What would be the advantage, in Faraday’s experiments (Fig. Below) +lld)mvcs65o, of using coils with many tov d5cm6+ ll)surns?

What is the difference begqy 7a2b oqcxb)70mm3tween magnetic flux and magnetic field?

Suppose you are holding a circular ring of wire and s7lns0k ijp *3f8/+bq)y:wzn lqu9j l juddenly thrust a magnet, south pole first, away from you toward the center of the circle. Is a current induced in the wiq3jlqsniwp)jl+ u:9 7bzlf8jy *n /0k re? 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 long straigh1y8n trocup10 )o n/qjt wire carrying a steady current as shown in (Fig. Below81r c/pot)01ojyuq nn ). Find the direction of the induced current in each loop.

Suppose you are looking along a line tu4qrkhe4 v *u4 2tu4o*kypv dmd27(j ype)9wvhrough the centers of two circular (but separate) wire loops, one behind the other. A battery is suddenp2uk ydj*yv*)dt 4v re4q7m924v4hu(uk wepo ly 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 dii;wwbc 455i;k o avtm 5+hcii0rection of the induced current in resistor $R_A$ when
(a) coil B is moved toward coil A, ----待选择----increasedecrease 
(b) when coil B is moved away from A, ----待选择----increasedecrease 
(c) when the resistance $R_B$ is increased. ----待选择----increasedecrease 

In situations where a small signal must travel over a distance, a “shih2gxr2 x g5d,aelded cable” is used in which the signal wire is surrounded by an insulaarg,x225h g dxtor and then enclosed by a cylindrical conductor carrying the return current. Why is a “shield” necessary?

What is the advantage of placing the two insulat dxffi,;gdq*) ed electric wires carrying ac closd *gf,qd)x i;fe together or even twisted about each other?

Explain why, exactly, the lights may dim br1-va(y sp if1xiefly 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. Exp11 yvf sa-ix(plain the difference.

Use (Fig. Below a) and (Fig. Below b) plus the right-hancjmiy2a,4 uq3v ikmq) 6)hn/ od rules to show why the m3jq)c4q 6aui/nv )iyhom,k2counter torque in a generator opposes the motion.
a
b

Will an eddy current brake (Fig. Below) work on a copper ok/h jnm7bp4f88 in;t pr aluminum wheel, or must the wheel be ferrop /;88hf4itk jnnbmp7magnetic? Explain.

It has been proposed that eddy currents be used to help sort solid waste fo+q 4iiqehg3ed *cxo10 r recycling. The waste is first ground into tiny pieces and iron removed with a dc magnet. The waste then is allowed to slide down an incline over permanent magnets. How will this aid in the separation of nonferrous metals (Al, Cu, Pb, 3d0io h c1x*+eiqq 4gebrass) from nonmetallic materials?

The pivoted metal barz(**(z kyp/xhncr2, z. qcxf d8-bope with slots in (Fig. Below) falls much more quickly through a magnetic field than does a solid bar. p2 ropb8fc/cd k-y *xn.z*((,hzqzxe Explain.

If an aluminum sheet is held between the poles of a l uny1gx 8xh:*zarge bar magnet, it requires some force to pull it out of the magnetic field even though the sheet is not f8 x1zux:n* yhgerromagnetic and does not touch the pole faces. Explain.

A bar magnet falling inside a vert 0;1rtek2hyfw ical metal tube reaches a terminal velocity even if the tube is evacuated so that there ihfr;102kew y ts no air resistance. Explain.

A metal bar, pivoted at one end, oscillates freely in the absence of;nf* fvayb50x ,2xw1nwyp*x*3k y t.r x puep2 a magnetic field; but in a magnetic fipp2xyw yufxvtrfwb* nxnpy*2xk 13a. e,*0;5eld, its oscillations are quickly damped out. Explain. (This magnetic damping is used in a number of practical devices.)

An enclosed transformer has four wire leads coming from it. How could you detjjunca97n ;8 i5p4tz hermine the ratio of turns on the two coils without taking the transformer apart? Hoznhjj;45u8cnti9 7 a pw would you know which wires paired with which?

The use of higher-voltage lines in homes — say, 600 V or 1200 +xz-gtfk ; /gtV — would reduce energy waste. Why are th;/+tfz k- gtgxey not used?

A transformer designed for a 120-V ac input will often “burn out” if cmafz v*1 a34pqonnected to a 120-V dc source. Explain. vfz3q14m*a p a[Hint: The resistance of the primary coil is usually very low.]

How would you arrange two flat circular coils so that their mutual inductan chc6hwk1+s x 0d+n9iko3/vp tce wa 6xv90ts/dck oc k+i3w hph+n1s
(a) greatest,
(b) least (without separating them by a great distance)?

Does the emf of the battery in (Fig. Below) affect the time neep4 h, k2/dqmnjded for the LR circuk j/dmnh4 2,pqit 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 volta(op 6gzad6y2m ge across
(a) an inductor, ----待选择----yesno 
(b) a capacitor, be greater than the rms voltage of the ac source? Explain. ----待选择----yesno 

Describe briefly how the frequency of the source emf aq/zjebzk1 pf 6::g3qj ffects the impedance of
(a) a pure resistance,
(b) a pure capacitance,
(c) a pure inductance,
(d) an LRC circuit near resonance (R small),
(e) an LRC circuit far from resonance (R small).

Describe how to make the impedance in an LRC circuit a minipvsiw9iupwkqa30l8+w (fx:3 i b(o 5fmum.

  The magnetic flux through a coil of wire containing twon,+km rl3lvx mh,aj :1 loops changes from -50Wb to +38 Wb in 0.42hm :,1lkvlrxj3m+ a n, s. What is the emf induced in the coil?    V

  The rectangular loop shown in (Fig. Below) is pushed into the uett3. *gdczc az+c 54magnetic field which points inward. In what direction is theztuctga3c*e+d.4c z5 induced current?  ----待选择----counterclockwiseclockwise 

  The north pole of the magnet in (Fig. Below) is being inserter2r0 /n bgsan w5))wjzd into the coil. In which direction is the induced current flowing througrrbs 2z0j5 )anng ww)/h 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. The loo q*u 9)s-gj1dkonuj q:p/hkb7;0vh kv p is removed from the field in 0.15 s. What is the averankdojp/ uqs1v gb hu0h:*k) 9j7kq;-vge induced emf?    $ \times10^{-2 }\;V$

  A 12.0-cm-diameter loop of wire is initially oriented perpendiculkd;cv- bjb;3b; wv tl:ar to a 1.5-T magnetic field. The loop is rotated so th;wlv cvjbb;t ;-:db k3at its plane is parallel to the field direction in 0.20 s. What is the average induced emf in the loop?    $ \times10^{-2 }\;V$

  A 10.2-cm-diameter w+ialfb da13.mqbg c 45ire coil is initially 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 field is changed to one of 0.25 T pointing down. What 41alqfc i5bm3+ga. bd 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 fiely2 )u: myd o9l0ndhr b*+45k xsofk1rkd.
(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 resisuu:o;28dah , tgao *zator in (Fig. Below) is slowly increased, what is the direction of the current induced in theh*ut,d ;aa:g8au2 ooz small circular loop inside the larger loop?  ----待选择----counterclockwiseclockwise 
(b) What would it be if the small loop were placed outside the larger one, to the left?  ----待选择----counterclockwiseclockwise 

  What is the direction of the indgi/3(2tsjjfib a y+s 4uced current in the circular loop due to the current shown in each pf 3j+js (4tisa/ gbi2yart 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 0;c xm a7wzv-xfrom the loop shown, in what dir0z;7ax wvx mc-ection is the induced current in the loop?  ----待选择----counterclockwiseclockwise 

  The magnetic field perpendicular to a circular wishi).50urmpyvqf// cu ff5a 2re loop 12.0 cm in diameter is changed from +0.52T to -0.45 T in 180 ms, where means the field points away from an 25.)/uh/puv f 0a5rfqmcyi s fobserver 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 atk z;e sh81ob9t5 ynn+a,qx1 wh a speed of 15.0cm/s If the magnetic field iq, 1hkhn8e9;5nzsto+xb1a wy s 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 bi88j)2 dzqxr2+toc s lies in a 0.75-T magnetic field pointing into the paper. If the loop’s diameter changes from 20.0 cm to 6.0 cm in 0.50 c 8djr)22bi oxq+8zsts,
(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 13p7pzd b6v;) p6,vfu qm.2 cm long and generates an emf of 120 mV while )pqd6vpb ,m6u;vfpz 7moving 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 with tct xlc2 47) hemt a(xlimzj32( 2sx:rdimensions shown in (Fig. Below) is situated inside a region of uniform magnetic fiettl(3i2c x)ex4m2cst xj2:lzh am7 r(ld 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 diok11 arz cysh.35k2hp 5.9go v 7njupmameter of 2.5 cm. A 10-turn coil is wound tightly around the center of the solenoid. If the current in the solenoid increases uniformly from 0 to 5.0 A in 0.60 s, what will be the induced emf in the short coil 31s52y u.9ghm5kzja npkr 1 .7opchov during this time?    $ \times10^{-4 }\;V$

  In (Fig. Below), the rod moves with a speed of .fqiyfp6;n 0w7 (wzcqrjn(k1 1.6m/s is 30.0 cm long, and has a r;jr1kf(f 6wz inc wn0qq. (yp7esistance 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 wirehorzr8mot2u . yb(2f)8.qk w,xqeb* r 2.6 mm in diameter. A uniform magnetic field, perpendi)k xo(yzh *b2ue.wm.8rt q frbq,82rocular 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-di.qz8qm)ro6zp3 j7pqh jr6bx1 ameter circular loop of czq 8j36 objq6r r)m17hx.zp qpopper 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 generate a peak output voltage of 24.0 V. Thde/eck8xv p b8 ymjz5(v ,h)ptv2.i3b e square armature consists of windings that are 6.0 cm on a side and rotates in a field of 0.420 T at a rate of 60.0rev/s How many loop(dc ),hb8vzxje 5/ vyebv 2mpi3.kp8 ts of wire should be wound on the square armature? $\approx$    loops(Round to the nearest integer)

  The generator of a car idlingr7x r.i6j*cm(hht w vih7 q62q at 1100 rpm produces 12.4 V. What will the ou tput be at a rotation speed of 2500 rpm, assuming nothing e *6rhqr vw76qhihxc(72j.ti m lse changes?    V

Show that the rms output (Section 18–7) of an ac gener /d th) (,o,zp arwxl1vkf5:hrjs4s q+ator is $V_\mathrm{rms}=NAB\omega/\sqrt{2}$, where $\omega=2\pi f.$

  A simple generator has a 320-loop square coil 21.0va9qp g.0h2lj cm on a side. How fast must it turn in a 0.650-T field to produce a 120-V peak g.29ja qph0vl output? $f$   rev/s

  A 450-loop circular a9*0qhul 2 n*1cqjgog5:f knn frmature coil with a diameter of 8.0 cm rotates at 120rev/s in a uniform magnetic field of strength 90qh 5 :n*1qfng gu clj2nkof*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 has 1z-e *hfw5:sxelx0ia 6000 turns and produces an rmhse5-i ae xz0wl6*:fxs voltage of 150 V and an rms current of 70.0 A.
(a) What is the peak current produced?    V
(b) What is the area of each turn of the coil?    $ \times10^{-2 }\;m^2$

  A motor has an armature rjr+ w.o.0u)yh+qwxjhz-h i0e +hycn, esistance of $3.25\Omega.$ If it draws 8.20 A when running at full speed and connected to a 120-V line, how large is the back emf?    V

  The back emf in a motor is 72 V when operating at 1800 rpm. What would be the s(gqrka -pr-0dag*xu r + +:l6mheik3back emf at 2500 rpm (h0 -+kr6g e:+r gkxsdmpali qu*-r3aif the magnetic field is unchanged?    V

  The back emf in a motor is 95 V when the motor is o6j*ze,yq;w jwk rh *8iperating 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 runnih6,z*jj* ; eqy iwrk8wng at 2500 rpm? reduce the magnetic field to    % of its original value

  What will be the current infz/n /la5/b3dn7iek y the motor of Example 21–9 if the load causes it to run at half sbd n yz///ki5le7 3nfapeed?    A

  A transformer is designed to chan 0g6 jev5q8;vfozyv 6mge 120 V into 10,000 V, and there are 164 turns in the primary coil. Howv5;q yf8 mevo6j6zv0g many turns are in the secondary coil? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ $\approx$    turns

  

  A step-up transformer increaseskt-r;mh6gw v5 25 V to 120 V. What is the current in the secondary coi -;h tmgv65kwrl as compared to the primary coil?   

  Neon signs require 12 kV for their operation. To operate from a 240 allorfw/6+ol*7x 2cj-V line, what must be the ratio of secondary to primary turns of the transformer? What would the voltage outpu +rxlc6ajoll* 7/o2wf t be if the transformer were connected backward?
$\frac{N_\mathrm{s}}{N_\mathrm{p}}$ =   
$V_s$ =    V

  A model-train transformer plugs into 120-V ac an jm6msf(rw v:4d draws 0.35 A while supplying 7.5 A to the train4 f6wmjsmvr:(.
(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 *tjfj3 +- owagV, and the input current is 22 A. a+ gowt3jf-* j
(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+j69w r3mj/7 t lshsve input voltage is 120 V and the output current is 15.0 A. What are the output voltage andh3 7tw/jsesljrm6 v9 + 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 t7inhl a tjzv9c7 p,-;1d 7wr.x1k hhluown 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 over twoqezil7:, lsxo 6eo 8b)09jg ap $0.100-\Omega$ lines. Estimate how much power is saved if the voltage is stepped up from 120 V to 1200 V and then down again, rather than simply transmitting at 120 V. Assume the transformers are each 99% efficient.    kW

  If the current in a 180-mH coil changes steadily from 25.0 A to 10.p(/z ) q1ajgr; cdj9ch0 A in 350 ms, what is the p/ gj zdjc( 1arh9;q)cmagnitude of the induced emf?    V

  What is the inductance of a coil if the coil produces an emf of 2.50 V wh*d4l1 grhg + pdysgsq: (xx98wen the current in it changes hs+px9:g (1g8 dsxql4*y d rwgfrom -28.0mA to +31.0mA in 12.0 ms?    H

  What is the inductance L of a g z,ngt:l(e *v0.60-m-long air-filled coil 2.9 cm in diameter containing 10,000 loops? *z(ev:gtlg,n    H

  How many turns of wire would be required to make a 156 f hxkk 3y) qm23n- f1)edqqtw6bnomw)g-kv30-mH inductance out of a 30.0-cm-long air-filled coil with a diametk3qb nmdqkx)h- f6 tvg2efn kqm))31wywo -56er of 5.2 cm? L$\approx$    turns (Round to the nearest integer)

  An air-filled cylindrical inductor has 2800 turns, at85.wo2xlv4v ydt ( abnd it is 2.5 cm in diameter and 28.2 ctdx4vy2tl (vw5 oab8.m long.
(a) What is its inductance?    $ \times10^{-2 }\;H$
(b) How many turns would you need to generate the same inductance if the core were iron-filled instead? Assume the magnetic permeability of iron is about 1200 times that of free space.

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

A long thin solenoid of length l and croscdb8 ccdyaa*6 r-fn+m5- rie+ s-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 solenocq3yqp79v -dzv os6p ,) 4nl7ldhpx9j id is unwound and used to make another tightly wound solenoid of twice9n z p odsdxvpylp)64l,-7v qcjqh79 3 the diameter. By what factor does the inductance change?   

  The magnetic field inside an air-fi-.+-q ew)6p7io7phtowp fl7v4qn r dzlled solenoid 36 cm long and 2.0 cm in diameter is 0.80 T. A.weiv7ntp) lfd4w7o po- +q-7qph zr6pproximately how much energy is stored in this field?    J

  At a given instant the current through an inductor is 50.0 mA and isrs4 oi/u dvfp/i( j98g 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 ord9j gi /vs/4f8( ipouf 10 from the initial value?
U =    $ \times10^{-5}\;J$
$\Delta$t=    s

  Assuming the Earth’s gin)3 cr66ul04 zgemyqcl s-9magnetic field 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 constants does the current in xf ml),y-,9taaroemht s8r .2(Fig. Below) reach within
(a) 10%,    $\tau$
(b) 1.0%,    $\tau$
(c) 0.1% of its maximum value?    $\tau$

  Two tightly wound solenoids have the same length and cm 2j8*ws/ywdn 7nwp 6circular cross-sectional ar8dj 6nw7 y*w/cpmns2wea. But solenoid 1 uses wire that is half as thick as solenoid 2.
(a) What is the ratio of their inductances? $\frac{L_1}{L_2}$ =   
(b) What is the ratio of their inductive time constants (assuming no other resistance in the circuits)? $\frac{\tau_1}{\tau_2}$ =   

  What is the reactance ofu9))29io.irmujsjhbg6 v 8y b 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 g t4 / 0byrkuxybi:6iq,7qs:ja reactance of $660 \mathrm{k} \Omega ?$    Hz

  At what frequency will ai)bx1m4kp6jy4mfzd1ugc,v0 $2.40-\mu F$ capacitor have a reactance of $6.70 \mathrm{k} \Omega ?$    Hz

Plot a graph of the reactance of xd e) vxo-.0j iw.fn3ups+, kua $1.0-\mu F$ capacitor as a function of frequency from 10 to 1000 Hz.

Plot a graph of the reatg8*. uyxdw / 2uw *cp99cplsactance of a 1.0-mH inductor as a function of frequency from 100ygw8p p x2tc s/9c*l*du9aw.u to 10,000 Hz.

  Calculate the reactance of, and rms current in, a 160-mH radio coil 17, o umuu0(xocq 9(;n mv3zhxrx1ibxconnected to a 24n m; ,((3x hoxrzocux0uu 1qi197bv xm0-V (rms) 10.0-kHz ac line. Ignore resistance.
$X_L$ =    $\Omega$
V =    $ \times10^{-2 }\;A$

  An inductance coil operates at 6g3 is;wdeg,,lv+laz0m vd(l240 V and 60.0 Hz. It draws 12.8 A. What is the csl, wvlldgmg3e0da, (6zi +;voil’s inductance? $X_L$ =    $ \times10^{-2 }\;H$

  (a) What is the reactance of a well-insulag n 2 my9lrz-.s tj(7ltf syv0,x.9enbted $0.030-\mu F$ 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 voltag g9xc4 i(,lgq z)*loage, an rms current of 70 mA passing through the human body for 1.0 s could be lethal. What must be the imped x 4ogglz9,(ic)l aqg*ance of the body for this to occur?    $ \times10^{3 }\;\Omega$

  What is the resistance of a ke83b h97 soujcoil 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 3v/e+(9mok5kr5x -l npif ea tLRC circuit connected to a 10.0-kHz, mi+t- nvk 5exk(ap e3/olrf95 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 420-mH induh9de95iq:e ;li 3eebne dnr:-ctor is driven by an ac power supply. At what frequency is the impedance double that of the impedance at 6 ;:he ed59q-elbnni: ed r39ie0 Hz?    Hz

  (a) What is the rms curren wvur:*+-fd sct in an RL circuit when a 60.0-Hz 120-V rms ac voltage is applied, where:v -fsuw* +dcr $R=1.80\mathrm{~k}\Omega,$ 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 dksaej 4z,8t6m; j*mi61e vhlan 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 cozjpz cjqqf)i-01+-j4 s , txhznnected to a $55.0-\mu H$ coil of resistance $3.00\Omega.$ What is the resonant frequency of this circuit?    $ \times10^{5 }\;Hz$

  The variable capacitor in the tuner of an AM radio has a capacitance ox,0feakhq 6 wimn v0:)f 2800 pF wh ,whq)x:fanke6vmi 00en the radio 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 and am4in2s5ao-6jg 6pmp$R=4.40\Omega$.
(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 - *pbvv gzbz3-glo9/tin the plane of the page as shown in (Fig. Below). When swit -/ bvtb9ogvlpzz*-3gch 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 resistance o:j7ev ne3pt5 .duspg. f $5.20\Omega.$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 9nzz (yl .jatj,mu g+/W but requires only 12 V. It contains a transformer that converts 120-V houseagzl yj.j,u+z m9(nt/ hold 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 lb ,k3 ucnde5ln3r;6gd .lz9) o3s:ekyskpr0p ocated 118 km from a town that requires 50 MW of power at 12 kV. Two transmissi;yrz,5d l0 ncp6) lokkb s9skrd:e3u33.p ngeon 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 trykdu:j( 2nbj:hdzall;4 *1b fansformer which has an 80% efficiency are connected to 110-V ac. The secondary winding:;ad (: b4lkzjj ynd2l*b1fuhs are connected across a $2.4-\Omega$ 75-W lightbulb.
(a) Calculate the current through the primary windings of the transformer. $P_S$ $\approx$   A
(b) Calculate the ratio of the number of primary windings of the transformer to the number of secondary windings of the transformer. $\frac{N_\mathrm{p}}{N_\mathrm{s}}$   

  A pair of power transmission lines each have no a0gngd2 h; *be77(mefre ):vsn.bs 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 railsb.z ks7)nk; ciqm ,gc. rest 32 cm apart on a 6.0$^{\circ}\,$ ramp. They are joined at the bottom by a $0.60-\Omega$ resistor, and at the top by a copper bar of mass 0.040 kg (ignore its resistance) is laid across the rails. The whole apparatus is immersed in a vertical 0.55-T field. What is the terminal (steady) velocity of the bar as it slides frictionlessly down the rails? v =    m/s

Show that the power loss in transmissioxo hf2gzvp /e,uu / :dqn/;lf:n 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 5.04e- i,m5csddl 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 brgc rm.mjqj;e6.r.u c7+5: l7lr nu nprotected against sudden surges in current. In particular, after the power is turned on the current should rise no more than 7.5 mA in the fir 5;cm:rmjgrl.n.cu6. nrj bq+el 7r 7ust $120\mu s$ 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 cop2m0 ukzs ye3.il is placed between the pole pieces of an 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 they m.k23sue0zp emf is to be 120 V? $|\varepsilon|$    T/s

  Calculate the peak output voltage of a simple generator whos7cr (l lw,oa7ae square armature windings a(w ,orlcal77a re 6.60 cm on a side; the armature contains 155 loops and rotates in a field of 0.200 T at a rate of 120rev/s. $\varepsilon_{peak}$ =    V

  Typical large values for electric and magnetic fields attained in a+5vue(rb o*xeq 3z/qt 4r6mllaboratories are aqroetqx6b3uz(e4+ *r 5lv/am bout $1.0\times10^4\mathrm{~V/m}$ and 2.0 T.
(a) Determine the energy density for each field and compare.
$u_E$ $\approx$    $ \times10^{-4 }\;J/m^3$
$u_B$ $\approx$    $ \times10^{6 }\;J/m^3$
$\frac{u_B}{u_E}$ =   $ \times10^{9 }\;$
(b) What magnitude electric field would be needed to produce the same energy density as the 2.0-T magnetic field?    $ \times10^{8 }\;V/m$

  What is the inductance L of the primary of a transformer whose input is 223hnn- pl k9rm-q2uu(e0 V at 60.0 Hz if the current drawn inq93-l eu umnpkr2-(hs 5.8 A? Assume no current in the secondary.    H

  A 130-mH coil whose resis cd; rn-p 4jkbuu.0.mttance 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 connected to a 36-V batter0,bov9mnk:w o /fd n,gy. When connected to a 60-Hz 120-V (rms) source, the current drawn is 3.8 A (rms). Determine the inductance and resv wkdo9mnn b gfo:0/,,istance of the coil.
$V_{dc}$ $\approx$    $\Omega$
L $\approx$   $ \times10^{-2 }\;H$

  A 135-mH inductor with odrlpf04tdavu zx4z has- . t/ 45r7p*$2.0-\Omega$ 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 th .t7rh )iq5gu+/ergpge voltage across the capacitor (or inductor) to the voltage across the resistor, at resonance. The larger the Q factor, th+ig)u.hr5g/p 7et rqge 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$