What would be the advantage, in Faraday’s experiments (Fig. Bejzaurbv euhi79f28k3k/ +ibrv o+1v , low), of using coils with many turns? fah e uir89/iu2,+ vv1 vbrkkb+oz37j

What is the difference between magnetic flux and magnetir0(.sh p:mq 4arvbn4ec field?

Suppose you are holding a circular ring of wire and suddenly tbhnhzce k aeu)+kx*4ilo 0-88hrust 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 answer is yes, specify the dirchik ko8b)e4e*xl-ha 0 +8 uznection.

Two loops of wire are moving in the vicinity of a very long sbi;.jp bkllq(wkx: : 9traight wire carrying a steady current as shown in (Fig. Below). Find the direction of the induced currei ;:q(:lblkx9wjbpk .nt in each loop.

Suppose you are looking along a m)pp(tv. hx *,olf9wx line through the centers of two circular (but separate) wire loops, one behind the other. A bv*(l ) hx9pox .pftm,wattery 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 directb :bgr0p5 blt4ion 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 smallvgl4*t ky7w2v signal must travel over a distance, a “shielded cable” is used in which the signal wire is surrounded by y ktv*w4 v2lg7an 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 insulatc )e3m2fwmj v*ed electric wires carrying ac close together or even twisted about eawmvm 2 *3ec)fjch other?

Explain why, exactly, the lights may 3m o*wqcw2u72 vrt6-c hqm1 ytdim briefly when a refrigerator motor starts up. When an electric heater is turned on, the lights may stay dimmed as long as the heater *1qmcu2w yt- h omqt 26r3w7vcis on. Explain the difference.

Use (Fig. Below a) and (Fig. Below b) plus the r--ro7r7na+z0kh:pi czuy y8u dyb z- 9ight-hand rules to show why the counter torque7zcur-oy9 z:hd0ui knb8+z-7apyyr- in a generator opposes the motion.
a
b

Will an eddy current brake (Fig. Below) work on a copper v:f)r wkb*ja- or aluminum wheel, or must the wheel *brwfvaj)-k: be ferromagnetic? Explain.

It has been proposed that eddy currents be use k4t4(:fydzudrf*k :s d 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 pzfu4tf y(:4 d rdks:*kermanent 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) pd o)9. ,hnfgu9q)l2zmjyv i/falls much more quickly through a magnetic field than does a solid bar. Explain.) pu z,y)2vjf/im gq9o dl.nh9

If an aluminum sheet is held between the poles of a large bar magnet, it rezrxu5n6c gk q -wx7i,7quires some force to pull it out of the magnetic field even thougkg ruiqnc,57zx7w-6 x h the sheet is not ferromagnetic and does not touch the pole faces. Explain.

A bar magnet falling inside a vertical metal tube reaw4 1tj 5*ffkujw/ lny/ches a terminal velocity even if the tube iswf*/uyf4/5wlj n1tj k evacuated so that there is no air resistance. Explain.

A metal bar, pivoted at one end, osc e8 7kg 91xw3/y6zzwir(gzvjj illates freely in the absence of a magnetic field; but in a magnetic field, its oscillations are quickly damped out. Explain. (This magnetic damping is u8gwx1 z3gk6wzj7je/9( zv yirsed in a number of practical devices.)

An enclosed transformer has four wire h. 7*)p fk9efil:en)v*scqyf leads coming from it. How could you determine the ratio of turns on the two coils withouf .:n) eeylihq)9vpk c*sf7* ft taking the transformer apart? How would you know which wires paired with which?

The use of higher-voltage lines in homes — say, 600 V or 1200ut .pp 4fx380 :hkotptp,/og p V — would reduce energy wasoht p3 fkp8poxgp 0 /4.t,:utpte. Why are they not used?

A transformer designed for a 120-V ac input will often “burn out” if conne2 uuj*jgqb*fq)u wyx71 cx6 q+cted to a 120-V dc source. Explain. [Hint: The resistqwc* )g+b6 u f x*y172uuxqjqjance of the primary coil is usually very low.]

How would you arrange two flat circular coils so thx /a1blkmjs6 )6l+2x hp um5smat their mutual inductance wahs/62) spx6bm1 l+am l5jxmkus
(a) greatest,
(b) least (without separating them by a great distance)?

Does the emf of the battery in (Fig. Below) i5 -cl7 j1)nkqt;eodsde ;zp:affect the time needed for the LR circuit to reach opq e7:; k51-net) izjcd;d ls
(a) a given fraction of its maximum possible current,
(b) a given value of current? Explain.

  In an LRC circuit, can the rms voltage acroz-y(ok97a oo fss
(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 impedance oy .qmy8-7j lcaf
(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 mf eh-zxdfo .ehpf 4j* 8i)5;aa minimum.

  The magnetic flux through a c(1xvx. oyex*coil of wire containing two loops changes from -50Wb to +38 Wb in 0.42 s. What1 x x.vo*cex(y is the emf induced in the coil?    V

  The rectangular loop shown in (Fig. Below) is pusohdx v8 bf: )7vz4(qn7fxq7 ijhed into the magnetic field which points inward. In what direction is the induced curfj n 7: zdqqbo77xfvh8 4x)i(vrent?  ----待选择----counterclockwiseclockwise 

  The north pole of the magnet in (Fig. Below) is being inserted into the r./ubc1.n ogp coil. In which direction is the induced current flowing through the resis nbp1 .rou/.gctor 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-bda4 mix chk/:5s:e7yT magnetic field. The loop is removed from the field in 0.15 s. W:ey id ak bxc:m4/75shhat is the average induced emf?    $ \times10^{-2 }\;V$

  A 12.0-cm-diameter loop of wire is initially oriented perpendicular to:pz lc 202-e )l+nexpmpmp ynp..hj* k a 1.5-T magnetic field. The loop is rotated so that its plane is parallel to the field direction in 0.20 s. What is the average induce pj*xmemp.:2nz0)h.en-+p kcp ly2pl d emf in the loop?    $ \times10^{-2 }\;V$

  A 10.2-cm-diameter wire coil is initially oriented so h6*frpyb6a;j wn+ 7gsthat 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 d;hspn76rb+yf6 wj g* aown. What is the average induced emf in the coil?    $ \times10^{ -2}\;V $

  A 15-cm-diameter circular loop of wire is placed in a 0.50-T magnetic field:e kevh(6 vkv-.
(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) eo0jja 9 qk5b3is slowly increased, what is the dir3qkeb0 j9a5j oection of the current induced in the small circular loop inside the larger loop?  ----待选择----counterclockwiseclockwise 
(b) What would it be if the small loop were placed outside the larger one, to the left?  ----待选择----counterclockwiseclockwise 

  What is the direction o82vnm/m:udnmy -zn9t f the induced current in the circular loop due to the current shownm 8y -t2: n9dmznnum/v in each part of (Fig. Below)?
a  ----待选择----counterclockwiseclockwise0 
b  ----待选择----counterclockwiseclockwise0 
c  ----待选择----counterclockwiseclockwise0 
d  ----待选择----counterclockwiseclockwise0 

  If the solenoid in (Fig. Below) is being pulled away from f: c0b1936e kqew vdxwthe loop shown, in what direction is the induced current in the looxfqdw 69k e cw0:v3e1bp?  ----待选择----counterclockwiseclockwise 

  The magnetic field perpendicular to a circ zi(wv4-bcfg23n c9dnular wire loop 12.0 cm in diameter is changed from +0.52T 3(ndz icfbvg nc49w-2to -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 j4t63z, ,3r55jy mg;zo ueuvzxq0 foa12.0 cm long and is pulled at a speed of 15.0cm/s If the magnetic field is 0.800 T, calyx qmz340 ju6et gz,rv,; u fj355zaooculate
(a) the emf developed,    $ \times10^{-2 }\;V$
(b) the electric field felt by electrons in the rod.    V/m  ----待选择----updown 

  A circular loop in the plane of the paper lies in a 0.75-T magnetic field pointi( l6qexase8f5uf4 5kz ye e11nng into the paper. en5e15 z(u1sf8f6exe qkl a4yIf the loop’s diameter changes from 20.0 cm to 6.0 cm in 0.50 s,
(a) what is the direction of the induced current,  ----待选择----counterclockwiseclockwise 
(b) what is the magnitude of the average induced emf, $|\varepsilon|$ $\approx$    $ \times10^{-2 }\;V$ (retain one decimal places)
(c) if the coil resistance is 2.5$\Omega$ what is the average induced current?    $ \times10^{-2 }\;A$

  The moving rod in (Fig. Below)is 13.2 cm long and generates an emf of 120 mV mk7* q)*a( dsss 1qfadwhile moving in a 0.90-T magnetic field. d)a*7 sqs1mk aqds *f(
(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 rectanz-f p(v; vtyp+gular loop of wire with dimensions shown in (Fig. Below) is situated inside a region of uniform magnetic field of 0.550 y;(f v+p z-tpvT. The total resistance of the loop is $\mathrm{0.230~Ω}$ Calculate the force required to pull the loop from the field (to the right) at a constant velocity of 3.40m/s Neglect gravity.    N

  A 500-turn solenoid, 25 cm long, has a diameter of 2.5 cm. A 10-turngkst pif5z,5t; bl76g coil is wound tightly around the center of the solenoid. If the current in the solenoid increases uniform,bg6t57; kli fp5zgstly from 0 to 5.0 A in 0.60 s, what will be the induced emf in the short coil during this time?    $ \times10^{-4 }\;V$

  In (Fig. Below), the rod moves with a speed of 1.6m/s is 30.0 cm long, anamy5*6ps hb5cd has a resista55pa6mh* c bsynce of $\mathrm{2.5~Ω}$ The magnetic field is 0.35 T, and the resistance of the U-shaped conductor is $\mathrm{25.0~Ω}$ at a given instant. Calculate
(a) the induced emf, $\varepsilon$ $\approx$    V(retain two decimal places)
(b) the current in the U-shaped conductor, $I\approx$    $ \times10^{-3 }\;A$ (retain one decimal places)
(c) the external force needed to keep the rod’s velocity constant at that instant. $F\approx$    $ \times10^{- 4}\;N$ (retain one decimal places)

  A 22.0-cm-diameter coil consists of 20 turns of circular copper wire 2.. o-rkklmbp2,6 mm in diameter. A uniform magnetic field, perpendk 2probk.ml,-icular to the plane of the coil, changes at a rate of $8.65\times10^{-3}\mathrm{~T/s}.$ Determine
(a) the current in the loop, $|\varepsilon|$ $\approx$    A (retain two decimal places)
(b) the rate at which thermal energy is produced.    $ \times10^{-4 }\;W$

  The magnetic field perpendicular to a single 13.2-cm-diamoa0 iik5*ft 2ceter circular loop of copper wire decreases uniformly from 0.750 T to zero. If the wire is 2.25 mm in diameter, how much chargec20tii *5ofak moves past a point in the coil during this operation?    C

  A simple generator is used to genes:m kehie5i +8e, 8a6bdz mk3urate a peak output voltage of 24.0 V. The square armature consists of windings th8smh de 6e ba,:i8 5kuie+m3zkat are 6.0 cm on a side and rotates in a field of 0.420 T at a rate of 60.0rev/s How many loops of wire should be wound on the square armature? $\approx$    loops(Round to the nearest integer)

  The generator of a car idling at 1100 rpm produces 12.4 V. Whath a8lu/nhfk6 5 will the ou tput be at a rotation speed of han klu86hf5/2500 rpm, assuming nothing else changes?    V

Show that the rms output (Section 18–7) of ayvi+cso v/2 8hl s -)d,/4sl1nj:tyzp6djexqn ac generator is $V_\mathrm{rms}=NAB\omega/\sqrt{2}$, where $\omega=2\pi f.$

  A simple generator has- ubf)lr6 h ;kpu)f2xe a 320-loop square coil 21.0 cm on a side. How fast must it turn in a 0.650-T field to produce a 120-V peak output? 6b)eh x;)fk pful-2 ru$f$   rev/s

  A 450-loop circular armature coil with a diameter o eq.w)2tna 1qzf 8.0 cm rotates at 120rev/s in ae)zn twq.1qa2 uniform magnetic 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 haszs8r yc5ph06z w4h*dveu2b576 zmw j x 1000 turns and produces an rms voltage of 150 wzdec5 j vb5wps2 0xh r 4zz8766myhu*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 armatk5 4( afacieyr9.8usxure resistance of $3.25\Omega.$ If it draws 8.20 A when running at full speed and connected to a 120-V line, how large is the back emf?    V

  The back emf in a motor is 72 V when pbk 5.af5m-vcdjj hwl8*) 3a ioperating at 1800 rpm. What would be the back emf at 2500 rpm if the magd3kwjfav- jbcl 8m* p)hia55.netic field is unchanged?    V

  The back emf in a motor is 95 V when the motor isow .6qrmqp8e - operating at 1000 rpm. How would you change the motor’s magm8qoq. 6r-wepnetic 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 qp-r, c +xu/y21buiwi–9 if the load causes it to ru/ryu+-pw2cx,u ibiq 1n at half speed?    A

  A transformer is desz,juty0)ug;rh t*7fe igned to change 120 V into 10,000 V, and there are 164 turns in the primary coil. How many turns are in the secon g t7u*0zr fjh,;ue)tydary coil? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ $\approx$    turns

  

  A step-up transformer increases 25 V to 1xac(l*oas6qq5: z kzg yep5 1*20 V. What is the current in the secondary coil as compared to the primary coil? y*x e15kq:qcpzl*s5gaoz 6(a   

  Neon signs require 12 kV for their operation. To operate from a 240-p +0b h 8aq-hwxx*hyw)wx/0rrV line, what must be the ratio of secondary to primary)p0rwwyxbxh-a h rw q*x/8h +0 turns of the transformer? What would the voltage output be if the transformer were connected backward?
$\frac{N_\mathrm{s}}{N_\mathrm{p}}$ =   
$V_s$ =    V

  A model-train transfor4 a4 r( 5ypqhaauj-czqaqy.- ,mer plugs into 120-V ac and draws 0.35 A while supplying 7.5 A to the yy4 qhu qj5pa.a4r,z ac-a-(q 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 current is 22 A.m jaf*5rxg l2* 5 jamx*fgl*r 2
(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.f94wu 9d 6kc2em5.ye .m blti::m*che g qfpu4 The input voltage is 120 V and the output current is 15.0 A. What are the output voltage and input currenteqbm44 m2 9*k6fm:f : 5.lw.uyihcgue9tpdc e ? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ =    V
$\frac{I_\mathrm{s}}{I_\mathrm{p}}$ =    A

  If 30 MW of power at 45 kV (rms) arrives at a town fdz h.;dytrf4*pbs :r75st/ t nrom 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 t0(ue2zzjp a1y wo $0.100-\Omega$ 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 st ;npzk 5/w0 6(y)ukucqd1enrseadily from 25.0 A to 10.0 A in 350 ms, w5(e1 zd;ns)6 qrk uwuc/kpn0yhat is the magnitude of the induced emf?    V

  What is the inductance of a coil if the coil produpl 8*1* zllmte; rh7ha0to9ku33zk lq ces an emf of 2.50 V when the current in it changes from -28.0mA to +31.0mA in 12. z elaoh9p* 1zq8mr3*7l0;khktl3lt u 0 ms?    H

  What is the inductance L of a 0.60-m-long ,i:)chac 6 lpb4, tjsxair-filled coil 2.9 cm in diameter containing 10,000 )ix,lt:6c bpaj4 s,h cloops?    H

  How many turns of wire would be required to make a 130-mH inductance-zq4o9c vi6ye :oa0a1x :lc ru out of a 30.0-cm-long aiavyie94 rc1l0ao: :xcz6quo-r-filled coil with a diameter of 5.2 cm? L$\approx$    turns (Round to the nearest integer)

  An air-filled cylindrical inductor has 2800 turpg dihhupgd1 1 :qck7mmu4:q e; rb-0ej,w 0p6ns, and it is 2.5 cm in diameter and 28.2 cm b: 07q6j1r:gipgmuche uk4p 1;w-e,hm0q ddplong.
(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 croj y 6m;w(f2kzmss-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 wym ** rxr+tt nk2ik9;qhxa ;x/ound solenoid is unwound and used to make another tightly wound solenoid of twi2*;/tm+ ai krqk;*ry thxnx9xce the diameter. By what factor does the inductance change?   

  The magnetic field inside an air-filled solenoid 36 cm longqlih; z c98vbtug0;a8 and 2.0 cm in diameter is 0.80 T. Approximately how much energy is stored in this fiel hz 0ul;ib8aqvc t8g;9d?    J

  At a given instant the current through an inductor is 6xav.1l zef4c:u -iy p50.0 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 from the initzi46.vcxpl yeu- f a:1ial value?
U =    $ \times10^{-5}\;J$
$\Delta$t=    s

  Assuming the Earth’s magnetic fc lnn2zpyn90c8ff*fesj (oh :m+k9v6 ield 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 constan.: uy )dmtl l9pr9 ai 5dnxp:lc7g2k-u ie0fw9ts 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 haven beunah *-5 nt-xg7l- the same length and circular cross-sectional area. But solenoid 1 uses wire that is half aln-bxt-7 u*egn h-n5as 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 o/4wcc:vfw: 4 ap6 emzgf 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 reazu9h69-fgb:d9f yy 7h 8 acbmnctance of $660 \mathrm{k} \Omega ?$    Hz

  At what frequency will a p2jdft( v40mg4ps f /b$2.40-\mu F$ capacitor have a reactance of $6.70 \mathrm{k} \Omega ?$    Hz

Plot a graph of the reactance o .9 xhevq+keaw+ jld ,(c8qdv.f a $1.0-\mu F$ capacitor as a function of frequency from 10 to 1000 Hz.

Plot a graph of the reactance of a 1.0-mxgd s+3j3 ujr*t6+v8ue v: oemH inductor as a function of frequency from 100 tose8t6vg jj*r:+u ouxem33 vd+ 10,000 Hz.

  Calculate the reactance of, and rms current in, a 160-mH radio c+ fyblqn g-+ oi:kse/8*bu:i 7ltodw/oil connected to a 240-V (l d:bg t7*on+o+iyw b/uk/:sf-8 lieqrms) 10.0-kHz ac line. Ignore resistance.
$X_L$ =    $\Omega$
V =    $ \times10^{-2 }\;A$

  An inductance coil operates at 240 V and 60.0 Hz. It draws 12.8 A. What is tw q1*06,ncjmha;lv(4f k0 mjmf uhe1che cou*hc400nq 1l fmehj (1fv,kjmw c;6 mail’s inductance? $X_L$ =    $ \times10^{-2 }\;H$

  (a) What is the reactan;/y gpw7yopsx n55r.r ce 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 huma :x/czq5cx3ctjcwm:nt- 8w3m * a)g kvn body for 1.0 s could be lethal. What must be mc/ wnmgcxk:*ja8tc 3t)3wz-qv :5xc the impedance of the body for this to occur?    $ \times10^{3 }\;\Omega$

  What is the resistance of a coil if its iti ,f- bblx6)w c:egc+5r,onnmpedance is $\mathrm{235~Ω}$ and its reactance is $\mathrm{135~Ω}$    $\Omega$

  What are the total impedance, phase angle- hl imwmds;c (1(;yphiuxc 8+, and rms current in an LRC circuit connected to a 10.0-kHz, 725-V (rms) sd hs;u(yc xl(mp1i8i +c;m-hwource 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 by an ac power supply. Au: u6ycr - :wp9;csw)g4xla frt what frequency is the impew4u -rc)u :96cw gy;arplxsf:dance double that of the impedance at 60 Hz?    Hz

  (a) What is the rms current in an RL circui/dk iaiz5,- jjda0 .ldckr+u)t when a 60.0-Hz 120-V rms ac voltage isziud-)jld/k 5+ ,ar0jdcak i. 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 current in an RC circuit if6qtvz no;b(9drx7o - r $R=8.80\mathrm{k}\Omega,C=1.80\mu\mathrm{F},$ 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 connectefpa(s z 93 qtf(c)wwp1*wq7up 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 capacitanc k,92wy moe5bye of 2800 pF when the rad keb95y,y 2wmoio is tuned to 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 a4*5 twqgto g6l5vqndk 4ltn 3k4z)9dkg xl4i5 nd $R=4.40\Omega$.
(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 the pao)p* bihw. np- zft63on m7f-bge as shown in (Fig. Below). fb-n o7.i *p6-mnhbo3 w)p ztfWhen switch S is thrown in the left-hand coil,
(a) what is the direction of the induced current in the other loop?  ----待选择----counterclockwiseclockwise 
(b) What is the situation after a “long” time?
(c) What is the direction of the induced current in the right-hand loop if that loop is quickly pulled horizontally to the right?  ----待选择----counterclockwiseclockwise 

  A square loop 24.0 ckm +(exvv7crlnj:: )qm on a side has a resistance of $5.20\Omega.$It is initially in a 0.665-T magnetic field, with its plane perpendicular to $\vec{\mathbf{B}},$ but is removed from the field in 40.0 ms. Calculate the electric energy dissipated in this process.    $ \times10^{-3 }\;J$

  A high-intensity desk lamp is rated at 45 W but requires only 12 V.;qk g2y1nc s9--tiklkvs 8.xx It contains a transformer that converts 120-V househol-cv1 kkq ngt8-x 9 2.ki;yslxsd 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 plan: bww:)dz po2ft 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 :o2dpwb)wf: z 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 80l *k opiht-8hg4cu48l% efficiency are connected to 110-V ac. The secondary wi 4 hocltu8*-phk4igl8 ndings 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 lines5 2a v .6gsxebrzma+)l 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 -fhwenpgz r9a tv ,882cm 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 gb;j0cy5k.y ofd t /9xin transmission lines, $R_L$ is given by $P_{\mathrm{L}}=\left(P_{\mathrm{T}}\right)^{2}R_{\mathrm{L}}/V^{2},$ where $P_T$ is the power transmitted to the user, V is the delivered voltage, and $R_L$ is the resistance of the power lines.

  A coil with 150 turns, a rw 8q 6 r* u;9gpeuck1kwy7bc5 51vebmcadius of 5.0 cm, 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 protected against su hgt.31wmd 4;lznc5 07sxrg ludden surges in current. In particular, after the power is turned on the current should risel3gm1cd4ngw. 5zls;hu 7t 0x r 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 ise/ uma,:t mxu*qo)9un placed between the pole pieces of an electromagnet. When the magnet is turned on, the flux thqeu9,:mn a)uomx u/*t rough 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 volzzm8x 9. fb;fwp4qh n,tage of a simple generator whose square armature windings are 6.60 cm on a side; the armature contain f .,qb4mzhwxp n8f;z9s 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 magnetic0) *5houj t fjnlx:w-y fields attained in laboratories are o txly0wh5*)-uj jf :nabout $1.0\times10^4\mathrm{~V/m}$ 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 inp k;m4. 1s gflklkwb+7cut is 220 V at 60.0 Hz if the current drawn is 5.8 A? Assume no cblm7klk ;w1s + .cf4kgurrent in the secondary.    H

  A 130-mH coil whose resistance di1u +rt06u vbis $\mathrm{18.5~Ω}$ is connected to a capacitor C and a 1360-Hz source voltage. If the current and voltage are to be in phase, what value must C have?    $ \times10^{-7 }\;F$

  An inductance coil draws 2.5-A dc when connected to a a-ktlj5da8v2u4r (r c 36-V battery. When connected to a 60-Hz 120-V (rms) source, the current drawn is 3.8 A (rms). Determine the inductance and resisa2v-j rka5ult(8 cd4 rtance of the coil.
$V_{dc}$ $\approx$    $\Omega$
L $\approx$   $ \times10^{-2 }\;H$

  A 135-mH inductor witiho)e216up2 wca m0ry h $2.0-\Omega$ 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 thuxi8jnxw427y e voltage across the capacitor (or inductor) to the voltage across the resistor, at resonance. The larger the Q factor, the sharper the resonance curve will b2yji74ux 8 wnxe 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$