i d k 7n4.l1T. 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 the sl gxa1rk4t7hnxd lp:4 .*tl1icreen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting from rest acquires a/; f9r 3lrt+,hnaa3flcfj c36.3 keV of KE in moving from point A to point B./l 3a 3ffrrt3fnjha,a+c;c l9
(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 4.2 MJ ofkdiogi 4u96: o v35vfp 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 Eartjlwfj7z*c2pf4, tpvl)- g, rrh’s surface whose magnitude 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 vbr2 vux ircl) 4;9/rajolts 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 remain station2 u/r a;rj)rcl9 x4ibvary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough stored energy to heat rolnb6 k8 e7uwq(kk e;r)nwv2) q+o 1k2.5 kg of water from 21$^{\circ}\,C$ to 95$^{\circ}\,C$. What is the potential difference across the plates?    V

  An uncharged capacitor is conn aq/te2s /f1*uf e:vovected to a 24.0-V battery until it is fully charged, after which it is disconnected from the battery. A slab of paraffin is then inserted between the plates. ts a: fq*v/eof2/eu1vWhat will now be the voltage between the plates?    V

  Dry air will break down ifcth8s,,iae4lf5u + 8oti +tq3mi 7rco 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 a-ca)- cidrl 1of an equilateral triangle (side L) as shown in Fig-c rcail -)da1. 17–30. 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 connected to a 9.0-V battery. If a piece of Py8nn6 og 7ybvp4rex glass is placed between the plates, how much charge will then flow from the 64pybo7n nvg8 battery?    $ \times10^{-8 }\,C$

  An electron is acceleratep.rf/) vz pkvcfe92 n:d h.m-fd horizontally 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 diffpfnrhe v:km2p.f 9vc.z)/- d ference of 250 V (Fig. 17–31). At what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capacitance *ex :.p22p xy- zfdgysu-k+ cj$C_1$ 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-f/niq,h e ;hpn0:wfjfe a: 8qt+illed parallel-plate capacitor for a :0nf eht8/w p nefq;a,:+jiq hcircuit 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 the Earth there is an elecc6yfox)xx wdz 5( bj ghk+zmr c jp*,:f9m4..mtric 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 pulsed nitrogen laser 4grj c u1n-)+go-q xvahas 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 diffefou 0*d*avoqh-; ) jbrrence between the Earth and the bottom of the thuhd*ovo0 qabru) * ;jf-nderclouds 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 enouaj4w ;h k :7fn81bipn.irpoacv 3l/e u*g(7umgh 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 keplpw a(rv buou:8cgk.mjfpni7 e n4i;h3/7 *1at 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 fr hf4(;b 0 kk6xtwjfvg)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.x9;-g.w, u w- mdnwjkm8pt8ul1-cm-diameter coins separated by a 0.15-mm-thick pi.8- g;wt,k wm8dwl un u-9xmpjece 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 a/x/sf0 o/ 4oc riimnk-rea $2.0cm^2$ 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 h 9.-wa iphxv .l7q d3fkxst1+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 shoxr5+ z; 7oy,s/m.+hujgw yxh wx m(q8c .uf:piwn 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$