What would be the advantagem-s op:3izf+i4j: unq , in Faraday’s experiments (Fig. Below), of using coils with mfui-o4p s z3nj: :+mqiany turns?

What is the difference between magnetic flux 4 f-.84rqodwdxr3 ujp,o ma1uand magnetic field?

Suppose you are holding a circw z00ootf y45ac311oaf 6jo23 uqltp z5tt/jgular ring of wire and suddenly thrust a magnet, sou6p tt5gajaoo3f/t0c14j5o u0 2wfqoytlz 1 z3th 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 direction.

Two loops of wire are moving in the vicinity of9sr4tbjh2ya;0d; e,5 jzq dxg a very long straight wire carryingb5 4h;rxjdgytzd;a,9qjs2 e0 a steady current as shown in (Fig. Below). Find the direction of the induced current in each loop.

Suppose you are looking along a line through the centers 0ohqx0t d+bk:7jc(slof two circular (but separate) wire loops, one behind the other. A battery is suddenly conq 0lkc s(7dxh:jb+ot0nected to the front loop, establishing a clockwise current.
(a) Will a current be induced in the second loop?
(b) If so, when does this current start?
(c) When does it stop?
(d) In what direction is this current?
(e) Is there a force between the two loops?
(f) If so, in what direction?

  In (Fig. Below), determine the direction of the induced current in resib :z h 1w05nirsv -v1fwtd2w.bstor $R_A$ 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 0kgmmhs;6gh /;jstf9x;v s d (signal must travel over a distance, a “shielded cable” is used in which the signal wire is surrounded by an id(m/svhs;x;f 9 gths k6m0jg;nsulator and then enclosed by a cylindrical conductor carrying the return current. Why is a “shield” necessary?

What is the advantage of placing the two insulated electric wires xz1q9rsl za2: carrying ac close togez:az9r2 xqs1lther or even twisted about each other?

Explain why, exactly, the lights may d :45eqw)mbn89 npeeafn ,+jclim briefly when a refrigerator motor starts up. When an electric heater is turned on, the lights may stay dimmed as long as the heater is on. Explainjb l+qwfepn9 54n8n m:)e,eca the difference.

Use (Fig. Below a) and (Fig. Below b) plus the right-hand rules to shvnes: bpmfa m (gtjs 5b9wx, 7-1z c-fnfsq8,+ow why the counter tors qmsfefn:-,+( ,gb 8-abtx pn17mjz59 fsv wcque in a generator opposes the motion.
a
b

Will an eddy current brake (Fig. Below) work on a copper or aluminum whe6e( wgxp/svy ey in5 pxjj.6((el, or must the wheel be ferromagnetic? Explasxgwiyp /56e j x(e(6nyv(pj. in.

It has been proposed that eddy currents be 8 e1lng3x fwu+rlr sx4+9kot; 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 o+3fl rt+8rxx1sl9 eg 4k;nuw 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 (Fig. Below) falls much mojiqb-i n46e; .qwa0olre quickly through a magnetic field than does a 0lqabi64 i-w.q nj; oesolid bar. Explain.

If an aluminum sheet is held 32e5 ajrte f(:mzo/ jhbetween the poles of a large bar magnet, it requires some force to pull it out of the magnetic field even though the sheet is not ferrom 5tejm2ah:j3z( eorf/agnetic and does not touch the pole faces. Explain.

A bar magnet falling inside a vertical metal tube reaches a t87 k:g(i+0wvaa fkyo merminal velocity even if the tube is evacuated so that there is no air resistance. Explain kv0 :w( gy8iamo+7akf.

A metal bar, pivoted at one end, oscillz ;hvp g:9,y 1e.gtgud-hgr+eates freely in the absence of a magnetic field; but in a magnetic field, it9g.reghu vhy;pezg,td-g +1:s oscillations are quickly damped out. Explain. (This magnetic damping is used in a number of practical devices.)

An enclosed transformer has four wcna *a7,sdu /mcy2o.pmv/cr/ ire leads coming from it. How could you determine the ratio of turns on the two coils without taking the tr ,a* /y.nmm7cup //dcsroavc2 ansformer apart? How would you know which wires paired with which?

The use of higher-voltage lines in homes — say, 600 V or 1200 V —sob.d 4s 8u/)ijw po8v would reduce evou8.b/p4sd s ji)w8 onergy waste. Why are they not used?

A transformer designed for a 120-V ac input will often “burn out” if cvc 4pqhrb 7o0tc:e-.ts .,pwt onnected to ae7c: vtot4wcb.h0pq.r - ,ps t 120-V dc source. Explain. [Hint: The resistance of the primary coil is usually very low.]

How would you arrange two flat circular coils r( j0:tn+cspydv* * mbso that their mutual inductance was 0m*cs*pny (tb+vd: jr
(a) greatest,
(b) least (without separating them by a great distance)?

Does the emf of the battery in (Fig. Below) affect the time nee m 21ht1*cugmfded for the LR circuit to reah t 1g*m12ufcmch
(a) a given fraction of its maximum possible current,
(b) a given value of current? Explain.

  In an LRC circuit, can the rma.t8wqz m w*,8l h*y fptts/:os voltage across
(a) an inductor, ----待选择----yesno 
(b) a capacitor, be greater than the rms voltage of the ac source? Explain. ----待选择----yesno 

Describe briefly how the fv9o5,p pm ioqfwy- -;drequency of the 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 impedanc )g:ctx +ux.a,d-vz-we f yg6ze in an LRC circuit a minimum.

  The magnetic flux through a coil of wire containing two loops change4-d:9d( y 7.gsu/qouxctnxqk oq g p du0g447gs from -50Wb to +38 Wb in 0.42 s. What is the emf induced(d q 4gqnd kgyd7uqs0g9-x.o47 /ut uog: cpx4 in the coil?    V

  The rectangular loop shown in (Fig. Below) is pushe4 w2fii42 b 7jns9*z mhurqv4:7bpzwhd into the magnetic field which points*hin9:mhv7 wp4iurbzs2z4 f 2b4qw7 j inward. In what direction is the induced current?  ----待选择----counterclockwiseclockwise 

  The north pole of the magnet in (Fig. Belo,x.jo oj v /r)jp (cx;e)xle;ew) is being inserted into the coil. In which direction is the induced curro.c x)eo;pj(,;ee xxj/ rl vj)ent 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 field;8xzi 0a r3egn;lzhc ng(-l4j . The loop is removed from the field in 0.1lhg80 zga(3xij;n r- 4nz;el c5 s. What is the average induced emf?    $ \times10^{-2 }\;V$

  A 12.0-cm-diameter loop of wire is initially oriented perpendicularkj30f p5hg6; ykug.wo to a 1.5-T magnetic field. The loop is rotated so that its6whgukj 3ok.0p fg ;y5 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 ir dlvj2c3 (9nqnitially oriented so that its plane is perpendicular to a magnetic field of 0.63 T pointing up. During the course of 0.15 s, the fieldc rvd 9qlj2(3n 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 loio7w hvb j):3ok.u (u0 +unfvxop of wire is placed in a 0.50-T magnetic field.
(a) When the plane of the loop is perpendicular to the field lines, what is the magnetic flux through the loop?    $ \times10^{-3 }\;Wb$
(b) The plane of the loop is rotated until it makes a 35$^{\circ}\,$ angle with the field lines. What is the angle $\theta$ in Eq. 21–1 for this situation? $\theta$ =    $^{\circ}\,$
(c) What is the magnetic flux through the loop at this angle?    $ \times10^{-3 }\;Wb$

  (a) If the resistance of the resistor in (Fig. Below),vxz*grq so-y tmsrcmm,* z b.26vq3- is slowly increased, what is *sbv-* qm-ry q2 g,,3mvzroxs c.zt6mthe direction 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 of tha2,px5 ,8 +ns/was:rdipd b0+f jvisae induced current in the circular loop due to the current shown in each part ofd,ns/8 5ai+2rp0wa,+ sai xpb d:jv sf (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 oxm. /4uoq11xthrk 4n shown, in what direction /t r.nkom4qhu11xo4 xis the induced current in the loop?  ----待选择----counterclockwiseclockwise 

  The magnetic field perpendicular to a circular wire loop)t3 a1oz/ehkt-p n z.;r-xzuy 12.0 cm in diameter is changed from +0.52T to -0.45 e1z- z 3tnxt a;-hk.yz u/)ropT in 180 ms, where means the field points away from an observer the observer.
(a) Calculate the induced emf.    $ \times10^{-2 }\;V$
(b) In what direction does the induced current flow?  ----待选择----counterclockwiseclockwise 

  The moving rod in (Fig. Below) is 12.0 2qpuogyc ,n3(8 s:xi fcm long and is pulled at a speed of 15.0cm/s If the magneti so3 xc8i q(yfnp:,ug2c 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 th)vc;wteo 5 p,iq)k v5ag/t : qhzoq23ue plane of the paper lies in a 0.75-T magnetic field pointing into ,; qc5)vutiohz)vq5k /ogta2p3wqe:the paper. If 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 ox +5z, em7kk*wm; kncd*f0ahgf 120 mV while mov zw0 ckf* 7n,a 5;m+hmkgk*xdeing in a 0.90-T magnetic field.
(a) What is its speed?    m/s
(b) What is the electric field in the rod?    V/m  ----待选择----updown 

  Part of a single rectangular loop of wire 2i(/- tufveyyapem4 .with dimensions shown in (Fig. Below) is situate .pyfia2e-ety( 4vum/d inside a region of uniform magnetic field of 0.550 T. The total resistance of the loop is $\mathrm{0.230~Ω}$ Calculate the force required to pull the loop from the field (to the right) at a constant velocity of 3.40m/s Neglect gravity.    N

  A 500-turn solenoid, 25 cm long, has a diameter of 2.5 cm. A 10-tucv1e;blu (o- xrn 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 indce(blu 1xo-;v uced 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 q .lzw*9pe,nfb md6)along, and has a resip*,6 b ned)ma9q.zflw stance 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 2x 2 tbvvubx3,5 4chpc7.6 mm in diameter. A uniform magnetic field, perpendicular to the plane of tvhxc ,b37t pb2cu x54vhe 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 perpenph9kf/bj/s w- z29ksu.1ndz xdicular to a single 13.2-cm-diameter circular loop of copper wire decreases uniformly from 0.750 T to zero. If the wire is 2.25 mm in diameter, how mk 9/ udsj2/k nzh9sfz1w bpx.-uch charge moves past a point in the coil during this operation?    C

  A simple generator is used to generate a peak outputf cof3jbb;; r,c:ild - voltage of 24.0 V. The square armature consists of windings that are 6.0 cm on -,cf;icr3j:dfb; o bla 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 idlin7spdlz5z6(k h g at 1100 rpm produces 12.4 V. What will the ou tput be at a rotation6z d s7kzl(p5h speed of 2500 rpm, assuming nothing else changes?    V

Show that the rms output (Section q l 2)+3g40cbmktuu b2ppvi2k18–7) of an ac generator is $V_\mathrm{rms}=NAB\omega/\sqrt{2}$, where $\omega=2\pi f.$

  A simple generator h+ 8ltf6ex;nv,yg:yt3r idx2cas a 320-loop square coil 21.0 cm on a side. How fast must it turn in a 0.650-T field to pro f ltigr 2cx 6v;8xdny+yte3,:duce a 120-V peak output? $f$   rev/s

  A 450-loop circular armature coil with a diam u)+i.q; hbozmeter of 8.0 cm rotates at 120rev/s in a uniform qzb .m+h;ui)omagnetic 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. jt2egukyh2 j5 ;:;ggrIt has 1000 turns and produces an y:e ;g ;uth5j2jgg r2krms 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 armature6jx) .z00tcc)r5, i +l) fawpipfxkm t 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 w/v se86tn i;vx-xwgx )hen operating at 1800 rpm. What would be the back emf e) x t6nxxs/-8;gwvviat 2500 rpm if the magnetic field is unchanged?    V

  The back emf in a motor is vu90:pzw lzh/ 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? reduce the magnetizl9 /h:uvpz0w c field to    % of its original value

  What will be the current in the motor of Example 21–9 if the load causeg7g9nr/g6 6 i( bdiq7m0mnrxzs it to run at half spe7in i/m70nq6xbg(mr6 r9 zgdged?    A

  A transformer is designed to change 120 V into 10,000 V, and there 5gz9k r 4hcf-bare 164 turns in the primary coil. How many turns are in the c -b rz9g4fk5hsecondary 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 the98d sj(5mfri(7dtbwn y :*oqk secondar:k7*(s5 imnfw ( rbdydqtj98oy coil as compared to the primary coil?   

  Neon signs require 12 kV for their operation. To operatenc* af+ul de,pc7hbnh*;.ty7 from a 240-V line, what must be the ratio of secondary to primary turns of the transformer? What would tdnf7;hthba lnc cy.pu,e +* 7*he voltage output be if the transformer were connected backward?
$\frac{N_\mathrm{s}}{N_\mathrm{p}}$ =   
$V_s$ =    V

  A model-train transformer plugs bufuhu 6wvu+ iwp;l0o7lh2ho ip1+7- into 120-V ac and draws 0.35 A while supplying 7.5 A to the train.owh01 7-u u7 2uih;6ilfho++p uvblpw
(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 currenm8jv cl:)okq2t is 22 A. :m jkovc8 lq)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 )4cuh.rw0ssn ehi g4/ primary turns and 1340 secondary turns. The input voltage is 120 V and the output cusi40uer sh . 4gc/nhw)rrent is 15.0 A. What are the output voltage and input current? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ =    V
$\frac{I_\mathrm{s}}{I_\mathrm{p}}$ =    A

  If 30 MW of power at 45 kV (rms) arrives at a th lq)r ror(zj fs(.n10own 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 2t5. s2sfr yikf 9d*ijp )rwf-r v*ne6over 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,*+*:wgb jfosskvy1u .0 A to 10.0 A in 350 ms, what is the magnitude of the indusfvujbkwo* gs+ *y1: ,ced emf?    V

  What is the inductanc:c p yac tmq6+yo q-hv j1hr2.wudn:))e of a coil if the coil produces an emf of 2.50 V when the curreny: 6r dcun)h qqmc-vy1):ot.aph2+j wt in it changes from -28.0mA to +31.0mA in 12.0 ms?    H

  What is the inductance L of a 0.60-m-long air-filled cskd:ba*xwp 8 1 fp:nk*/ud vsawgp/: 0p7(ydeoil 2.9 cm in diameter containing 10,:kd ys/w:da xu0ep( g bfpk */87a *w:1pnpvds000 loops?    H

  How many turns of wire would be required to maketa ;nbgx7sv55q ks rtw 8623q6p md3pz a 130-mH inductance out of a 30.0-cm-long air-filled coil with a diamete3 vg6md52t6nq5wxrkst p; b37 pqz8sar of 5.2 cm? L$\approx$    turns (Round to the nearest integer)

  An air-filled cylindrical inductor has 2800 tui4k+ i-ard r.grns, and it is 2.5 cm in diameter an-iga .drik r+4d 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 le ks9lm9j(k5la2bs54t ,c7qugzmnz;l ngth l and 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 solenoo*)kccxi3d;- 3a, a* d1tb clfb +pyqkid is unwound and used to make another tightly) kcdpi1 +3qlb;t xao,daccf by* 3*k- wound solenoid of twice the diameter. By what factor does the inductance change?   

  The magnetic field inprt ih3,fbp55sz eag;b3 9qw h0x;eq*side an air-filled solenoid 36 cm long and 2.0 cm in diameter is 0.80 T. Approximbx,0thwieh9as3bqg5;3; 5 fze pq *p rately how much energy is stored in this field?    J

  At a given instant the current throughbi )h oc:asze5 sko9a1*cfn-- an inductor is 50.0 mA and is increasing at the rate of 115mA/s. What is the initial energy stored in the inductor if the inductance is known to be 60.0 mH, and how long does it take for the energy to increase fzsie5 1s-:9 ch a)okob*-ncaby a factor of 10 from the initial value?
U =    $ \times10^{-5}\;J$
$\Delta$t=    s

  Assuming the Earth’s magnetic field averages abou xctwg- l7 kjz78i548ksc zyqkosx+20t $0.50\times10^{-4}\mathrm{~T}$ 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 withr ztpymkfc*uk6-ywlas 7z.5 0fb-6 2 xin
(a) 10%,    $\tau$
(b) 1.0%,    $\tau$
(c) 0.1% of its maximum value?    $\tau$

  Two tightly wound solenoids have the same length and circular cross-sect s ,v9t,zyxhz )fb8o*mional area. But solenoid 1 uses wire that is half as thick as solenoid ,hvx)bz mst8,o*9zy f2.
(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 g qnk62 gvng,,f; am5na $7.20-\mu F$ 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 ofv8 vm zttra;vht/*6q+ $660 \mathrm{k} \Omega ?$    Hz

  At what frequency willfx3gj)8fj:(kgw) qc l a $2.40-\mu F$ capacitor have a reactance of $6.70 \mathrm{k} \Omega ?$    Hz

Plot a graph of the reactav2f+rrog ) b/qb. rvt*nce of 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-mH inductor as a function of frequency f,cl+c8, a8lqq ky 2mc j;(agberj;y mg+l 8kc2,bq (a8qlcac,eom 100 to 10,000 Hz.

  Calculate the reactance of, and rms +t 5t-ehfwgca gzcoy4d i( 2))current in, a 160-mH radio coil connected to a 240-V (rms) 10.0-kHz ac g+)d( z )-t5fc4iwey aotc2ghline. Ignore resistance.
$X_L$ =    $\Omega$
V =    $ \times10^{-2 }\;A$

  An inductance coil operates at 240 V ane5zi:f c:vdvuj:g j jt( 91(ipd 60.0 Hz. It draws 12.8 A. What is the coil’s inductance?ge pj(: zjuv9:d: 51ficj(t vi $X_L$ =    $ \times10^{-2 }\;H$

  (a) What is the react,v6 j-,iu wlivgjg w(+ance 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 tb6qmb tt8 .x58 o,egorhrough the human body for 1.0 s could be lethal. What must be thb.m5gq trot, 6xb8o e8e impedance of the body for this to occur?    $ \times10^{3 }\;\Omega$

  What is the resistance of a o9+ cei/2) hgn zcsu:t4piu*scoil if its impedance is $\mathrm{235~Ω}$ and its reactance is $\mathrm{135~Ω}$    $\Omega$

  What are the total impedance, phase angle, and rms current in an LRC circubu/i+ot- /7,mblp fzc89id neit connected to a 10.0-kHz+toidfb98uinc/emp 7,-/ lz b, 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 m8e*:0 s r5hui6 qrwq1*nyhgub +/wx ja 420-mH inductor is driven by an ac power supply. At what frequency is the impedance double th r51 yq8b*mwx g6h*urnw0hui sqj:+/eat of the impedance at 60 Hz?    Hz

  (a) What is the rms current in an RL circuit when a 60.0-Hz 120-V rms ac bx*/ 9vm3(mxhz)l dj jvoltage is apl3mxj9vm(x)* zjhbd / plied, 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 currenti)m;2u wzxq 5p; ttur4g 7u43f/v spyu 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 connz*jc z,bnfyr9-6( mjlected 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 tunef6d0l l+3kz icr of an AM radio has a capacitance of 2800 pF when the radio is tuned to a station at 58iz ld+f0kl36c 0 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 anbu2co,j *p0zsr nu:z*d $R=4.40\Omega$.
(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 currendhk73oa*5r lhhja* w,esv7a.hkfi- * t loops in the plane of the page as shown in (Fig.7dhila ksh fk7v,e3*h 5**ar-o.j awh Below). When 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 cm on a side has a resistaz1b)rpa7ram . nce 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 but3j5c9m5zpr+gsr k x z; requires only 12 V. It contains a transformer that converts 120-V househorm3;+9 prcs5 xzzkgj5 ld voltage.
(a) Is the transformer step-up or step-down? this is a  ----待选择----step-downstep-up  transformer
(b) What is the current in the secondary coil when the lamp is on?    A
(c) What is the current in the primary coil?    A
(d) What is the resistance of the bulb when on?    $\Omega$

  Power is generated at 24 kV at a generating plant located 118 km from 7q1cei*/hdcx4( rmg sa town that requires 50 MW of power at 12 kV. Two transmission lines from the plant to the towcrh cedx*4mg(7 i1q/sn 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 :) )xn57-oin geivbz fan 80% efficiency are connected to 110-V ac. T fbigi)ex5:)n- 7 znovhe 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 transmissions7zko+2 irlq:uyp o)* lines each have a $0.80-\Omega$ resistance and carry 740 A over 9.0 km. If the rms input voltage is 42 kV, calculate
(a) the voltage at the other end, $\approx$    kV
(b) the power input, $\approx$    $ \times10^{7 }\;W$
(c) power loss in the lines, $\approx$   $ \times10^{5 }\;$W
(d) the power output. $P_{out}$ $\approx$    $ \times10^{7 }\;W$

  Two resistanceless rails rest 32 yx*e6e(sg77r 0di18aa mds cs 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 trans/svvyfz1 vip h d4cpj38n50i +mission 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 resis cqb25yz jcjlxchaf,ckm 5c-u35. .)x tance 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 ;s) t1z4n wh4 )pdnhamprotected against sudden surges in current. In parpnhsw1) ) mt;4an4hzd ticular, after the power is turned on the current should rise no more than 7.5 mA in the first $120\mu s$ The device has resistance $\mathrm{150~Ω}$ and is designed to operate at 55 mA. How would you protect this device? L $\approx$    in series(retain two decimal places)

  A 25-turn 12.5-cm-diameter coil is placed between the pole pieces of an ect s6de-d .6a;fsu( lz:igcq: lectromagnet. When the magnet is turned on, the flux through the coil changes, inducing an emf. At what r6 cc.ddz s:ie sa-lfgqu6;t :(ate (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 voltage of a simple generator whose square armatukq3zh qfn5kjx+,s;b)re windings are 6.60 cm on a side; the armature contains 155 loops and rotates inqkxfks) n5bqjzh ,;+3 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 labo/n5bti+ ag (oxratories are about(igoa/ t+ n5xb $1.0\times10^4\mathrm{~V/m}$ 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 sdgoz/a9na* t.cy;f 4of a transformer whose input is 220 V at 60.0 Hz if sd*oyan/4a.czg;t 9f the current drawn is 5.8 A? Assume no current in the secondary.    H

  A 130-mH coil whose resistance0za l,)qlp* .0;bmjgr+tangy 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 2.5-A dc when 4gl/(-w 4qaw- mqyqjjoi 2hb*connected to a 36-V battery. When connected tjqam /q-lqjob4wh*gw (4y -i 2o a 60-Hz 120-V (rms) source, the current drawn is 3.8 A (rms). Determine the inductance and resistance of the coil.
$V_{dc}$ $\approx$    $\Omega$
L $\approx$   $ \times10^{-2 }\;H$

  A 135-mH inductor withslsbzcyc l q),t) jqz y7).4;i $2.0-\Omega$ 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 o jimilua*qnl:bb 266 4f the voltage across the capacitor (or inductor) to the voltagn6il2ai* l4bju :qbm 6e across the resistor, at resonance. The larger the Q factor, the sharper the resonance curve will be and the sharper the tuning.
(a) Show that the Q factor is given by the equation $Q=(1/R)\sqrt{L/C}.$
(b) At a resonant frequency $f_0=1.0\mathrm{~MHz},$ what must be the values of L and R to produce a Q factor of 550? Assume that $C=0.010\mu\mathrm{F}.$ L $\approx$    $ \times10^{-6 }\;H$(retain one decimal places) Q =    $ \times10^{-2 }\;\Omega$