What would be the advantage, in xlkv 6hx:8eg.px,rt 7 Faraday’s experiments (Fig. Below), of using coils with many turns? hk .p,xvr tg:xl6 7x8e

What is the difference between magh9;5k bqr 9weh, xsc0wnetic flux and magnetic field?

Suppose you are holding a circular ring of wire andb- wry cy *i6e;+up*kl suddenly thrust a magnet, south pole first, away from you toward the center of the circle. Is a current induced in the wic;eupwilb y-+ y *r*k6re? Is a current induced when the magnet is held steady within the ring? Is a current induced when you withdraw the magnet? In each case, if your answer is yes, specify the direction.

Two loops of wire are moving in the vicinity of a very loqkr kxej// +dbv1i; s/ o/5ojf-ga)csng straight wire carrying a steady current as shown in (Fi)o-+/xvkqsa5 g rcdbo/i je;fs1kj / /g. Below). Find the direction of the induced current in each loop.

Suppose you are looking along a line through the centers of two cixw4k uk3o.,r crcular (but separate) wire loops, one behind the other. A battery is sud.wxrk ok34, ucdenly 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 tm i2 mcmov0ja.5c+m)ghe direction 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 m.d* nv3z0kz-s wok7ysignal must travel over a distance, a “shielded cable” is 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” necessarwozz0vk.d-kn*3my s 7 y?

What is the advantage of placing the two i 6xil9::s8 cw:ycm:zwkpqf)onsulated electric wires carrying ac close togethes6y zqwx co9cmw kpf::l8i:):r or even twisted about each other?

Explain why, exactly, the lights may dim briefly when a refrigo vtd,z, tko:/erator motor starts up. When an electric heater is turned on, the lights may stay dimmed as long as the heater is on. Explainkzo: ,/v ,dott the difference.

Use (Fig. Below a) and (Fig. Below b) plus the right-hand rules to show whq ra kx2 ye(tdkmzi3(srup 3p+ 58u+ mdx8i7q2y the counter torque in a generator opposes the 7y(32ir k2mzi 3xe ppus5qm dkut(xdqa8 r++8motion.
a
b

Will an eddy current brake (Fig. Be fd,g5h;zcg rg+l xyfb,(e8t3low) work on a copper or aluminum wheel, or must tyzg,5tgb3lg + ;8e ,hffxr cd(he wheel be ferromagnetic? Explain.

It has been proposed that eddy currents be used to help s8zqsy l;3os em)pcp +7ort solid waste for recycling. The waste is first ground into tiny pieclzm)y;pe 7cp 8s3o+sqes and iron removed with a dc magnet. The waste then is allowed to slide down an incline over permanent magnets. How will this aid in the separation of nonferrous metals (Al, Cu, Pb, brass) from nonmetallic materials?

The pivoted metal bar with slots in (Fi5jie8p*8o r2ujd) skwxnu 3 6mg. Below) falls much more quickly through a magnetic field than does 25i*ku36drpjxo s8mn 8u) ejwa solid bar. Explain.

If an aluminum sheet xwvx-r5 1br/ 6jvb 5ygis held between the poles of a large bar magnet, it requires some force to pull it out of the m bxvv5g6r j15yw- /rxbagnetic field even though the sheet is not ferromagnetic and does not touch the pole faces. Explain.

A bar magnet falling inside a vertical metal tube reaches a terminal veloci le l68mrp,y:hty eveney,p 6h:l l8rm if the tube is evacuated so that there is no air resistance. Explain.

A metal bar, pivoted at one end, oscillates fre ;ouj emo(v q;69s8lqeely in the absence of a magnetic field; but in a magnetic field, its oscillations are quickly damped out. Explain. (This magnetic damping is used in a nu; vq oeu6;9om8( qsljember of practical devices.)

An enclosed transformer has four wir kvh7 rrw+(z1ze leads coming from it. How could you determine the ratio of turns on the two coils witwr( kv7hz1r z+hout 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 1200 V — would reduce ;:g4/i8fme ka1 idt3wlndz 9f energy waste. kwg1imtaf: 98ldnz3 4dei /f;Why are they not used?

A transformer designed for a 120-V ac inp4pqi6 v8t )pi3 soul7i09jnfout will often “burn out” if connected to a 120-V dc source. Explain. [Hint: The resistance of the primary coil is usually 0js i7vpiuolqot6)i8f9p n43very low.]

How would you arrange two flat circular coils so that their mutual inductancd4 hg9 jfyobm9 b8v;u7e wadg9jfh8u4 7b9 y;v ombs
(a) greatest,
(b) least (without separating them by a great distance)?

Does the emf of the battery in (Fig. Below) affect the time needed for the LR cm*yuk rn)e:j-ircuit-k:)u jy*enmr to reach
(a) a given fraction of its maximum possible current,
(b) a given value of current? Explain.

  In an LRC circuit, can the rms voltage acr(kz19eifqc( y oss
(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;h6pfm nt-;au source emf affects the impedance of
(a) a pure resistance,
(b) a pure capacitance,
(c) a pure inductance,
(d) an LRC circuit near resonance (R small),
(e) an LRC circuit far from resonance (R small).

Describe how to make the impedak:8ackdmohe ebr. 8:d /ozf62 0 3fjyxnce in an LRC circuit a minimum.

  The magnetic flux through a coil of wire containing two loops bg5yz se a66a2ik0p.w changes from -50Wb to +38 Wb in 0.42 sgb2.aw6z y 0ka6sp e5i. What is the emf induced in the coil?    V

  The rectangular loop shown in (Fig. Below) is pushed into the magnetic fbwa92a16azv6si* bs b ield which points inward. In what direction is the induced current? sw1azab6*asv29i6b b  ----待选择----counterclockwiseclockwise 

  The north pole of the magnet in (Fig. Bupua r;w(e hq7;/wc4 nelow) is being inserted into the coil. In which directi/wp4;a (nhq uce7urw;on 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 iq x* 4k qbs0mg8yis4yi8u q5h6n a 1.10-T magnetic field. The loop is removed from the field in 0.15 s. What 8iq0sk*5 g sq i64xbumqy48yh is the average induced emf?    $ \times10^{-2 }\;V$

  A 12.0-cm-diameter loop of wire is initially oriented perpendicular to a 1.vtu;q/6/e cf s*gxov m*h)k5k 5-T magnetic field. The loop is rotated so that its plane is parallel to the field direction ivk*t5cx/kms /*uv;6)q h ofegn 0.20 s. What is the average induced emf in the loop?    $ \times10^{-2 }\;V$

  A 10.2-cm-diameter wire coil is initially oriented so that its h/vc.ks6 7etlplane is perpendicular to a magnetic field of 0.63 T pointing up. During the course of 0.15 s,.te k7hlc s/6v 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 .wbgkh6 ukr34is 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 increaz;9v) gl;tb .9bk,hevg1w n ofsed, what is the direction of the current induced in the small cir gg )9v1 ; wv9nf,bhl;o.tkezbcular 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 loop48,6pdno o5 4r5yndihp 6s oxz due to the current shown i8o4os5h64nx nrp zd6 yopd5i,n 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 the loop sho6l9 *,v jy-gwluu fma)q pl;vk,y z;4cwn, in what direction is the induced current in the ,*;yuv9cl; wm-4g k)v jall,zpqu fy6loop?  ----待选择----counterclockwiseclockwise 

  The magnetic field perpendicular d/ xnt7cx1gh- to a circular wire loop 12.0 cm in diameter is changed from +0.52T to -0.45 T in 180 ms, where means the fieldx xnc-1t h7d/g 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 e ju24tr36hua-u0pzg at a speed of 15.0cm/s If the magnetic f42p60h u-zj3 egruautield 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 paper lies in a 0.75-T magnetsg ;o2q9tyk8 :mvy2ibic field pointing into the paper. If the loop’s diameter changes from 20.0 cm to 6.0 cm in 0.50 skt;:qv 9y so2ybg 82mi,
(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 1203w +q.9vzbez, chw gu) mV while movinuw)g ,zce3h b+wq.9zv g in a 0.90-T magnetic field.
(a) What is its speed?    m/s
(b) What is the electric field in the rod?    V/m  ----待选择----updown 

  Part of a single rectangjd vgqk(rhxjo/u7 +t q1*nu 32ular loop of wire with dimensions shown in (Fig. Below) is situated inside a region of uniform magnetic field of 0.550 T. The total72jt3hu1joq*duq + kr( g/ xnv 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, ha6y)fes-*i wv pisrcun.+3 4 vus a diameter of 2.5 cm. A 10-turn coil is wound tightly around the center of the solenoid. If the current in the solenoid increases uniformly from 0 to 5.0 A in 0.60 s, what will be the indu+.v ir)u3yp fv-cws4ne6sui*ced emf in the short coil during this time?    $ \times10^{-4 }\;V$

  In (Fig. Below), the rod moves with a2soq3xuj)p c p-5a1 um speed of 1.6m/s is 30.0 cm long, and has a res5xoq a1cupmj u-2 3p)sistance 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:m vhda: 0f2 79sn-su8v4hynyo o ll7e of 20 turns of circular copper wire 2.6 mm in diameter. A uniform magnetic field, perpendicular to the plane of the coil, changes at a rate o deusn-7yf94lsh olmn0h: a 87vy2:ovf $8.65\times10^{-3}\mathrm{~T/s}.$ 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-diameter c;4zi mr2c okq3ircular loop of copper cmko3riqz ;24 wire decreases 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 used to : p)pic 8kt3grgenerate a peak output voltage of 24.0 V. The square armature consists of windings that are 6.0 cm on a si:t8kp c)3prigde 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. What will the ou tpb.j fl3j;txk l.imc89ut be at a rotation speed of 2500 rpm, assumiit 3cbjk 8x.j9l; lm.fng nothing else changes?    V

Show that the rms oumwkmn7 t: u.w-eghad 7/+suf* tput (Section 18–7) of an ac generator is $V_\mathrm{rms}=NAB\omega/\sqrt{2}$, where $\omega=2\pi f.$

  A simple generator has auy ns- sj*;;bnzw xa o)z7pb(, 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 7jx(;ob- ysnp zz w)bs a,u;*npeak output? $f$   rev/s

  A 450-loop circular armature coil with a diameter of 8.0 cm rkkol*d1f2 r6* wugur0otates at 120rev/s in a unifo rgo2kul0*fw1d*6ukr rm 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 fi0ej hug;:e3 ezeld of 0.030 T. It has 1000 turns and produces an rms voltage of 150 V and an rms current of 70.0 A.h e3z;:ejug 0e
(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 armat1egmn+, 4tcmi nj0n5d ure 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 j7 )mi;4mjfit 5rf yu5V when operating at 1800 rpm. What would be the back emf at 2500if j75yf);mi5m t4ujr rpm if the magnetic field is unchanged?    V

  The back emf in a motor iszpb2j31mted 2ru/1k i 95 V when the motor is operating at 1000 rpm. How would you change the motor’s magnetic field if you wanted to reduce the back emf to 65 V when the motor was running at 2500 rpm? rbz dum2 rj1ip/ 2etk13educe the magnetic field to    % of its original value

  What will be the current in the motor of Example igqs a+b iccrb w)*ypp5l((6o 3gk/w121–9 if the load causes it to run ati(ig/+og) qcpps5w*(ycr 1b3 6kblaw half speed?    A

  A transformer is designed to change 120 V into 10,000 V, and thedge-,ay t c9n+7o2da are are 164 turns in the primary coil. c+ 97gatnad,d oe -ya2How many turns are in the secondary coil? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ $\approx$    turns

  

  A step-up transformer increases 25j (7nvxuaqceayl *9.9p) le5e V to 120 V. What is the current in the secondary coil as compared to the e(9apc* 7 a95lue)jq vl.nyxe primary coil?   

  Neon signs require 12 kV for their operation. To operate from a 240-V line, wha03-(xckus-xx9ubmquw ; kwk ,t must be the ratio of secondary to pr k -;(uq ms-0ucbux 3xw9x,wkkimary 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 transformer pl:sd/eiu w1 l7sjpvn4n8owm4j9; qj 1eugs into 120-V ac and draws 0.35 A while supplying 7.5 A to theos w1i :e4nl7us4qnw/8d 9pjv jj1;me 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;r-b fsvl4 kp/ pb/ep/qomen(f .m. u: 22 A. fk(/- nmm pev./pob.rpu q:fb;es4/ l
(a) Is this a step-up or a step-down transformer? this is a  ----待选择----step-downstep-up  transformer
(b) By what factor is the voltage multiplied? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ =   

  A transformer has 330 primary turns and 1340 secondary turns. The input volta9dm aolx2h54jf 8f z jm52ica4ge is 120 V and the output current is 15.0 A. What are the output voltage amf h89i 5 z2cj42mfad ojax5l4nd input current? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ =    V
$\frac{I_\mathrm{s}}{I_\mathrm{p}}$ =    A

  If 30 MW of power at 45 kV (rms 2efs6 58gaxxz) 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 town ov5*skj x/ys+tpcadp49k rit:q 1*g:mt er 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 1/yb;iqgf8k1lw y (dd5wty0l1 80-mH coil changes steadily from 25.0 A to 10.0 A in 350 ms, what is the kdiy ywqfw/8lb 5yt 0d l1;1(gmagnitude of the induced emf?    V

  What is the inductance of a coil if the coil produces an emfj vunrd e8g2u130 ,jun of 2.50 V when the current in i r jnue3jug,v2 dnu018t changes from -28.0mA to +31.0mA in 12.0 ms?    H

  What is the inductance L of a f5 o3: g5dolgm0.60-m-long air-filled coil 2.9 cm in diameter containing 10,000 53:fgo5gl mod loops?    H

  How many turns of wire wg)l)f,l53 az tpt jf3iould be required to make a 130-mH inductance out of a 30.0-cm-loiltt)fpfl j353z,g)a ng air-filled coil with a diameter of 5.2 cm? L$\approx$    turns (Round to the nearest integer)

  An air-filled cylindrical inductzrk2z2ph w f-,a,ms) tor has 2800 turns, and it is 2.5 cm in diameter and 28.2 cm longmp zw, 2-h,fzatks)2 r.
(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 tf s4n;m ek*- l.tk0axcontains $N_1$ 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 so .bfkkg(wy(xd, t lpuo (o*hl8v 8j70a+elmf.lenoid is unwound and used to make another tightly wound solenoid of twice the diameter. By what factor does the inductance gav((olfkbfp .(+ojd87*et mu 8xl l,0.whk ychange?   

  The magnetic field inside an air-filled solenoix,bcfo5kc2 u2y e,8 ttd 36 cm long and 2.0 cm in diameter is 0.80 T. Approximately how much, ke xotyu25 cfbt,28c energy is stored in this field?    J

  At a given instant the currtq6jj1 ,e3dvhent through an inductor is 50.0 mA and is increasing at the rate of 115mA/s. What is the initial energy stored in the inductor if the inductance is known to be,h6 13v dqjtej 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 averages )k2ki)1k an vq0 alc8pabout $0.50\times10^{-4}\mathrm{~T}$ 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;2 o0(8w:oubdk3 cp4 l g+yzixj1dgw e 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 an+r(ueqt ,cq7*utv((t :w+rp o3bzrv td circular cross-sectional area. But solenoid 1 uses wire that is half as thick as sole* v+pu b t (c(v:u7q(rrt trz3qeo,wt+noid 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 t7g:hcgu q2 oxz*n;/ca $7.20-\mu F$ 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 reactance of h8il ggigl 98b63)l fv$660 \mathrm{k} \Omega ?$    Hz

  At what frequency wil0v rkx:z 0ot2gl a $2.40-\mu F$ capacitor have a reactance of $6.70 \mathrm{k} \Omega ?$    Hz

Plot a graph of the reactance of a guh nh6zbb5de9 5r3:f$1.0-\mu F$ capacitor as a function of frequency from 10 to 1000 Hz.

Plot a graph of the reactance of a 1.0-mH inductor as a functi+::q 9+:rkuem;nj a maviz y3qon of frequency from 1i;z:un: :3k9mya jr+ qqe+vma00 to 10,000 Hz.

  Calculate the reactance of, and rms current in, a 160-mH nxq8586wln ma radio coil connected to a 240-V (rms) 10.0-kHz acml qx5w 6n8na8 line. Ignore resistance.
$X_L$ =    $\Omega$
V =    $ \times10^{-2 }\;A$

  An inductance coil operates ats+a* 1yk f wn+1 rsmgl2i)1syz 240 V and 60.0 Hz. It draws 12.8 A. What is the coil’s i gz )n*k+isrm1+ywfs sl ay211nductance? $X_L$ =    $ \times10^{-2 }\;H$

  (a) What is the reactance of a well-insu37c u*pm6wnf: fsq+ vslated $0.030-\mu F$ 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 cyw7 e b wj2t*l-v+3.i,a0iuo ybz0ulmA passing through the human body for 1.0 s could be lethal. What must be the impedance o+zt03yoaw- yb, *lbe0jiu7lw2.v ic u f the body for this to occur?    $ \times10^{3 }\;\Omega$

  What is the resistance of a coil if its impedanc. qvjwu thai( 2r18fa 2kub:+ce is $\mathrm{235~Ω}$ and its reactance is $\mathrm{135~Ω}$    $\Omega$

  What are the total impedance, phase angle, anduoktg8 /a yp+*hua2u; rms current in an LRC circuit connected to a 10.0- a+pu8g*ua2/o; k hytukHz, 725-V (rms) source if $L=22.0\mathrm{~mH},R=8.70\mathrm{~k}\Omega,$ and
Z $\approx$    k$\Omega$
$\phi$ =    $^{\circ}\,$
$I_{rms}$ =    $ \times10^{ -2}\;A$

  A resistor in series with a es +xuqn p9j+-2mfzx8420-mH inductor is driven by an ac power supply. At what frequency is the impedance double f9nz -+mquje +x2ps8xthat of the impedance at 60 Hz?    Hz

  (a) What is the rms current in 1 jrlu4iqn3 h-an RL circuit when a 60.0-Hz 120-V rms ac voltage is ar 4qhl1-jn3u ipplied, 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 mhm qp w21ygr1hg v( (c.,jp4d2a.t yzcurrent 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 co8dtk45s h+rvexqby7 u: y o/* tqs3b9innected 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 capacitorpmb3 lw8dn- ey,anp. w(1d;y i in the tuner of an AM radio has a capacitance of 2800 pF when the radio i mpn,yi1dp.n a -l3b8yw;wd(es 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 = 14qhn4 v(*6su l q7d9ioi ebz*)w.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 current loops in the plane of the page as shfph52ox6q wh8u7n km9own in (Fig. Below). When switch S is thrown in the left- oknp x75h6m89w uhqf2hand 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 p62yv5- qr(n)t jkixra side has a resistance of $5.20\Omega.$It is initially in a 0.665-T magnetic field, with its plane perpendicular to $\vec{\mathbf{B}},$ but is removed from the field in 40.0 ms. Calculate the electric energy dissipated in this process.    $ \times10^{-3 }\;J$

  A high-intensity desk lamp is rated at 45 W but requires only 12 V. It contains qz pj.3wyd(e+ :rr0gsa transformer that converts 120-V household v0+sq(:d3r eywrz gp.joltage.
(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 aynt ynmt w 1ga 9*;e(n9moq44zt a generating plant located 118 km from a town that requires 5(ynnz* may49 4tow m1g9tq;ne0 MW of power at 12 kV. Two transmission lines from 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 80% efficienc6 * (ihhxw a-arnlg/kt(m6bz pw,tp10y are connected to 110-V ac. The secondary windings areg0b hha -xt, (pm*np r1izl a6/kwtw(6 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 pj8ibo q19. kzlines each have a $0.80-\Omega$ resistance and carry 740 A over 9.0 km. If the rms input voltage is 42 kV, calculate
(a) the voltage at the other end, $\approx$    kV
(b) the power input, $\approx$    $ \times10^{7 }\;W$
(c) power loss in the lines, $\approx$   $ \times10^{5 }\;$W
(d) the power output. $P_{out}$ $\approx$    $ \times10^{7 }\;W$

  Two resistanceless rails rest 32 cm apa6xrsq 8)a1 9*k :pka jysa+xhort 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 ic14ww (ue (rox 81wjrv34g/+r lkntiin 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 rad2bdq.izu20 vwius 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 sudden surges in cur1 5z78nme u6dg ck;z02zjfvtlrent. In particular, after the power is turned on the current should rise no more tl z;fjvzekg1mt02u5cn z 7d68han 7.5 mA in the first $120\mu s$ The device has resistance $\mathrm{150~Ω}$ and is designed to operate at 55 mA. How would you protect this device? L $\approx$    in series(retain two decimal places)

  A 25-turn 12.5-cm-diameter coil is placed between the pole pieces of anh86(6 2p 0a1an 9ii eled3zi kuj9zyvb electromagnet. When the magnet is turned on, the flux through the coil changes, inducing an emf. At what rate (in T/s) must the field produced by the magnet change if the emf is to be 120 V?ziibal0un y96z2jp1iae 6k(d 3e 89hv $|\varepsilon|$    T/s

  Calculate the peak output voltage of a simple generator whose square armaturegyr 6 fa(wuv+c f-d,*. fi6cpe windings are 6.60 cm on a side; the armature contains 155 loops and rotates in a field of 0.206f-u*v wa,.d6y+gi c e(crpff0 T at a rate of 120rev/s. $\varepsilon_{peak}$ =    V

  Typical large values for electric and magnet9f,r)vy6z5 hof v--e homof:uic fields attained in laboratories are abou -6e,orfu hozvm vf:59f)o-hy t $1.0\times10^4\mathrm{~V/m}$ 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 2oa; jdy.rjcihc4 xq:10czh4of a transformer whose input is 220 V at 60.0 Hz i hc;xach4:r dic 2o .0jqyzj14f the current drawn is 5.8 A? Assume no current in the secondary.    H

  A 130-mH coil whose resistaf.(2;ax7z.mz x )tzfbg z: leance is $\mathrm{18.5~Ω}$ 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 2liyi3+( n dceg-g8 1yz.5-A dc when connected to a 36-V battery. When connected to a 60-Hz 120-V (rms) source, the current drawn is 3.8 A (rms). Determine thei 8gyi(nlycd13- gz+e inductance and resistance of the coil.
$V_{dc}$ $\approx$    $\Omega$
L $\approx$   $ \times10^{-2 }\;H$

  A 135-mH inductor with ;2vn3qb jag.z;9zxby sr7d(s $2.0-\Omega$ 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 ta rj1i:f30f6o-a xs sohe ratio of the voltage across the capacitor (or inductor) to the voltage across of3ox a:6rifs0aj 1s -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$