What would be the advantage, in Faraday’s dna-priq 5 )lp /0qvk;experiments (Fig. Below), of using coils with makvl pir/5 qq-;)np a0dny turns?

What is the difference betwfxcsk( wd- s2/een magnetic flux and magnetic field?

Suppose you are holding a circular ring ofsz og:dn4-8 y vn((8jenebov1 wire and suddenly thrust a magnet, south pole first, away from you toward the cev-ed jnn b8no:z(1(y o4gvs8e nter 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 of a very long sds3z i6c92ow2fah1 skwf hc7/traight wire carrying a steady current as shown in (Fig. Below). Find the direction of the induceoc w 2fhsf 367w/1i 2sdc9zhakd current in each loop.

Suppose you are looking along a h/e lgm)a(16h 8oqhuwline through the centers of two circular (but separate) wire loops, one behind the other. A b /a eo)umqh( 8w61lghhattery is suddenly connected to the front loop, establishing a clockwise current.
(a) Will a current be induced in the second loop?
(b) If so, when does this current start?
(c) When does it stop?
(d) In what direction is this current?
(e) Is there a force between the two loops?
(f) If so, in what direction?

  In (Fig. Below), determine the direction of the induced current in resistor8mdv,y8sv ex9ui(zm k y/7t h; $R_A$ 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 distan d;jq-ii 2 y.bt6prbp :bn5n2bce, a “shielded cable” is used in which the i: ydibnjbr-t.b6;q25pb2 n psignal wire is surrounded by an insulator and then enclosed by a cylindrical conductor carrying the return current. Why is a “shield” necessary?

What is the advantage of placing the0n1u)io0z xpu-vy aw: two insulated electric wires carrying ac close to 0uuzv w0 ypoai)x1:-ngether or even twisted about each other?

Explain why, exactly, the lights may dim briefly when a refri p u44vw aw6)b*ohk)psgerator motor starts up. When an ele)kwh4*w 4bsa) vp 6opuctric heater is turned on, the lights may stay dimmed as long as the heater is on. Explain the difference.

Use (Fig. Below a) and (Fig. Below b) plus the right-han*sx+i) xrpnu. ym s5jas:0uh jlw92 +td rules to show why the counter torque in a generator opposes theu.+ntjxu)*i5lhss yx p sra2wj:0m9 + motion.
a
b

Will an eddy current brake ( brwx.eek)rrt:; (i x7Fig. Below) work on a copper or aluminum wheel, or must the wheel be ferrtr)kx(r:wexr b7ei. ;omagnetic? Explain.

It has been proposed that eddy curqfp;qj0 -mb:n rents be used to help sort solid waste for recycling. The waste is first ground into qb0-mf:n;pj qtiny 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, brass) from nonmetallic materials?

The pivoted metal bar with slots in (Fig.)dihj,jhm)a;u(u8nu Below) falls much more quickly through a magnetic fi iau8 h )n)d(;jmj,uuheld than does a solid bar. Explain.

If an aluminum sheet is held between the poles of a large bar maaxn*rg4hb27 egnet, it requires some force to pull it out of the magnetic field even though the sheet is not ferromagnetie har*n2g 7b4xc and does not touch the pole faces. Explain.

A bar magnet falling inside a vertical metal tube reaches a terminal velo*q aa7gv(zstr1s4f . +vco fv;city even if vfqg(ar+v a1zc7 fs.;4t vso* the tube is evacuated so that there is no air resistance. Explain.

A metal bar, pivoted at one end, oscillates f 6 1,y)ae7jcpguc f0enreely in the absence of a magnetic field; but in a magnetic field, its oscg )0,auj1 ecn6ycfep7illations 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.dq/s ss0(7wbo kh) 4rd t+bqp1 How could you determine the ratio of twbp+dht7 sordq)0 (q b4s/sk1urns on the two coils without taking the transformer apart? How would you know which wires paired with which?

The use of higher-voltage lines in homes j3:r4 vgv2y(mxtn axhudc 154— say, 600 V or 1200 V — would reduce energy waste. Why are they n1tyu 4x j5x g3c4md a:2vn(rhvot used?

A transformer designed for a 120-V ac input will often “burn ouxm tm,xy v9b8jt 3+jn1p v)nb)t” if connected to a 120-V dc source. Explain. [Hint: The resistance of the primary coil is usually veryx vt9n+m8j3 mv,bbyjt 1p)x)n low.]

How would you arrange two flat circulauh.gk.n + 7l,pv:a;:5q*mijdv lym m tr coils so that their mutual inductance wa l kjvm:h7i+yv,uqmg* p;ldam :n5.. ts
(a) greatest,
(b) least (without separating them by a great distance)?

Does the emf of the baa5/ j.egkj*6knc s;sh ttery in (Fig. Below) affect the time needed for the LR circuit to reach ac6*j hk5 gjss./;ekn
(a) a given fraction of its maximum possible current,
(b) a given value of current? Explain.

  In an LRC circuit, can the rms voltage acrbcga6j6wpl ) e8dtx gqce(10 6oss
(a) an inductor, ----待选择----yesno 
(b) a capacitor, be greater than the rms voltage of the ac source? Explain. ----待选择----yesno 

Describe briefly how the frequency of the source emf affects be (37zd-ttt9 bu-omgthe 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 iky-ac*b*zrtr 3*8wkthe impedance in an LRC circuit a minimum.

  The magnetic flux through a coil of .reti m4 dai*6o4p+h y bg+3qfwire containing two loops changes from -50Wb to +38 Wb in 0.42 s. What is the emf induc h*4+f6 e boryatmp4i di3+gq.ed in the coil?    V

  The rectangular loop shown in (Fig. Below) i7r02,s , . :vbpwudnoyc8ovk rs pushed into the magnetic field which points inward. In what direw,ckds0,up o b7.:y no8vr2rv ction is the induced current?  ----待选择----counterclockwiseclockwise 

  The north pole of the magnet in (Fig. Below1i 3ac qk;jp7n) is being inserted into the coil. In which direction is the induced current flowing through the resistor Ri ; cjp37ka1nq?  ----待选择----from right to leftfrom left to right 

  A 9.6-cm-diameter circuln3aqjtchf 7b)39cnm ,)z(u cy ar loop of wire is in a 1.10-T magnetic field. The loop is removed from the field in 0.15 s. What is the average indu 93n mh3bf,t(qnc)7cyj)azu cced emf?    $ \times10^{-2 }\;V$

  A 12.0-cm-diameter loop of wire is initially orientn b69..du sjpwed perpendicular to a 1.5-T magnetic field. The loop is rotated so that its plane is parallel to the field direction in 0.20 s. What is the average induced e s..uwpj9d b6nmf in the loop?    $ \times10^{-2 }\;V$

  A 10.2-cm-diameter wire )cnsfz 89d*gn v;kr2pdrt8m:/dgp 2bcoil 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, therm 2/td p2n v98dkns;) :c*d8zbrpggf 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 loop27tjmg/x);r d mz9k 6lldnu.o 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 resisto n6 :eqru4f*l s-mpb6(fftmk.r in (Fig. Below) is slowly increased, what is the direction of the current induced in the small circulaf.6q mpmlfkn- *tu64es fb( r:r 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 t42srb rlz0e n7he induced current in the circular loop due to the current shown in each part of (Fig. 7 nze r4rbsl02Below)?
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 -.mkc6ieq8dx 6mcvg22 oqbw. from the loop shown, in what direction is twb .ig6mm8q o- 62ev2.qc xcdkhe induced current in the loop?  ----待选择----counterclockwiseclockwise 

  The magnetic field perpendicular to a circular wire loop 12.0 pvpxfs b: j3.1cm in diameter is changed from +0.52T to -0.45 T in 180 vp31xsjbp.:f 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 cm lon;3d-o 5h-ybmd.jg fuk g and is pulled at a speed of 15.0cm/s If the magnetic field is 0.800 T, calcula3 dgy.j- u-fdkh5bm;ote
(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( pi;bgh ,0y0j/ m+eeorwxj5i paper lies in a 0.75-T magnetic field pointing into the paper. If the loop’s diameter changes from 20.0 ; e5mi+wpb irjxe0 jhy/(,0og 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 an9h9ed ks0q gq.:0 erin emf of 120 mV while moving9:e ed .nqikqs 00g9hr 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 dimensions shown in (:q ; el,52j1zsd98 cdmcrt08sl ebrdeFig. Below) is situated inside a region of uniform magnetic field of 0.550 T. The total resistance of the15l028e del9;e dbcj ,s zq:t 8sdrmcr 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. 7p:s(cy9ggo0us/u-rjaj s ,u 5 cm. A 10-turn coil is wound tightly around the center of the solenoid. If the current in the solenoid increa/gga,y:-ursuc o0 s7sp 9ujj(ses uniformly from 0 to 5.0 A in 0.60 s, what will be the induced emf in the short coil during this time?    $ \times10^{-4 }\;V$

  In (Fig. Below), the rod moveu0t s5m0 pz/ nc5(3gxr lls7ojs with a speed of 1.6m/s is 30.0 cm long, and has a resistance l0(culj5ms05/zo g 7pxrns3tof $\mathrm{2.5~Ω}$ 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 2n 4-g kw-xhv9o0 turns of circular copper wire 2.6 mm in diameter. A uniform magnetic field, perpendicular to the plane of the coil, chao9vw- h4n-xk gnges 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-diameter circular loop of cm lw2ki)typ cw- 5i2w8opper wire decrease5ity wim82k cpwl 2w)-s 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 ojjh/lspwg ;:ok ,.v 5eutput voltage of 24.0 V. The square armature consists of windo:ghekwj,vp.; 5ls /jings that are 6.0 cm on a side and rotates in a field of 0.420 T at a rate of 60.0rev/s How many loops of wire should be wound on the square armature? $\approx$    loops(Round to the nearest integer)

  The generator of a car idling at 1100 rpm produces 12*yjtaqwm u5hq 5kj .lgle ,by6b;5, w-.4 V. What will the ou tput be at a rotation speed of 2500 r6 -lyq5uy qw*,jbwag5jb tm k.e,5h;lpm, assuming nothing else changes?    V

Show that the rms out lj /c0k/au4(+wj6 bxje+uwdh put (Section 18–7) of an ac generator is $V_\mathrm{rms}=NAB\omega/\sqrt{2}$, where $\omega=2\pi f.$

  A simple generator has a 320-loop square coil 21.0 cm on a side. How4gcyr,r + 0vas fast must it turn in a 0.650-T field tog avs4 r,y0+rc produce a 120-V peak output? $f$   rev/s

  A 450-loop circular armature coil with a diameter of 8.0 cm rotates axps.3n/puq p(p/i; y nt 120rev/s in a uniform magnetic field of strength 0.55q p3.xi/p ;u p(pnyn/s 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. )m9y9 okag pz iv5qvn vt5ss3n+k(p33 It has 1000 turns and produces an rms voltage o3op5s 9 vt3n kg9i+n(yvaks 3pq m5)zvf 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 resisv7f b,di3mm3tv,mh f;tance 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 operatinck5eg+cqxa0 1 g at 1800 rpm. What would be the back emf at 21+cke5x gqc a0500 rpm if the magnetic field is unchanged?    V

  The back emf in a motor is 95 V when the motor is operating at 1000 rpm. He8a +oh ud0cbm wg43mwj4wd4 7ow would you change the motor’s magbdg wh7jo8dm aue344 04ww+mcnetic field if you wanted to reduce the back emf to 65 V when the motor was running at 2500 rpm? reduce the magnetic field to    % of its original value

  What will be the current in v vq sk,31lg fb+p;y;p hno8:0cah7oj the motor of Example 21–9 if the load causes it to run at hps, ny0c1hpjao7; +vq:;bv kf8 hgo3lalf speed?    A

  A transformer is designed to change 120 V i:ep+:emd o21:c wyqb pnto 10,000 V, and there are 164 turns in the primary:pbw1d +qe2 ycem:po : coil. How many turns are in the secondary coil? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ $\approx$    turns

  

  A step-up transformer increases 25 V to 120 V. What is the cjco t8/y:on*o urrent in the secondary coil as compared to the primary coil?8:/ocn oot* jy   

  Neon signs require 12 kV for their operation. To operate from a 2400 fc7c t5bfagd4br1w4ov7z u .-V line, what must be the ratio of secondary to primary turns of the transformer? What would the vf4v7u0t1bz. g f rcowd54 abc7oltage output 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 and draws 0.35 A while supplyingy18c .qm3ddy( xr2wyn:l qt7dv xt:y3 7.5 yvyq 3x :( tq 3nytdx.dd2w87 lr1ym:cA to the train.
(a) What voltage is present across the tracks?    V
(b) Is the transformer step-up or step-down? this is a  ----待选择----step-downstep-up  transformer

  The output voltage of a 95-W transformer is 12 V, and tl8ct40rn3ybug *r5p 1 axeff3he input current is 22 A. ynx1arf8bc3r3 * ute4l 0gp5f
(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 primad,9yc: 4zj ni sz9k6sqry turns and 1340 secondary turns. The input voltage is 120 V and the output cszz4,9 skq69nij:c dyurrent 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 to+weo ys u::suaqcc2+7wn 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 overo un3t0)22ht rnmk)hdvt44kj 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 stead7ih37izrog( su hyb ;)ily from 25.0 A to 10.0 A in 350 ms, what is the magnituh r3y giu (o)b7s7izh;de of the induced emf?    V

  What is the inductance of a coil if the coil produces an emf of 2.50 V when the .r *8we s4rll;yms6bacurrent iw.ar 6*y8m les4sb l;rn 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-filledj9vv(ouy01ib n *fh j- coil 2.9 cm in diameter containing 10,000 loop vb9yn-1iuvj*hj0o(f s?    H

  How many turns of wire would be required t aj2,xzeop)3wg p-c u8o make a 130-mH inductance out of a 30.0-cm-long air-filled coil with a diameter of 5.2a p-,3jx)8gcu ozwe p2 cm? L$\approx$    turns (Round to the nearest integer)

  An air-filled cylindrical inductor has 2800 turns, cci* ep 08:yww,-xm*x-rf oo cand it is 2.5 cm in diameter and 28.2 cm loyf*-w,08p:cio r*- cewm oxcxng.
(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 crosss59hq4tpmz8yj kwdf)z /s( ,f -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 tightly8,mjfct0m7 epg3mvq q255 welv:vv t6 wound solenoid is unwound and used to make another tightly wound solenoid of tw 8gqq6j ,evt 703w5vtfve c v:5mmml2pice the diameter. By what factor does the inductance change?   

  The magnetic field inside an air-filled solenoid 36 cm long and 2.0 cm in di7 sd0eknz+ 9s*ew)cuot ;t1me ameter is 0.80 T. Approximately how much energy is stored in this fien7otkes+ *u ee 9ztcd)w0;s1mld?    J

  At a given instant the current through an izgfq s8;sixnx88o r/04kv xq m u3h,s2nductor 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 enerq28,s 4gzs8qx 0xmn v;3fx r8k/ iohsugy to increase by a factor of 10 from the initial value?
U =    $ \times10^{-5}\;J$
$\Delta$t=    s

  Assuming the Earth’s magnetic fixpr 6pn)ur5.h eld 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 (Fig. Belo j1.5j y.m abvgcne; 6/ml9qrrw) reach within
(a) 10%,    $\tau$
(b) 1.0%,    $\tau$
(c) 0.1% of its maximum value?    $\tau$

  Two tightly wound solenoids 0 -lp9+xaixijyl6c 1lhave the same length and circular cross-sectional area. But solenoid 1 uses wire thatjx9+i6x pi1clly -la0 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 reactancrt.1e/pro83 ekn sky. e of a $7.20-\mu F$ capacitor at a frequency of
(a) 60.0 Hz,    $\Omega$
(b) 1.00 MHz?    $ \times10^{ -2}\;\Omega$

  At what frequency will a 22.0-mH inductor have a ln7/jl1i:ww0bfw0hoje- 2lb reactance of $660 \mathrm{k} \Omega ?$    Hz

  At what frequency will a -sjm+tu7-n qr $2.40-\mu F$ capacitor have a reactance of $6.70 \mathrm{k} \Omega ?$    Hz

Plot a graph of the reactan6uf+ 1z qep;fygtzgk(1 u3 ,pmce 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 frequ qnaoo+q(l;r8v, ob i3tsqn :*ency from 100v+onqrbq:no q8 ,i(; 3l*asto to 10,000 Hz.

  Calculate the reactanc4y( 0i+bx36m+pdy uwsc-d x iyr6 o zlz):b8uce of, and rms current in, a 160-mH radio coil connected to a 240-V (rms)p ux( biz6c u-3+z6l8c)ywy mo0+x ys:di4bdr 10.0-kHz ac line. Ignore resistance.
$X_L$ =    $\Omega$
V =    $ \times10^{-2 }\;A$

  An inductance coil operates at 240 Ve-./4e. 6mvbgnzww w(g v 9lua and 60.0 Hz. It draws 12.8 A. What is the coil’s inductanc4g mn-w/vzeu ew9l 6a.gw(v. be? $X_L$ =    $ \times10^{-2 }\;H$

  (a) What is the reactance of a well-insula(h/ .uxl s-perted $0.030-\mu F$ 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 volt: zzi9 vbuhh3j) ft- 4kdp3,txage, an rms current of 70 mA passing through the human -p u9h:zb3,v4 d3tfz) hxiktj body for 1.0 s could be lethal. What must be the impedance of the body for this to occur?    $ \times10^{3 }\;\Omega$

  What is the resistance of a coil if its imp6ja) 9zm+ 6hbr awd)iuxe0pi8edance 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 circuit2 bjjh6 q7hmpottjt/ 3yy*;h: kev9 5x connected to a 10.0-kHz, 725-V (e7 6h ;bj 92/5mq*yvypxho:jkth t3jtrms) 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 4203i gmvx.w6g2 h 4e0okh-mH inductor is driven by an ac power supply. At what frequency is the impedance double that of the 3h vmxi6 k2w4gohg.0e impedance at 60 Hz?    Hz

  (a) What is the rms current in an RL circuit when a 60.0-Hz 1;cnaf fz h/.6vug*b8x20-V rms ac voltage . f;auh zx8/bv6gf* ncis applied, where $R=1.80\mathrm{~k}\Omega,$ and $L=350\mathrm{~mH}?$    $ \times10^{ -2}\;A$
(b) What is the phase angle between voltage and current?    $^{\circ}\,$
(c) What are the rms voltage readings across R and L?
$V_{rms \,R}$ $\approx$    V (Round to the nearest integer)
$V_{rms\,L}$ =    V

  (a) What is the rms current in an RC circuit if zb;2ggo: jav1$R=8.80\mathrm{k}\Omega,C=1.80\mu\mathrm{F},$ 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 cos7/s: uj:d lysnnected 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 haskljxpa/srf: 845;kkv . ls;pc a capacitance of 2800 pF when the radio is tuned tx /c8vj rpl; ; k.:fp4kl5ssako 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 Laax)r rt4kgtp+(vvu 2, /g3d p = 14.8 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 currebcw-v5c)g98zz ,wdo nnt loops in the plane of the page as shown in (Fig. Below). When swz,d-cgz w)95wvo8c nbitch 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 hasg+7 k3-0vljhemf-ns do(bae,i n (9 ei 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 requik2 - bg)++vb0 xxgaymjres only 12 V. It contains a transformer that converts 120-V hbkmjgxy )0b+-2 va +xgousehold 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 sn ;z +smgm 738xw pu/p-n0neuzqun./plant located 118 km from a town that requires 50 MW of power at 12 kV. Two transmission lines from the plant to the tu 0u7/pgm/zsunmnzxq3;8 + en s-n.wpown 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% efficiency are connectedg +hmd6t7z2pi1 2lt cp to 110-V ac. The secondary windings are connected acrosszd p27+ mgp2ih6 1tltc 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 transmi0vu *x 6ch+nbn4ehvg9ssion 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 railv(mf 2 j(rk5dcs 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 transmi1pvqu.ls34u xssion 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, a qu yb+pk .)v.fkbf49end a resistance of $\mathrm{12~Ω}$ surrounds a solenoid with $230\mathrm{~turns/cm}$ and a radius of 4.5 cm; see (Fig. Below). The current in the solenoid changes at a constant rate from 0 to 2.0 A in 0.10 s. Calculate the magnitude and direction of the induced current in the coil.
I =    $ \times10^{-2 }\;A$
 ----待选择----left to rightright to left 

  A certain electronic device needs to be protected against su e0h)*w4ml 0fy+ +zed3 hho-nv*zrxo idden surges in current. In particular, ayx f3h+w*)-dhooenzi0*e04z vl + mh rfter 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 )/d:)xqtolm) ov edc q 7m0e/xpole pieces of an electromagnet. When the magnet is turned on, the flux through the coil ce)t)x7 //o dqv)odm0q:l excm hanges, inducing an emf. At what rate (in T/s) must the field produced by the magnet change if the emf is to be 120 V? $|\varepsilon|$    T/s

  Calculate the peak output voltage of a simple generator whose square armat1u4.wjt1 ;)org brvphure windings are 6.60 cm on a side; the armature contains 155 loops and rotates in a field of 0.200 T at a rate of 1rrb 1o;g p.thwv4ju) 120rev/s. $\varepsilon_{peak}$ =    V

  Typical large values for electric and magnetic fields attained in laboratoriess6: ch8fay m0x are abou0a 8 6:xsfmyhct $1.0\times10^4\mathrm{~V/m}$ 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 t yh8q5e6 vrp(fn1suq(he primary of a transformer whose input is 220 V at 60.0 Hz if the current drawn is 5.8 A? Assume no current in thyhpv q q(f(s8n1u6r5ee secondary.    H

  A 130-mH coil whose resist)pru pfbv 5obz(4mcg+su-+- pance 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 u2d pnmpzr/e9n87 ap u h+mc0:36-V battery. When connected to a 60-Hz 120-V (rms) source, the current drawn is 3.8 A (rms). Determine the induct +/2:upnham r 0nm7cuzp 9de8pance and resistance of the coil.
$V_{dc}$ $\approx$    $\Omega$
L $\approx$   $ \times10^{-2 }\;H$

  A 135-mH inductor with9( b 1mmefvrga7/xh-y $2.0-\Omega$ 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 reso4*9drp(yfpzfbh hc m :d--v,bnance circuit can be defined as the ratio of the voltage across the capacitor (or inductor) tochbv*-dh f(mdr,-p z bf4 yp9: the voltage 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$