What would be the advano9 (xsbq2tg x:tage, in Faraday’s experiments (Fig. Below), of using coil :xgbt2(oxqs9s with many turns?

What is the difference betwee;p2b brb8ks r(n magnetic flux and magnetic field?

Suppose you are holding a circular ring of wire and suddenly thrust a r 6.y2w tc4x-ie*hdljmagnet, south pole first, away from you toward the center of the cy.*6rxt c dlwehj-4 2iircle. Is a current induced in the wire? Is a current induced when the magnet is held steady within the ring? Is a current induced when you withdraw the magnet? In each case, if your answer is yes, specify the direction.

Two loops of wire are moving in the vicinity of a very long straight wire carr9pm3bhwn/z 8( h +ddctying a steady current as shown 9hcdn3z8hmdw/+b (p tin (Fig. Below). Find the direction of the induced current in each loop.

Suppose you are looking along a qohc;.l+ 2d koline through the centers of two circular (but separate) wire loops, one behind the other. A battery is suddenly connected to the front loop, establishi;l2co.qh+ dokng 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 ind n-n8ixmnujacm*cs,n3s9 -8guced 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 sma3ux )phm.slk ;drx+ u(ll signal must travel over a distance, a “shielded cable” is used in which the si slpu+xmhdxk )r3.u;(gnal wire 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 iny(s o lgj+qmu///oo1msulated electric wires carrying ac clq//y/o1+o(j mgluosmose together or even twisted about each other?

Explain why, exactly,ak;vkc-* q40h ibb+qug f1wc+wes6 2v2.qezz the lights may dim briefly when a refrigerator motor starts up. When an electric heater is turi zq.kv + q h*c b1wfces20v4b z+k2-;agque6wned on, the lights may stay dimmed as long as the heater is on. Explain the difference.

Use (Fig. Below a) and (Fig. Bel-olzq8/ 2kb 6 mv/6q70qql ldf;ibqyjow b) plus the right-hand rules to show why the counter torque in a generator opobq dq2ml f6q z/6 /vlb7y0;jikq8lq-poses the motion.
a
b

Will an eddy current brake (Fig. Below) worka,p8yoxq ; 6uhiz; 7ukak/ib: on a copper or aluminum wheel, or must the wheel be ferromagnetic? Explain. o; uxqi7i6;zy:k 8hu aka p,b/

It has been proposed that eddy currents be used to help sort solid waste r avu7b:0p s.l-nbia3for recycling. The waste is first ground into tiny pieces and iron removed with a dc magnet. The waste then is allowed to a:-.7r bnapsvu0 lbi3slide down an incline over permanent magnets. How will this aid in the separation of nonferrous metals (Al, Cu, Pb, brass) from nonmetallic materials?

The pivoted metal bar with slots in (Fig. Below) falls much more quicklv0meh62o )p6h7oxqw -kd n*ity through a magnetic field than does a solid bar. Exht xmp2d 6o7qv0n 6iekwh)o*-plain.

If an aluminum sheet is held between the poles of basfn t8l*56 zcw4+ona large bar magnet, it requires some force to pull it ouoc +nfa8z6w 5 nt4b*slt of the magnetic field even though the sheet is not ferromagnetic and does not touch the pole faces. Explain.

A bar magnet falling u wroyt*-g u(:cvwh:m)f5re: inside a vertical metal tube reaches a terminal velocity even if the tube is evacuated so that there is n ctv-g :o*wmrw 5eh: )fruu(y:o air resistance. Explain.

A metal bar, pivoted at one end, oscillates freely in the abse72m::paz fxuu g; a34ga3zrrg nce of a magnetic field; but in a magnetic field, its oscillations are quip u xg7z a:zrgmr4u:a a3g23f;ckly damped out. Explain. (This magnetic damping is used in a number of practical devices.)

An enclosed transformer has four wire leads coming from it. Hg u gvdldnn.d 6(/9q3gow could you determine the ratio of turns on the two coils without taking the transformer apart? How woq3 v.d/gndl ggn6d(9uuld you know which wires paired with which?

The use of higher-voltage lines in homes — say, 600 V or 1200 V — would reduce.g0k u ep09a3vvr rl54vxw1oa energy waste. Why are they not used?eka94p53owvrv.x 10vr l gau 0

A transformer designed for a 120-V ac input will often “bub;. 6vg mnuv;zg)*,ke..dvc w/ ry jjkrn out” if connected to a 120-V dc source. Explain. [Hint: The resistance of the pr .g;cdk vvu.zv),;/6*ynkwebjj.g m rimary coil is usually very low.]

How would you arrange two flaxvm-sdk8 4l oa/lb9 fhs1m80kt circular coils so that their mutual inductance was k 0sslm-bkf8av1lhd m89x/o 4
(a) greatest,
(b) least (without separating them by a great distance)?

Does the emf of the battery in (Fig. Below) aff/r;rlj h4ok. xect the time needed for the LR circuij/.l rh4okr;x t to reach
(a) a given fraction of its maximum possible current,
(b) a given value of current? Explain.

  In an LRC circuit, can the rms voltag4s0w*lws 09jn d )fbvw2c+txje 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 sourcd zpv/dkz84 rxj vv+rew6d;:2 e 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 f*m +u9 (2 vo ys*2rfpe/eghupa minimum.

  The magnetic flux through a coil of wireayu r nc, +q0mkm-9.je containing two loops changes from -50Wb tk. -9mc0juma ,r +nyeqo +38 Wb in 0.42 s. What is the emf induced in the coil?    V

  The rectangular loop shown in (Fig. Below) is pushed into the magnetic field6 6 k00zp9 c:mrd hc-fchecvx; which points inward. In what direction is the ihmcd 0cx pv6efz ;0ckhr:c69-nduced current?  ----待选择----counterclockwiseclockwise 

  The north pole of the magnet in (Fig. )pmi *z8ndft pbg-q65Below) is being inserted into the coil. In which direction izmq6bf )p nd- p5g8t*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 loop of wire is in a 1.10-T magnetic fi*y.(1.eb t/ jqdy dmmueld. The loop is removed from dqemy .t/1dy*j.b(u mthe field in 0.15 s. What is the average induced emf?    $ \times10^{-2 }\;V$

  A 12.0-cm-diameter loop of wire is initially oriented perpenkrq((in jts9-kc1 4ml dicular to a 1.5-T magnetic field. The loop is rotated so that its plane is parallel to the f49 -cj1(nl mk( qstrikield direction in 0.20 s. What is the average induced emf in the loop?    $ \times10^{-2 }\;V$

  A 10.2-cm-diameter wire coil istc5y, m wq5+uh initially oriented so that its plane is perpendicular to a magnetic field of 0.63 T pointing up. During the course of 0.15 s, the field is changed to one of 0.25 T pointing down. What ,mqt 55+hycu wis the average induced emf in the coil?    $ \times10^{ -2}\;V $

  A 15-cm-diameter circular loop of wibv0at6 trfi(( re 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. Below) is slowly increased,afdpkfa 5c**a9zc 1h. what is the direction of the current induced in thp*d 1a5a.ch cza*k9f fe 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 ingi7 87hee. t g0+kqyjjp2x 5nu the circular loop due to the current shown in each part of (Fig. B.gpqte0h ij7+ 8kj57 ex2ugyn elow)?
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.uuch .6 li4av; Below) is being pulled away from the loop shown, in what direction is the inducedhuic4v u;l6.a current in the loop?  ----待选择----counterclockwiseclockwise 

  The magnetic field perpendicular to a circular wire loop 12.0 cm in diit uj;+b; erg/;nnuncb +3kn2ameter is changed from +0r c;jnbe;t/ n; 3 gib+nkun+2u.52T 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 lon02q +.-9m ucairi onewg and is pulled at a speed of 15.0cm/s If the magnetic fielrm 9- +cw02iaioqeu n.d 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 tsdg dr +269s e*d. d;cnj4hlbfhe paper lies in a 0.75-T magnetic field pointing into the paper. If the loop’s dia r 9;j.sb+lcf*ng dd2dhe64dsmeter 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 gxj2,(im/po(j c;asct q j :h:and generates an emf of 120 mV while mjqacx/,m (2hj tjp(c:: ;s iogoving 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 d y39y77s1l gmp8 ru9 ev24nsnucu.xa dimensions shown in (Fig. Below) is situated inside a region of uniform magnetic field of 0.550 T. The total resi9xya7 yerpu gmn u81. v7 4c3ln2ssdu9stance 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, hasyexo 0arz7v )/ 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 uniformly from 0 to 5.0 A in 0.60 s, what will be the induced emf in the short coil xay7v/0z o)e rduring this time?    $ \times10^{-4 }\;V$

  In (Fig. Below), the rod moves with a speed of 1.6m/s is 30.0 cm long, w qunt7 3x2h7g)8b lkfand has a resistance of h g)kn lf7bu8 23w7xqt$\mathrm{2.5~Ω}$ 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 circudp2 +pnhogu4 5 . v,rpx:iejr5lar copper wire 2.6 mm in diameter. A uniform magnetic fi2+5d5:eojpripg4v n u .rp,xh eld, 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 perpenhewcb)wv c3cdk86 s.04 ( qqojdicular to a single 13.2-cm-diameter circular loop of copper wire decreases uniformly from 0.754v0)ec b3jqq od.wc ws8k c6h(0 T to zero. If the wire is 2.25 mm in diameter, how much charge moves past a point in the coil during this operation?    C

  A simple generator is *aa, 7kywi;q rused to generate a peak output voltage of 24.0 V. The square armature consists of windings that are 6.0 cm on a side and rotates in a field of 0.;yki7qr *, waa420 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 3nz ty xzpks0we67 1u01100 rpm produces 12.4 V. What will the ou tput be s0z73tu e xykznwp601at a rotation speed of 2500 rpm, assuming nothing else changes?    V

Show that the rms output (Section 1 tjoj5s,:: nv,vlt 0zl8–7) 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 cos7ge7qwbnm;c/b 71o ehp4d/.j ub.g gil 21.0 cm on a side. How fast must itc;nmg4s//e do.7g eu qwg7b.phb 1bj7 turn 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 rotates at 1uu 9 e4ddso7i) uz/ oc9it,7qu20rev/s in a uniform maguo 7 u/9c 4qiusid)otdu9z7,e 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 85 Hz in a magnetic field of 0.030 T. It has 100u ,wnp1hqix+: eq sn100 turns and produces an rms voltage 0n1q1+n ie,u xpq:shwof 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 resistance l fs1vqd890-l aadzms)9 x6qq k9joi;so t ,5oof $3.25\Omega.$ 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 operating1xszlt:tw/aw:m gp .; at 1800 rpm. What would be the back emf at 2500 rpm if the magnetic field is unchan:m/ zl1wtp t.g: xaws;ged?    V

  The back emf in a motor is 95 V when the motor is operating at 1000 rpm. How 1w).gjxlrv vjmca ), 0would you change the motor’s magnetic field if you wanted to reduce the back emf to 65 V when the motor was runningjgam01x,.ljvr))wv c at 2500 rpm? reduce the magnetic field to    % of its original value

  What will be the current in the motor of Example 21–9 if the lrnjwi8lgpd2d3jw5 4v w),nv-oad causes it to run dwvnw2 n 8jigr54-)3jl dpwv, at half speed?    A

  A transformer is designed to change 120 V ih9ak 3w3 zldy4nto 10,000 V, and there are 164 turns d9za3y34khlw in the primary coil. How many turns are in the secondary coil? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ $\approx$    turns

  

  A step-up transformer increases 2zk(2di zpz) mf(q5)ed 5 V to 120 V. What is the current in the second)5d efkd((z2 m zpziq)ary coil as compared to the primary coil?   

  Neon signs require 12 kV for their operation. To operate from a 240-V lix ;roq- 6 5azhs)pwfs)lh;sj 1ne, what must be the ratio of secondary to primary turns of the transformer? What would the voltage output be if the transformer werf lp)zs1- w;aq ;h)jors5h6xs e connected backward?
$\frac{N_\mathrm{s}}{N_\mathrm{p}}$ =   
$V_s$ =    V

  A model-train transformer plugs into 120-V ac and draws 0.35 A whstop: -ssoaju +d **3pile supplying 7.5 A to the tauspd pt*+s *:so -o3jrain.
(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 current is g3ah+qzc-mj, 0 k6p6yhnfs0c 22 A. kapnz6-0 3g c ,sm qc+fhh60yj
(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 1340 secondary turns. The input vol,0v8k;+m hqudc fycmi;l b+9.mixz +mtage ic+;. 9 ihu fdy,mivm+;m0x+qm8cl zkbs 120 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) gi ne, 4 wf01*xeyp-oiarrives 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 town over twok suzn 6ln(0*x $0.100-\Omega$ lines. Estimate how much power is saved if the voltage is stepped up from 120 V to 1200 V and then down again, rather than simply transmitting at 120 V. Assume the transformers are each 99% efficient.    kW

  If the current in a 180-mH coil changes steadily from 25.0 A to 10.0 ,0gs*6c, v5xybsn6jen z oq-uA in 350 ms, whasg6n o5xn- u*0byzse,q jc 6,vt is the magnitude of the induced emf?    V

  What is the inductance of a coil if the coil produces an emf of ,l(2k cqvtg; mak, pw02.50 V when the (,0 lkamgkcq v 2wp;,tcurrent in it changes from -28.0mA to +31.0mA in 12.0 ms?    H

  What is the inductance L of a 0.60-m-long air-filled coil 2.9*mwk5u b9d ff( cm in diameter containwdu9f5 fmkb (*ing 10,000 loops?    H

  How many turns of wire would be required to make a 130-mH inductance om /w6(mus**sfho kdt9ut of a 30.0-cm-long air-filled coil with a diameter 9m6 hduw kss omt(*/f*of 5.2 cm? L$\approx$    turns (Round to the nearest integer)

  An air-filled cylindrical inductor has 2800 turney1+jj1ri -0) vcx xmgs, and it is 2.5 cm in diameter and 28.2 cm long.0cx11igyxr- jejv)+ m
(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 l/cc3 r02ub1+wpdim 7j r)cp yand cross-sectional area A contains $N_1$ closely packed turns of wire. Wrapped tightly around it is an insulated coil of $N_2$ turns, (Fig. Below). Assume all the flux from coil 1 (the solenoid) passes through coil 2, and calculate the mutual inductance.

  The wire of a tightly wound solenoid is unwound and used to make another tz*zo hsb;trsvg0xm :e/v r*9)b 7qo+jightly wound solenoid of twice the diameter. b+qs:)jot*s h*zz9 r xe7mvbvr0;/ ogBy what factor does the inductance change?   

  The magnetic field inktpi+6z lsn m 49ip9k.side an air-filled solenoid 36 cm long and 2.0 cm in diameter is 0.80 T. Az psi.l49kk +n9m t6pipproximately how much energy is stored in this field?    J

  At a given instant the current - n+9 mqff4;;dv9 cuxkdn z7r yy0dlg)through an inductor is 50.0 mA and is increasing 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 to increase by a factor of 10 fq9;;nzfr+c 74dnd0yyvf9 mkdxu-)lgrom the initial value?
U =    $ \times10^{-5}\;J$
$\Delta$t=    s

  Assuming the Earth’s magnetic fielo-h.zo- 8r49a,hclv jbxr; 6tuys9ked 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 -sc;b6ui0zg: emj v xpad-mcbbn *3,/does the current in (Fig. Below) reach within
(a) 10%,    $\tau$
(b) 1.0%,    $\tau$
(c) 0.1% of its maximum value?    $\tau$

  Two tightly wound solm49f: i2 fk:f0sqvuq8cbab;h :epbk ( enoids have the same length and circular cross-sectional area. But solenoid 1 usesmfbfkh( :cfp:sv uqqba20:4 be 8 ki;9 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 reactance of1zz: ,hn:j (ia8xfsczliv8yp4 ;kzq8 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 reactan4jc3u .a)1 ov rjcdy7 1(7 gbfhsk2aiwce of $660 \mathrm{k} \Omega ?$    Hz

  At what frequency will *g0ytd9y d, bca $2.40-\mu F$ capacitor have a reactance of $6.70 \mathrm{k} \Omega ?$    Hz

Plot a graph of the reactance of nz7 y18l,wpaso lh mxd-,:5bxa $1.0-\mu F$ capacitor as a function of frequency from 10 to 1000 Hz.

Plot a graph of the reactance f9( 4 onygj4g:-ipkdl of a 1.0-mH inductor as a function of frequency from 109jk4i4gdn (l:pg- y of0 to 10,000 Hz.

  Calculate the reactance of, and rms current in,a,+x)jtc6s jwq)c m::bh ljg , a 160-mH radio coil connected to a 240-V (rms) 10.0-kHzxmb)sw)q :h +tajc6gcl:,, jj 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. tfj;;0ljt+bly;6a c q8 A. What is the coillyjtclj ft;a6 ;0; +qb’s inductance? $X_L$ =    $ \times10^{-2 }\;H$

  (a) What is the reactance of a well-insulatee2mbod/ wzxin) pd6 w)xn;th+w3v20ed $0.030-\mu F$ 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 current of 70 mA passing through the h9 vrim6(j k)f0n 9fvl krd9hs5uman body for 6 isf9lfk 9r(h)d5v kjnr9v0m1.0 s could be lethal. What must be the impedance of the body for this to occur?    $ \times10^{3 }\;\Omega$

  What is the resistance of a c1n1eiqc1b y :yg*yskw/.g8s eoil if its impedance is $\mathrm{235~Ω}$ and its reactance is $\mathrm{135~Ω}$    $\Omega$

  What are the total impedance, phase angle, and rms ccl kvj rou1i;h*/ 3 p5fd.1kpce1v8 bburrent in an LRC circuit connected to a 10.0-kHz, 725-V (rms) sourkurbpv3 bi j5 1d cv; e.ol1h*1cp/kf8ce 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 seriesu:.k/vmg3by s with a 420-mH inductor is driven by an ac power supply. At what frequency is the impedance doub.:/u b3 vksgmyle that of the impedance at 60 Hz?    Hz

  (a) What is the rms current in an RL circuit when a 60.0-Hz 120-V a/5yo s)z5 p mrq3brf.*s0krlrms ac voltage is appliedsyrm5* zolr). /f3k0rp b5aqs, 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 current73 pmxtt;lt wy41sc+w 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 connecteg7gw vt -psi.ftp.7)sd e/i7d d 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 radifx9pbe xf)6tplyv4u 8o((g j+o has a capacitance of 2800 pF when the radio is tuned to a station at 580fl6xjx(8 +9ubov4ey ) tgp f(p 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 ,0*+m9gyj 6,g )bglqvxk kcwt$R=4.40\Omega$.
(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 lookinu4 b f( )hwbjnki,tw47g at two current loops in the plane of the page as shown in (Fig. Below). When switch S is thrown int(kwbwu,hf44 bi )nj 7 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 has a ggd gq7v-zrvf8m):9qn c6x9v 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 wfytmi )* rk)yme 6x4945 W but requires only 12 V. It contains a transformer that converts )xe m6w9rmtk*4y f)yi120-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 kg( omx(/o ;qjaV at a generating 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 resistance oj;m(/ gxqo(aof $0.10\mathrm{~}\Omega/\mathrm{km~}.$ 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 transfom4bdwt yde c3( -ph60yrmer which has an 80% efficiency are connected to 110-V ac. The secondary windings are connected acroytcby4d6-w3( m0dep hss 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 transmission7m) 5qa:acqiupy1e o( 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 apart on u0 +mwl pnfhvv+ shxj1x9q(4/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 li5texvof w:1qg a1e)m /nes, $R_L$ 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,(5iz,kqawayq*nh 9 6 l 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 device needs to be protectrm c1 hn+0zmt pk6;o7ged against sudden surges in current. Ihm m6nrz+17g0pot ;kcn 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 76v.)sfm1hmvdv e 7iqplaced between the pole pieces of an electromagnet. Whe 7.m7h1d 6)ve vsfmqivn 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 V? $|\varepsilon|$    T/s

  Calculate the peak outputtm .n(l.z5-uxlhos ;p voltage of a simple generator whose square armature windings are 6.60 cm on a side; the ams;txh(-. l nulo.p5z rmature 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 laborm 4tzc,p+p9vqi w4:w patories are a:44ictq, w9vmpw pz+ pbout $1.0\times10^4\mathrm{~V/m}$ 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 transforvj+bmn3jld56w8p: xuxo uj 7,mjb( x5mer whose input is 220 V at 60.0 Hz if the current w 7b 8jx,3+jo(5 nv5jmbpxudl:xjmu6 drawn is 5.8 A? Assume no current in the secondary.    H

  A 130-mH coil whose resistance is3s 5zbu iqx+4s $\mathrm{18.5~Ω}$ 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 toshbjv:m88r7sdqx kqm 0e0(z 1gf )iq - a 36-V battery. When connected to a 60-Hz 120-V (rq )zd r vfihmx8q(kj8bg: 7s-0s 10eqmms) source, the current drawn 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 with j+s;; qdi9j .2szrsdh$2.0-\Omega$ 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 resonance4q.hll2bjt q 4l 8zowpo*jrux-r3c*8 circuit can be defined as the ratio of the voltage across the *4.j8r lqql 8jx*3hopb uc-2wl4ot rzcapacitor (or inductor) to the voltage across the resistor, at resonance. The larger the Q factor, the sharper the resonance curve will be and the sharper the tuning.
(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$