If you charge a pocket comb(o )10l z b 7qotc 9iopoib-2 mbvme1df5-g0qb by rubbing it with a silk scarf, how can you determine if the comb is positively or negatively c 1q 0mb-po m z9b5 q(i0ibg-cbdoo2fo71tl)veharged?

Why does a shirt or blouse taken from a clothes dryer somezs3ksiy+f.rrf / 4) eitimes cling to your bosy fszik3 reri)4/f+.dy?

Explain why fog or rain droplets tend to form around ions or electrons in d5.t3/-w bxx tmxo xp9mglq;2the aix2 t m dgxto x;q/3p-xmlw95b.r.

A positively charged rod is brought close to a neatup ;winofr/65 k ;a5utral piece of paper, which it attracts. Draw a diagram showing the separation of 5aa;/ t n;wpourif5k6charge and explain why attraction occurs.

Why does a plastic ruler that has been rubbed with a cloth have the abii/,*yil-.5f w dtz9k zajx3ne/,kl yelity to pick up small pieces of nx3ikki,ydw-*y el, 9ftzzajl /e./5 paper? Why is this difficult to do on a humid day?

Contrast the net charge on a conductor to the “free charges” in the conducysh(em,pg -+ 6q;e * /yrxwfsplpi 8r)tor.

Figures 16–7 and 16–8 show how a charged s *vl8(bxf r-tkk 6bj(rod placed near an uncharged metal object can attract (or repe( 86 (tvrkb-jxskl fb*l) electrons. There are a great many electrons in the metal, yet only some of them move as shown. Why not all of them?

When an electroscope is charged, its two leaves repel eacrce9 w :e5f xo:)aw3lbv i(ax;h other and remain at an angle. What balances the electric force of repulsion so that the leaves dw5:cie3e (;wa)abxxr9lfo: von’t separate further?

The form of Coulomb’s law is very similar to that for Newtonb hjpl;g-i.-ewl* q4c’s law of universal gravitation. What are the differences bet gc--i; l.qe*b l4phjwween these two laws? Compare also gravitational mass and electric charge.

We are not normally aware of the gravitational o7;p-:yn1 clnjey. rxxr electric force between two ordinary objects. What is the reason in each case? Givn.e 7:ycpjyrnl x1;-xe an example where we are aware of each one and why.

Is the electric force a conserb.8g e)/ua2rkkq7tj o;-yvgw vative force? Why or why not? (See Chapter 6.)

When a charged ruler attracts small pieces of paper, sometimes a cd+-svdoa/ : kh. ,gwmpiece jumps quickly away after touching the ru./w+ -avogdh:m d kcs,ler. Explain.

Explain why the test charges we use 7 :bxzeigst+1when measuring electric fields must be small17z: g+sbitx e.

When determining an elekvzbi25ex ,7p ctric field, must we use a positive test charge, or would a negativzi v2,xk7 eb5pe one do as well? Explain.

Draw the electric field lines surrounding two negative electric charges a di b3fu-o 0upe2ustance l b oe 0upfu3-u2apart.

Assume that the two opposite charges in Fig. 16–31a are 12tlu zmfe))j+ lnlml),4r6o1l .0 cm apart. Consider thmj +6 ufo)l 1 ne)mlrllz4,)tle magnitude of the electric field 2.5 cm from the positive charge. On which side of this charge — top, bottom, left, or right — is the electric field the strongest? The weakest? Explain.

Consider the electric fbta* gv4d/9dxlcl4da+z/ g j7ield at points A, B, and C in Fig. 16–48. First draw an arrow at each point indicating the direction of the net force that a positive test charge would experience if placed at that point, then l//zlcdd*vl4+t4 aj9gdb7 g xa ist the points in order of decreasing field strength (strongest first).

Why can electric field linen zi3-lw*t x psq)ae9 vc+wnm04d/h8k s never cross?

Show, using the three rules for field lines given in Seckecp8k n6k kl*v7mn(x4o6i1c tion 16–8, that the electric field lines starting or ending on a single point chargexv6kk np64 *k(mi8c1knl oc7e must be symmetrically spaced around the charge.

Given two point charges Q and 2Q, poic90myl99x a distance l apart, is there a point along the straigl9y 9ic0px9moht line that passes through them where E=0 when their signs are (a) opposite, (b) the same? If yes, state roughly where this point will be.

Consider a small positive test charge located on an electric fielzlvi7e 168 (x8rt uu8z g/jsujd line at some point, such as point P in Fig. 16–31a. Is the direction of the jrz /1igvt8 6sl7z( juu8uxe8velocity and/or acceleration of the test charge along this line? Discuss.

Sketch the electric field lines for a uniform line of charge which is infinitel:(ksm m-b c- 6-w qnqg-z(httay long. (Hint: Use symmetry.) Is thmh -(sqcaqz- n(-m k tw-:6gbte electric field uniform in strength?

If the electric flux through a clob v3vvs, au,h-7hw xo.jhkw 2;sed surface is zero, is the electric field necessarily zero at all points on the surface? Explain. What about the k,ao-2v.b; w,hvh ujxwhvs3 7converse: If $\overrightarrow{E}=0$ at all points on the surface is the flux through the surface zero?

A point charge is surrounq,f3n y z4.bzm 7xanp8ded by a spherical gaussian surface of radius r. If the sphere is replaced by a cub xzy z8bn3 mqp4a,n.7fe of side r, will ${\mathrm{\Phi }}_E$ be larger, smaller, or the same? Explain.

  

  How many electrons make up a charge of++ rx njzx5/si $-30.0\mu C?$   $\times {10}^{14}electrons$

  What is the magnitude of the electric force of attraction between an ircz:c qs4m,z d3/ ilp*ton nucleu czti,zsc*l q4:3dmp/s $(q=+26e)$ and its innermost electron if the distance between them is $1.5\times {10}^{-12}m?$    $\times {10}^{-3}N$

  What is the repulsive electrical syp7yytvu1m( o0-a+ y force between two protons $5.0\times {10}^{-15}m$ apart from each other in an atomic nucleus?    N

  What is the magnitud irut( c)/4tu5ng oan)e of the force a $+25\mu CC$ charge exerts on a $+3.0mC$ charge 35 cm away?    N

  Two charged dust particles exert a force oc3jqrj1 8qn)ei4k v0d iq2a 0wf $3.2\times {10}^{-2}N$ on each other. What will be the force if they are moved so they are only one-eighth as far apart?    N

  Two charged spheres are 8.45 x u-x5v1 7inc:rzex )gkrjq(e bx) q+;cm apart. They are moved, and the force on each of them is found to have been tripled. How far apart arj)v+-eeq);5x7in k1xbx(x: zrrcq gue they now?    cm

  A person scuffing her feet on a wool rug on a dry day accumulate jl*(5ruo3pc7wjl29 gr ih(+v m*rejzs a net charge of(3 zw o *7eu(llvc9*r2rji5rjphjm+g $-42\mu C.$ How many excess electrons does she get,    $\times {10}^{14}electrons$
by how much does her mass increase?    $\times {10}^{-16}kg$

  What is the total charge of eo-x0 vv9tc pe/5i uoge+(o s:all the electrons in 1.0 kg of $H_{2}O?$    $\times {10}^{7}C$

  Compare the electric force holding the electr; +/8p db8gk b3+om:kp djjjpnon in orbit $(r=0.53\times {10}^{-10}m)$ around the proton nucleus of the hydrogen atom, with the gravitational force between the same electron and proton. What is the ratio of these two forces?    $\times {10}^{39}C$

Two positive point charges are a fixed distance apart. The sum of their charge0zvhrz1) 0oraozol; g(qg 9 -ds is h(-1r0;o)zoaqz0 d vlgz9rgoWhat charge must each have in order to
(a) maximize the electric force between them,
(b) minimize it?

  Particles of charge ogyt1n3p-/a ocx *c-s$+75$,$+48$ and $-85\mu C$ are placed in a line (Fig. 16–49). The center one is 0.35 m from each of the others. Calculate the net force on each charge due to the other two.

$F_{+75}$=   $NN$
$F_{+48}$=   $NN$
$F_{-85}$=   $NN$

  Three positive particles of equal cha -cosu+;4mt wyrge, $+11.0\mu C$ are located at the corners of an equilateral triangle of side 15.0 cm (Fig. 16–50). Calculate the magnitude and direction of the net force on each particle.


the force on the lower left charge is of magnitude    N, and
will point    ${}^{\circ }$below the-x axis. The force on the lower right charge is of magnitude    N, and will point    ${}^{\circ }$below the +x axis.

  A charge of 6.00 mC is placed at each corner of a square kp *sur y/quuxvrh, 8 *1ewd.-0.100 m on a side. Determine the magnitude and direction of the force o ,8suqr/ 1r wxhdue-u*yv.k*pn each charge.
$F_4$ =   $\times {10}^{7}N$
$\theta$ =    ${}^{\circ }$

  Repeat Problem 14 for the case when two of the positive ky5 af0r0*2j0.so iy cxstxx5charges, on opposite corners, are replaced by nega 5o. 0ta ssykxjxx50*f2cyi0r tive charges of the same magnitude (Fig. 16–51).
$F_4$ =   $\times {10}^{7}N$
$\theta$ =    ${}^{\circ }$

  At each corner of a square of s0,k tj tw1-plyide l there are point charges of magnitude Q, 2Q, 3Q, and 4Q (Fig. 16–52p 01 tywj,tkl-). Determine the force on (a) the charge 2Q, and (b) the charge 3Q, due to the other three charges.
$F_{2Q}$ =    $\frac{k{Q}^2}{l^2}$
${\theta }_{2Q}$ =    ${}^{\circ }$
$F_{3Q}$ =    $\frac{k{Q}^2}{l^2}$
${\theta }_{3Q}$ =    ${}^{\circ }$

  Three charged particles are placed at the corners of an equilateral triangle .ohjas6bn1ai8* ,r f(y icz6h1swd c- of side 1.2 abh6 s1jc 8hii1sof ydwa6r.-nz*(c, 0 m (Fig. 16–53). The charges are $+4.0\mu C,$$-8.0\mu C,$ and $-6.0\mu C.$ Calculate the magnitude and direction of the net force on each due to the other two.
$F_1$ =    N
${\theta }_1$ =    ${}^{\circ }$
$F_2$ =    N
${\theta }_2$ =    ${}^{\circ }$
$F_3$ =    N
${\theta }_3$ =    ${}^{\circ }$

  Two point charges have a p1 p4iyir(uj)f 8q/q itotal charge of $560\mu C.$ When placed 1.10 m apart, the force each exerts on the other is 22.8 N and is repulsive. What is the charge on each?
q = $5.54\times {10}^{a}C$ a =  ,
$5.54\times {10}^{b}C$ b =   
Q-q = $5.54\times {10}^{a}C$ a =  ,
$5.54\times {10}^{b}C$ b =   

Two charges, $-Q_0$ and $-3Q_0$ are a distance l apart. These two charges are free to move but do not because there is a third charge nearby. What must be the charge and placement of the third charge for the first two to be in equilibrium?

  A $+4.75\mu C$ and a $-3.55\mu C$ charge are placed 18.5 cm apart. Where can a third charge be placed so that it experiences no net force?    cm

  Two small nonconducting spheres have a totw:)1 g1em+x zoapbn1a al charge of $90.0\mu C.$
(a) When placed 1.06 m apart, the force each exerts on the other is 12.0 N and is repulsive. What is the charge on each?    $\times {10}^{-6}C$$$    $\times {10}^{-6}C$
(b) What if the force were attractive?    $\times {10}^{-6}C$$$    $\times {10}^{-6}C$

  A charge Q is transferred from an initially uncharged plastic ball to an ideni f pm u,+ln-qud8q1(ztical ball 12 cm away. The force of attraction is then 17 mN. Hm1(i ldn,u +qu-f pz8qow many electrons were transferred from one ball to the other?    $\times {10}^{12}$ electrons

  What are the magnitude and direction of the electric forc0qcyt wqa83n(e on an electron in a uniform electric field of strnwc 0q 83(aqtyength $2360N/C$ that points due east?
   $\times {10}^{-16}N$
 ----待选择----westeast 

  A proton is released in a uniform electric fa49+w5gnq 3qvwn sjb7ield, and it experiences an electric force bjn3g a 59qsw+47qwv nof $3.75\times {10}^{-14}N$ toward the south. What are the magnitude and direction of the electric field?
   $\times {10}^{5}N/C$
 ----待选择----southnorth 

  A downward force of 8.403muprv a n/s-9xyve+ N is exerted on a $-8.8\mu C$ charge. What are the magnitude and direction of the electric field at this point?    $\times {10}^{5}N/C$ ----待选择----updown 

  What are the magnitude and direction of the electric field 20.0 cm directg.r-1 od:afwg7sya h- ly above an isolatwr --o ha:ys7.agd fg1ed $33.0\times {10}^{-6}C$ charge?    $\times {10}^{6}N/C$ ----待选择----updown 

  What is the magnitudenj( hf5rh+(it of the acceleration experienced by an electron in an electr(i 5(j nhhrt+fic field of $750N/C?$ How does the direction of the acceleration depend on the direction of the field at that point?    $\times {10}^{14}m/s^2$  ----待选择----opposite to the field in line with the direction of the field 

  What are the magnitude and direction of the electric field at a point midwa 6 f:ynqm9 esw-)yxqgfm utc38pa)qf71 coe,3y betwef7cgm1m -qt8,3eqcf :ansp6e)9 f yxq o 3wuy)en a $-8.0\mu C$ and a $+7.0\mu C$ charge 8.0 cm apart? Assume no other charges are nearby.    $\times {10}^{7}N/C$ ----待选择---- towards the negative charde opposite to the negative charge 

Draw, approximately, the electric field lines about tw y9.w3iazyqa9o point charges, $+Q$ and $-3Q$ which are a distance l apart.

  What is the electric field streng qkpi(t /y.;s inp;f1tth at a point in space where a proton $(m=1.67\times {10}^{-27}kg)$experiences an acceleration of 1 million “g’s”? $\approx$    N/C（Round it to one decimal place.）

  An electron is released from rest in a uniform electnt j/a.(7gk :gob 4gaxric field and accelerates to the north t g /oj(.bgg4:nkaxa7at a rate of $115m/s^2.$ What are the magnitude and direction of the electric field?    $\times {10}^{-10}N/C$ ----待选择----northsouth 

  The electric field midway between tv8unvwu2n 6 g bath8s +qp;89ywo equal but opposite point charges is $745N/C,$ and the distance between the charges is 16.0 cm. What is the magnitude of the charge on each?    $\times {10}^{-10}C$

  Calculate the electric field at the center of a square 52.5 cr kk7t6xfw04m3x bvv*m on a side if one co tv*xw60vx3kmbfk7 r4rner is occupied by a $+45.0\mu C$ charge and the other three are occupied by $-27\mu C$ charges.    $\times {10}^{6}N/C$ at    ${}^{\circ }$

  Calculate the electric field at one corner of a square 1.00 m on a sid -iqxqgm6zoj ;3(e (mde if the other three corners are occupizxdm;oj ig- q(q m(e63ed by $2.25\times {10}^{-6}C$ charges.    $\times {10}^{4}N/C$   ${}^{\circ }$ from the x-direction.

Determine the direction and magnitude of the electric field at the point Pchrshou 8)53awd 22sg in Fig. 16–54. The charges are separated by a distance 2a, and point P is a dista3dhar2o)sc5usg2 8h wnce x from the midpoint between the two charges. Express your answer in terms of Q, x, a, and k.

  Two point charges, $Q_1\equiv 25\mu C$ and $Q_2=+50\mu C,$ are separated by a distance of 12 cm. The electric field at the point P (see Fig. 16–55) is zero. How far from $Q_1$ is P?    cm

(a) Determine the electric fi9v xj,.9fe;h ni5w87dpxpfldeld $\overrightarrow{E}$ at the origin 0 in Fig. 16–56 due to the two charges at A and B. (b) Repeat, but let the charge at B be reversed in sign.

  Use Coulomb’s law to determine the magnitude and direction of the eajoa4u f,49 i: u ((ithdclnx(lectric field at points A and B in Fi h4c(,uoi at :nl9xij f(du(4ag. 16–57 due to the two positive charges $(Q=7.0\mu C)$ shown. Are your results consistent with Fig. 16–31b?
$E_A$ =    $\times {10}^{6}N/C$
${\theta }_A$ =    ${}^{\circ }$
$E_B$ =    $\times {10}^{7}N/C$
${\theta }_B$ =    ${}^{\circ }$
(16-51)
(16-31b)

  You are given two unknown point (mx hki bu0crd2fo;(- charges, $Q_1$ and $Q_2$ At a point on the line joining them, one-third of the way from $Q_1$ to $Q_2$, the electric field is zero (Fig. 16–58). What is the ratio $Q_1/Q_2?$   

Determine the direction and magnitude of the electric field at the point P showaaboyo imu+: *;)5 devn in Fig. 16–59. The two charges are separated by a distance of 2a. Point P is on the perpendicular bisector of the line joining the charges, a distance x from the midpoint between them. Express your answers in d:va; +yo)a5obi me*uterms of Q, x, a, and k.

  An electron (mass $m=9.11\times {10}^{-31}kg$) is accelerated in the uniform field $\overrightarrow{\mathbf{E}}(E=1.45\times {10}^4\mathrm{N}/\mathrm{C})$ between two parallel charged plates. The separation of the plates is 1.10 cm. The electron is accelerated from rest near the negative plate and passes through a tiny hole in the positive plate, Fig. 16–60.
(a) With what speed does it leave the hole?    $\times {10}^{6}m/s$
(b) Show that the gravitational force can be ignored.

  An electron moving to the ri0;zfqgn*+s ,ujuqp p(ght at 1.0% the speed of light enters a uniform electric field parallel to its direction of motion. If the+(uzuj fpq,s0gp *q;n electron is to be brought to rest in the space of 4.0 cm,
(a) what direction is required for the electric field,  ----待选择----rightleft 
(b) what is the strength of the field?    N/C

  The total electric flux from a cubical box 2ytde-qqs(x:f4pi)v q;67tm6s a- k tq8.0 cm on a side is $1.45\times {10}^{3}N\cdot m^2/C$. What charge is enclosed by the box?    $\times {10}^{-8}C$

  A flat circle of radius 18 cm iq8l/eh y 5gs69(rylfdrs8+txs placed in a uniform electric field of magnitude56lrd 9/t8xyf+ ylsh ( esgq8r $5.8\times {10}^{2}N/C$ What is the electric flux through the circle when its face is
(a) perpendicular to the field lines,    $N\cdot m^2/C$
(b) at 45° to the field lines,    $N\cdot m^2/C$
(c) parallel to the field lines?   

  In Fig. 16–61, two ok)g *+.*e mn:w algrvhv3 e llvhg(.-fbjects, $O_1$ and $O_2$ have charges $+1.0\mu C$ and $-2.0\mu C$ respectively, and a third object, $O_3$ is electrically neutral.
(a) What is the electric flux through the surface $A_1$ that encloses all three objects?    $\times {10}^5$$N\cdot m^2/C$
(b) What is the electric flux through the surface $A_2$ that encloses the third object only?   

A cube of side l is placedgctg)noi(ei s;38; s zy7 6yqs in a uniform field $E=6.50\times {10}^{3}N/C$ with edges parallel to the field lines.
(a) What is the net flux through the cube?
(b) What is the flux through each of its six faces?

  The electric field between two squarek8 )qn ing3g5kbf5c.f metal plates is The plates are 1.0 m on a side and are separated by 3.0 cm. What is the charge on each plate (5.ncfgq)8ik5gbf k 3n assume equal and opposite)? Neglect edge effects.    $\times {10}^{-9}C$

  The field just outside a 3.50-cm-radius metal bal 0b3(wbd.90 l+ttyy rdzp4fkdl is $2.75\times {10}^{2}N/C$ and points toward the ball. What charge resides on the ball?    $\times {10}^{-11}C$

  A solid metal sphere of radius 3.00 m carries asi* 3)fwuet 9r total charge of $-3.5\mu C$ What is the magnitude of the electric field at a distance from the sphere’s center of
(a) 0.15 m,   
(b) 2.90 m,   
(c) 3.10 m,    N/C
(d) 6.00 m?    N/C
(e) How would the answers differ if the sphere were a thin shell?

A point charge Q rests at the center of an uncharged thin spherical comu s saa;4s3p,nducting shell. (See Fig. 16–33.) What is the electric field E as a function of r (a) for r less than the inner radius of the shell, (b) inside the shell, and (c) beyond the shell? (d) Does the shell affect the field due to Q alone? Does the charge Q affect the sp a,3u 4;ssamshell?

  The two strands of the helix-sha )qu8h9l*sujkjw757)blu v lm ped DNA molecule are held together by electrostatic forces as shown in Fig. 16–44. Assume that the net average charge (due to electron sharing) indicated on H and N atoms is 0.2e and on the indic) jlljkluu)w*shm9778u v5 bq ated C and O atoms is 0.4e. Assume also that atoms on each molecule are separated by $1.0\times {10}^{-10}m$. Estimate the net force between
(a) a thymine and an adenine;    $\times {10}^{-10}N$
(b) a cytosine and a guanine. For each bond (red dots) consider only the three atoms in a line (two atoms on one molecule, one atom on the other).    $\times {10}^{-10}N$
(c) Estimate the total force for a DNA molecule containing ${10}^5$ pairs of such molecules.    $\times {10}^{-5}N$

  How close must two electrons be if the electric force between them s.bx(rp6 2fwj6 at xb88)d zxpis equal to the weight ofx x862bd8fjr.6t pxp()wszba either at the Earth’s surface?    m

  A 3.0-g copper penny has a positive c(xx9v*xl roi3 harge of $38\mu C$. What fraction of its electrons has it lost?    $\times {10}^{-10}$

  A proton $(m=1.67\times {10}^{-27}kg)$ is suspended at rest in a uniform electric field $\overrightarrow{E}$. Take into account gravity at the Earth’s surface, and determine $\overrightarrow{E}$.    $\times {10}^{-7}N/C$  ----待选择----updown 

  Measurements indicate that there is an electric field surrounding the Earth. Itp4 jtjchdfqs-e 4yo /: u.0nu:s magnitude iq - n4e 40oy.j cd:j:/phtsufus about $150N/C$ at the Earth’s surface and points inward toward the Earth’s center. What is the magnitude of the electric charge on the Earth? Is it positive or negative? [Hint: the electric field outside a uniformly charged sphere is the same as if all the charge were concentrated at its center.]    $\times {10}^{5}C$  ----待选择----positivenegative 

  (a) Given the local electric field of what is the.h*;ajy c u+v(a)t9 vko9uty dpr-vs8 acceleration experienced by an electron near the surface of a)8 *v y.u-;+jv v99t ashkrytd(ocupthe Earth?    $\times {10}^{13}m/s^2$, ----待选择----updown 
(b) What about a proton?    $\times {10}^{10}m/s^2$, ----待选择----updown 
(c) Calculate the ratio of each acceleration to $g=9.8m/s^2$ For the electron: $\approx$    $\times {10}^{12}$ For the proton: $\approx$    $\times {10}^9$

  A water droplet of radius 0.018 mm remains statifrp k) yh: -tw2;7rvhlv:i jf;onary in the air. If the downward-directed et :rv;f wy) hr7ij2:pf;kh -vllectric field of the Earth is $150N/C$ how many excess electron charges must the water droplet have?    $\times {10}^6$ electrons

  Estimate the net force between dm m;cvrrlk9)ra9/9 z the CO group and the HN group shown in Fig. 16–62. The C and Ozl 9r)/k vrdmr99;acm have charges $\pm 0.40e$, and the H and N have charges $\pm 0.20e$, where $e=1.6\times {10}^{-19}C$. [Hint: Do not include the “internal” forces between C and O, or between H and N.]    $\times {10}^{-10}NN$

  In a simple model of the hydrogen atom, the electron revolves in a chfat l z0i39,dircular orbit az 9ht d,0lfi3around the proton with a speed of $1.1\times {10}^6\text{，}m/s,$. Determine the radius of the electron’s orbit. [Hint: See Chapter 5 on circular motion.]    $\times {10}^{-10}m$

  Suppose that electrical attraction, rather2p qzgvjw: )k+ than gravity, were responsible for holding the Moon in orbit around the Earth. If equal and opposite charges Q were placed on the Earth and the Moon, what should be the value of Q to mainpw :gv+k 2)zjqtain the present orbit? Use these data: mass of $Earth=5.98\times {10}^{24}kg$, mass of $Moon=7.35\times {10}^{22}kg$, radius of $orbit=3.84\times {10}^{8}m$. Treat the Earth and Moon as point particles.    $\times {10}^{13}C$

  An electron with speey;ppxf8 m ypplr2f h22+0 0 hqwdkq,l5d $v_0=21.5\times {10}^{6}m/s$ is traveling parallel to an electric field of magnitude $E=11.4\times {10}^{3}N/C$.
(a) How far will the electron travel before it stops?    m
(b) How much time will elapse before it returns to its starting point?    $\times {10}^{-8}s$

  A positive point cha 1g(bxuo(g;3gl)l sq yrge $Q_1=2.5\times {10}^{-5}C$. is fixed at the origin of coordinates, and a negative charge $Q_2=-5.0\times {10}^{-6}C$. is fixed to the x axis at $x=+2.0m$ Find the location of the place(s) along the x axis where the electric field due to these two charges is zero.    m from $Q_1$,   m from $Q_2$

A small lead sphere is encased in insulating plastic and suswb2xp (qiyy5tydx :v: 4sd,m. pended vertically from an ideal:q td, wxpy5 imsb2xy4dv:(. y spring $(k=126N/m)$ above a lab table, Fig. 16–63. The total mass of the coated sphere is 0.800 kg, and its center lies 15.0 cm above the tabletop when in equilibrium. The sphere is pulled down 5.00 cm below equilibrium, an electric charge $Q=-3.00\times {10}^{-6}C$ is deposited on it and then it is released. Using what you know about harmonic oscillation, write an expression for the electric field strength as a function of time that would be measured at the point on the tabletop (P) directly below the sphere.

  A large electroscope is made with “leaves” that are 78-cm-long wires 4/1om zfc f8eewith tiny 24-g spheres at the ends. When charged, nearly a4/fefm8 ze1o cll the charge resides on the spheres. If the wires each make a ${30}^{\circ }$ angle with the vertical (Fig. 16–64), what total charge Q must have been applied to the electroscope? Ignore the mass of the wires.    $\times {10}^{-6}CC$

  Dry air will break down and generate a spark if the electric field exceeds azbpbll21*0a2 9tda ne yb5xh/bout bdt9a *20 bl1an/2 epxh 5yzbl$3\times {10}^{6}N/C$. How much charge could be packed onto a green pea (diameter 0.75 cm) before the pea spontaneously discharges? [Hint: Eqs. 16–4 work outside a sphere if r is measured from its center.]    $\times {10}^{-9}C$