What would be the advantage, in Faraday’s experiments (Fig. Below), of u.cu )mqvwwv68 sing coi.8 vmq cwu6wv)ls with many turns?

What is the difference between magnetic flux an.3; l chsruwx;cup1t5d magnetic field?

Suppose you are holding a c5 vmo30:shtv8w 0f4k ajyq, 9rd9rdmwircular ring of wire and suddenly thrust a magnet, south pole first, away from you toward the center of the circle. Is a current induced in the wire? Is a current induced when the magnet is held steady within the ring? Is a current induced when you withdraw the magnet? In each case, if your anf4dmy3 wrv9sjv 5ao t8:kw009 rq,hmdswer is yes, specify the direction.

Two loops of wire are mo9cj olo4xht ka9b3cdq9254hlving in the vicinity of a very long straight wire carrying a steady current as shown in (Fig. Below). Find the direction of the induced currenooc54dl3t9k9ax jl b24qh9cht in each loop.

Suppose you are looking along a line through the centers of two circular n0 ws0p-s(fuubut0d go7g,3k(but separate) wire loops, one behind the other. A bat0pgu-u0 ,w3 nsk (gbfdto0su7tery 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 direco (ntbl4 -c9moc oo+tq bqhrl/0e3*+ htion of the induced current in resistor $R_A$ when
(a) coil B is moved toward coil A, ----待选择----increasedecrease 
(b) when coil B is moved away from A, ----待选择----increasedecrease 
(c) when the resistance $R_B$ is increased. ----待选择----increasedecrease 

In situations where a small signal must travel ovej u0fcj+ xme;rgmhf k gu( 7:*wvi:01kr a distance, a “shielded cable” is used in which the signal wire is surrounded +gm0(w*fgmv: k1 uhekx:r7 0 ijc;f ujby 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 insulahgk2s70;a n apted electric wires carrying ac close together or even twisted about eac0a2ap7sg; k nhh other?

Explain why, exactly, the ligha. ( dyrff7yc:ts may dim briefly when a refrigerator motor starts up. When an electric heater is turned on, the lights may stay dimmed as dyy( ff7r:ca. long as the heater is on. Explain the difference.

Use (Fig. Below a) anp0xu rzw- 64kv, ehha,d (Fig. Below b) plus the right-hand rules to show why the counte,x-,4 hzwhe6pu 0kavrr torque in a generator opposes the motion.
a
b

Will an eddy current brake (Fig 61b/egwzl5phlvjte b3 49( jk. Below) work on a copper or aluminum wheel, or must the wheel be ferromag53j w6b klh ( v4eeg/ljt1p9zbnetic? Explain.

It has been proposed that eddy curre/mt 8.) i*ukbrabr,a,jhm7a lnts 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 permanentb.j87m, bhat*la /a)mi r,kru 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 qukup5z ,i6g(4x gjux )xickly through a magnetic field than does a solid bar. Explaix(ui ,zgx46kux )jpg5n.

If an aluminum sheet is held between the poles of a large bar magnet, it re0 sy)rpl gx 2e/f5(fsvx1*tpkquires some force to pull it out of the magnetic field even though the sheet is not ferromagnetic and does not touch the pfsx /f)p*vyrl52pg0setx 1(kole faces. Explain.

A bar magnet falling inside a vertical metal tube reaches a terminal v r1m,fjqh7 rzc5;sk :yelocity even if the tube is evacuated so thatq,r1 czs r 7hf5yjm;:k there is no air resistance. Explain.

A metal bar, pivoted at one end 7 y9wz8d ooy-w(5eoko, oscillates freely in the absence of a magnetic field; but in a magnetic field, its oscillations are quickly damped out. Explain. (This magnetic damp (785-okzdw 9yoooywe ing is used in a number of practical devices.)

An enclosed transformer has four wire leads coming from it. How cou xq);o/tfdh et,t r:8uld you determine the ratio of turns on the two coils without taking the transformer apart? How would you xt/hd8t:),fqrute ;o know which wires paired with which?

The use of higher-voltage lines in homes — say, ypcv6+ c-j84n. g2.ubnr mqgd 600 V or 1200 V — would reduce energy waste. Why are they not uscgqc+m 6gd-nbj8 4p2nvu r y..ed?

A transformer designed for a 120-V ac input will often “burn out” if connected sup8vy7:j1o ywj+t-; yy7f rvto a 120-V dctj 7fy1:uywvy-8 p7r yjv+o ;s source. Explain. [Hint: The resistance of the primary coil is usually very low.]

How would you arrange two flat circular coils so that their mutual inductagk:loj ,57hj-ypt *.4hbaf jence was j :j k,eagl .7-5jty4obh*hpf
(a) greatest,
(b) least (without separating them by a great distance)?

Does the emf of the battery in (Fig. Below) affect the time k4b j5ukjs/m p ok58l9yi2f j7needed for the LR circuit toukk5 m kj5lb98/if4sj72opy j reach
(a) a given fraction of its maximum possible current,
(b) a given value of current? Explain.

  In an LRC circuit, can the rms voltage ac i-3xghe6jg15t. jvj7xsx qfqmap *f+bk . e5+ross
(a) an inductor, ----待选择----yesno 
(b) a capacitor, be greater than the rms voltage of the ac source? Explain. ----待选择----yesno 

Describe briefly how the frequency of the source emf affects the 24ahvmpqsp qyqy: 4 7z(p.v9simpedance 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 make9 h:c(8kesj ud the impedance in an LRC circuit a minimum.

  The magnetic flux through a coil of wire u j: /yyrty:y;containing two loops changes from -50Wb to +38 Wb in 0.42 s. What is the emf induced in the coijy:/yu:; ytry l?    V

  The rectangular loop shown in (Fig. Below) is pushed into (: qjp )tl0 gz(bspu(xthe magnetic field which points inward. In zbj(p)0 : (tul sg(pxqwhat direction is the induced current?  ----待选择----counterclockwiseclockwise 

  The north pole of the magnet in (Fig.ep v rr;v)gk wfmen07(/a7 9qg Below) is being inserted into the coil. In whichg7 g(0e )k ;vv/wr7ap rfn9mqe direction 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,rmnzcb tg jk:/v3 +0*/qdtsb field. The loop is removed from the fieljd kc, brm3vbq *t+tg:nz/ /0sd in 0.15 s. What is the average induced emf?    $ \times10^{-2 }\;V$

  A 12.0-cm-diameter loop of wire is initially orien:3qmbl) nuq+ e1fxx /t73lcw yted perpendicular to a 1.5-T magnen3x7x)ylb+ec 3l q/umqfwt:1 tic field. The loop is rotated so that its plane is parallel to the field direction in 0.20 s. What is the average induced emf in the loop?    $ \times10^{-2 }\;V$

  A 10.2-cm-diameter wire coil is ini.rpl3d8p ul i94 xgg+ytially oriented so that its plane is perpendicular to a magnetic f.9u r+4p 8gxyllidp3g ield of 0.63 T pointing up. During the course of 0.15 s, the field is changed to one of 0.25 T pointing down. What is the average induced emf in the coil?    $ \times10^{ -2}\;V $

  A 15-cm-diameter circular loop of wire is placed in a 0.50-.u2bj ci e v-r2j6cs-kT 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.)6jyoq67l, inn e o)0qeog7o w Below) is slowly increased, what is the direction of the current induced in the small circular loop inside the larger loop? )o) y, 6qe 70iqonwe7noj6glo ----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 of4 ybku jle,x( tb;q.8b the induced current in the circular loop due to the current shown in each pk 8 uet 4jxblqy.b;(,bart of (Fig. Below)?
a  ----待选择----counterclockwiseclockwise0 
b  ----待选择----counterclockwiseclockwise0 
c  ----待选择----counterclockwiseclockwise0 
d  ----待选择----counterclockwiseclockwise0 

  If the solenoid in (Fig. Below) is being pulled away from the loop shown,:k0v4elw2b7 8f qib8lb uy:x .ssvom-)h.jl t in what direction is the induced currellmyb 8eo:xhsq.j4b- iv s2:lu 78k)vwft0 b .nt in the loop?  ----待选择----counterclockwiseclockwise 

  The magnetic field perpendicular to a circul4vvhvmty5: *-, ekt4i+np wpi ar wire loop 12.0 cm in diameter is changed from +0.52T to -0.45 T in 180 ms, where means 5*pk4e+wv4n mp,-htiv iy v :tthe 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 6f;y/8pfb luxo3; my iat a speed of 15.0cm/s If the magneti ;io u3lypx8 mffb6y;/c 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 papery9:lzb xy ;did43bp6o vrlit42zvy-2 lies in a 0.75-T magnetic field pointing into the paper. If the loli b62yizr -lp443v92yddvt: yobz ;xop’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 generates an ew m, t(iv4 4uhizzmi3c n;+0kcmf of 120 mV while moving in a 0i+h4zcw ,(04mitikzvcu m n; 3.90-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 ub-f* ,db hqe4lyw lqq 37gm8;(Fig. Below) is situated inside a region of uniform magnetic field of 0.550 T. -7, q4bbg8qyw df*l3qmhl e;uThe 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 s7 gb,.z gj(ojf9z1t qa 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 qg(j 9stz,fb zog 1j.7short coil during this time?    $ \times10^{-4 }\;V$

  In (Fig. Below), the rod moves withc7qj5 o -xf80rpupx6v a speed of 1.6m/s is 30.0 cm long, and has a resistance ofq 7pu -xx0po vr865fcj $\mathrm{2.5~Ω}$ 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 *9b9ymvtacj 6 h*o9eumm in diameter. A uniform magnetic field, perpendicular to the plane of the co6eb a9tuh*c9 9yojm *vil, changes at a rate of $8.65\times10^{-3}\mathrm{~T/s}.$ Determine
(a) the current in the loop, $|\varepsilon|$ $\approx$    A (retain two decimal places)
(b) the rate at which thermal energy is produced.    $ \times10^{-4 }\;W$

  The magnetic field perpendicular to a single 13.2-cm-di 115o3 ok-ru ddqy,t fzgn82dhameter circular loop of copper wire decreaset,oy 3ho5fk 1nu1z8 gr-d 2qdds uniformly from 0.750 T to zero. If the wire is 2.25 mm in diameter, how much charge moves past a point in the coil during this operation?    C

  A simple generator is useh9 f vcndgth:r.+69 gcd to generate a peak output voltage of 24.0 V. The square armature consistn dvf:cht9.hgr6g+9 cs 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 idling3b.5 btvqv gf5 at 1100 rpm produces 12.4 V. What will the ou tput be at a rotation speed og3fvvt 5q5b. bf 2500 rpm, assuming nothing else changes?    V

Show that the rms output (Section 18–7) of an ac generator in nbm,voe84mg-2x4op s $V_\mathrm{rms}=NAB\omega/\sqrt{2}$, where $\omega=2\pi f.$

  A simple generator has a 320-lokah-4x6fayo- h44jnr op square coil 21.0 cm on a side. How fast must it turn in a 0.650-T field to producnxy f a-6 oa4rj4k-h4he a 120-V peak output? $f$   rev/s

  A 450-loop circular armatuqc/i )e(zdy: lre coil with a diameter of 8.0 cm rotates at 120rev/s in a uniform magneticldc (iy:z /)qe 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 ina- z- oojsc8v2 a magnetic field of 0.030 T. It has 1000 turns and produco8voc2zj s- a-es an rms voltage 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 resistance 7cpt;6y1rzw s/z/ac/m6o,pf1p a- a3kp qyub of $3.25\Omega.$ If it draws 8.20 A when running at full speed and connected to a 120-V line, how large is the back emf?    V

  The back emf in a motor is 72 V when operating at 1800 rpm. What would be the 06 ba:l j4esq4lsh9qn back emfsaq0: nl64 elh4 sb9jq at 2500 rpm if the magnetic field is unchanged?    V

  The back emf in a motor is 95 V when the motor is operating at 1000 rpm. Ho tef.o 5vsa1clmh bu2.c2b4;rw would you change the motor’s magnetic field if you wanted to b2t;roucc.b2.hl 15m ef avs4 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 if the load cagmgtw4zzoil5 io66y+:vsgf74b wp9zh ;b 5z *uses it to run at half speed?4wo755;i zg*6omg ybh9p+6zsz4w lfi tvg :zb    A

  A transformer is designed to change 12l7 g1fcte9 n 8.urq*zl0 V into 10,000 V, and there are 164 turns in the p.zlnr1fc98tul7 * qegrimary coil. How many turns are in the secondary coil? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ $\approx$    turns

  

  A step-up transformer increases 25 V to 120 V. What is the current in 3u(lm85rhg3fnx .yz(4e pmqfthe secondary coil as compared to the p.fphf mqzlx g3 3ynu ((rm548erimary coil?   

  Neon signs require 12 hvt( v4epxq2al1 d(73kzibr.gk7u-v kV for 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 voltage output be if the trh32(z qbx.4vi1-ea7(gtl7v du k k pvransformer were connected backward?
$\frac{N_\mathrm{s}}{N_\mathrm{p}}$ =   
$V_s$ =    V

  A model-train transformer plugs into 120-V ac* vid to(jpu 8mv g+p:t45wca9 and draws 0.35 A while supplying 7.5 A9+p m 8vawvcui4j:tp* g o(5td 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, and the input currentkp.w, i /5ndcx is 22 A. id w/cpx5,. nk
(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 33a* ldi8eu0j9 n0 primary turns and 1340 secondary turns. The input voltage is 120 V and the output current is 15.0 A. What are the output voltage and i*0 ae9l iuj8ndnput current? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ =    V
$\frac{I_\mathrm{s}}{I_\mathrm{p}}$ =    A

  If 30 MW of power at 45 kV (rms) arrives at a town fro f tqh)*rz83(j1wwnfs m 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,b(y-sig i on.r)(zi ln 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 Aazi5bi nl-(hkt r 6)y9 to 10.0 A in 350 ms, what is the magnithyrlka -) (iin96zbt 5ude of the induced emf?    V

  What is the inductance of a coil if the coil produ8 s u7d6tqtil wmoe :-rqc532nces an emf of 2.50 V when the current in it changes from -28-7n 6ow 3qtcs imlet u582drq:.0mA to +31.0mA in 12.0 ms?    H

  What is the inductance L of a 0.60-m-long a2;zw6dqr eydy 0nn4 t1ir-filled coil 2.9 cm in diameter containing 10,ydy2n61 r4z0q w;e tdn000 loops?    H

  How many turns of wire would be required to make a 130-mH inductancfmkx 24.m f2hsid4nbs hz4c y1e4u.2ge out of a 30.0-cm-long air-filli4ssd4 h4.uc f4nykez1g22 .h2mmbfx ed coil with a diameter of 5.2 cm? L$\approx$    turns (Round to the nearest integer)

  An air-filled cylindrical inductor has 2800 turns, and it is 28 lu7r *j :hbcz4 v;swlx6vy)q.5 cm in diameter lwz4y:j busq h86v7clv;x *) rand 28.2 cm long.
(a) What is its inductance?    $ \times10^{-2 }\;H$
(b) How many turns would you need to generate the same inductance if the core were iron-filled instead? Assume the magnetic permeability of iron is about 1200 times that of free space.

  A coil has $2.25-\Omega$ resistance and 440-mH inductance. If the current is 3.00 A and is increasing at a rate of 3.50A/s what is the potential difference across the coil at this moment?    V

A long thin solenoid of length l an+8 yh ;li8po/cmkt d3miz:x8 kd 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 to7wjfi31c kqb 1 make another tightly wound solenoid of twice t 1qjc3 7bkwi1fhe diameter. By what factor does the inductance change?   

  The magnetic field inside an air-filled solenoid 36 cm lonch.w h*zj,8q jp xj(8zg and 2.0 cm in diameter is 0.80 T. Approximately how muc8q8jzj*p hxzj ,( .chwh energy is stored in this field?    J

  At a given instant the current through an induck2qh hxrx+3hs( 7 az(j4j oh3jtor is 50.0 mA and is increasing at the rat hhqh x3k27 z3x j(+4oasjjr(he 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 from the initial value?
U =    $ \times10^{-5}\;J$
$\Delta$t=    s

  Assuming the Earth’s magnetic field average us:qk 6fmkw .g3p7zw9s 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 withi1 (fianrsddxe2d:/i 0n
(a) 10%,    $\tau$
(b) 1.0%,    $\tau$
(c) 0.1% of its maximum value?    $\tau$

  Two tightly wound solenoids have the same length andqekv7yfp; 9)- rpu;oh circular cross-sectional arpku pf q7;rvo e-h9y);ea. But solenoid 1 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 axya b6qt6+( )/fzty el $7.20-\mu F$ 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 a b dwn10w(mx:m7bm ;jhave a reactance of $660 \mathrm{k} \Omega ?$    Hz

  At what frequency wigl 3- lmd962a dxdnq+0eii(z hll a $2.40-\mu F$ capacitor have a reactance of $6.70 \mathrm{k} \Omega ?$    Hz

Plot a graph of the reactance of2zc cy.gxixtv-b: )+b a $1.0-\mu F$ capacitor as a function of frequency from 10 to 1000 Hz.

Plot a graph of the re(nop/b r xuf6 /kgyo.3actance of a 1.0-mH inductor as a function of frequency fr(kby6 fo3urpx/n /go.om 100 to 10,000 Hz.

  Calculate the reactance of, ak ke xez79lm ged1tp 5f972a5fnd rms current in, a 160-mH radio coil connected to a 240-V (rms) 10.0-kHz ac line. Ignore resist xa72km5zef7e fk5etg919 lpdance.
$X_L$ =    $\Omega$
V =    $ \times10^{-2 }\;A$

  An inductance coil operates at 240 V and 60.0 Hz. It draws 12.8 A. Wha2e)* y:gqgtpr7ugxo2 2r-j yet is the coil’s induc u2 egt*y-q g7p2orej):2xrygtance? $X_L$ =    $ \times10^{-2 }\;H$

  (a) What is the reactan tus,7tb;k w(sr2qzrza:p /n5ce of a well-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 of 70 mA passing through the hjg3d )ib69q yygk-4mp uman body for 1.0 s could be lethal. What must be tiq6b)yyg9 -3 gmpjk4d he impedance of the body for this to occur?    $ \times10^{3 }\;\Omega$

  What is the resistanf7uegjci )2l0rr4u)nce 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, anx,tzavnz, .j /f7 vnnlnc0)6pd rms current in an LRC circuit connected to a 10.0-kHz, 725-V (rms) sour.6x),v n nza tjv,fncn7l0p/ zce if $L=22.0\mathrm{~mH},R=8.70\mathrm{~k}\Omega,$ and
Z $\approx$    k$\Omega$
$\phi$ =    $^{\circ}\,$
$I_{rms}$ =    $ \times10^{ -2}\;A$

  A resistor in series with a 420-mH inductor is driven bypm79h; / t pgzb;evgu1 an ac power supply. At what frequency is the impedance douhe79bm1 zt/;v gpgpu ;ble that of the impedance at 60 Hz?    Hz

  (a) What is the rms current in an RL circuit )b x lv5-6i rmfd6rb)ei*w(huwhen a 60.0-Hz 120-V rms ac voltage is applr*6xwe ir(5 id6lvf) bu)bm h-ied, 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 current in an RC9pkcqs3h d4q) 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 connecte g)ixuo z.q- 7gjb/nq4d to a $55.0-\mu H$ coil of resistance $3.00\Omega.$ What is the resonant frequency of this circuit?    $ \times10^{5 }\;Hz$

  The variable capacitor in the tuner of an AM radio has a capacitance 4+ rzk*iged52u s8hyd of 2800 pF when the radio is tuned to a station at 580 keiz 8g4+y5 us2* hddrkHz.
(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 = 1zl.e:x/f/li.b yrquw 0nzq0 3 4.8 mH and $R=4.40\Omega$.
(a) What value must C have to produce resonance at 3600 Hz?    $ \times10^{ -7}\;F$
(b) What will be the maximum current at resonance if the peak external voltage is 150 V?    A

  Suppose you are looking at two c1l *v/ wv 0ll jqpqfraq.q18n+urrent loops in the plane of the page as shown in (Fig. Below). When switch S is t w 1jql18l+.fnqv q0rpl*/qa vhrown in the left-hand coil,
(a) what is the direction of the induced current in the other loop?  ----待选择----counterclockwiseclockwise 
(b) What is the situation after a “long” time?
(c) What is the direction of the induced current in the right-hand loop if that loop is quickly pulled horizontally to the right?  ----待选择----counterclockwiseclockwise 

  A square loop 24.0 cm on a side has a resistancs8x0+*+xy4p-2mtrzb- e 7mzbmmj n wbe 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 desq6sapmqf7,;tl .sbe3d hwg- a 1,5xbnk lamp is rated at 45 W but requires only 12 V. It contains a transformer that converx 3e t,b-f.7h6awspbq1; ndq5gas,lmts 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 at5i74ay8+,oub u:i s) py s6 wckeri9em 24 kV 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 resistanc ya5escpyurwib,i :emk u+ 794o)6is8e 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 transform m :gi8qj1u ey.psqv-:;yjiqi4dpe0( er which has an 80% efficiency are connected to 110-yv : 4ipeq(ej :mi08-iqj . du;yqs1gpV ac. The secondary windings are connected across a $2.4-\Omega$ 75-W lightbulb.
(a) Calculate the current through the primary windings of the transformer. $P_S$ $\approx$   A
(b) Calculate the ratio of the number of primary windings of the transformer to the number of secondary windings of the transformer. $\frac{N_\mathrm{p}}{N_\mathrm{s}}$   

  A pair of power transmission lines each2 +:bqh yhav2kqdy w *-bmm:g: 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 railp2+fcavykdlp f.9.l+ s rest 32 cm apart on a 6.0$^{\circ}\,$ ramp. They are joined at the bottom by a $0.60-\Omega$ resistor, and at the top by a copper bar of mass 0.040 kg (ignore its resistance) is laid across the rails. The whole apparatus is immersed in a vertical 0.55-T field. What is the terminal (steady) velocity of the bar as it slides frictionlessly down the rails? v =    m/s

Show that the power loss in transmissifee/i2 tpmu8, kfa2h)m +eyr5 on lines, $R_L$ is given by $P_{\mathrm{L}}=\left(P_{\mathrm{T}}\right)^{2}R_{\mathrm{L}}/V^{2},$ where $P_T$ is the power transmitted to the user, V is the delivered voltage, and $R_L$ is the resistance of the power lines.

  A coil with 150 turns, a radius of 5.0 cm, and a resistpkk*+qc km;nz aqc0 61ance 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 devozl0ukrw5 nmn*2p -o,(f2d mkice needs to be protected against sudden surges in current. In particular, after the power is turkkmu,w-*p n( r0mnol2 d2fz5oned on the current should rise no more than 7.5 mA in the first $120\mu s$ The device has resistance $\mathrm{150~Ω}$ and is designed to operate at 55 mA. How would you protect this device? L $\approx$    in series(retain two decimal places)

  A 25-turn 12.5-cm-diameter coil is placed between the pole pieces 9du3,x8nkuv l of an electromagnet. When the magnet is turned on, the flux through the ux,v8lu3d9k ncoil 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 o5p),g 0lji lequtput voltage of a simple generator whose square armature windings are 6.60 cm on a sj5le i0g ql)p,ide; 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 attained in laboh96vxg akl la z6k,be+l90e;aratories are ,9aa +lhkgakxe b;ll6 ze096vabout $1.0\times10^4\mathrm{~V/m}$ 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 primarykddi8y) .c p8lpq.cl fw9g xx.c, -1uc of a transformer whose input is 220 V at 60.0 Hz if the current drawn is 5.8 A? Assume no current in the seco-8..p yx.u)k8xc9pwl ci1qf gddlc, cndary.    H

  A 130-mH coil whose resistance z 1 xxkba040pzis $\mathrm{18.5~Ω}$ 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 cona4f5k7 am9rdl4 5 cs m6+gscd-ol1qghnected to a 36-V battery. When connected to a 60-Hz 120-V (rms) source, the curre4g- oh6 gals1dks+cdmf mc4l955rqa7nt 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 w)hrkame 6q xi7dp3uj(jndg 8 0 x5 ck*f1to(4$2.0-\Omega$ resistance is connected in series to a $20-\mu\mathrm{F}$ capacitor and a 60-Hz, 45-V source. Calculate
(a) the rms current, $I_{rms}$ =    A
(b) the phase angle. $\phi$ =    $^{\circ}\,$

  The Q factor of a resonance circuit can be defined as the ratio of the voltage a7 l)hdq .wavr.cross the capacitor (or inductor) to the voltage across the resistor, at resonance. The larger the Q factor, the sharper the resonance curve willvhr l7).waqd. 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$