What would be the advantage, in Faraday’s experiments (Fig. Below), ofn1 e*l64u bikq using coils with many4q*1ieuk nbl 6 turns?

What is the difference between magnetic flux a trkvm): u2qppz2r4s 6nd magnetic field?

Suppose you are holding a circular ring of y1 ca*4g5ea/tte0 ens bm 4p0fwire and suddenly thrust a magnet, south pole first, away from you toward the center of the circle. t5ye 0/ as*p 1em0cgfanb4te4Is 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 of a very vbivi l7)i-l2 long straight wire carrying a steady current as shown in (Fig. Below). iv2bli7v)l i -Find the direction of the induced current in each loop.

Suppose you are looking along a line through the centers of twob/y,t ips vu7v9,q( 8dys(, pntr,zuz circular (but separate) wire loops, one behind the other. A battery is suddenly,ypz8 v/sd(v by ,t,nutriu pz( ,7qs9 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 the direction of the induce/+:q bzjgdyy q-9)wxld 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 signal must travel over a distaa*dc+rso un9 n5:- eb b*sc3dvd:kk5qnce, a “shielded cable” is used in which the signal wire is surrounded by an insulator and then enclbq *edsvn3s5-un d9a* 5:rbo+ dkc:ckosed by a cylindrical conductor carrying the return current. Why is a “shield” necessary?

What is the advantage of placing the two insulated electric wir gpb -ta:((8uwb6t jlot+f;p3ypxex0 es carrying ac close together or even twisted aboup6(x :epp +3 ogxbtywta; 0j8 l-t(fubt each other?

Explain why, exactly, the lights s*mf:mz. y 9bfy .ezim- 8q8dwmay dim briefly when a refrigerator motor starts up. When an electric heater is turned on, the lights may stay dimmed as long as the heater is on. Explain the diffwq f .- zy98m*fbizd:s 8ym.emerence.

Use (Fig. Below a) and (Fig. Below b) plus the right-hanhu+o8 byv 65m0y/lad q b1cye.60vypnd rules to show why the counter torque in a generator opul0y0.y1nb8/ ov m 6 d6bhc q+eyv5yapposes the motion.
a
b

Will an eddy current brake (Fig. Belowflc;fo6 h 3za5) work on a copper or aluminum wheel, or must the wheel bc5za 6f3lof;h e ferromagnetic? Explain.

It has been proposed that eddy currents be used to help sort s8(c6 lmd3kflqv e5w0l olid waste for recycling. The wastel3l6 f(0lec kvdwq5m8 is first ground into tiny pieces and iron removed with a 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. Bep,mzm k6 5*4g uurnv3xq8a3pw low) falls much more quickly through a magnetic field than does a solid bar. Explain.64p*3zpkqgunaw v 3,rxmu 85m

If an aluminum sheet is held between the poles of a large bara3p iwe d,ombw2+9y5d vheo:4 magnet, it requires some force to pull it out of the magnetic field even though the sheet is not ferromagnetic and does +ei2yoaw,epdohw4 :vdmb593 not touch the pole faces. Explain.

A bar magnet falling inqibb5yzr)2-/ /t )foaisc3wnas/bx ite.9.b side a vertical metal tube reaches a terminal velocity even if the tube is evacuated so that there is no air resist/y.af )obt i/9tsz wa.nr3e bs5bxc -/i)q2biance. Explain.

A metal bar, pivoted at one end, oscillateup*t 0j5:z8y+kpo uucpb,: vd s freely in the absence of a magnetic field; but in a magnetic field, its oscillations are quickly dampov8:d,5z pu*:u+p b ptjcu0y ked out. Explain. (This magnetic damping is used in a number of practical devices.)

An enclosed transformer has four wire leads com9u):h51psai(u d08zkal e akb ing from it. How could you determine the ratio of turns on the two coils without taking the transfor9ah (p:ai50auzkdu ek)bs8 1lmer apart? How would you know which wires paired with which?

The use of higher-voltage lines in homes — say, 600 V or 1q:-h4bwj o *id5 em8bb200 V — would reduce energy waste. Why are theqbb * :wh5bj-i4 omd8ey not used?

A transformer designed for a 120-V ac indjj edy;yea *e a)c).*tp*y5 tput will often “burn out” if connected to a 120-V dc source. Explain. [Hint: The resistance of the primary coil is usualt*tydjpj ;yaa) *.)yc5eed e*ly very low.]

How would you arrange two flat circular coils so that their mutual inductanc)3an .11v *f styuinu .p/dkgc*7jojke was /s1fp*n* 1 vc) 3.kuo idya7g.utjkjn
(a) greatest,
(b) least (without separating them by a great distance)?

Does the emf of the battery in (Fig. Below) affect the time needed t -b ikyqiqz8)qq537( qg sez0for the LR circuit to reach 57)ks8g0 q qtqqeyq z( 3bi-iz
(a) a given fraction of its maximum possible current,
(b) a given value of current? Explain.

  In an LRC circuit, can th) 5:scdyk,z l1raajg3e rms voltage 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 freq7fol 65:n0um1b y7ripa/qrgeuency of the 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 impedance in an LRC circuit a minihowv3v9rcblu t:5ma q24d2n i4:cv-fmum.

  The magnetic flux through a coil of wire containing two loops chv-m cb --6bszeanges from -50Wb to +38 Wb in 0.b b6 zm-c-ves-42 s. What is the emf induced in the coil?    V

  The rectangular loop sp: - k mh3n t)ok/nhw7tpb0p.dhown in (Fig. Below) is pushed into the magnetic field which points inward. In what directiono: .kkwppbhn -t t0m/ 3pdh)n7 is the induced current?  ----待选择----counterclockwiseclockwise 

  The north pole of the magnet in (Fig. Be 8sy- +awg+w,t-2 vyyawx 8d gzzt(dh+low) is being inserted into the coil. In which direction is the induced current flowddwt+y- zsxhw-(y g,y8gat82 w+ vza +ing 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-Thkrq9lgnn5o js. q+(1 magnetic field. The loop is removed from the field in 0.15 s. What is the average indulnjk( .n+1 hsr59g oqqced emf?    $ \times10^{-2 }\;V$

  A 12.0-cm-diameter loop of wir(6das- du-b kpf(x h(rbyz4*re is initially oriented perpendicular to a 1.5-T magnetic field. The loop is rotated so that its plane is parallel to the field direction in 0.20 s. What is the average indkd(bf6(xdyzhars pbr- u 4( *-uced emf in the loop?    $ \times10^{-2 }\;V$

  A 10.2-cm-diameter wire coil is initially oriented so that its plane is perlsb :rzn)rf9k m5t3* gjer(2ypendicular to a magnetic field of 0.63 T pointing up. During the course of (b 2:slr*e)g n53f zyjtrmr9k0.15 s, the field is changed to one of 0.25 T pointing down. What is the average induced emf in the coil?    $ \times10^{ -2}\;V $

  A 15-cm-diameter circ 6tu xm5xcvke65o v hnx:lo9)3ular loop of wire is placed in a 0.50-T magnetic 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 (Fig. Belowdxasto 4 8yz2v64* )c x lyxltw+-eg2w) is slowly increased, what is the direction of the current induced in the small circular loop inside t txl-g6ywlo ys28c xaev*zdxt+4 )4 w2he 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 f+/:.zkn ha i +f2fnfht6l)dd to the current shown in each part of (Fififk fh6 . n:f+dt2z)/dn+hlag. 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 away from the loop shown, i; e 4.* nc: d6agcfcdht 3sa0pfc0kp,cn what direction is the induced kcdf 6h3:4eagp cdp ;0,t*c s0an.cfccurrent in the loop?  ----待选择----counterclockwiseclockwise 

  The magnetic field perpendicular to a circular j ;e1k g4h +md ;)4yfz9itlp 1ml)xxihwire loop 12.0 cm in diameter is changed from +0.52T to -0.45 T in 180 ms, where means the field points away from an obserzk;)xdp+jlm) gf1 ;yit i4xl49h1 m hever 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. Bl yjm,ki(y* 6-eyf;t felow) is 12.0 cm long and is pulled at a speed of 15.0cm/s If f,e -yyf mk jiyl;*t(6the 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 thf)bu 0jvdi*g oa,eg8 s3jl z)7e plane of the paper lies in a 0.75-T magnetic field pointing into the paper. If the loop’s diameter changes 7 o dgevj,lzg)*b si)u08ajf3from 20.0 cm to 6.0 cm in 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. Bo z/tc8h cdd6*elow)is 13.2 cm long and generates an emf of 120 mV while moving in a 0.90-T magnetz d/oc*8 6thcdic 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 wirjvw9o ;fy q.p,e with dimensions shown in (Fig. Below) is situated inside a region of uniform magnetic field of 0.550 T. The total resistance .jw;fqp,vo 9y 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, zfo 3).1k n*dht1ffo;pim 6 hchas a diameter of 2.5 cm. A 10-turn coil is wound tightly around the center of the solenoid. If the current in the solenoid increases u.poc11f)tz6od 3 h*;h ki fnfmniformly from 0 to 5.0 A in 0.60 s, what will be the induced emf in the short coil during this time?    $ \times10^{-4 }\;V$

  In (Fig. Below), the rod moves with a sper;zrxz08f0. adnrq: q ed of 1.6m/s is 30.0 cm long, and has a rend z8:aq. 00fqr rrxz;sistance 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 .un c6ru1vel5fbx (e3 of 20 turns of circular copper wire 2.6 mm in diameter. A uniform magnetic field eu.cnu(vb1f6 3rx le5, perpendicular 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 perpendicud9 ts:ka fv;(o6gt (g da:,adglar to a single 13.2-cm-diameter circular loop of copper 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 o :( fdt dvg;6k,:asoagatdg9(peration?    C

  A simple generator is usb9eosc8 8bjdb9u h *); vghtd:ed to generate a peak output voltage of 24.0 V. The square armature consists of windings that are 6.0 cm ono*e ;g9sv 98j cdhub) hbdb8t: a side and rotates in a field of 0.420 T at a rate of 60.0rev/s How many loops of wire should be wound on the square armature? $\approx$    loops(Round to the nearest integer)

  The generator of a car idling at 1100 rpm produces 12.4 V. What will the ou t51g 6y)b:fd7e7x z -zvuuphe ctr63fcput be at a rotation spe6b3crpeyu1f-vx 5zthuc g:d ) 6zf7e7ed of 2500 rpm, assuming nothing else changes?    V

Show that the rms outpl0: h .5ep/bib d0hnv24dbupgc.v2pgut (Section 18–7) 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 on a side. How fast m0.d.zlp n1hy8l lsbg0ust it tzb 1ll g.d0yp.nlh 0s8urn in a 0.650-T field to produce a 120-V peak output? $f$   rev/s

  A 450-loop circular armature coil with a diameter of 8.0 cm roi61pxj9gjt/q e:b zr77 1s7 v)bgwvwvtates at 120rev/s in a un7j qvjpw6/ zt1ierb:9gwsv)7 v71bgxiform magnetic field of strength 0.55 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. Itmf-z de4e2 r1t has 1000 turns and produces an rms voltage of 150 V and an rms curze4-2m1 tefrdrent 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 resista0 kag(im5.to.ee iwhpc +x6;knce 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 motor is 72 V when operating at 1800 rpm. What1),3 eg7ztlp79d gdsd7x 0 ielnzup*g would be the back emf at 2500 rpm if the magnetic field i,0gp3 9z i7xl*dt l1ded7)gn z gpseu7s unchanged?    V

  The back emf in a motor is 95 V when the motor is opbw jc36* u5pseerating at 1000 rpm. How would you change the motor’s 5 j*upwsc3b6emagnetic field 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 Examplep i4bxk-/afitzm 6e6 : 21–9 if the load causes it to run at half speedme-ifz :4bka p 6/x6it?    A

  A transformer is designed to change 120 Vse0-fos6wk e( into 10,000 V, and there are 164 turns in the primary coil. How many turns are in the secondae6wfe0ss -o (kry coil? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ $\approx$    turns

  

  A step-up transformer increases 25 V to 12x(m5 gf ,su0qq0 V. What is the current in the secondary coil as compared to the primary coil? g0sf5xuq mq (,  

  Neon signs require 12 kV for their operation. To operate from a 2-r)ogf v hu1z/ 1rvo72 woq-cy40-V line, what must be the ratio of secondary to primary turns of the transformer? What woc qy11-rgr v f/-v2h)wou7 oozuld the voltage output be if the transformer were connected backward?
$\frac{N_\mathrm{s}}{N_\mathrm{p}}$ =   
$V_s$ =    V

  A model-train transformer plugs into 120-V ac and drawsljo4ga4rc.dz3 r336e5rwr+x 1c jgqf 0.35 A while supplying 7.5 A to the tjrjz6ag3454r3ld1 3 owxe c c+r. qfrgrain.
(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, and the input currente*tnciz6v++i+ fd r4ou;* rxn is 22 A.ii f*4zrc te+vnrn+; + dxou6*
(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 primary turns and 1347rih-1 laz w/f z7yw53ju ;nun0 secondary turns. The input voltage is 123w u/5y7;7nz -jr1hanzful wi0 V and the output 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 town4/pfzf/w )co( drvo4f b,ef4y from a generator 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 town over c p9xoiakq t. g.gah9 p:xo)1.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 steadilfqd 4uzzn 0zxi il +8n-s*x99vy from 25.0 A to 10.0 A in 350 ms, what is tn 8fld*nsz-z4i u90qi v z+xx9he magnitude of the induced emf?    V

  What is the inductance of a coil if the coil produces an emf of 2wja y/0bpsd84g3xuqk c7 l-t: .50 V when the current in it changes from -28.0mA -:bq0yck/lgxud4awp73tj 8sto +31.0mA in 12.0 ms?    H

  What is the inductance L of a 0.60-m-long air-filled of kl9i9cwc,km r+(k )coil 2.9 cm in diameter contai9m)+9rclk,fk wic(o kning 10,000 loops?    H

  How many turns of wire would be :act- v xjm7o4required to make a 130-mH inductance out of a 30.0-cm-long air-filled co:m 7ja vcx-to4il with a diameter of 5.2 cm? L$\approx$    turns (Round to the nearest integer)

  An air-filled cylindrical i w,ri7 mcvzu,g.oyj) ;nductor has 2800 turns, and it is 2.5 cm in diameter and 28.2 cm 7ygrwzcijo) m .,;,vu 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 length l and cross-sectional area A contjh*x 305zudd5hl6h.0x8 b ymvr5ziig ains $N_1$ 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 unwoun5+xso dze- fs4d and used to make another tightly wound se4x -od5s+fszolenoid of twice the diameter. By what factor does the inductance change?   

  The magnetic field inside an air-filled solenoid(km pv7.kq9jm63c csf 36 cm long and 2.0 cm in diameter is 0.80 T. Approximately how much energy is stored in this f.fqc m7k6 vk(pm9scj3ield?    J

  At a given instant the current through an inductor is 50.03 w3 wqryqfw1-2q 2hbw mA and is increasing at the rate of 115mA/s. What is the initial energy stored in tq2h qqwbr-w 1w33wfy2 he 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 field averagp o9c8igo,r ci 7ojfq; *m(myr hn19+yes 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 (Fig. Below) rea;b -y7;rho )1ikx nuauch within
(a) 10%,    $\tau$
(b) 1.0%,    $\tau$
(c) 0.1% of its maximum value?    $\tau$

  Two tightly wound solenoids have the same length and circular cross-sectional arr lbvd hm+85s2ea. But solenoid 1 uses wire that is half as thick ah2dmlsb+r5 v 8s solenoid 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 reactanceca6xq od40j0w yn3s3 5t8bzsygsi ,so t 97o)b of 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 reactanceqg n/4na0-9v yjqh*gf of $660 \mathrm{k} \Omega ?$    Hz

  At what frequency will bgz( bm8:f(ss a $2.40-\mu F$ capacitor have a reactance of $6.70 \mathrm{k} \Omega ?$    Hz

Plot a graph of the reactance of a 2k3 ud-u4 u).tdf rv2scds+pl$1.0-\mu F$ capacitor as a function of frequency from 10 to 1000 Hz.

Plot a graph of the reactance of a 1.0-mH f5ep;ef) w2pk6bcf asoq484z8ddr 2r inductor as a function of frequency from 100 to 10,000 Hz. ez)8p pdc5 qa4dbs fo;82f r4er2fw6k

  Calculate the reactance of, and rms current i8o*n p rh8fo7veq5ku( n, a 160-mH radio coil connected to a 240-V (rms) 10.0-kHz ac line. Ignore resistruh q* f7(o8vek8po5n ance.
$X_L$ =    $\Omega$
V =    $ \times10^{-2 }\;A$

  An inductance coil operates at 240 V and 60.0 Hz. Itjxrh;7 d1dzs , pv-k. ,t+s3a( ydqoel draws 12.8 A. What is the co,t;3ed(jk7r a l+ .d vh-p1xoqysdsz,il’s inductance? $X_L$ =    $ \times10^{-2 }\;H$

  (a) What is the reactance of a o)2tog 14/dqimwx2dk93yek)cl; eutwell-insulated $0.030-\mu F$ 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 vo;tl g ihz vlz63+aw.5qltage, an rms current of 70 mA passing through the human body for 1.0 s could be lethal. What must be the impedance of t.ag ;vq56 zi+3hzwl lthe body for this to occur?    $ \times10^{3 }\;\Omega$

  What is the resistance of a coil if ityc i.t, wrlg,)y ,ik;is impedance is $\mathrm{235~Ω}$ and its reactance is $\mathrm{135~Ω}$    $\Omega$

  What are the total impedance, phase angle, and rms c *rpf tughy( p*w;,lj:b +rma9urrent in an LRC circuit connect:r ;prath+*wj*b9y,f( plg umed to a 10.0-kHz, 725-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 42tyl4ff(2 e s-h7t2kk i0-mH inductor is driven by an ac power supply. At what frequency is the impedance double that of the im ( 2klyth7ift-24ke fspedance at 60 Hz?    Hz

  (a) What is the rms current in an RL circuit when a 6cjch7 n7,zak: 5owdhg/ *sfl :0.0-Hz 120-V rms ac voltage is applied, where zhdkonc/aw*5f7c:s lhgj 7,: $R=1.80\mathrm{~k}\Omega,$ 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 RC c-cwm5)kxx. hxircuit 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 ;)wl,jebl m sokzm9.:connected 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 radio has a capacitance of 2800 t0m0ggm( lobkpx 42:h +ozs*x)kr2 vmqe10 yqpF when the ra(ktp0 *)2+g o2soq1bx e hxkqzm:m0lmv4rg y0dio 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 = 14.8 mH and iw i4zaa sunj ;(9:erg8o,i9d $R=4.40\Omega$.
(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 current loops in the plane of the page as show0nrznqu qk 6s9;,e5zmt 8k(zkn in (Fig. Below). When switch S is6sqrk,(ktmn0;qn5 z zku z89e thrown in the left-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 hrlk c6 o q97:iot(ndq 2d2d1lbas a resistance 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 requires only 12 V. It contaieang;fds/h 5)8xr mz -8gvc)hns a transformer that converts 120-V househ/n)gr)- hd 8c hv sf85;zgmxaeold 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 g*u (ap bq2io0located 118 km from a town that requires 50 MW of power at 12 kV. Two ubpi(* 0 aog2qtransmission lines from the plant to the town each have a 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 gu fiusbn3c)zf7, s +id17pt0are connected to 11s0s)u,1idczfb7n7u 3i tf +gp0-V ac. The 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 tran, d6ho.8*e5 b rocqeuk;mrzu(smission lines each have a $0.80-\Omega$ 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 ra*v+tp0mhkaj -muh;0+ d5 pxs ails 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 loss in transmission lines,)y :s s7 *ymzounav9c9 $R_L$ 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 co4ijf- +be,et e 3jn(kc scue24,pt 8of 5.0 cm, and a resistance 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 devicepq,zsy6s7 r gkka1z1 3 needs to be protected against sudden surges in currensp1szg3 zk7r y1a,6k qt. In particular, after the power 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 placed betwee2 miigvvm)47qnq .vj .n the pole pieces of an electromagnet. When the magnet is turned on, the flux through the coil changes, inducing an emf. At what rate (in T/s) must the field piiv. 4q.gn qm)2jvv7 mroduced by the magnet change if the emf is to be 120 V? $|\varepsilon|$    T/s

  Calculate the peak output voltage of a simple generator whose squy7ci g knmh7n40+/xk) 4 4/ansxgl kmjare armature windings are 6.60 cm on a side; the armaturhgxk0snk 4 7/i7mmn x+ljg)44ync a k/e contains 155 loops and rotates in a field of 0.200 T at a rate of 120rev/s. $\varepsilon_{peak}$ =    V

  Typical large values for electric and magnetic fields attained in labor(6so,xx q*gh batories are x6g ,sh *qbx(oabout $1.0\times10^4\mathrm{~V/m}$ 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 ofnhc+h*dx j:2 4o nku2v the primary of a transformer whose input is 220 V at 60.0 Hz if the current drawn is 5.8 A? Assume no current in the secondavucnoh 24*kh+d:jnx2ry.    H

  A 130-mH coil whose resistance i;,dghw7yyja .* kni z 60gfq4fs $\mathrm{18.5~Ω}$ 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 connew1/f7 jot5tw/ m*d ppj8ir u(jcted to a 36-V battery. When connected to a 60-Hz 120-V (rms) source, the current drawnow/tjj*w( /8fp1 mt 57dpurij is 3.8 A (rms). Determine the inductance and resistance of the coil.
$V_{dc}$ $\approx$    $\Omega$
L $\approx$   $ \times10^{-2 }\;H$

  A 135-mH inductor witek2l0q h0li dl y2mrfc+o/9pd0 5owh1h $2.0-\Omega$ 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 ohf-f,ossrng) n :o bol;;ok4.f the voltage across the capacitor (or inductor) to the voltage across the resistor, at resonancgb,; nf oon).oofh-s4r s :;lke. The larger the Q factor, the sharper the resonance curve will be and the sharper the tuning.
(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$