What would be the advantage, in Faraday’s experiments (Fig. Below), o2fc d -ui d5af.h;hf+df using coils2 ;aduf.dh+5i-fc dhf with many turns?

What is the difference between magnetic flux and magnetic 8;c hjhv06r5hq :iraqfield?

Suppose you are holding a ciu9hhmbtqm xxl :6 23p,/ugb2jrcular ring of wire and suddenly thrust a magnet, south pole first,2h mu x6gblxbuqthm:j 932p/, away from you toward the center of the circle. Is a current induced in the wire? Is a current induced when the magnet is held steady within the ring? Is a current induced when you withdraw the magnet? In each case, if your answer is yes, specify the direction.

Two loops of wire are moving in the vicinity o, 7aj4nq2bbu0)sv)rfh8a o tz f a very long straight wire carrying a steady current as shown in (Fig. Beloztqbv o )n2 r ,h7)asjb8au40fw). Find the direction of the induced current in each loop.

Suppose you are looking aluu;f e pliut+,/ 3 a-jll2rjm.ong a line through the centers of two circular (but separate) wire loops, one behind the other. A battery is sudd/, juluu+ amf- ;l2i.rtp3eljenly connected to the front loop, establishing a clockwise current.
(a) Will a current be induced in the second loop?
(b) If so, when does this current start?
(c) When does it stop?
(d) In what direction is this current?
(e) Is there a force between the two loops?
(f) If so, in what direction?

  In (Fig. Below), determine thev j bp)go5o6f) ,qsai2 direction of the induced current in resistor $R_A$ when
(a) coil B is moved toward coil A, ----待选择----increasedecrease 
(b) when coil B is moved away from A, ----待选择----increasedecrease 
(c) when the resistance $R_B$ is increased. ----待选择----increasedecrease 

In situations where a small sigh gw bjt6. zu+i,xysrt ir-;,:nal must travel over a distance, a “shielded cable” is used in which the signal wire is surrounded by an insulator and then enclosedgsxj,izh;6u+ yr-rb,iw :.t t by a cylindrical conductor carrying the return current. Why is a “shield” necessary?

What is the advantage of placing the two insulat rybwn1(s)rki 2tkud;j /g.v5 dz,fd; ed electric wires carrying ac close together or even twisted a(d d;y /ji5kd .)z1,kfv ;r2 twrgsubnbout each other?

Explain why, exactly, the lights may dim bg r,v2(0vuh1 bmj4ua priefly when a refrigerator motor starts up. When an electric heater vuhum0(1g2 v4bj ,rpais turned on, the lights may stay dimmed as long as the heater is on. Explain the difference.

Use (Fig. Below a) and (Fig. Below b) plus the right-hand rules to showh4zih, 9kt6ac why the count94hc,h t k6izaer torque in a generator opposes the motion.
a
b

Will an eddy current brake (Fig. Below) wor4bm: ;s0ql:wagcufv: k on a copper or aluminum wheel, or must the wheel be febc:gvla4 um s:q;: 0fwrromagnetic? Explain.

It has been proposed that eddybe 5jq j0.n(hj currents be used to help sort solid waste for recycling. The waste is first ground into tiny pieces and iron removed with ae( j0hjj5 .bnq dc magnet. The waste then is allowed to slide down an incline over permanent magnets. How will this aid in the separation of nonferrous metals (Al, Cu, Pb, brass) from nonmetallic materials?

The pivoted metal bar with slots in (Fig. Below) falls;th y7p)jtu 6ngm:x,c .;ixozaz/c 2e much more quickly through a magnetic fiem6.;:p;2octycxxe zn zhigat , 7/u)jld than does a solid bar. Explain.

If an aluminum sheet is held between the poles of a large bar magnet, it requiredo p f.0 0o)e83 bsf8ll(koayts some fo 0bl.ff)8odes8ok p o0aly( t3rce to pull it out of the magnetic field even though the sheet is not ferromagnetic and does not touch the pole faces. Explain.

A bar magnet falling inside a vertical metal tube reaches teof7m yyr ;r1 j wz740)hyj8h f3h.aka terminal velocity even if the tube is evacuated sfhrh7 1rf3tmoa 8e)4jw7zk0y;h .yyj o that there is no air resistance. Explain.

A metal bar, pivoted at one end, oscillates freely in the absence of a magnetd bc0w1sr0i koqs(-/ hic field; but in a magnetic field, its oscillations are quickly damped out. bio0s1q-/r sdkc( hw0 Explain. (This magnetic damping is used in a number of practical devices.)

An enclosed transformer has four wire leads coming from it0uoblg e w.r t53w(nf). How could you determine the ratio of turns on the two coils without tae bufw )gw.50n t3olr(king the transformer apart? How would you know which wires paired with which?

The use of higher-voltage lines in homes — say, 600 V or 1200 V — would ryttk0 /vpj cz- h;ft-av-zn/6educe enerjp v0n- /z fthtkct;-6z/ -ayvgy waste. Why are they not used?

A transformer designed for a 120-V ac input will often “burn out” if connecteufkoj1.q. 2-rp db4el k j48ipd to a 120-V dc source. Explain. [Hint: The resistance of the primar.4 k-p8ij4.2o pdr kbquef 1ljy coil is usually very low.]

How would you arrange two flat circular cu+ yc5hnrvct31t*6p x oils so that their mutual inductance wasy6uh 3n5t1x*c+ cpt vr
(a) greatest,
(b) least (without separating them by a great distance)?

Does the emf of the battery in (Fig. Below) affect the time needed f gg:tqf/sy, ,t2 1hcaqnj a:5aor the LR circuit to reach a ,j5t2:gqq nhasa t:y/c,1fg
(a) a given fraction of its maximum possible current,
(b) a given value of current? Explain.

  In an LRC circuit, can the rms vol4q 9lya7w9v-yemk wu/tage across
(a) an inductor, ----待选择----yesno 
(b) a capacitor, be greater than the rms voltage of the ac source? Explain. ----待选择----yesno 

Describe briefly how the frequency of tk+bd4c/,wnk lhe source emf affects the impedance of
(a) a pure resistance,
(b) a pure capacitance,
(c) a pure inductance,
(d) an LRC circuit near resonance (R small),
(e) an LRC circuit far from resonance (R small).

Describe how to make the nze 4k8 ab)ss cf*0ch;impedance in an LRC circuit a minimum.

  The magnetic flux through a coil of wi .u *7+bin djh-ofdsw6re containing two loops changes from -50Wb to +38 Wb in 0.42 s. What is the emf induced in the wid fj76+obd hs-n u*.coil?    V

  The rectangular loop shown in (Fig. Below) is pushed into u3s2. j3)lr. httswh gthe magnetic field whichwsht 3lu.3 t s2gh.)rj points inward. In what direction is the induced current?  ----待选择----counterclockwiseclockwise 

  The north pole of the magnet).2da ww oerahjq-8k6 in (Fig. Below) is being inserted into the coil. In which direction is theod-2 j)6.8ewqkhraw a induced current flowing through the resistor R?  ----待选择----from right to leftfrom left to right 

  A 9.6-cm-diameter circular loop of wire is in a 1.10-yi4p he zh.ow3y/7 e5:fvgl -fT magnetic field. The loop is removed from theew-ih5ohffg4p :z. yev3yl/7 field in 0.15 s. What is the average induced emf?    $ \times10^{-2 }\;V$

  A 12.0-cm-diameter loop of wire is initially oriented perpendiculaqlm s gv7/s-vk; 7)uvhr to a 1.5-T mal7us)7q /hmv-v vgks;gnetic field. The loop is rotated so that its plane is parallel to the field direction in 0.20 s. What is the average induced emf in the loop?    $ \times10^{-2 }\;V$

  A 10.2-cm-diameter wire coil is initially ofb: on1xds zb4d,l;7briented so that its plane is perpendicular to a magnetic field of 0.63 T pointing up. During the course of 0.15 s, the field is changed to one of 0.25 T pointing down. What is theb:fs7 d;xbozb,4 dn1l average induced emf in the coil?    $ \times10^{ -2}\;V $

  A 15-cm-diameter circular loop of wire is placed in a 0.50-T magnetic3r0,9afc(; y m8:d hgis tkuza field.
(a) When the plane of the loop is perpendicular to the field lines, what is the magnetic flux through the loop?    $ \times10^{-3 }\;Wb$
(b) The plane of the loop is rotated until it makes a 35$^{\circ}\,$ angle with the field lines. What is the angle $\theta$ in Eq. 21–1 for this situation? $\theta$ =    $^{\circ}\,$
(c) What is the magnetic flux through the loop at this angle?    $ \times10^{-3 }\;Wb$

  (a) If the resistance of the resistor in (Figk7 1+.gqrmsbp2bvkc2w l 499xfvr -4 nbu5vr h. Below) is slowly increased, what is the direction of the current induced in5hx 2bvrf-9sl9 1p7kr .4 ucrkbvgq n+vmw2b4 the small circular loop inside the larger loop?  ----待选择----counterclockwiseclockwise 
(b) What would it be if the small loop were placed outside the larger one, to the left?  ----待选择----counterclockwiseclockwise 

  What is the direction of the induced current in the circular loop due to the cq+x 1d heeevo8+g j6f/urrent shown in each part of (qe1g6jex +8d ov h/e+fFig. Below)?
a  ----待选择----counterclockwiseclockwise0 
b  ----待选择----counterclockwiseclockwise0 
c  ----待选择----counterclockwiseclockwise0 
d  ----待选择----counterclockwiseclockwise0 

  If the solenoid in (Fig. Below) is being pulled awf*h4wg1bbzun*iz ww sg478uo 4/ rkp*ay from the loop shown, in what direction isnu4zhw7*1s*bfk ruw /4 gw4pogb*i8z the induced current in the loop?  ----待选择----counterclockwiseclockwise 

  The magnetic field perpendicular to a circ 1s7ay hz)ath-fpt1p )ular wire loop 12.0 cm in diameter is changed from +0.52T to -0.45 T in 180 ms, where means the field1a)ya-1pfts ht7p) zh points away from an observer the observer.
(a) Calculate the induced emf.    $ \times10^{-2 }\;V$
(b) In what direction does the induced current flow?  ----待选择----counterclockwiseclockwise 

  The moving rod in (Fig. Below) is 12.0 cm long and is pullexz ur4,y zj2)k+l1oq ai-/phed at a speed of 15.0cm/s If tl+/ e izpuxh2 ,za yj1q-o)4krhe magnetic field is 0.800 T, calculate
(a) the emf developed,    $ \times10^{-2 }\;V$
(b) the electric field felt by electrons in the rod.    V/m  ----待选择----updown 

  A circular loop in the plane of the paper lies in a 0.75-T magnetic field point r1jw x(zjfuhe2gasw*1x0-* ping into the paper. If the loop’s diameter changes from 20.0 cm to 6.0 cm h-w1aegsjfp r*w0juz 1*x2 (xin 0.50 s,
(a) what is the direction of the induced current,  ----待选择----counterclockwiseclockwise 
(b) what is the magnitude of the average induced emf, $|\varepsilon|$ $\approx$    $ \times10^{-2 }\;V$ (retain one decimal places)
(c) if the coil resistance is 2.5$\Omega$ what is the average induced current?    $ \times10^{-2 }\;A$

  The moving rod in (Fig. Below)is 13.2 cm long and generates an emf *di m/5x -unqs+9esj gof 120 mV while movingex5s 9j-qs+m dng/i u* in a 0.90-T magnetic field.
(a) What is its speed?    m/s
(b) What is the electric field in the rod?    V/m  ----待选择----updown 

  Part of a single rectangular loop of wire bqyyy.uwt-*. v .k sfv av4c-,with dimensions shown in (Fig. Below) is situated inside a region w *. fyuky.v.y -atb-cq 4s,vvof uniform magnetic field of 0.550 T. The total resistance of the loop is $\mathrm{0.230~Ω}$ Calculate the force required to pull the loop from the field (to the right) at a constant velocity of 3.40m/s Neglect gravity.    N

  A 500-turn solenoid, 25 cm long, has a diameter of 2.5 cm. A 10-tg( fzsuc )wx:hlw3:6 gurn coil is wound tightly around the center of the solenoid. If the current in the solenoid increases uniformly from 0 to 5.0 A in 0.60 s, what will be the induced emf in the short coil during twc( w6 lgzfx)h::gu3shis time?    $ \times10^{-4 }\;V$

  In (Fig. Below), the rod moves with a speed of 1.6m/s is 30.0 cppog ;/: v,1hn i u4r6i r:ogb7jid0xim long, and has a resistancgi,oi4ro d::1hi rx0n/ pgijpu67;bv e of $\mathrm{2.5~Ω}$ The magnetic field is 0.35 T, and the resistance of the U-shaped conductor is $\mathrm{25.0~Ω}$ at a given instant. Calculate
(a) the induced emf, $\varepsilon$ $\approx$    V(retain two decimal places)
(b) the current in the U-shaped conductor, $I\approx$    $ \times10^{-3 }\;A$ (retain one decimal places)
(c) the external force needed to keep the rod’s velocity constant at that instant. $F\approx$    $ \times10^{- 4}\;N$ (retain one decimal places)

  A 22.0-cm-diameter coil consists of 20 turns of circular copper wirep.bnwv 507 byw 2.6 mm in diameter. A uniform magnetic field, perp0y7b n.v pbww5endicular to the plane of the coil, changes at a rate of $8.65\times10^{-3}\mathrm{~T/s}.$ Determine
(a) the current in the loop, $|\varepsilon|$ $\approx$    A (retain two decimal places)
(b) the rate at which thermal energy is produced.    $ \times10^{-4 }\;W$

  The magnetic field perpendicular to a single 13.2-cm-diameter circulat j:s90xw g:lh2c,lov r loop of cop:o2lv0sh 9ctlg:x ,jw per wire decreases uniformly from 0.750 T to zero. If the wire is 2.25 mm in diameter, how much charge moves past a point in the coil during this operation?    C

  A simple generator is used to generate a peak output voltage of 29d /hkj -zux:vnzzk 304.0 V. The square armature consists of windings that are 6.0 cm on a side and rotates in a field of 0.420 T at a rate of 60.0rev/s How many loops of wire should be9hxk/ku3jn0v- zz : zd wound on the square armature? $\approx$    loops(Round to the nearest integer)

  The generator of a car 6g,lkky mo 6( m. yzasp3xu.b:idling at 1100 rpm produces 12.4 V. What will the ou tput be at a rotation speed of 2500g:y .3pylxbu6 ,m6.skm (zk oa rpm, assuming nothing else changes?    V

Show that the rms output (Section 18–7)zzus-w lf eq)a+ll,+7o 4lr) y of an ac generator is $V_\mathrm{rms}=NAB\omega/\sqrt{2}$, where $\omega=2\pi f.$

  A simple generator has a 320-loop square coil 21.0 cm q24,cyl6 nwzu:c n 0omon a side. How fast must it turn in a 0.650-T field to produce a 120-V peak output? n24y 06nmoqu z w,:ccl$f$   rev/s

  A 450-loop circular armature coil with a diameter of 8.0 cm rotates at 120r5wntnj20 cs5 jev/s in a uniform magnetic field of strength 0.5552tnsc5 wnj0j T.
(a) What is the rms voltage output of the generator? $\approx$    V (Round to the nearest integer)
(b) What would you do to the rotation frequency in order to double the rms voltage output?  ----待选择----oncedoubletriple  the rotation frequency

  A generator rotates at 85 Hz in a magnetic field of 0.030 T. It 1a:cs9wtik. hhas 1000 turns ankw9h s.a:ci1 td produces an rms voltage of 150 V and an rms current of 70.0 A.
(a) What is the peak current produced?    V
(b) What is the area of each turn of the coil?    $ \times10^{-2 }\;m^2$

  A motor has an armature resistancv fd* r)h:;zj6lfj1 ete of $3.25\Omega.$ If it draws 8.20 A when running at full speed and connected to a 120-V line, how large is the back emf?    V

  The back emf in a mot* w7 bfgsmpal;4l5c8hor is 72 V when operating at 1800 rpm. What would be the back emf at 2500 rpm if the magnetic ;8c57b f4lma gshl*pwfield is unchanged?    V

  The back emf in a motor is 95 V when the motor is opetd u:nj vqc,:8)gbnd8rating at 1000 rpm. How would you change the motor’s magnetic fiel8bq cv,d)n jtg8::nudd if you wanted to reduce the back emf to 65 V when the motor was running at 2500 rpm? reduce the magnetic field to    % of its original value

  What will be the current in the motor of Example 21–9 if the load cal4clem6n21ooj .z z zcg z;0y/ af5mw4uses it to run at hac6znz0z4o;m 2g/cwal5e. 4j 1y ozf mllf speed?    A

  A transformer is designed to change 120 V into 10,000 Vc (8ccth eps52uoz.p ., and there are 164 turns in the primary coil. How many turns are in p58 pet.c.c(2ous czhthe secondary coil? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ $\approx$    turns

  

  A step-up transformer increases 25 V to 120 V. What is the curre,rcczbk .eq1 ka/,o5t2tqbg ,nt in the secondary coil r,c5bkc /g ,1aq t,zqoekb2. tas compared to the primary coil?   

  Neon signs require 12 kV for their operation. To operate from a cn9p.ant6 q +y240-V line, what must be the ratio of secondary to primary turns of the transformer? What would the voltage output be if the transformer were connected qn t9apy6+cn.backward?
$\frac{N_\mathrm{s}}{N_\mathrm{p}}$ =   
$V_s$ =    V

  A model-train transformer plugs into 120-V ac and draq ire h(hl0xa)0+o8p qws 0.35 A while supplying 7 0 i8a)0eq+xqhh olpr(.5 A to the train.
(a) What voltage is present across the tracks?    V
(b) Is the transformer step-up or step-down? this is a  ----待选择----step-downstep-up  transformer

  The output voltage of a 95-W transformer is 12 V, an pcm3ikln02(qp 3 z; xg(c4bo29 rfrjtd the input current is 22 A. lqo3kmi bf4pgz9x;r (c3 pr2ncj 0t(2
(a) Is this a step-up or a step-down transformer? this is a  ----待选择----step-downstep-up  transformer
(b) By what factor is the voltage multiplied? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ =   

  A transformer has 330 primsx3 3lcf+u 9 1-qb pvyepfenw45b b7(jary turns and 1340 secondary turns. The input voltage is 120 V and the outputcn 9ufsj5bvf7b xpq4w3p ye -(e+1 3lb current is 15.0 A. What are the output voltage and input current? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ =    V
$\frac{I_\mathrm{s}}{I_\mathrm{p}}$ =    A

  If 30 MW of power at 45 kV (rms) arrives at a town from a gener ;)s.wrhv qh/dator via $\mathrm{4.0-Ω}$ transmission lines, calculate
(a) the emf at the generator end of the lines, $\varepsilon$    V
(b) the fraction of the power generated that is wasted in the lines. fraction wasted   

  65 kW is to arrive at a towp*4 rafjj fy56n over two $0.100-\Omega$ lines. Estimate how much power is saved if the voltage is stepped up from 120 V to 1200 V and then down again, rather than simply transmitting at 120 V. Assume the transformers are each 99% efficient.    kW

  If the current in a 180-mH coil changes steadily from 25.0 A to 10.0 A in 350 msh 0y*ixb vu.0;lcqe) l, what is the h0u0lx.bilye ; )*qvc magnitude of the induced emf?    V

  What is the inductance of a coh 0gn1ucdg,4nkk6r u ,il if the coil produces an emf of 2.50 V when the current in it changes from -28.0mA to +31.0mAur4,kn,1ku h d 6cgn0g in 12.0 ms?    H

  What is the inductance L of a 0.60-m-long air-filled en f kzn)g-c((iqcke s)g.4 (fcoil 2.9 cm in diameter containinsg4.feg(qn(i f e c-)c)kk(zng 10,000 loops?    H

  How many turns of wire would be required to8(-8zao h6i7ptw qxpbr3 qs5 zll: r*b make a 130-mH inductance out of a 30.0-cm-long air-filled coil with a 3airlro68b:*zlbw7p(q 5s h8q -p x tzdiameter of 5.2 cm? L$\approx$    turns (Round to the nearest integer)

  An air-filled cylindricalcew3opgg5 ge-hb4(xq2/ay,8 ; muoor inductor has 2800 turns, and it is 2.5 cm in diameter and 2 cmpo25- x4h8;o3,wg brgq eyaeu/go(8.2 cm long.
(a) What is its inductance?    $ \times10^{-2 }\;H$
(b) How many turns would you need to generate the same inductance if the core were iron-filled instead? Assume the magnetic permeability of iron is about 1200 times that of free space.

  A coil has $2.25-\Omega$ resistance and 440-mH inductance. If the current is 3.00 A and is increasing at a rate of 3.50A/s what is the potential difference across the coil at this moment?    V

A long thin solenoid of lnz )*(jje c n60cdbzl0ength l and cross-sectional area A contains $N_1$ closely packed turns of wire. Wrapped tightly around it is an insulated coil of $N_2$ turns, (Fig. Below). Assume all the flux from coil 1 (the solenoid) passes through coil 2, and calculate the mutual inductance.

  The wire of a tightly wound solenoid is unwound andt5xp hf ,:tt+7.srgrmv+y4kp used to make another tightly5p,rt+sx y+hrtv m7kgf p :.4t wound solenoid of twice the diameter. By what factor does the inductance change?   

  The magnetic field inside an air-filled solenoid 36 cm (d0eu sieif*pb x) a96(r/d9tlk 1nb llong and 2.0 cm in diameter is 0.80 T. A(9)(px61ud fbiai9sednrb 0te*lkl /pproximately how much energy is stored in this field?    J

  At a given instant the current through an inductor is 50.0 m bsg iim)37bt4A and is increasing at the rate of 115mA/s. Wh7)3tig 4smbib at is the initial energy stored in the inductor if the inductance is known to be 60.0 mH, and how long does it take for the energy to increase by a factor of 10 from the initial value?
U =    $ \times10^{-5}\;J$
$\Delta$t=    s

  Assuming the Earth’s magnetic fie,)6y(fwyfqp-v2wnv50nl vcj w 6d br,ld averages about $0.50\times10^{-4}\mathrm{~T}$ near the surface of the Earth, estimate the total energy stored in this field in the first 10 km above the Earth’s surface.    $ \times10^{15 }\;J$

Determine $\Delta I/\Delta t$ at t = 0 (when the battery is connected) for the LR circuit of (Fig. Below) and show that if I continued to increase at this rate, it would reach its maximum value in one time constant.

  After how many time constants does the current in k: r rzats,-:pyi8 q8qy1 (sy8b0ksxa(Fig. Below) reach within
(a) 10%,    $\tau$
(b) 1.0%,    $\tau$
(c) 0.1% of its maximum value?    $\tau$

  Two tightly wound solenoids have the samekfi9 jlotx 7-z,x;1gp length and circular cross-sectional area. But solenoid 1 uses wire that is half as thick as gx-,tp97ifx 1jlkz;osolenoid 2.
(a) What is the ratio of their inductances? $\frac{L_1}{L_2}$ =   
(b) What is the ratio of their inductive time constants (assuming no other resistance in the circuits)? $\frac{\tau_1}{\tau_2}$ =   

  What is the reactance ofc; qn1 b+5em(zm )dn6roai 8iv a $7.20-\mu F$ capacitor at a frequency of
(a) 60.0 Hz,    $\Omega$
(b) 1.00 MHz?    $ \times10^{ -2}\;\Omega$

  At what frequency will a 22.0-mH inductor have a reao+ (gp. xqgdz)ctance of $660 \mathrm{k} \Omega ?$    Hz

  At what frequency willaxk9h q- rdm sr*dtau)/+ ei+( a $2.40-\mu F$ capacitor have a reactance of $6.70 \mathrm{k} \Omega ?$    Hz

Plot a graph of the reactanc7rav 78pcynls*m2o lvk 7e 0k5/i:eboe of a $1.0-\mu F$ capacitor as a function of frequency from 10 to 1000 Hz.

Plot a graph of the reactance ozib ps-t3c 8i5f a 1.0-mH inductor as a function of frequency from 100 to 10,0 3p-i cstz8i5b00 Hz.

  Calculate the reactance of, and rm;0ykoch -0 za8i a(twns current in, a 160-mH radio coil connected to ;8 0khi -awtzo( y0anca 240-V (rms) 10.0-kHz ac line. Ignore resistance.
$X_L$ =    $\Omega$
V =    $ \times10^{-2 }\;A$

  An inductance coil operates at 240 V and 60.0 Hz. It draws 12.8 A. What la0e -0nf (ns qus*q*8 ebcn g:tr46sdis the coil’s iuc- 60as sndn 0*(bqq:8eslrt eg4*nfnductance? $X_L$ =    $ \times10^{-2 }\;H$

  (a) What is the reactance of a well-in)ttf12gyz f f8sulated $0.030-\mu F$ capacitor connected to a 2.0-kV (rms) 720-Hz line?    $\Omega$
(b) What will be the peak value of the current?    A

  $\mathrm{A~30-k}\Omega$resistor is in series with a 45-mH inductor and an ac source. Calculate the impedance of the circuit if the source frequency is
(a) 50 Hz,    $ \times10^{4 }\;\Omega$
(b) $3.0\times10^4\mathrm{~Hz}.$    $ \times10^{4 }\;\Omega$

  $\mathrm{A~3.5-k}\Omega$ resistor and a $4.0-\mu F$ capacitor are connected in series to an ac source. Calculate the impedance of the circuit if the source frequency is
(a) 60 Hz,    $ \times10^{3 }\;\Omega$
(b) 60,000 Hz.    $ \times10^{3 }\;\Omega$

  For a 120-V rms 60-Hz voltage, an rms cuk(lqli7z ly4cj,k5 hx c,i3 6sx-wog)rrent of 70 mA passing through the human body for 1.0 s could be lethal. What must be the impedanceoq4i 5swgz kli(ycxc7 -hx,3l, jl k6) of the body for this to occur?    $ \times10^{3 }\;\Omega$

  What is the resistance of a coil if its impedasod )) nx7zvd-i,2sxq*gb;q fnce is $\mathrm{235~Ω}$ and its reactance is $\mathrm{135~Ω}$    $\Omega$

  What are the total impedance, phase angle, and8bmq b ;5owcyr *sbsca(,9g 6g rms current in an LRC circuit connected to a 10.0-kHz, 725 yw sqrggc9,bc5bb;sm( 68ao*-V (rms) source if $L=22.0\mathrm{~mH},R=8.70\mathrm{~k}\Omega,$ and
Z $\approx$    k$\Omega$
$\phi$ =    $^{\circ}\,$
$I_{rms}$ =    $ \times10^{ -2}\;A$

  A resistor in series with a 420-mH inductor is driven by anj:-, szvcrrupvk;w t;agt/ /6rq7 9xi ac power supply. At what frequency is the impedance double that of the impwj, uv/gt 6cr-arr;ivp7z:x; ktsq /9 edance at 60 Hz?    Hz

  (a) What is the rms current /tnvs89s jf f xc2xar l-:)yr,in an RL circuit when a 60.0-Hz 120-V rms ac voltage is applied, wheres/-fv),l y f 89rs2jaxnrx t:c $R=1.80\mathrm{~k}\Omega,$ and $L=350\mathrm{~mH}?$    $ \times10^{ -2}\;A$
(b) What is the phase angle between voltage and current?    $^{\circ}\,$
(c) What are the rms voltage readings across R and L?
$V_{rms \,R}$ $\approx$    V (Round to the nearest integer)
$V_{rms\,L}$ =    V

  (a) What is the rms current in an R +r8nl jqs ky3vc)b3f4C circuit if $R=8.80\mathrm{k}\Omega,C=1.80\mu\mathrm{F},$ and the rms applied voltage is 120 V at 60.0 Hz?    $ \times10^{-2}\;A$
(b) What is the phase angle between voltage and current? $\phi$ =    $^{\circ}\,$
(c) What are the voltmeter readings across R and C?
$V_{rms\,R}$   V
$V_{rms\,C}$    V

  A 3500-pF capacitor is co3 (kveic ::ry ep0pqdp/8c m6fnnected to a $55.0-\mu H$ coil of resistance $3.00\Omega.$ What is the resonant frequency of this circuit?    $ \times10^{5 }\;Hz$

  The variable capacitor in the tuner of an AM raluy3o.ewlry 0c 8-4 jndio has a capacitance of 2800 pF when theo3ye4l -j.y0nu crw 8l radio is tuned to a station at 580 kHz.
(a) What must be the capacitance for a station at 1600 kHz? $C_{1600\mathrm{~kHz}}$ $\approx$    pF(Round to the nearest integer)
(b) What is the inductance (assumed constant)?    $ \times10^{ -5}\;H$

  An LRC circuit has L = 14.bo thj* st*x;fq vy))3 0v,lov8 mH and $R=4.40\Omega$.
(a) What value must C have to produce resonance at 3600 Hz?    $ \times10^{ -7}\;F$
(b) What will be the maximum current at resonance if the peak external voltage is 150 V?    A

  Suppose you are looking at two cupm/7-kom 8y q45jd jw1i1np s9elyl p-rrent loops in the plane of the page as shown in (Fig. Below). When switch S is thrown in the lefoe-p/k1msl5ji4yjmp-l n pw dq18 9y7t-hand coil,
(a) what is the direction of the induced current in the other loop?  ----待选择----counterclockwiseclockwise 
(b) What is the situation after a “long” time?
(c) What is the direction of the induced current in the right-hand loop if that loop is quickly pulled horizontally to the right?  ----待选择----counterclockwiseclockwise 

  A square loop 24.0 cm on a side has a resistaf 3t r3x:9u/pcj*pr sgnce of $5.20\Omega.$It is initially in a 0.665-T magnetic field, with its plane perpendicular to $\vec{\mathbf{B}},$ but is removed from the field in 40.0 ms. Calculate the electric energy dissipated in this process.    $ \times10^{-3 }\;J$

  A high-intensity desk lamp is rated at 45 W but rhbr *x)/d 1kvpequires only 12 V. It contains a transformer that c* ) xpvrkh/bd1onverts 120-V household voltage.
(a) Is the transformer step-up or step-down? this is a  ----待选择----step-downstep-up  transformer
(b) What is the current in the secondary coil when the lamp is on?    A
(c) What is the current in the primary coil?    A
(d) What is the resistance of the bulb when on?    $\Omega$

  Power is generated at 24 kV at a generating plant located 118 km from a town tho w,mdwltdhl)e):t1-3wt nl odx,:4nat requires 50 MW of power at 12 kV. Two transmission lines from the plant to the town each have aonttm4:lnw d dd13) w:o-lw tx,h e,)l resistance of $0.10\mathrm{~}\Omega/\mathrm{km~}.$ What should the output voltage of the transformer at the generating plant be for an overall transmission efficiency of 98.5%, assuming a perfect transformer? V $\approx$    kV

  The primary windings of a transformer which has an 80% efficiency are codr9ovv*eq x 220 zex/gnnected to 110-V ac. Thzxo x 22v*v90g/deerqe secondary windings are connected across a $2.4-\Omega$ 75-W lightbulb.
(a) Calculate the current through the primary windings of the transformer. $P_S$ $\approx$   A
(b) Calculate the ratio of the number of primary windings of the transformer to the number of secondary windings of the transformer. $\frac{N_\mathrm{p}}{N_\mathrm{s}}$   

  A pair of power transmission lines each have aohrv( oaxie4p*; bcw(i 3kud 0n.o,.(sioi7r $0.80-\Omega$ resistance and carry 740 A over 9.0 km. If the rms input voltage is 42 kV, calculate
(a) the voltage at the other end, $\approx$    kV
(b) the power input, $\approx$    $ \times10^{7 }\;W$
(c) power loss in the lines, $\approx$   $ \times10^{5 }\;$W
(d) the power output. $P_{out}$ $\approx$    $ \times10^{7 }\;W$

  Two resistanceless rail e,d1qnw2 bjik 0sre(2uh;r 0espymp3ua298 us rest 32 cm apart on a 6.0$^{\circ}\,$ ramp. They are joined at the bottom by a $0.60-\Omega$ resistor, and at the top by a copper bar of mass 0.040 kg (ignore its resistance) is laid across the rails. The whole apparatus is immersed in a vertical 0.55-T field. What is the terminal (steady) velocity of the bar as it slides frictionlessly down the rails? v =    m/s

Show that the power *b 8q+ ja5xdd;pvbkcv- ou,5floss in transmission lines, $R_L$ is given by $P_{\mathrm{L}}=\left(P_{\mathrm{T}}\right)^{2}R_{\mathrm{L}}/V^{2},$ where $P_T$ is the power transmitted to the user, V is the delivered voltage, and $R_L$ is the resistance of the power lines.

  A coil with 150 turns, a radius of 5.0 cm, and a resistanc32f)wo7yl6n + z xttumlcwb+v+x sa 64e of $\mathrm{12~Ω}$ surrounds a solenoid with $230\mathrm{~turns/cm}$ and a radius of 4.5 cm; see (Fig. Below). The current in the solenoid changes at a constant rate from 0 to 2.0 A in 0.10 s. Calculate the magnitude and direction of the induced current in the coil.
I =    $ \times10^{-2 }\;A$
 ----待选择----left to rightright to left 

  A certain electronic device needs to be pr 3pc.xtc:kn p-ntvf, 6otected against sudden surges in current. In particular, after the power nc pvtc-tn.3,6xk :pf is turned on the current should rise no more than 7.5 mA in the first $120\mu s$ The device has resistance $\mathrm{150~Ω}$ and is designed to operate at 55 mA. How would you protect this device? L $\approx$    in series(retain two decimal places)

  A 25-turn 12.5-cm-diameter coil is pl8oe: vl-fr2u pivstiof+4*v( s gvvqgc0(7 j9aced between the pole pieces of an electromagnet. When the magnet is turned on, the flux through the coil changes, inducing an emf. At what7((vl 94so ivope 2jgr8vfuvi-:v f ct+q0*gs rate (in T/s) must the field produced by the magnet change if the emf is to be 120 V? $|\varepsilon|$    T/s

  Calculate the peak output voltage of a simple generato+)ocu l(o/zbqe d6:ylr whose square armature windings are 6.60 cm on a side; the armature contains 155 loops and rotates in a field odo ll bz:o)y q6/ce(+uf 0.200 T at a rate of 120rev/s. $\varepsilon_{peak}$ =    V

  Typical large values for electric and magnetic fielvx) a l j9hq8xgc53q4as)e; eu- h)ovvds attained in laboratories aru g8)hv )hxc v-x5a3e v9lj) q;4sqoeae about $1.0\times10^4\mathrm{~V/m}$ and 2.0 T.
(a) Determine the energy density for each field and compare.
$u_E$ $\approx$    $ \times10^{-4 }\;J/m^3$
$u_B$ $\approx$    $ \times10^{6 }\;J/m^3$
$\frac{u_B}{u_E}$ =   $ \times10^{9 }\;$
(b) What magnitude electric field would be needed to produce the same energy density as the 2.0-T magnetic field?    $ \times10^{8 }\;V/m$

  What is the inductance L of the primary of a transformer whose input if yo1j eg72nn4s 220 V at 60.0 Hz if the current drawn is 5.8 A? Assumgo4 y j7nnf1e2e no current in the secondary.    H

  A 130-mH coil whose resistance isi;sxl0*n ; 0 l)p0kc6;uzny:kyhp doy $\mathrm{18.5~Ω}$ is connected to a capacitor C and a 1360-Hz source voltage. If the current and voltage are to be in phase, what value must C have?    $ \times10^{-7 }\;F$

  An inductance coil draws 2.5-A dc when )hjonr twy- e(4fy)n)xq 4 7puconnected to a 36-V battery. When connected to a 60-Hz 120-V (rms) source, the current drawn is 3.8 A (rms). Determine the inductance and resistancehow) (nq f)xt n4u4r)7yypje- of the coil.
$V_{dc}$ $\approx$    $\Omega$
L $\approx$   $ \times10^{-2 }\;H$

  A 135-mH inductor with u. hk ,dsauh -k*wtl:1$2.0-\Omega$ resistance is connected in series to a $20-\mu\mathrm{F}$ capacitor and a 60-Hz, 45-V source. Calculate
(a) the rms current, $I_{rms}$ =    A
(b) the phase angle. $\phi$ =    $^{\circ}\,$

  The Q factor of a resonance circuit can be defined as the ratio of the vw n i:up )s1w,tku:c6qoltage across the capacitor (or inductor) to the voltage across the resistor, at resonance. The larger the Q factor, the sharper the resonance curve will be and the sharper the tuning. )s qwuc1::unt6k, piw
(a) Show that the Q factor is given by the equation $Q=(1/R)\sqrt{L/C}.$
(b) At a resonant frequency $f_0=1.0\mathrm{~MHz},$ what must be the values of L and R to produce a Q factor of 550? Assume that $C=0.010\mu\mathrm{F}.$ L $\approx$    $ \times10^{-6 }\;H$(retain one decimal places) Q =    $ \times10^{-2 }\;\Omega$