If two points are at the saxdyaw 47h3n 6zme potential, does this mean that no work is done in moving a test cha zn6h4w73xadyrge from one point to the other? Does this imply that no force need be exerted? Explain.

If a negative charge is initially at rest in an electric field, will ittyx* r rylnm(kc t, 1wyb qgn./398ou- move toward a region of hig1 3rr.ql 8n9/yognm( cu x*yt,yb-kt wher potential or lower potential? What about a positive charge? How does the potential energy of the charge change in each instance?

State clearly the difference (a) between electric potential and electric field, ,rh2 vjz1ij9 k(b) between electr,vi hz1j2rjk 9ic potential and electric potential energy.

An electron is accelerated by a pozi b8e9cw k0t):u5z :lcoh-prtential difference of, say, 0.10 V. How much greater would its final speed bhe :5 0ob:)z8k-wprtlc 9 iczue if it is accelerated with four times as much voltage? Explain.

Is there a point along the line joining3vnaoj 9um:.j two equal positive charges where the electric field is zero?vajmjnu:o . 93 Where the electric potential is zero? Explain.

Can a particle ever move from a region of low electric pt ;y)y :hflww*bb1*h potential to one of high potential and yet have its electric potential energy decreasl:*pt;)hhy *fb wyb1w e? Explain.

Compare the kinetic ene hotbh+acun(qlu5i129n( l1vrgy gained by a proton $(q=+e)$ to the energy gained by an alpha particle $(q=+2e)$ accelerated by the same voltage $V$.

If $V\,=\,0$ at a point in space, must $\vec{E}\,=0$ there? If $\vec{E}\,=0$ at some point, must $V\,=\,0$ at that point? Explain. Give examples for each.

Can two equipotential lines cross? Ex)6mzxjr fh5 xh u7jk/)plain.

Draw in a few equipotential lizkduw28ihk6e99)7n sa r -njdnes in Fig. 16 – 31b.

What can you say about20raykhe2 z*b the electric field in a region of space that has the same potenaz 2yhk*2br 0etial throughout?

A satellite orbits the Earth along a gravitational equipotential line. fj trmz.i*e 5r k(lf+7What shape must the orbit berlr *j+ktz( 7ff5me i.?

When dealing with pramumq mpv* gs ,if.z47 +j2+rmictical devices, we often 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 othe pi.,r7i jzu2+mmvqs*mg+m4 fr points?

When a battery is connected to a capacitm2zb6: lfzqx 2(-yto jeqcu-;or, why do the two plates acquire charges of the same magnitude? Will this be tru6lbu(o x-y fe:-;mzt2cq2zjq e if the two conductors are different sizes or shapes?

We have seen that the capacitance C depends on the size, shape, and posiaobut2tpo)hke:0v ;; tion of the two conductors, as well as on theo;h v:apute;kb)0to2 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 field do in modst.hq b4h*xoj2 o- 2dving 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 frv4iq9aw vz:x 4,vt/5vfv* mwcom a point with a potentivq,9t:vm 5vzvf 4cwx *ai /4vwal 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) if it accetokbrd+h3r 89.3odqd lerates through a potential difference of 23,000 V in a TV picture tub d3t+qrb d89.oohrdk3e?
   $ \times10^{-15 }\,J$
   eV

  An electron acquires0ut4ytnmr6(ua3ie. .p ws3i ; xvl r 0e1nzo,n $7.45 \times10^{ -16}\,J$ 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 parallel plates 5.8 mr- b1wv naly3,m apart if the potential difference between t aw1bl,-v3yn rhem is 220 V?    $ \times10^{ 4}\,V/m$

  An electric field of vddb u31 )n3 xs6pim;o$640V/m$ 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 conneck2 ggny tmo3t 13;h0hyted 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 46pljvwhd q.v6irwwbwhx 6; ah(g769/ 5-V battery is $1500V/m$ How far apart are the plates?    m

  What potential difference is needed to give a helium gq fzq uo/g0k (48ghq1nucleus $(Q=2e)$ 65.0 keV of kinetic energy?    $ \times10^{4 }\,V$

  Two parallel plates, connected to a 200-V power supply, are separaten9m 4zi7 w0+qiab3g pxd by an air gap. How small can the gap be if the 3g+4wmbzxq i i90a p7nair 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 for 7:k8zecz hf+wce 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 kinetkkh6qt-,3 ekwfw 5e4i ic 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 +4l.g.eoa.1gx fchbu is 3.2 keV?    $ \times10^{5}\,m/s$

  An alpha particle (which is a helium nuclqi,mp*yek8 (kq17 ranry o8+xeus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed?    $ \times10^{7}\,m/s$

  What is the electric potential 15k9kimvos;5khm3ieh,m b3(el4: 4ai l.0 cm from a $4.00\mu C$ point charge?    $ \times10^{ 5}\,V$

  A point charge Q creates an enwmq c: nm7uiml; -l28 fe.q5zlectric 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 a/t (geiy k)u)no 0.cwthe shape of a football. This conductor carries a net negative o)yg./tk i n0e u(a)wccharge, $-Q$. Draw in a dozen electric field lines and two equipotential lines.

  (a) What is the electric plp6kqd 70 smw1otential 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 me 1xw0mmtn90 are arranged at the corners of a square of side L as shown in Fig. 17–25. xtw0 m9mm01en What is the potential at the fourth corner (point A), taking $V\,=\,0$ at a great distance?

  An electron starts from rest 32.5 cm c c +hblj3-m)(z ugvync sasb*7c6n7)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 g yt+pih5-7wgc reat distance apart tot+ pw7c yh5ig- $1.0 \times10^{-10 }\,m$ from one another (at the corners of an equilateral triangle)?    $ \times10^{-18 }\,J$

  Consider point a which is 72 c+-s3u lxo8w1 iqbg0p xm 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 used to accelerate a proton (radius9rok6.ymvr*cbgm ) k09s ui 9o $1.2 \times10^{-15 }\,m$) 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 sek fcq2qa8(,htb,b3 qf parated by a distance d, as shown in Fig. 17–27. Deteraq 2, qq3hkcb( f,ft8bmine 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 the4yfki s.nr )f8-d olk8zy b7n9 hydrogen atom, an electron orbits a proton (the nucleus) in b)yfozfy sd7nk8r ni4k8.l-9a 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 a2bb4e bgh()fo re $ 0.53\times10^{ -10}\,m$. apart. What is their dipole moment if they are at rest?    $ \times10^{-30 }\,C\cdot\,m$

  Calculate the electric poten89zr do kag;c /bv)sh2wv(+b otial 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, points from the negn)o,p h3 *wwtfr)kd7 native to the positive charge. The water molecule, Fig. 17–28, has a dipole mo,wd f7r 3)pno *nhkt)wment 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 -hj .x csz*zn7b t,o7wbuqx+3hold $+2500\mu C$ 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 capacis: vvp*jv 61 :ahuay9stor 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 mcp+)jgs0 rxli ad+r 5;inus charges of $ 16.5\times10^{-8 }\,C$. What is the voltage across the capacitor?    V

  The potential difference betweelimn a )t.cm0 -;gn-bmn two short sections of parallel wire in air is 120 V. They carry equal and opposite charge of m-lb) -in.gtnm amc ;0magnitude 95 pC. What is the capacitance of the two wires?    $ \times10^{13 }\,F$

  How much charge flows from each termilewi 2yk)/5ms nal of a 12.0-V battery when it is connected e5sik mly2)/ wto a $7.00-\mu F$ capacitor?    $ \times10^{-5 }\,C$

  A 0.20-F capacitor is desired. What area mu(h;)zfuuuz/p : l+ofbst the plates have if they are to be separatedl( /fu fp)z uhoz+ub:; by a 2.2-mm air gap?    $ \times10^{ 7}\,m^2$

  The charge on a capacitor increa tirs- :n k(u inpy. 12xo01lmvd)nmf6ses 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 *vnu( xu6z ;z:wr(rx k$8.5 \times10^{ 5}\,V/m$ 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 opposithk4m 9./all4s+(g bv8th so cae $5.2\mu C$ 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 plates ofxcn,2wphy efq zk,25 tw a5.4p 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*kfs -m7aag a--V battery (Fig. 17–29a) and then is disconnected from the battery. When this fg7-k a-aasm*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 ono viq* zb*qk5, a side that are separated by 1.8 mm of paro,qbikz 5 **vqaffin?    $ \times10^{-11 }\,F$

  What is the capacitance of a pair of circular platesej a3s*wmk:kx55z 5my with a radius of 5.0 cm separated by 3.2 mm ofjma5xw3 *5mskky:5 ze mica?    $ \times10^{-10 }\,F$

  A 3500-pF air-gap capacitor is connected to z 2na6dnyr zq;;5-j tba 22-V battery. If a piece of mica is placed between the plates, how much charg-z5y; q2;z6dr jta nnbe will flow from the battery?    $ \times10^{ -7}\,C$

  The electric field between the plates of a paper-s q,wd5fl+uvy -eparated $(K=3.75)$ 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 capacitoe;6deo nx((a) k cppv5r. How much energy is stored?    $ \times10^{-4 }\,J$

  A cardiac defibrillator is used to shock a heart that is beating erraticalhvo zb jv2)nh,8 t)1kmly. A t bohv1v2zh,)mknj)8 capacitor 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 betw e:fkd+g;; jpm+yd;zteen 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 oppo ;my :gpdf;+;ekzj+tdsite and of magnitude $420\mu C$.    J

  A homemade capacitor is assemblgkqyit,x :f 57xvk/7 xzy.en) ed by placing two 9-in. pie pans 5 cm apart and connecting them to the opposite terminals of a 9-V battery. Esy7x7 q5i:xke).g,/vfxtykn ztimate
(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 :q(a;k2b +gzhgd ,u rffixed 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 d.sid3bdvvlg10 d3 f 4capacitor change if (a) the potential difference is doubled, and (b) the charge on each plate is doubled, as the capacitor remains connec04d ivs.bfdl31 d3v gdted 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, electvbd q 5n, 6r lr(e:n5vru2w0ubdd/r4hrons 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. Estimate the value of E.vrn d:,wrn025qu4ul65r/eb hvr( dbd    $ \times10^{5 }\,V/m$

  Electrons are accelerated by 6.0 kV in a CRT. The screen is 30 cm wiglc:ve; zn81k*d4x myde and is 34 cm from the 2.6-cm-long defl:vndxlm*4c8ykze g;1 ection plates. Over what range must the horizontally deflecting 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 js2+6z1fe(m0obo t2x z py:d x2kcc6 lkeV of KE in moving from point A to p6blyt:jsx p02zmzf1x k 6cc2e(o2od+oint 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 cha;) tcjou1mr6 yrge 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 3 fmgxlt6mz80e:d bsy7,g/ekfield near the Earth’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 accen ;.nyzrfkq7 ,lerated 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, would be needed to balance the downward force of gravity so that an electron would remain stationary? qy7f knr.;,znAssume that the electric field is uniform.    $ \times10^{ -12}\,V$

  A huge 4.0-F capacitor has enough stored energy to heat j0*(/t- abldmos pae9tkl/y,2.5 kg of water from 21$^{\circ}\,C$ to 95$^{\circ}\,C$. What is the potential difference across the plates?    V

  An uncharged capacitor is connected to a 24.0-V battery until it is fully charwec( 91h d7hoiged, after which it is disconnected from the battery. A slab o7w9i ed1 hc(ohf paraffin is then inserted between the plates. What will now be the voltage between the plates?    V

  Dry air will break down8r,p8uv72 syqmlx9 vn if 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 of9i3u em2ad5f q an equilateral triangle (side L) as shown in Fig. 17–30. Determine the potentimuq5i 2f d9ea3al 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 conn1)k8dvcm j ly6obh4s6 ected to a 9.0-V battery. If a piece of Pyrex glasco68k)vy6j1s dl4h mb s is placed between the plates, how much charge will then flow from the battery?    $ \times10^{-8 }\,C$

  An electron is accelerated horizontally from rest in a television picturis*klcv)- h-,q 2b ha jcsqg0gw:1)ek utq,f(e 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 difference of 250 V (Fig. 17–,ul)0ft- kwkqh s1i(c che bajsg g :,v-2q*)q31). At what angle $\theta$ will the electron be traveling after it passes between the plates?    $^{\circ}\,$

A capacitor of capaciy+3sywzlgz ax0 a9gb:/pi:m ;tance $C_1$ 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 m l8jyw58nhg5h 8o;s aair-filled parallel-pa 8mj8lnh;w os8gh 5y5late capacitor for a circuit you are building. To make it a reasonable size, suppose you limit the plate area to What would the gap have to be between the plates? Is this practically achievable?    $ \times10^{-16 }\,m$  ----待选择----YesNo 

  Near the surface of the Earth there is an electric field of a7my zko+ vso6dd gq+5+bout $150\,V/m$ 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 x+c c) )mqbrk n/g0auy.mu8(ypulsed nitrogen laser has a $0.050\mu F$ capacitor with a maximum voltage rating of 30 kV.
(a) Estimate how much energy could be stored in this capacitor.    J
(b) If 12% of this stored electrical energy is converted to light energy in a pulse that is 8.0 microseconds long, what is the power of the laser pulse?    $ \times10^{5 }\,W$

  In lightning storms, the potential difference between the Earth and the bottombe/t0yk4m cv- of the thundercvb ty4k m0-/eclouds 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, ultraviouh gg rgof55l1+rl 6a-let (UV) light provides enough energy to some electrons in barium metal to eject them from a surface at high speed. See Fig. 17–33. To measure the maximum energy of the electrons, another plate above the barium surface is kept at a negative enough potential that the emitted el fgg1l+ -u6hr55oarlgectrons 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 from an b :7;gg7o x4pfa, hvfeidentical $+33\mu C$ 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 separateeu sf/618w u sua2qh0md by a 0.15-mm-thick piece of pa8a/ 2u ufmqhss1 u0we6per $(K=3.7)$ 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 capacitorqt hotjtz,m.cfwwy70d x q.q8 +9 mew+a6(cx* with plate 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 eaj gmv/cp5(b f 8n1+jbwch other. Their charges are $Q_1$=$Q_2$=$5.0\mu C$, and their masses are $m_1=1.5mg$ and $m_2=2.5mg$
(a) If $Q_1$ is released from rest, what will be its speed after a very long time?    m/s
(b) If both charges are released from rest at the same time, what will be the speed of $Q_1$ after a very long time?    m/s

  Two charges are placed as shown in Fig. 17gsts6ko2 ngl+b,9d; n –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$