If two points are at the sab:f;l k;6ekawme potential, does this mean that no work is done in moving a test charge from one point to the other? Does this imply that no force need be exert;klw;k:eba 6 fed? Explain.

If a negative charge is initially at rest i5w8*ldsopbk q+,9ave6 zm uw 2n an electric field, will it move toward a region of higher potential or lower wz6v5l*mu b9a o,+ewd2k s 8qppotential? 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 fk9p)h2 lc giw2ield, (b) b2 c)ip2lkghw9etween electric potential and electric potential energy.

An electron is accelerated:kxha5 m r26wo by a potential difference of, say, 0.10 V. How much gre56: ro h2kawmxater would its final speed be if it is accelerated with four times as much voltage? Explain.

Is there a point along 9hfu-ca;jtea(zt83djj ky ,. the line joining two equal positive charges where the electric field is zero? Wherjt;.8yh9c-ujdz3ja k ea t(,f e the electric potential is zero? Explain.

Can a particle ever move from a region of low electric potentir 3ahu.gcjc-+u8 : 9vlfaq;3u yxvnf 5al to one of high potential and yet have its electric98jlrn3 +vcfa:qhg.u v3 cuay;u x-f5 potential energy decrease? Explain.

Compare the kinetic energy gained by a pro 4rk b/ploh:z/y-c4 zcton $(q=+e)$ 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 crn(ss -tow op54oss? Explain.

Draw in a few equipotento95 ,u ji3 hr nj44ar.b1nbxquial lines in Fig. 16 – 31b.

What can you say about the electric field in a region of spa fn2 dhwef/,jl06z.se ce that has the same potentif,0nz f ee/6wj2l.hdsal throughout?

A satellite orbits the Earth along a gravitational equipotl 65 ;gjnj /xjzqu8uz+ential line. What shape mu;z/gjn 5jq+j8x uz6l ust the orbit be?

When dealing with practical devices, werpqj;6zj qrn6zj5r+ ; often take the ground (the Earth) to be 0 V. If, instead, we saidqj zrz6 6p;jrnj;+r5 q 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 two pl +neiij3v p;(y fw8/likhl75 lates acquire charges of the sai(5;/ll j ek8 wl3iihvpfy7n+ me magnitude? Will this be true if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on the size, shape, ae2)z ik8lnja9 .n2 anqnd position of the two conductorseijn 9lzq n.na8)a2k2, as well as on the dielectric constant K. What then did we mean when we said that C is a constant in Eq. 17 – 7?

  How much work does the electric field1s;qlc-pk ts b(3boi, 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 moving a proton from a point withot l+il;l5gmd v3y4*am0rz/w 4t zvz1 a potentialy3 m4la* 5i+v d/t0or4zltzv zml g;w1 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;ck*u6 *7bcjt nq2wcllb 9(gsw-u4 jq an electron gain (in joules and eV) if it accelerates through a potential difference of 23,000 V is **lgtcu w(6q b-c2;j7bn4k9qjw ulcn a TV picture tube?
   $ \times10^{-15 }\,J$
   eV

  An electron acquiresbd7u4hz7a r55nmfzi ) $7.45 \times10^{ -16}\,J$ of kinetic energy when it is accelerated by an electric field from plate A to plate B. What is the potential difference between the plates, and which plate is at the higher potential?
   V
plate ----待选择----AB 

  How strong is the electric field between two parallehnz ((ro-bogznv k) 967kwj y0l plates 5.8 mm apart if the potential diffehoo(k96kg0w zbnjr z-)vy n( 7rence between them is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of j8k0l6y7at vr $640V/m$ is desired between two parallel plates 11.0 mm apart. How large a voltage should be applied?    V

  The electric field bx :4f,rectd0abqh (8k etween two parallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  The electric field between c7* q vg2 mv3nmaqnb xj-.7a2rn4)hq ttwo parallel plates connected to a 45-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a helium nucleus mg ;x p5iqta; k)67uag$(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power su rq dzxo6rh9 q3et dh93:ks.5jpply, are separated by an air gap. How small can the gap be if the air is not:39j qrqse5.zh 3 ddk ot96xrh to become conducting by exceeding its breakdown value of $E\,=3 \times10^{ 6}\,V/m$?   $ \times10^{-5 }\,m$

  The work done by an external7ij*tm+t gyiff.q ):b k:,a8kmeak mbx,1ug8 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 electron with kisg uxb1g.aqu6+pm 76d-p ji 3znetic 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 energy is 3.2 t rttgug)r.suf) /4j :keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is w 1 zy5kb;4rjja 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 ; 1gstg4;mcft from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an electrqqg. o9n/ f6 z33v v5pv3fyyxwic 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 a3fdz f57owk 9s net negative kf do5sf 9z3w7charge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric potential a kr1q8h2 w,iyidistance 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 cornerw s-s1xm5 i,n q0v; uax3 4menwaq6s4cs of a square of side L as shown in Fig. 17–25. What is the potential at the four,s53 xe0aq4a- 4 w;1unmqmcsvnis6 w xth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm from a fixe5 cwn.anxx) +od 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 tu 3s 74dfpvu8uo 2p-tqo bring three electrons from a great distance apart tu u7f 8p sdt2po3uqv-4o $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a whichp d;m9n gi6ub; is 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 u),h:l)wqai hz7ard9s sed 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 opposittkt nd0y/lfv/i3s-r4jyv)b) e charges are separated by a distance d, as shown in Fig. 17–27. Determine a fo vy) rn i)0d3jv lkb4tyst/f-/rmula 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 orbic ,or7adkuoz 5)9 4xhsts a proton (the nucleus suz7ca45roo)h dkx9,) in a circular 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 arez+mscuta ro9d86 l70m $ 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,;o z lmw,;prw 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, po4j db qeo-10qrints from the negative to the positive charge. The water molecule, Fig. 17–28, has a dipole momeqo-dje 14qb r0nt 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 hold2 bw7aa(i4cye5 zru4 z $+2500\mu C$ 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 capacit4,s;um4w w ybior 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 *g*h,s y q;+b(xcpjab charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference bet8*y xscl))tfrslu+ buq,x,f . ween two short sections of parallel wire in air is 120 V. They carry equalf8.qu)xc*+,y)tx,s l urslf b and opposite charge of magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each terminal 28yi:v gmi-8-uzttz n of a 12.0-V battery when it is connected to a8g: 2 y zmtu--nzi8vti $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What ang(ed6,h6-ok4qi , r f;pdruurea must the plates have if they are to be separated ,ud-qup o; ( r4r6eh,nfkg d6iby a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacits eia7u e,x+r670ze jbor increases 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 wj( ) *xa ay wx8/vqg:sgbb;nc282ehn$8.5 \times10^{ 5}\,V/m$ 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 opikq4j5;0r u wmposite $5.2\mu C$ 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 elec8j 9/k otclrn+tric 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) and thentq,wbk lw +rd 2qt1i+7 is disconnected from the batteryt2qw+ 7iwdl q1,bk+tr . 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 onlak -d:vjfs s-yb040l a side that are separat0l4-:db faskyj0-v ls ed by 1.8 mm of paraffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circul2fhim*h7 -1iur s70s8 +ofoat:bxoz sar plates with a radius of 5.0 cm separated by 3.2 mm of :b8+7 1oossmtrhsu 2f-hzxii o70f *amica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor; 2zjp kzg:d6 *wegz9t is connected to a 22-V battery. If a piece of mica is placed between the plates, how much charge d zt*ez;2k9:jggzp w 6will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field betw6uc fvr : .mjr*.kvo+dbqos+:een the plates of a 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 capacitor. How e 6b1zijpm26nmuch energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heartbyh9s 3 .w:u e9ycu27na5u/ ztmcyzk2 that is beating erratically. A capacitor in this de2nscwy7mz hu:by.9teauuc3 9yz/ 52k vice 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 fiel /lww1r-1en zjd between two square plates, 8.0 cm on a side, separated by a 1.5-mm air gap? The charges on the plates are equal and opposite and- nwz l1/1ejrw of magnitude $420\mu C$.    J

  A homemade capacitor is assembled by placing pa9kl4t 6zlzt153)f f j2dck5br *dsstwo 9-in. pie pans 5 cm apart and connecting them to the opposite terminals of a 9-V battery. Estimate p fsc) 5atl26*f5tkb1ldr9 j4kd3zz s
(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 capa*o:4lwf e (amscitor 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 s wr jpmd; 3a(qm6kfoq+t0s; b*tored in a capacitor change if (a) the potential difference is doubled, and (b) the chwm*sbqf;r (qp0ma okt3 ;jd6+arge on each plate 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 accelerated horizontally by 7.0 kV.m3hj3jy4 n4ma +hhnz h8+)noh 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 mj8hy +z44mhhn+n oh3a jh) n3center. Estimate the value of E.    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a px 7*iodzq )8nCRT. 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 7p oz)ixnq*8 dacross the screen?    $ \times10^{5 }\,V/m$ to    $ \times10^{5 }\,V/m$

  An electron starting frk.:pt e*bumr th,7i 1t1 jkmpdl9tj0( om rest acquires 6.3 keV of KE in moving from point A to p ,l.t1j0rdjh7(m9piktutp :e b*1mktoint 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 transfer3( (i3frkx ulm tn*i:ms 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 mage :edmhw6re c5,i)x t3nitude 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 j uusm --p0)zj:upcn. tube, electrons are 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 3.0ps- p: cuzuun- jjm).0 cm, would be needed to balance the downward force of gravity so that an electron would remain stationary? Assume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough stored energy to heat 2.5 kg of;( n3bzvpixs hn3v0k ( water from 21$^{\circ}\,C$ to 95$^{\circ}\,C$. What is the potential difference across the plates?    V

  An uncharged capacitor is eg4w*aj,l9fe if w 6aur+x(ym d4. 3ooconnected to a 24.0-V battery until it is fully charged, after which it is discfrl6jf.e49y ,g iaamxo d(euw*4+3woonnected from the battery. A slab of paraffin is then inserted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down ibm+k /ec 4fwx4gzg(0 ov- )uqif the electric field exceeds $3.0 \times10^{6 }\,V/m$. What amount of charge can be placed on a parallel-plate capacitor if the area of each plate is $56cm^2$?    $ \times10^{-7 }\,C$

Three charges are at the corners of an equilateral triangle (side L) as9 q g;86vqxebk3dv/lt shown in Fig. 17–30. Determine the potential at the midpoint of each of the sides. v k e;lq3/qvb8gx96td

  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 o*gti/8k r qgzxuv y*3*f Pyrex glass is placed between the plates, hyzq8i*grg 3 t */v*xukow much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest i7sp8 2sfo :rdfjt2t:rgomp8 fi-7l7 en 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 hsrptgsot 7f m82:j: lfo 78p7d2-eri fave 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 capacitance3muu:6gni5xl1t m ww; $C_1$ 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 w z.iew3hk38lfr;ye j4ant to make a 1-F air-filled parallel-plate capacitor for a circuit you are building. To make it a reasonable size, suppose you limit the plate area to What would the gap have to be between the plates? Is this practically achiek wl;3ezf.j 3h i4yr8evable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there2qgg+rp,.us cdqa (p8 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 pulsed nitrogen lase mqjs9hy4jdk-3* ;8un2hscsb r 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 th:h()wwm*4 mybf v;j ob2ik5cc e Earth and the bottom of the thunderclouds 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 w;* k) mo :2by5hwbf 4cjci(vmarea 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 some electfe dpt+ mc2 uu5sp09h*rons in barium metal to eject them from a surface at high speed. See Fig. 1u*f de0 59puc2h+tpms 7–33. To measure the maximum energy of the electrons, another plate above the barium surface is kept at a negative enough potential that the emitted electrons are slowed down and stopped, and return to the barium surface. If the plate voltage is $-3.02V$ (compared to the barium) when the fastest electrons are stopped, what was the speed of these electrons when they were emitted?    $ \times10^{6 }\,m/s$

  A point charge is placed 36 cm fro90-cv q+ blfi5ss 60irj9krfvm 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 coi*l+6 9t (bipk7nmxynb3f e+lvns separated by a 0.15-mm-thick piece of nm7 b 9+klpl +bvfx(n 3*6iyetpaper $(K=3.7)$ 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 he,qd+0mt s0 dmx3x2y 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 ap9 :mgyyr ess)9art 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 shrr zke/n u:e7-own 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$