What would be the advantage, in Faraday’s expeg. nr4.3 vmhry)teiq)z 7cek;riments (Fig. Below), of using coils with many trg .ee 4 ;qy7znrkitchv.)m)3urns?

What is the difference between magnetic flux and magnetic fier5wx*lz a+9 gxld?

Suppose you are holding a circular ring of wire azszq u;q.h10fhg95 lzg :rtif(l:s a8nd suddenly thrust a magnet, south pole first, away from you toward the cugltiqfz0rhgfq59 8s. l: (ah1 zs ;z:enter 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 movinn8j4 sbmk -j88kfu,us g in the vicinity of a very long straight wire carrying a steady n us4msk8-ujf,jk8 b8 current as shown in (Fig. Below). Find the direction of the induced current in each loop.

Suppose you are looking along a line lgv0ukeb/(7 1/ +2vils kfzg,gdee7mthrough the centers of two circular (but separate) wire loops, one behind the other. A battery is suddenly connec7 ezv/ d(1 ufvsl0k2ige, 7e/lkgbm+gted 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 induced current i e f.6 0b.ykuu)8we p 9kielyl(ra8kvwy+ih44n 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 utu2*qifx2zz hb4loxukq h( td ; *42*over a distance, a “shielded cable” is used in which the signal wir2;44lzuq(x bfk * hui*thd2q*2zux ote is surrounded by 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 wires ww.ua)6n eug ts4;j/ zcarrying ac clouj 4/ng.wzu6etwa)s; se together or even twisted about each other?

Explain why, exactly, the lights may dim briefly when a refrigerator;rqqj;r 1 ;duh motor starts up. When an electric heater is turned on, the lights may stay dimmed as long as the heater u; ;rh;rqdjq1is on. Explain the difference.

Use (Fig. Below a) and (Fig. Below b) plus the righ; ebc4 9ens;ojt-hand rules to show why the counter torque in a gboes4; jn9;ceenerator opposes the motion.
a
b

Will an eddy current brake (Fig. Below) work on a copper or alumin;bg7,qs5jl a zum wheel, or must the wheel beg,bq;75 sljza ferromagnetic? Explain.

It has been proposed that edrd2zw zm.;0xz dy currents be used to help sort solid waste for recycling. The waste 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;0wz .2zmzd rx materials?

The pivoted metal bar with slots in (Fig. Below) falls much more quickly t(i0ln0w. jb345guce ( kaqe jchrough a mkl5 .w3 u0cc nee0 qjab4((jigagnetic field than does a solid bar. Explain.

If an aluminum sheet is held between the poles of a large bar magnet, it v -yx9mx1gz 6jfd1+i xrequires some force to pull it out of the magnetic field even though the sheet is not ferromagnetic and does not touch my+zdi- g6x jvx91 f1xthe pole faces. Explain.

A bar magnet falling inside a vertical metal tube reaches a ted7kye;tiq1 9 vrminal velocity even if the vk 1qdte yi97;tube is evacuated so that there is no air resistance. Explain.

A metal bar, pivoted at one end, oscillates freely in t3.5ldus;k ck . hciau2he absence of a magnetic field; but in a magnetic field, its oscillations are quickly damped out. Explain. (This m 2kda3li.5cu ku.shc;agnetic damping is used in a number of practical devices.)

An enclosed transformer has four wire leadsc rn0ge,)ri69 p*roj x coming from it. How could you determine the ratio of turns on the two coils without taking the transformer apart? How would you know which0 9cj*6prg i,rx)o nre wires paired with which?

The use of higher-voltage lines in homes — say, 60kd;k93fdr . fhbz07m r0 V or 1200 V — would reduce energy wast 7r9 rhdb3mfz;k0kf.d e. Why are they not used?

A transformer designed for a 120-V ac input wil/in9 / a j0 xw1d:-ysfwb(fvmkl often “burn out” if connected to a 120-V dc source. Explain. [Hint: The resistancevsxb :j0(nifw /1aywmk-f d 9/ of the primary coil is usually very low.]

How would you arrange two flat ciu c.5hw ox b 01)wwo1l(pad1oa 2nsbb;rcular coils so that their mutual inductance was w.as;n5oa b hodbwo11 b0(c1 l)2xpwu
(a) greatest,
(b) least (without separating them by a great distance)?

Does the emf of the 46a3 erodsj/q +t 9ys1ycx 1eubattery in (Fig. Below) affect the time needed for the LR circuiy3rdx49 /c 1s6y ejae1+usqtot to reach
(a) a given fraction of its maximum possible current,
(b) a given value of current? Explain.

  In an LRC circuit, can the rmsx3iys ;* yrif*suuz8f5+g-dv 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 frequency of th0 t9zglvy nx,h35e9lae 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 impedan r9ar+pv;v5u pce in an LRC circuit a minimum.

  The magnetic flux through a coil of wi.ozi1 qm/b4h*37p 0rve xps rere containing two loops changes from -50Wb to +38 Wb in 0.42 s. What i7eq3hbp* /. 1vri4 xmzpe0so rs the emf induced in the coil?    V

  The rectangular loop shown in (Fig. Below) is pushed into the magnetic field whizsl9v;8y 7rrm8;zen/ ocb, g jch o9lnry7em8z;cr /8gj; vzs,bpoints inward. In what direction is the induced current?  ----待选择----counterclockwiseclockwise 

  The north pole of the magnet in (Fig. Below) is being inserted inl 8,1xo1v p+cvpq5nr sto the coil. In which direction is thepn1s pcxvo,lrv 8 q+15 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 wir7 )wh,e) q/xed odvy*bbq:jw*e is in a 1.10-T magnetic field. The loop is removed from the field in 0.15 s. What is /ex)qe*7,o bw bw d)q *dyjh:vthe average induced emf?    $ \times10^{-2 }\;V$

  A 12.0-cm-diameter loop of wire is in reimw8(gw i,7itially 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 induc8w wg iim(7re,ed emf in the loop?    $ \times10^{-2 }\;V$

  A 10.2-cm-diameter wire coil is initially oriented so th- ht4u2 ut he8e5vxyv4at its plane is perpendicular to a magnetic field of 0.63 T pointing up. During the course of 0.15 s, te2yt uvhu v44eh 5x8-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 circular loop of wire is placed in a 0.50-T magnetic 2co/kr ,u q6 u)mvg:k7wnerr6 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 resist j5zzid.b:sa4 v/w3uuor in (Fig. Below) is slowly increased, what is the direction of the current induceau3 dj.5uw:v/sz4zb id 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 tl l/uvgj tvy8fn(y1;,l ;p.p zo the current shown in each part of (Fig.,.t; luj lzngyv/lpy v;fp 81( 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 shge,hhdx.l+4 3a n xbu em-x0j5own, in what direction is the induced current ixhejun, 5 bm4gd-+h.x 0ael3x n the loop?  ----待选择----counterclockwiseclockwise 

  The magnetic field perp/0wl/ vjchv;mptsg9j(1jbpc .dm. u 9endicular to a circular wire loop 12.0 cm in diameter is changed from +0.m t0pl.p( /cwj cg9uhj s9;jb/vvm1.d52T to -0.45 T in 180 ms, where means the field 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 pulled at a speed of 1mv(ok-kgj;o6qd x(73 xsfp z+5.0cm/s If t3 xgpj-so7k fdko;+ q6(zvm(xhe 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 pa4q8.x xcu,pznbo,a v9per lies in a 0.75-T magnetic field pointing into the papouvcn ,.x,xpz9q8ab 4er. If the loop’s diameter 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 s.*rpxvv1j 65+dhgfe ates an emf of 120 mV while movvhp+j 6x*gsefv .5 rd1ing 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 with dimensions shown in (Fryb6abf. .e5uig. Below) is situated inside a region of unif.aef bbr65y. uorm 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-turn coil i:6ll0 rgbm*zt s wound tightly around the center of the solenoid. If the current in the sollgrb 0m*:6 ltzenoid 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 wk2tw, 23yaiywcaa05a t+-oq /nsoeb-ith a speed of 1.6m/s is 30.0 cm long, and has a re2aa/-0y ws batk nq3,tyiac o+-o5ew2sistance 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 tu8t,xavl 9uu. ha k5za;m(tx ,xrns of circular copper wire 2.6 mm in diameter. A uniform magnetic field, perpendicular to the plane of the coil, changes at a rate ofkth8 u. m,vx5;lzaau xx9 ta,( $8.65\times10^{-3}\mathrm{~T/s}.$ 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 zukvuqf7y6 / h8.5rwf-diameter circular loop of copper wire decreases uniformly from 0.750 T to zero. If therfu.6fh/u5k 8 zq7wyv 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 volk zd);ddg,t7u1pz kt*tage of 24.0 V. The square armature consistsdzk1 d)gtk, utpzd7*; 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 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. f(u,t j48-y s(tqr o+4 utftzpWhat will the ou tput be at a rotation fp4fu, z tt(- r4ujtotsq+y(8speed of 2500 rpm, assuming nothing else changes?    V

Show that the rms output (Section 18–7) of an ac generator is lzbz/d*9tl q5 $V_\mathrm{rms}=NAB\omega/\sqrt{2}$, where $\omega=2\pi f.$

  A simple generator h d*7 uv fdg10dr* ubo5.6qmvhjas a 320-loop square coil 21.0 cm on a side. How fast must it turn in a 0.650-T field to produce a 120-V pu.51 gormjhuf * *b 6d0vqdv7deak output? $f$   rev/s

  A 450-loop circular armatureyflr 31 dx2geqz4zy nj(*x: .f coil with a diameter of 8.0 cm rotates at 120rev/s in a uniform magnetic field of strength 0.:xj*dx flz 2g.3re1(yqf nz y455 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. Itc o s5*)qxqb)y has 1000 turns and produces an rms voltage o)xyc 5s*qbq )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 rekw 16-ae :iqcmsistance 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 whzx nrsaxgoet.u812 7 +:x 7brzen operating at 1800 rpm. What would be the back emf at 2500 rpm if the magnetic fxsx bua ze+t1nr78z7.g: r2 xoield is unchanged?    V

  The back emf in a motor is 95 V when the motor is operating at 1000 rpm. How wy*jdmyfcl )3mlm54j/ ould you 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 magne lyd *)j4ylmm3 mc5f/jtic field to    % of its original value

  What will be the current in the motob(kle/m9)v lb uctq-c97(hw a 4a)m yzr of Example 21–9 if the load causes it to run at hac 9u alb -)( b4)wmkcq/zla y7mh9v(telf speed?    A

  A transformer is designed to change 120 V into 10,000 V, a( i y t/(jm+ynt dw9p.nw/:bxd3zzn0) b /pcvmnd there are 164 turns in the primary coil. How many turns are in the st v w:czxn(z .3dpdm/inybt9pn0)b yj+m/w( /econdary coil? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ $\approx$    turns

  

  A step-up transformer incrjyl342 4s xkgm*w vwzx0bfh1*eases 25 V to 120 V. What is the current in the secondary coil as compared to thewz x kgjb1hf*w3m4sxv y* 0l42 primary coil?   

  Neon signs require 12 kV for their operation. To operate :z5v ,ucbs 5sg ujj*1zfrom a 240-V line, what must be the ratio of secondary to primary tub gu1u vss,*zj5j z5c:rns of the transformer? What would the voltage output be if the transformer were connected backward?
$\frac{N_\mathrm{s}}{N_\mathrm{p}}$ =   
$V_s$ =    V

  A model-train transformer *q (ov agdakaui,)k-1y.:k5 r wnzqu /plugs into 120-V ac and draws 0.35 A while supplying 7.5 A tod/ *wo-k,a. )k n(y5u ia agqqu:vrk1z 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/ ovq6l hyw(9c V, and the input current is 22 A.v9 6(hywo/q cl
(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 dzqbt.d:pp ni 8i(x d4,3p4g mprimary turns and 1340 secondary turns. The input voltage is 120 V and the output current is 15.0 A. What are the output ppgnqb8zi : (4d3pi 4d xm,td.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 4:(uvaa7uow /h9mc d0c k4lw4. vumv+x5 kV (rms) arrives at a town 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 tow gq0in 81bbbgas*vv /,n 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 chanm;ejecp0hwzr7oc) 0 izh 66l7ges steadily from 25.0 A to 10.0 A in 350 ms, what is the mae 6wz oh) i0hmjcl6cpe7 7rz0;gnitude of the induced emf?    V

  What is the inductan4*y/ k rlt4gw61mrygu ce of a coil if the coil produces an emf of 2.50 V when the current in it changes from -28.0mA to +k4rylm6yt 4/ 1urw *gg31.0mA in 12.0 ms?    H

  What is the inductance L of a 0.60-m-long air-filled coilnekz1sx z:x /d 6k* pr 9ant/*rvd76rf 2.9 cm in diameter containing 10,000 tkr*vnz* ran/k1dsrx p96f ezx d7/6:loops?    H

  How many turns of wire would be requifq *;ss3f cv3dred to make a 130-mH inductance out of a 30.0-cm-long air-filled coil with a diameter of 3s* dvf;cs3fq5.2 cm? L$\approx$    turns (Round to the nearest integer)

  An air-filled cylindrical inductor has 2800 tux3+u5xlv b7g)s yvmqi kf/anf:t9 ,8drns, and it is 2.5 cm in diameter and 28.2 cm lqb7ya8fsk,i :9vl /xg5du+xtv3nm f)ong.
(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 cogp t bw +*60ql8yc.wnkntains $N_1$ 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+6q-2wbdlnjo : haa8d3:fk:6 qr cuwl solenoid is unwound and used to make another tightly wound solenoid of twice the diameter. By what factor does the inductana+f8-wwq 2jqrkacl6 d b:dl u3n :h6:oce change?   

  The magnetic field inside an air-filled solenoid 36 cm vpc/hslk3 mp.fg,q2.long and 2.0 cm in diameter is 0.80 , fvl.ps3 mhpgk .c/q2T. Approximately how much energy is stored in this field?    J

  At a given instant the current through an inductor is 50.0 mA and is i7 cpc3 v1dypa7u;+iicncreasing at the rate of 115mA/s. What 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 i3u7vp ap17;d c+cycito increase by a factor of 10 from the initial value?
U =    $ \times10^{-5}\;J$
$\Delta$t=    s

  Assuming the Earth’s magnetic field ewnyh f(f :l3n6(0v(ct* labqaverages 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) reach wig+yvjhig0 ;q, .ne m+g kcqi+9hmbl pbz*5s1,thin
(a) 10%,    $\tau$
(b) 1.0%,    $\tau$
(c) 0.1% of its maximum value?    $\tau$

  Two tightly wound solenoids have w0 (b fc-o3vxprim(on;)uag, 0 rpj/ athe same length and circular cross-sectional area. But solenoid 1 uses (,an cuo ifvxr;j3rm-/0(p0g baw p o)wire 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 reactancmq ovf .u2g1x;e 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 ha/aau tzy7:a9g2iy 20 ptzb pjnx:u v;3ve a reactance of $660 \mathrm{k} \Omega ?$    Hz

  At what frequency will a /,4u-daghn xi- sl (wf(o rh- ddt,nx-$2.40-\mu F$ capacitor have a reactance of $6.70 \mathrm{k} \Omega ?$    Hz

Plot a graph of the re4t kns3q)p +md t-t*hkactance of a $1.0-\mu F$ capacitor as a function of frequency from 10 to 1000 Hz.

Plot a graph of the reactance of a 1.0-mH inductor as a func s0 faou 0xqd1afga;(+tion of frequency from 100 to d01xa+;fg aa sou0q f(10,000 Hz.

  Calculate the reactance of, and rms currxv:824xsd ie3 nfx e32 tkj:iient in, a 160-mH radio coil connected to a 240-V (rms) 10.0-kHi2:8xet : d4ix3fe snj2 ik3vxz 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 i2w t tob8n.jmd2u 2c;ns the coil’2t;.ncbj mon 282tuwds inductance? $X_L$ =    $ \times10^{-2 }\;H$

  (a) What is the reactance of a well-insc* mkk:psoeyuuv0x7h /o6q m4zt8*5 n6+l f aeulated $0.030-\mu F$ 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 vgxvq 94*df*qna/y ku( sg 5ud8oltage, an rms current of 70 mA passing through the human body for 1.0 s could be lethal. What must be*s8qa4d /dv*n y5ufg9q (kgux the impedance of the body for this to occur?    $ \times10^{3 }\;\Omega$

  What is the resistance:.sqb t x2ye1f of 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 ra* ltm7o,pt 1lgyop 7.ms current in an LRC circuit connected to a 10.0-kHz.a t1op7*olp7tg m,ly, 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 cdlf l7s6/lx7dnw/h 0420-mH inductor is driven by an ac power supply. At what frequency is the impedance /lsfdlw/0c7x76 n ldh double that of the impedance at 60 Hz?    Hz

  (a) What is the rms cu**8y /-udpt-l3+bn ipgm 33l ukrnqtprw-t w3rrent in an RL circuit when a 60.0-Hz 120-V rms ac voltagetnurnq3k-p+ /i*w3-glpy-m3 tw dtr3 u p 8l*b is applied, 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 curren q ,i 6vidz:737pbowvjcaz -6wt 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 (kre, vk. 6:y0.kecev 1zbmecconnected 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 tune6 pzc uenrh67-; lmc1fr of an AM radio has a capacitance of 2800 pF when the radio is tuned to a station a1-f hu;przn l6 7me6cct 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 a:dt, h3w v5z1aj h0ysbnd $R=4.40\Omega$.
(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 parvis m/v; /c0lane of the page as shown in (Fig. Below). When switch S 0vvc/i ;s/arm is 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 axu*ul9 6cpbmz,o3xj ed/oh:3 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 only 12 V. It contaiwyx ,8 f(qyi6dns a transformer that converts 120-V household(y,6wxi8yfq d 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 5v1c s4jx40baay 1jl4na( zrmthat requires 50 MW of power at 12 kV. Two transmission lines from the plant to axvy5a sn1b jm410c(zlr4a4 jthe 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 whetr8 e 6zd2jht4(pvo .ich has an 80% efficiency are connected to 110-V ac. The secondary windings are connected across atoj8p 4rhevtdz( 6 e.2 $2.4-\Omega$ 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 transmis-r:+3jhok afz2k(mugl 9lw b9 sion 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 a ;ud p(r:3u v.m.t-ixgr tmkf9part 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 j y wu*wq;e11rin 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, a, +xwa2fsbm7g nd 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 device needs d 9 ab4j5qjjkw, (x4 zoqpi.c*to be protected against sudden surges in current. In particular, after the power is turned on the current should rise no modjp* jx w9i c,oq5(jbzk.qa44 re 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 between the pole pieces of an epxy *s cf,ktgx )gr:;vt(c /p2lectromagnet. When the magftkp x,t x:yps )g;2*(ccr/vgnet 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 V? $|\varepsilon|$    T/s

  Calculate the peak output voltage of a simple generator whose square armatu)cl1g8-00c kvqrjs2wr 9ipgk k,8e kpre windingp q0k8cki8rkrgv 2-lw ,kegcjs0 )19 ps 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 magnetic fields attaig:m + a+wl zjuf+p44yzned in laboratories are abal4f +p zg++w4yz:mu jout $1.0\times10^4\mathrm{~V/m}$ 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 tjc omov-8x w/le m v.kdnrcyvt73 m-6:-2hk2nransformer whose input is 220 V at el omk2vc-n6j --m hvor/xw27 ym.3: nkd8tcv60.0 Hz if the current drawn is 5.8 A? Assume no current in the secondary.    H

  A 130-mH coil whose resistance ise) chai3 pt2 gi. r esvsm0s1*m-u0wm9 $\mathrm{18.5~Ω}$ 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 to a 36-V battery. When connecqg0l0 +6aamic 7a4vd yted to a 60-Hz 120-V (rms) source, the current drawn is 3.8 A (rms). Determine the inductance aaygq 4ai076l0+mdac vnd resistance of the coil.
$V_{dc}$ $\approx$    $\Omega$
L $\approx$   $ \times10^{-2 }\;H$

  A 135-mH inductor witg4zku5aqk5ez qf39u.d xv/ ; ph $2.0-\Omega$ 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 o8, *zsf5hs7m bnw s2 :kn-+ubr2v pkasfeh-.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 resonance curve will be and the sharper the tumzsfbos, :a2 b vhkss-.2 unre7 h*n-w5 f+kp8ning.
(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$