What would be the advantage, in Faraday’s experiments (Fig. Below)+q* hxxu.)qg hw iz f-xmb:yp.:4 vg.o, of using coils .fp+.x:wh4x xyq u:m -zhgqib v*).og with many turns?

What is the difference between magnetic flux and mz ik t*no;ox )1te;dew bq4+w)agnetic field?

Suppose you are holding a circular ring of wire a9hhf2-) uln-hwb ittv+x ; 2qxg2,gh2 la4dzsnd 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 t22-;2 hbz idq-hx l)w, lhugs9xhftn2ta4 v+ghe 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 wptdmsn+f ( 7ih7 p2hl/ire carrying a steady current as 7idlh pts/fh+7pn2m ( shown in (Fig. Below). Find the direction of the induced current in each loop.

Suppose you are looking along a line through the centers of two circulaoy-6;rg:a-sy z u1rjdr (but separate) wire loops, one behind the other. A battery1 6r-js-rd;oy:ag yu z is suddenly connected to the front loop, establishing a clockwise current.
(a) Will a current be induced in the second loop?
(b) If so, when does this current start?
(c) When does it stop?
(d) In what direction is this current?
(e) Is there a force between the two loops?
(f) If so, in what direction?

  In (Fig. Below), determine the direction of the induced current in resistorhi+rxa)s q:v4r ac/a7w. 5jro $R_A$ when
(a) coil B is moved toward coil A, ----待选择----increasedecrease 
(b) when coil B is moved away from A, ----待选择----increasedecrease 
(c) when the resistance $R_B$ is increased. ----待选择----increasedecrease 

In situations where a small signal must travel over a distance, a “sh efn-x3ce:b38ly onn2ielded cable” ieb2 e3y:fnxn3- o c8nls used in which the signal 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 insulated electribn*n1ay4v 7j ,n 1y5jc5id akic wires carrying ac close together jv 55n4,n1 cnyd 1baikyija7*or even twisted about each other?

Explain why, exactly, the lights may dim briefly when a ref xspa )/:ufs0frigerator motor starts up. When an electric heater is turned on, the lights may stay dimmed as long as the heater is on. Explain the difference.p ) ffx0ss/u:a

Use (Fig. Below a) and (Fig. Below b) plus the right-hand rules to)c*+ ixdf pghusf/*1ui d6hc- show why the counter torque in 6iipddh *-uf /g+)ucfsxh1*c a generator opposes the motion.
a
b

Will an eddy current braic50m;r0 auw-e z1 icom s./nake (Fig. Below) work on a copper or aluminum wheel, or musu / sio- aer0; 1mwimcna.0cz5t the wheel be ferromagnetic? Explain.

It has been proposed that eddy currents be used t 0 :oezojt,6xoo 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 :,jo6tx e0zoo, Pb, brass) from nonmetallic materials?

The pivoted metal bar with slots in (Fig. Below) falls much more quicklp-q2v o.( kynwp9x3pry through a magn93xq.w oppr-2k p(y vnetic field than does a solid bar. Explain.

If an aluminum sheet is held between the poles of a larg0 xzpr 0v id85pv yb:ltn7oq(w-x 37jre bar magnet, it requires some force to pull it out of the magnetic field even though the sheet is not ferromagnetic and does not touch the pole facew7 7-qoxjp:xy tv3r 5( lp nzd00brvi8s. Explain.

A bar magnet falling iyd(jfbj mduinx+-67pr4o 87 knside a vertical metal tube reaches a terminal velocity even if the tube is evacuated so -i4r+dud (x k8p7mjf7 y no6jbthat there is no air resistance. Explain.

A metal bar, pivoted at one mkrnw5xbr69*;df / ss end, oscillates freely in the absence of a magnetic field; but in a magnetic field, its oscillations are quickly damped out. Explain. (This md 9/ rkwxs6r;*nmbs5fagnetic damping is used in a number of practical devices.)

An enclosed transformer has four wire leads q+w :rub8 ne8lblj g)j+7dzsb .1cwr+ coming from it. How could you determine the ratio of turns on the two coils without taki rng:.+j1c b8sew) d7lw bq+zru +bl8jng the transformer apart? How would you know which wires paired with which?

The use of higher-voltage lines in homes — say, 600 V or 1200 V — w r;vv;e7 oubu),hr 3ahje)8qod 4 i*dwould reduce energyvurb4j dod*eu3i7q );ov;8rh )eah, w waste. Why are they not used?

A transformer designed for 90e9i:..ntm0e me z,g;v, cpky vt tzma 120-V ac input will often “burn out” if connected to a 120-V dc source. Explain. [Hint:me:g;.zcpviy9n zt9m, tm k v,e.00et The resistance of the primary coil is usually very low.]

How would you arrange two flat bob2 sa/ eda(e*0v 9ewcircular coils so that their mutual inductance was 9a2ev/bdoa*(w0 eseb
(a) greatest,
(b) least (without separating them by a great distance)?

Does the emf of the battery in (Fig. cyfv j6-h2i+ wh0m:jy* ;azw uBelow) affect the time needed for the LR circuit to reach*a2+yjmf06: ju-wwzy ;vc hhi
(a) a given fraction of its maximum possible current,
(b) a given value of current? Explain.

  In an LRC circuit, can the rms voltag p.5z) en 315kxshhpivev(w b:e 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 sour2g4o aigpjf8ci1a t; m;yz2i +ce 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 db jac7u,gx; b2gpcwiw1ikh) 2nj2 0 /an LRC circuit a minimum.

  The magnetic flux through a coil of wire c0xcbxd psa4hg wr *-h2k;,p 5hontaining two loops changes from -50Wb to x,rhdbs;5p40 a2x -gk p chhw*+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 fiel.yk snaua79hg tnv-oij89l k) 4 mv6v4d which points inward. In what direction is the in6gj i- .o9 )hy vnn7a4kvsm98luvat4 kduced current?  ----待选择----counterclockwiseclockwise 

  The north pole of the magnet in x9q,yu 9h54e:jko jf6yc n2hh(Fig. Below) is being inserted into the coil. In which direction is the induced current flowing through the resistor R?jhhy 52jn xc 9,e:64kq fu9ohy  ----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 wyeq/:)jd.ii5 j6bo j field. The loop is removed from the field .ieb5 )j/d j:wqj6oiyin 0.15 s. What is the average induced emf?    $ \times10^{-2 }\;V$

  A 12.0-cm-diameter loop of wire +f 2l)47 x:bsweo j.letjo ,c5hxjl2ois initially oriented perpendicular to a 1.5-T magnetic field. The loop is rotated so that its plane is parallel to the field direction in 0.20 s. Wfeo2 et5h:sj+w )ll .2o,oj47xcbj lxhat is the average induced emf in the loop?    $ \times10^{-2 }\;V$

  A 10.2-cm-diameter wire ck 4odh4 c+l+ya,0khgyoil is initially oriented so that its plane is perpendicular to a magnetic field of 0.63 T pointing 40yk 4cg+kdhl,a y+ohup. During the course of 0.15 s, the field is changed to one of 0.25 T pointing down. What is the average induced emf in the coil?    $ \times10^{ -2}\;V $

  A 15-cm-diameter circula+k:dum 3 jia /,m07eimf)avdzr loop of wire is placed in a 0.50-T magnetic field.
(a) When the plane of the loop is perpendicular to the field lines, what is the magnetic flux through the loop?    $ \times10^{-3 }\;Wb$
(b) The plane of the loop is rotated until it makes a 35$^{\circ}\,$ angle with the field lines. What is the angle $\theta$ in Eq. 21–1 for this situation? $\theta$ =    $^{\circ}\,$
(c) What is the magnetic flux through the loop at this angle?    $ \times10^{-3 }\;Wb$

  (a) If the resistance of the resistor in (Fig. Below) is slowly increased c 0eo2o-mpn f*hpw8,xylvs70, what is the direction of the currvoxyw7nfc8s,o* p-e l02hm0pent 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*xsxt p gnxqx/ 29h2 ,/mu:oag the current shown in each part of (Fxx/om s a22*/p9g hxnx: ugq,tig. 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 2,e 8 ;vzuoufkloop shown, in what directo; kz,uf u82evion is the induced current in the loop?  ----待选择----counterclockwiseclockwise 

  The magnetic field perpendicular to a circular wire l:5)1gxdzqm/xdiq)q f oop 12.0 cm in diameter is changed from +0.52T to -0.45 T in 180 ms, where m dq):1/id z5xqqf mxg)eans 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 ta.en)zmf16 3e8nf; ,q wopqz9 r+ svacm long and is pulled at a speed of 15.0cm/s If the magnetic fief.en8v;,+ezo 61q9anfzap qwt rms )3ld 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 the8y vn a0qzou+)+*r*kptf f +wb plane of the paper lies in a 0.75-T magnetic field pointing into the paper. If thebuovfpt+ )ka**q w0nf8r++ yz 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,: gcv)h y*pssy+fc 8f. Below)is 13.2 cm long and generates an emf of 120 mV while moving in a 0.90-T magnetic fih)*cf+gf :ps ,vyc 8yseld.
(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 (Fig. Belo 3ko(n2 - ffky 8+ht:9rrmlclqw) is situated inside a region of uniform magn+ h-9mo8f2 kfrn rcllq 3:t(kyetic 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 longwx(3s ls 0h*tp, has a diameter of 2.5 cm. A 10-turn coil is wound tightly around the center of the solenoid. If the current 0 l ht3x(s*swpin the solenoid increases uniformly from 0 to 5.0 A in 0.60 s, what will be the induced emf in the short coil during this time?    $ \times10^{-4 }\;V$

  In (Fig. Below), the rod moves with a speed o cxg n30e;bon,1s-sf+p3ruvof 1.6m/s is 30.0 cm long, and has a resistance o1f33xp,0; rusocn+ obs-ev ngf $\mathrm{2.5~Ω}$ The magnetic field is 0.35 T, and the resistance of the U-shaped conductor is $\mathrm{25.0~Ω}$ at a given instant. Calculate
(a) the induced emf, $\varepsilon$ $\approx$    V(retain two decimal places)
(b) the current in the U-shaped conductor, $I\approx$    $ \times10^{-3 }\;A$ (retain one decimal places)
(c) the external force needed to keep the rod’s velocity constant at that instant. $F\approx$    $ \times10^{- 4}\;N$ (retain one decimal places)

  A 22.0-cm-diameter coil consists of 20 turns of circular copper wire 2.6 mm i7o82u)w u,ln- jqpwmv*hil; gn diameter. A uniform magnetic field, perpendicuhp uo7qlw)8*i lmju;nv2,- gwlar 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 perpendif+ie8c fupyx:52mba+:q ea 9i cular to a single 13.2-cm-diameter circular loop of copper wire decreases uniformly from 0.750 T to zero. If the wire is 2.25 mmcf:ap yf5 a+i+9x ium2:qeeb8 in diameter, how much charge moves past a point in the coil during this operation?    C

  A simple generator isp, qpv3vlf2g71mq,wt t5i 2 cn used to generate a peak output voltage of 24.0 V. The square armature consists of75c3ip2l2f,mvwgpt vnq1 ,tq 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 pro l:-bu7mcihpju9 yc5irb+ w0 3duces 12.4 V. What will the ou tput be at a rotation speed of 7y5u-0 3iu+wchirb 9:clb jmp2500 rpm, assuming nothing else changes?    V

Show that the rms output (Section7mbb y cqm*y8j9 kl02t 18–7) of an ac generator is $V_\mathrm{rms}=NAB\omega/\sqrt{2}$, where $\omega=2\pi f.$

  A simple generator has a k l5.9e)f:btri2ya)tnq8wv apy (ac (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 peak output9wav5nq( (ecala f.r )p)iybtyk:8 2 t? $f$   rev/s

  A 450-loop circular armature coil with a diameter of 8.0 cm rotates at 12 0otqk-e+4:rpk hgda *0rev/s in a uniform magnp:kro* k0q-at d4h+ geetic 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 0.03i zmsv la3,q*+ps(m6c+(s: cim4hmuu0 T. It has 1000 turns and produces an rms voltage of 150 V and an rms current of 70.0 A p scmim ,4:ic u3m(+(h+vmq6*lass uz.
(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 res5jlv9i y getzk n sa+m7h11+im4yc0,qistance 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 /lm:n4bc id2 j;c/n9gzx -iik at 1800 rpm. What would be the back eg92lj :cni c;kz xm bid/4/n-imf at 2500 rpm if the magnetic field is unchanged?    V

  The back emf in a motor is 95 V when tx,ktff n)*u+the motor is operating at 1000 rpm. How would you chfutf), + kt*xnange 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 Example 21–9 (r2tm- xuq+ueif the load causes it to run at half speex-m2u u+(re tqd?    A

  A transformer is designed to change 120 V /nzj0 uz7g(us7:rf z linto 10,000 V, and there are 164 turns in the primary coil. How many(rs7 :z0z 7 ju/zungfl 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 current in the secobs x;m.kfl*f7r 5zmp*ndary coil as compared to the primary coib f*r*7x.slzpf ; mkm5l?   

  Neon signs require 12 kV for pgqr+ r ty;i.,their operation. To operate from a 240-V line, what must be the ratio of secondary to primary turns of the transformer? What would the voltagei tg rrpq.;,+y output be if the transformer were connected backward?
$\frac{N_\mathrm{s}}{N_\mathrm{p}}$ =   
$V_s$ =    V

  A model-train transformer plugsvlpl (jx5sv2l0o./w(jqke - m into 120-V ac and draws 0.35 A while supplying 7.o5.( p2vjq -ljl(0m svwek xl/5 A to the train.
(a) What voltage is present across the tracks?    V
(b) Is the transformer step-up or step-down? this is a  ----待选择----step-downstep-up  transformer

  The output voltage of a 95-W transformer is 12 V, aj)q. y qu8kql)nd the input current is 22 A. u)y .q q)8kjlq
(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 tu xge shubn. 1ew)t8s+.rns and 1340 secondary turns. The input voltage is 120 V and the output current is 15.0 A. What are the output voltage )8weeb1u +xt.ss. hgnand 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 (a0 ruw-vq *w m8f: jcpxb; fek,6o*ph/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 y u*r u-zbysa;7 tb i95liy110ak6uvytown over two $0.100-\Omega$ lines. Estimate how much power is saved if the voltage is stepped up from 120 V to 1200 V and then down again, rather than simply transmitting at 120 V. Assume the transformers are each 99% efficient.    kW

  If the current in a 180-mH coil changes steadily from 25.0 A to 10.0 A in 3u.zq6cbo;m8eqs ssyl* 7r3x.j, 2zsl50 ms, w zs. l6bc q2orsmysesqx.j,l*37z; u8hat is the magnitude of the induced emf?    V

  What is the inductance of a coil if the 4xoqpe nzw,;, coil produces an emf of 2.50 V when the current in it changes from -28.0mA to +31.0mA in 1x;n 4zop ,eqw,2.0 ms?    H

  What is the inductance L ofhp)bxohl+ ycm( 3ae 0q31, woj a 0.60-m-long air-filled coil 2.9 cm in diameter containing 10,000 loopsl3)y qbp w1moexo,03(hh+j a c?    H

  How many turns of wire would be required to make a 130-mH inductance out of a 307am*9; usjd(e xxm1qk.0-cm-long air-filled coil wudq m9 xs e*1jk(7xm;aith a diameter of 5.2 cm? L$\approx$    turns (Round to the nearest integer)

  An air-filled cylindghf-*x9y5 mhq hin(z 6rical inductor has 2800 turns, and it is 2.5 cm in diameter and 28.2 cm 9x5 q fz-nh(6*ihhgy mlong.
(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 conth3 vhkq;t8x3;3zqf,lg 7 yni bshr3-f ains $N_1$ closely packed turns of wire. Wrapped tightly around it is an insulated coil of $N_2$ turns, (Fig. Below). Assume all the flux from coil 1 (the solenoid) passes through coil 2, and calculate the mutual inductance.

  The wire of a tightly wound soleef/v jozp13 1snoid is unwound and used to make another tightly wound sfz1po/ 1 e3sjvolenoid of twice the diameter. By what factor does the inductance change?   

  The magnetic field inside an air-filled solenoid 36 cm long and 2.(qocyldw8*w cf* irq: m (iu73kls +7s0 cm in diameter is 0.80 T. Approximately how much energy is stored in this field(s8y cf+ iws 7 uk7oq:*ilq*wd 3(cmlr?    J

  At a given instant the current t ojbm(:2uyymn6 bz -+xhrough 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 tub-m( 6zbjx2on yy+m:o increase by a factor of 10 from the initial value?
U =    $ \times10^{-5}\;J$
$\Delta$t=    s

  Assuming the Earth’s magnetic field averaggc hf6n- tnqx gp no +k1dl3)/b3p8s(les 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 8b6:,mnofk aoconstants 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 solenoids have the same length and circular cross-sectional as6le *lc/h sc/uv (.zkreg* s;rea. But solenoid 1.lvrhss6;/ /k( lcz*se*ecug uses 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 of ay.l7;moc:t x d6 jhzy2 $7.20-\mu F$ 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 reactanlkmcoe9;/3 z5rf pfb2ce of $660 \mathrm{k} \Omega ?$    Hz

  At what frequency wiu+ls4 v*pg +aqll a $2.40-\mu F$ capacitor have a reactance of $6.70 \mathrm{k} \Omega ?$    Hz

Plot a graph of the reactance oq (ri( 5(cctx.pan4 nkf a $1.0-\mu F$ capacitor as a function of frequency from 10 to 1000 Hz.

Plot a graph of the reactance of ;uj vn*4 ls;wna 1.0-mH inductor as a function of frequency from 100 to 10,000 Hz. svu *;4nwjln;

  Calculate the reactance of, and rms currel.bndat)y rbyp5. 6m0nt in, a 160-mH radio coil connected to a 240-V (rms) 10.0-kHz bp .b.t0a) y5drml6yn ac line. Ignore resistance.
$X_L$ =    $\Omega$
V =    $ \times10^{-2 }\;A$

  An inductance coil operates axa5 4bqpvtb +0t 240 V and 60.0 Hz. It draws 12.8 A. What is the coil’s inductp+b a5bvqx 04tance? $X_L$ =    $ \times10^{-2 }\;H$

  (a) What is the reactance of a wem+ 8q 5 xxlp uhdx0hps//x7z+gll-insulated $0.030-\mu F$ capacitor connected to a 2.0-kV (rms) 720-Hz line?    $\Omega$
(b) What will be the peak value of the current?    A

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

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

  For a 120-V rms 60-Hz voltage, an rms current orlb7cy9n j 0.(pdtep 7f 70 mA passing through the human body for 1.0 s could be lethal. What must be the impedance of the(ppty90d c7 .bnj7 lre body for this to occur?    $ \times10^{3 }\;\Omega$

  What is the resistance of a coil lnz(cvs) 3j y1if its impedance is $\mathrm{235~Ω}$ and its reactance is $\mathrm{135~Ω}$    $\Omega$

  What are the total impedance, p j1f6/gj w*ifehase angle, and rms current in an LRC circuit connected to a 10.0-kHz, 725-V (rms) sourcjjf1 wgi6fe /*e 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 withb(b lide;)q 9fg*dh(eqh ;(kj a 420-mH inductor is driven by an ac power supply. At what frequency is the impedance double that of the impedance h9f (;iblq)qdbj*hg(e ; (ekd at 60 Hz?    Hz

  (a) What is the rms current in an RL circuit w s/lmc6ka0,ylblz 8d1 hen a 60.0-Hz 120-V rms ac voltage lsydk8c,m601ba /zl lis 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 c gdxp 64-jj +du3jbs8uurrent 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 connecteh0u1kc/g)rn/d7cg hj wnn0)i 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 radio has a capq4mt9p0vhb/p zv e2q/ acitance of 2800 pF when the radio is tuned to0v9 z/ehp4 tb/qv mpq2 a station at 580 kHz.
(a) What must be the capacitance for a station at 1600 kHz? $C_{1600\mathrm{~kHz}}$ $\approx$    pF(Round to the nearest integer)
(b) What is the inductance (assumed constant)?    $ \times10^{ -5}\;H$

  An LRC circuit has L = 14.8 mH and e:h54wj +dv gb3el7rq$R=4.40\Omega$.
(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 t*te8u)gln4e sz;0 tflhe page as shown in (Fig. Below). When switch S is thrown in the left-hand n*8zlf)tt ;0egs4 ule 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 z ieq g4l09mvyh-c9q5 d9ue6ohas 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,4mk-9xnkpp e 2frxw9 only 12 V. It contains a transformer that conve r fm 9xxkkpwn92-ep,4rts 120-V household voltage.
(a) Is the transformer step-up or step-down? this is a  ----待选择----step-downstep-up  transformer
(b) What is the current in the secondary coil when the lamp is on?    A
(c) What is the current in the primary coil?    A
(d) What is the resistance of the bulb when on?    $\Omega$

  Power is generated at 24 kV at a generating plant located 1-6l2 ( wxhmedkglz(i )18 km from a town that requires 50 MW of power at 12 kV. Two transmission lines f)lgh z(wked- l6imx (2rom the plant to the town each have a resistance of $0.10\mathrm{~}\Omega/\mathrm{km~}.$ What should the output voltage of the transformer at the generating plant be for an overall transmission efficiency of 98.5%, assuming a perfect transformer? V $\approx$    kV

  The primary windings of a transformer which has an wdhvkd7. j/: rhf,j1 j80% efficiency are connected to 110-V ac. The secondary windings are connectdjfwd7:rj/ jhh.v 1,ked across a $2.4-\Omega$ 75-W lightbulb.
(a) Calculate the current through the primary windings of the transformer. $P_S$ $\approx$   A
(b) Calculate the ratio of the number of primary windings of the transformer to the number of secondary windings of the transformer. $\frac{N_\mathrm{p}}{N_\mathrm{s}}$   

  A pair of power transmission lisjr9 n-0b7hsy nes 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 dub s.5qhqd+m+a;z1a.opjb . 32 cm apart on a 6.0$^{\circ}\,$ ramp. They are joined at the bottom by a $0.60-\Omega$ resistor, and at the top by a copper bar of mass 0.040 kg (ignore its resistance) is laid across the rails. The whole apparatus is immersed in a vertical 0.55-T field. What is the terminal (steady) velocity of the bar as it slides frictionlessly down the rails? v =    m/s

Show that the power loss in transmission tsc ;tvr qr-c18q922hz0zj xrlines, $R_L$ is given by $P_{\mathrm{L}}=\left(P_{\mathrm{T}}\right)^{2}R_{\mathrm{L}}/V^{2},$ where $P_T$ is the power transmitted to the user, V is the delivered voltage, and $R_L$ is the resistance of the power lines.

  A coil with 150 turns, a radius of 5.0 cm, and a resist/-ogw(yyqvd-3wihy llz51s1 ance 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 2-*zibbp+vy cto be protected against sudden surges in current. In particular, after the power is turned on the current should rise no more than 7.5 mAcz b p+2-biy*v 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 4( ozmnjn sc 3 rre.qn 294zvo2r2(irkelectromagnet. When the magnet iz rrz 4 nnc(2(rom2 vr2.jo4 9skqni3es 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 voqz,4u hednh u (eh;4*fcc rr8+ltage of a simple generator whose square armature windings are 6.60 cm on a side; tqeccr u,nez4rd8* ;f+uhh4h (he 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 e7rntce qglo 7d;g;,-ylectric and magnetic fields attained in laboratories are aby q-;,ltg dcn;7g ore7out $1.0\times10^4\mathrm{~V/m}$ and 2.0 T.
(a) Determine the energy density for each field and compare.
$u_E$ $\approx$    $ \times10^{-4 }\;J/m^3$
$u_B$ $\approx$    $ \times10^{6 }\;J/m^3$
$\frac{u_B}{u_E}$ =   $ \times10^{9 }\;$
(b) What magnitude electric field would be needed to produce the same energy density as the 2.0-T magnetic field?    $ \times10^{8 }\;V/m$

  What is the inductance L of the primary of a transformer whose input ise3ag rv ixqn;78i( i;/)stu3ug 2fuvs 220 V at 60.0 Hz if the current drawn is 5.8 A? Assume no current in the sesuvf 2qt)i/ r7; ug uasx8eg(i3inv;3condary.    H

  A 130-mH coil whose resistance isloov)l xwe1 (g ibz/-k/e(bz( $\mathrm{18.5~Ω}$ 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 cog6x,0qwvle4gay ru4*9w1 jqv nnected to a 36-V battery. When connected to a 60-Hz qgya,egurw6 lvq 9wv4j0x1 *4120-V (rms) 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 withf4 w0 kg2;fobic 63kxh $2.0-\Omega$ 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 zd ejay j n2tv86n/6r0can be defined as the ratio of the voltage across the capacitor (or inductor) to the volta0jn6v8 /aey zj2rtd6 nge 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$