What would be the advantage, i)2avcbn9v//7zp l j*jmazdv3z1 z 0nwn Faraday’s experiments (Fig. Below), of using coils wi zpnz z *vm7 /a0ldwav1/b3zjj)2 n9cvth many turns?

What is the difference between magnetic flux and magne c/lh u.hkd ick w40ad/:;v8rg8atuogs:n6b9tic field?

Suppose you are holding a circular/,eb2 +vc ow+9hwlu5(le f wug7vn)tz ring of wire and suddenly thrust a magnet, south pole first, 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 uveeg (w27t+bl c)vo+n ,fzhwl5u/w9 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 vicinio +o mq/ hdy8drtal4*uh6kw9 xv7g;d 773havrty of a very long straight wire carrying a steady current as shown in (Fig. Below). Fia3v xdr7;r6ql +9yh4*g dk 7owmv dhh7 a/tuo8nd the direction of the induced current in each loop.

Suppose you are looking along a line through the centers ofaam11x7in e25 a,bshx two circular (but separate) wire loops, one behind the other. A battery is suddenly connected to the front loop, establishing a clockwise c ea5bhx,2 mas7a1nx1iurrent.
(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 izux72e 9xxqd4 nduced 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 mustd)2z bx 2ak6:cloz +ss travel over a distance, a “shielded cable” is used in which the signal wire is surrounded by xas zzb2:d 2ls6+cko) an insulator and then enclosed by a cylindrical conductor carrying the return current. Why is a “shield” necessary?

What is the advantage of placing the two insulated electric wiresti5nk :hu,p)c carrying ac close together or even twisted about each othe ct:p,inkh5u) r?

Explain why, exactly, the lights may dim briefly when a refrigejh0( vguj-;9sm2d zjxq:b n* zz7,ksu rator motor starts up. When an electric heater isx,b(mjsj9v;02 k z*n hu:jszd-7zug q 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 sho urv,fgt829j wybm4l8v 7fb6ew why the counter torque in a genera6vewf f bmvt47bj lg2 ,y9ru88tor opposes the motion.
a
b

Will an eddy current brake (Fig. Below) work on a zxbo6 n yh04j:f;xsr,copper or aluminum wheel, or must the wheel be ryfs;nx0,:z6b hoj4x ferromagnetic? Explain.

It has been proposed that eddy currents be used to helpk 2obxsx( /jlmp1fm o9:0h+nb sort solid waste for recycling. The waste is first ground no1s0mm b(2+ b/pkhlfox x9j: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 slo.bq6jarho 8 gyb+(5kets in (Fig. Below) falls much more quickly through a magnetic fieldh+.b8qj (r5a6okby ge than does a solid bar. Explain.

If an aluminum sheet is held between the poles of a large bar magnet, it req ov7af.2m mc;quires some force to pull it out of the magnetic field even though the sheet is nfcm vq2a;mo7. ot ferromagnetic and does not touch the pole faces. Explain.

A bar magnet falling 4q z0c+0hiwd:tym l39 ec1yk zinside a vertical metal tube reaches a terminal velocity even if the tube is evacuated y0 9z:4wi0q+hd ck3e cml1tyzso that there is no air resistance. Explain.

A metal bar, pivoted at one end, osciltykecn xc9;4 huqs8 -5rto0ly5x9*vx lates freely in the absence of a magnetic field; but in a magnetic field, its oscillations are quickly damped out. Explain. (This n55t0x4cy;9-khsvxlr cqu9xt8e y* omagnetic damping is used in a number of practical devices.)

An enclosed transformer has four wire leads coming from it. How could you detewys5xx,zbe:l )j+igpc( ,o1/ saii7 prmine the ratio of turns on the two coils without taking the transformer apart? How would you know which wires paired with which17, bl5zp)ox+jgxc s, :ye pi/ swa(ii?

The use of higher-voltage lines ir.7 a)3ppbh hsyc30tr n homes — say, 600 V or 1200 V — would reduce energy waste. Why are they rhp ha .sct)3rb037 pynot used?

A transformer designed for a 120-V ac input will often “burn out” if connec,;i)q s p,dpdtted to a 120-V dc source. Explain. [Hint: The resistance of t qd,p)pt ;d,ishe primary coil is usually very low.]

How would you arrange two flat circular coils so that j 5 o8f/z dptoz99)yohtheir mutual inductance was zh)ptfzoy5d89 o/9 o j
(a) greatest,
(b) least (without separating them by a great distance)?

Does the emf of the battery in (Fig. Below) affect the time nf;6 5dhy 2xnckc2q,opm9 e6hheeded for the LR circuit to rec2 mhh;pxk,669 f5 hey cno2qdach
(a) a given fraction of its maximum possible current,
(b) a given value of current? Explain.

  In an LRC circuit, can the rms volt0qjw7xm pg8j3 :3b uigage 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 the source emf aoxjypj, 7h . zf6mmgp 22b;-gzffects 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 : tf ypku4 hith6fb*75in an LRC circuit a minimum.

  The magnetic flux through a coil oku4-h2*pylh6 vkr 4bj,a ( wbyf wire containing two loops changes from -50Wb to +38 Wb in 0.42 s. What is the emf induced in bvk lyp(y,kr4-ju 24h *wh ba6the coil?    V

  The rectangular loop shown in (Fig. Below) is pushed into the1 ghsc(5 if ki78gga3p(ikik6 magnetic field which points inward. In what direction is the induced currenfi3ki(gac 5 ki (h6 ki1ggp8s7t?  ----待选择----counterclockwiseclockwise 

  The north pole of the magnet in (0m3 ;i qn,asdy:b0 rf;n ha4blFig. Below) is being inserted into the coil. In which direction yn ,qfdr;aa;0 nbh 3 l0m4bsi:is the induced current flowing through the resistor R?  ----待选择----from right to leftfrom left to right 

  A 9.6-cm-diameter circular c8.u+fibr+)lvt7bb 6 7xlv mk loop of wire is in a 1.10-T magnetic field. The loop is removed from thr6ikc x f.b l)8vlvut7 +bb+m7e field in 0.15 s. What is the average induced emf?    $ \times10^{-2 }\;V$

  A 12.0-cm-diameter loop of +kdg. jco30 qcwire is initially oriented perpendicular to a 1.5-T magqo0.c+j3ckd g netic 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 oriented so -hjs rek-xbv7ae-(w1e1l3- byk:dghthat 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 the1eae 7 l yxwdk3(b1hr-ghvs--kb-j: e average induced emf in the coil?    $ \times10^{ -2}\;V $

  A 15-cm-diameter circular loop of wire is pl) 0piih5iqsvdbz s1.8 aced 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. Below) is slowly incaw t8c1ya (((y ix1+jzicqc5 vreased, what is the direqi(c z(1c5 i1 (wy va+8tcajxyction of the current induced in 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 th;b ws3q/uk 1 rhudol/(e currentl 3/bwkdu/ru hq(s;o1 shown in each part of (Fig. 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 9hyo/,k 9rwz,w w 7cwipulled away from the loop shown, in what direction is the induced currey9 hwor /9w,w 7iz,ckwnt in the loop?  ----待选择----counterclockwiseclockwise 

  The magnetic field perpendicular to a circular wire2 eynw s tn1o9v)*3g3y kbp:,9 svnigd 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 ag n ,sgsdpy)ve31knovbn39i : *tw2y9n 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. Beo3 w;rp5ygizk4)c(oh -tt9sp low) is 12.0 cm long and is pulled at a speed of 15.0cm/s If the magnetic field is 0.800 T, calculate tpz;thr4ick(5)pogyo9 3 -sw
(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 a4 .i4jxmwv0yk 0.75-T magnetic field pointing into the paper. If the loop’s diamek.y0 i4jmwx 4vter changes from 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. Below)is 13.2 cm long and gener*uo, u0cy0hcz:bnw 9oates an emf of 120 mV whiluhw bzc*n:o cu 9y0,0oe moving 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 rectangx4t+0jsrapx ) c9//m hk fxoy 0+uxr;oular loop of wire with dimensions shown in (Fig. Below) is situated inside a region of uniform magnetic fimyhk /urj)oasf x0ct+ xr + 4x;x/op90eld 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-turn coo ;dxte 00q5bx;ta o,ril is wound tightly around the center of the solenoid. If the current in the0oo xdba xrt,q5 t0;;e solenoid increases uniformly 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 speed of 1.6m/s is 30.0 cm lolw (t c.v1k4ging, and has a resistance w(t.k4c v igl1of $\mathrm{2.5~Ω}$ 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 ,*boe p6pzi1ncopper wire 2.6 mm in diameter. 61pnp biz *,oeA uniform magnetic field, 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 perpendicular to a single 13.2-cm-diame/8t1d:s+ n.3-fw fe q dfkfomuter circular loop of copper wire decreases uniformly from 0.750 T to zero. If the wire is 2.25 mm in diameter, how much cha3 m f-8sfo/wf:f +dqu. nk1etdrge moves past a point in the coil during this operation?    C

  A simple generator is use fsr1rdj9 3m6qf+gzd . btl63+holy*nd to generate a peak output voltage of 24.0 V. The square armature consists of windings that are 6.0 cm on a sid 3.lfmr d *fj 9h1s+bqtlg3do6y6rn+ze 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 ng:*xji qz*r1r30 rmj at 1100 rpm produces 12.4 V. What will the ou tput be at a rotation speed of 2500 rpm, assumingn* j 0r:i1 gx3rqmrj*z nothing else changes?    V

Show that the rms output (Section 18–7) of an ac generator im2plm*( o p:axs $V_\mathrm{rms}=NAB\omega/\sqrt{2}$, where $\omega=2\pi f.$

  A simple generator has a 320-loop square coil 21.0 cm on a side. How fast mkj a ku4+ln)t nkd,p4;2srt y0ust it turn in a 0.k+us;j0ap kkty )d,44n 2nt rl650-T field to produce a 120-V peak output? $f$   rev/s

  A 450-loop circular armature coil with a diameter of 8.hx 2y3a+i x ; 6ld+vozbw+c,o(4do iss0 cm rotates at 120rev/s in a uniform mag+b s3d yo+wi xx(2h;,szida4lovoc6 +netic 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 8511k 8u/4ls6vbau(5xn yz u,5 kjdyvy p Hz in a magnetic field of 0.030 T. It has 1000 turns and produces an rms voltage of 150 V and an rms cub p1y5knvy k vy14u5 a/uxz(sl,6ud j8rrent 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 armat22,7r ilx*r0*4xbi/. mma bsdxe qsiv7l ag5o ure resistance 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 rpmfwf+hu go +q,0jwe.z3 . What would be the back emf at 2500 rpm if the magnetic field is unchangedhuf eoqwf.w0z3+,g j+?    V

  The back emf in a motor is 95 V whentcq:9v(w2,c s- hvspu+ph. ox the motor is operating at 1000 rpm. How would yoxqp-wpc tcuos. hv:9h+ v 2,(su change the motor’s magnetic 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 s 5:k5rx gaa)x7q1xxfuax91wExample 21–9 if the load causes it to run at half speedfw):x97 xx5 s5raq1x1ukxa a g?    A

  A transformer is des;wggnes60zg+ .e 3zfp igned to change 120 V into 10,000 V, and there are 164 turns in the primary coil. How pw;z0 gf+ensg ze6g3.many turns are in the secondary coil? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ $\approx$    turns

  

  A step-up transformer increases 25 V to 120 V. What is the rm9cjo.fr +i+current in the secondary coil as compared to the i+jf+ .9mcrro primary coil?   

  Neon signs require 12 kV for their operation. To operate from a 240-V line, 49(xb71hxznuhebs3uz5m 5 p kwhat must be the ratio of secondary to primary turns of the transformer? What would the voltage output be if the transformer were conneu(h3xm97bz bxn5u 15hpek4szcted backward?
$\frac{N_\mathrm{s}}{N_\mathrm{p}}$ =   
$V_s$ =    V

  A model-train transformer plugs intoh 2 nd305uuv)67rti.jlspmw d 120-V ac and draws 0.35 A while supplying 7.5 A jr 2huu id5s3.wnvd mpl)t60 7to 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, and the input cuyc287 op 21ocvipljj2rrent is 22 A.cpy1jo 2pvc27j li 8o2
(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 330qax/j2g(gacr 79unt*.jc b r7 primary turns and 1340 secondary turns. The input voltage is 120 V and the output current is 15.0 A. What are the output voltage t gu9r2acq xn77bc.rj/g*j(aand 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 generator vnv )i/(mv)n:aw( x k-w wgpno)ia $\mathrm{4.0-Ω}$ 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 az2r7b-nzoj :c town 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 (0/405dinyqt ;ddy fa,llkxnw 3me .ato 10.0 A in 350 ms, whlqayddda4(/i nkxy0 50.tm3e;fl, n wat is the magnitude of the induced emf?    V

  What is the inductance of a coil if the coil produces an emf of 2.50 V o/mwf8fc7. fxlc;lf mu n0u.6 f+yhz* when the current in f o8c;./mu n6z7wlc0fff.y* lm +xhfuit changes from -28.0mA to +31.0mA in 12.0 ms?    H

  What is the inductance L of a 0.60-m-lyikvmk 0 rp242 wwe7c2ong air-filled coil 2.9 cm in diameter contain4 i2wv yc7wk0e 2mk2rping 10,000 loops?    H

  How many turns of wire would be requirech kmx1p/*. a(eflzji 12 dk:td to make a 130-mH inductance out of a 30.0-cm1zj (edkc /m.kai f1l2*:xthp-long air-filled coil with a diameter of 5.2 cm? L$\approx$    turns (Round to the nearest integer)

  An air-filled cylindrical inductor(z3 od7+cwuu.iv z9e w has 2800 turns, and it is 2.5 cm in diameter and 28.2 c io +dweu(9 vw7c.uz3zm 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-se jm6ai4g6 c /ok.ww,xrctional 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 and used to mac fd-b2fhl0)1zrtx2xwtw( 4r ke another tightly wound solenoid of twice the diam zrwxdlb22 t(tchw410ffx)-r eter. By what factor does the inductance change?   

  The magnetic field i fo--0jxr*mihls.p3 y-qk f k*nside an air-filled solenoid 36 cm long and 2.0 cm in diameter is 0.80 T. Approximately how much energy is stored in this field? k0l ysp fxf3qi -*h*rmk-.-o j   J

  At a given instant the current through an inductor is 50.0 mA czf;, 1 67g vsgbgw1iht wp4z;and is increasing at the rate of 115mA/s. What is the initi4wz6f gvp7h1i;cz 1wgt b ;gs,al 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 magnju)(0p,h ds ngetic field 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 (Fielbj irj /hx7wnos4m8r 09m9(g. Below) reach within
(a) 10%,    $\tau$
(b) 1.0%,    $\tau$
(c) 0.1% of its maximum value?    $\tau$

  Two tightly wound solenoids h) rg6 oo4i2qvtguyk 1l vo9+r*ave the same length and circular cross-sectional area. But solenoid 1 uses *yq1l2k 6ioovug+t 9rrv )go4wire that is half as thick as 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 reactance l v7mpx)7fu8de-jym 09t s,tk)de-pnof 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 reactabx b+a **uorq*nce of $660 \mathrm{k} \Omega ?$    Hz

  At what frequency will a a-jc tz,r4nz-$2.40-\mu F$ capacitor have a reactance of $6.70 \mathrm{k} \Omega ?$    Hz

Plot a graph of the reactance on7pe0u bk55 qnf a $1.0-\mu F$ capacitor as a function of frequency from 10 to 1000 Hz.

Plot a graph of the reactance of 9o:66xkb n t-cfw : wcu6zdos/a 1.0-mH inductor as a function of frequency from 100c6x zonbw: t-cu6fo69s dw k:/ to 10,000 Hz.

  Calculate the reactaq(y d+nm j x zo p8+pi5l8/yt2ds3tvc*nce of, and rms current in, a 160-mH radio coil connected to a 240-V 2 yx/38p(jopd8y* tvzts dn+i5q lcm+(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 draw:c +q (fbxjw9l 4ry6d:awvw+ms 12.8 A. What is the coil’s inwab j4vwxq:(l+c 9:r +dmyf6 wductance? $X_L$ =    $ \times10^{-2 }\;H$

  (a) What is the reactance of a well-insulatedx:+crsqo v4p)5go--iz5x/* d 1fb-nastfrbj $0.030-\mu F$ 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 curro0:1-l; w6 xxevv zuayio8,ofent of 70 mA passing through the human b 8;1vx,6z:0o-uixwyvo eoalf ody for 1.0 s could be lethal. What must be the impedance of the body for this to occur?    $ \times10^{3 }\;\Omega$

  What is the resistance of 6s(y5yr ;2uuufkcc/ l-rqp5v a coil if its impedance is $\mathrm{235~Ω}$ and its reactance is $\mathrm{135~Ω}$    $\Omega$

  What are the total impedance, phase angle, and rms current in an LRC circuql4y4 u4hmr5;bxk 3 yfit connected to a 10.0-kHz, 7my34 4rq;4fb u 5ykxlh25-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 drivehuuxu 0yqla;p *k -64in by an ac power supply. At what frequency is the impedance double t uk0hp*q6y4x-a; lui uhat of the impedance at 60 Hz?    Hz

  (a) What is the rms curr y+t+c8tpsmj 29 4nirlent in an RL circuit when a 60.0-Hz 120-V rms ac voltage is applied, lncijp+y4rsm8t 9t2+ where $R=1.80\mathrm{~k}\Omega,$ 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 c . j2ta81uixymge1:ot l+h o(durrent in an RC 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 connect3 m e6hiu71/h dzt ) g+i7pj5yvm1fg 6r:jkueded 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 h7f2rjpcoseza;u*h)h k mt oo2h0h; 59 as a capacitance of 2800 pF when the radio is tuned to a stati2k)o ;hh;ojur 59 oc*pmzta ehs2fh7 0on 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 u 2xlvdk75p)k 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 current loops in the plane of thex3qf+;pfk jv mb7pb:ct:s/* c page as shown in (Fig. Below). When switch S is thrown in the lk:+p cqbjx/ 3pcf7t s mb:*v;feft-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 p1n uzw*eztp m://xj0a side has 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 onlwp1y )f(hr +kplbn zcb :2.sc,y 12 V. It contains a trar ,l:hp2 1cczsb.(fbpywkn+)nsformer that converts 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 generatin posep31g+d 8yg plant located 118 km from a town that requires 50 MW of power at 12 kV. Two transmission lines from the plant to the town each have a resista3p1 o+ged8y psnce 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+ja3d .*pnjs5)/h ccthiirlb0 jy 6 8i transformer which has an 80% efficiency are connected to 110-V ac. The sjpic/t a83y s nl*506+jhdhi ).bicjrecondary 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 transm*/x -o4rrox4 sl3 em)vgnyi (nission 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 rails rest 32 cm apar(yz-r5 rcpw7 qpjld) 1t 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 zn;6v95 tfu :pw6+ax s afu,rpin 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 5t,w + scrxnnz7 s:u2qa 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 device needs to be protected against suddex ll7)qedjwy.)(z8 3 z 8hhga2h-c zoyn surges in current. In particular, after the power is turnedxhh.y8q28wo( gcll jzz3)hy) aed7z- 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 bgl ;fg 0/ocxd.etween 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 produced by the magnet change if the emf is to be 120 fo d0;gc .xl/gV? $|\varepsilon|$    T/s

  Calculate the peak output voltage of a simple geqtiz8 *gwx 2 j kgud;*0bl86s/le i)vfnerator whose square armature wingq e 2t;d)vx0kilsi *j6l*8fugbz/w8dings are 6.60 cm on a side; the armature 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 mag) 1op,vgio j*ne rb0*xnetic fields attained in laboratories arevop) *1i*eb 0,oxjgrn 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 tr zxlo43/u3iyq2z-v2pm;f szm ansformer whose input is 220 V at 60.0 Hz if the current drawn is 5.8 A? Assume no current in the seconlof;z siyxqzz2 3upmm 3/4-v2dary.    H

  A 130-mH coil whose r ,hfkpli5cq 8(esistance is $\mathrm{18.5~Ω}$ 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 connected tktq -iworz/ .0tv5 7fuo a 36-V battery. When connected to a 60-Hz 120-V (rms) source, the current drawn is0-tz rq fvtk5u.io/7w 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 with lk+vae::kee8r-op nv e t,3r :$2.0-\Omega$ 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 definetjuba.;g jy ,6d as the ratio of the voltage across the capacitor (or inductor) to the voltage across the resistor, at resonance. The larger the Q factor, the sharper the resonana.;tjy6 bujg,ce 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$