What would be the advantagedp+lc,15.ug vpq:tp rvek.)v , in Faraday’s experiments (Fig. Below), of using coil,qv.egdplk)c5:p u .v1 tr +pvs with many turns?

What is the difference b6 7n ca4f;+/zoj02 ysix pzowr;llr0n etween magnetic flux and magnetic field?

Suppose you are holding dj(bmp/cd kq4j c*l* ;wxp5s2 a circular ring of wire and suddenly thrust a magnet, south pole first, away from you toward the center of the circle. Is a currejd4cmxwq*5ld*2 p( c; ps bkj/nt 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 movi z9u5 1nli:,hipsq x,ang in the vicinity of a very long straight wire carrying a steady current as shown in (Fig. Below9pii1z5lu a,:sh,xn q). Find the direction of the induced current in each loop.

Suppose you are looking along a line throc6a+9v blz:qj 9i o6kustpo+;;e ry/pugh the centers of two circular (but separate) wire loops, one behind th6ju+:;ck 9l;tyzb so/ a+po e6vrpqi9e other. A battery 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 resm4d04. gughfmistor $R_A$ 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 y;qj *f)0xhf3r9crnf signal must travel over a distance, a “shielded cable” is used in which the signal wire is surrounded by an insu qfx90jrc ;ny f)*frh3lator and then enclosed by a cylindrical conductor carrying the return current. Why is a “shield” necessary?

What is the advantage of placing the two inryf eyg*t5oo6wm)k4o:ko :5msulated electric wires carrying ac close together or even twisted about each other?:wy oot gk)r 65ym o4:kme5fo*

Explain why, exactly, the lights may dim brief xv;; luq ygi-zy3w9p8ly 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. u9p;-y3v;yz8lgwi qx Explain the difference.

Use (Fig. Below a) and (Fig. Below b) plus the right-hand rules h8 ) cbeql (cjq)b)tn,to show why the counter torque )bhn8lbte q )c(c)q,jin a generator opposes the motion.
a
b

Will an eddy current brake (Fig. Below) wobzt um/z3p(7 u*cb 5-wo s7zuork on a copper or aluminum wheel, or mu/u 5 zcuoz7w3 p7(ms *ub-zbtost the wheel be ferromagnetic? Explain.

It has been proposed that eddy currents be used to help so y skmo5*yviqq2z 0-wf c )tr8h75c;crrt solid waste for recycling. The waste is first ground into tiny piecs vric f5-ryqoh);0cc 27* ztm58 wkqyes 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.i09r i 0nduf7d Below) falls much more quickly through a magnetic field than doi 0r9 ndfui0d7es a solid bar. Explain.

If an aluminum sheet is held between the poles of a large bar magnethm 9x q2sb-6; qqke:a2uc(+f,hgm xae, it requirese :2,qhcfqa+e29-qaughm 6; s(b xmkx some force to pull it out of the magnetic field even though the sheet is not ferromagnetic and does not touch the pole faces. Explain.

A bar magnet falling inside a vertical metal tube reaches a termip8v0ct4px n-iu arj)*nal velocity even if the tube is 0t ra 8*upxij- np)vc4evacuated so that there is no air resistance. Explain.

A metal bar, pivoted at one end, oscillate. sgcyjz3: r3 mcuzn57s freely in the absence of a magnetic field; but in a magnetic field, its oscillations are quickly damped out. Explain. (This magnetic damping is used in a numc3 uy3z7z5 nc: r.jgsmber of practical devices.)

An enclosed transformer has four wire u/)8f* *y3n low nycqpq-,5yscpep3f(xl c(aleads coming from it. How could you determine the ratio of turns on the two coils without taking the transformer apart? How would you know which-(*wc3lcs nuaq3 x5)opyc*ffyppe, ln/(yq 8 wires paired with which?

The use of higher-voltage lines in homes — say,4ys2 zmoa5,,myoz4in.;kf lr 600 V or 1200 V — would reduce energy waste. Why ;2yy,, fr.4om5o namk4zslizare they not used?

A transformer designed for a 120-V ac input will often “burn out” if connectig p pkpa pp8j)529uln jv6myacf0, x2yf-a.:ed to a 120-V dc source. Explain. [Hin) pu x-5p,af afjgkpn6: av9jy2 ymcl8.i2pp0 t: The resistance of the primary coil is usually very low.]

How would you arrange two flat circular coils so that their mutual inducta,t vgipvoyfaw8 6 b,73nce was o v,w3pf7byv86ga, t i
(a) greatest,
(b) least (without separating them by a great distance)?

Does the emf of the battery iby; )7bx)9lw djhb3( f,t jfvjn (Fig. Below) affect the time needed for the LR cidbbfjx( j3 w9v j, yh;))lt7fbrcuit to reach
(a) a given fraction of its maximum possible current,
(b) a given value of current? Explain.

  In an LRC circuit, can tf1x nu+r1tfj2 -eo/:kg7v5 ni mw4po the rms 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 frequency of the source emf affects the ie4 7qp;*qvlhs23v jotmpedance 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 circuv n2p,df2rb0x,/11uukfrzida m c 1s1aty 55fit a minimum.

  The magnetic flux thr457paqjxunaw- 9 5xmqough a coil of wire containing two loops changes from -50Wb to +38 Wb in 9qwpa54mu j5xq7-a xn0.42 s. What is the emf induced in the coil?    V

  The rectangular loop shown in (Fig.cqa/e/4g iiv; * g)tjc5 3 q 7f4xfavn*ub7xln Below) is pushed into the magnetic field which points inwarclqaqen*nui vc fab/g )x45t7/v;x* i4j7g 3fd. In what direction is the induced current?  ----待选择----counterclockwiseclockwise 

  The north pole of the magnet in (Fig. Below) is being inserted into the coil. Itk tgv mz4ts b7i+93ydvns -6;n which direction is the induced current flowing- 9vizgtbdnt6 sv;ty+k 3 s4m7 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. The la ilt w;epkv 092 yy,zi)zyig 1q 6g+:rz)w3xkoop is removed from the field in 0x,+0iqz6k )vkwzl9rp :y iai)g 1yg ;tez3y2w.15 s. What is the average induced emf?    $ \times10^{-2 }\;V$

  A 12.0-cm-diameter loop of wire is initially or + k,qprld35grus*ax65rrs(ciented 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 inducedxar r5 l s+d 6,rc*rgs3(p5kuq emf in the loop?    $ \times10^{-2 }\;V$

  A 10.2-cm-diameter wire coil is initially zl(k5wu9obj(ps ft8do if 0+2 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 is (f pfodt5k+sjb(0 w2 z9olui 8the average induced emf in the coil?    $ \times10^{ -2}\;V $

  A 15-cm-diameter circular loop of wire is placed in a 0.50-T magnetic field. yve bo l87ty51 ;/g1g+upasrn
(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 resis7y .6/fpw/fnz*n qkou tor in (Fig. Below) is slowly increased, what is th kfnyf*7/z6/ nwpuo. qe 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 the induced current in e(j)sbi 5wn2h the circular loop due to the current shown in each part of (Fig. Below25in(j)shb w e)?
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 9din)3u,,* rfqoqn prpulled away from the loop shown, in what3,9, nqqd* ruinor) pf direction is the induced current in the loop?  ----待选择----counterclockwiseclockwise 

  The magnetic field perpenhw m9b6qnze;.f 8xk7bynvs1 rx+xx52dicular to a circular wire loop 12.0 cm in diameter is changed from +0.52T to -xkz qynw5s8; f9b1nme+ b xvx .2r7xh60.45 T in 180 ms, where means the field points away from an observer the observer.
(a) Calculate the induced emf.    $ \times10^{-2 }\;V$
(b) In what direction does the induced current flow?  ----待选择----counterclockwiseclockwise 

  The moving rod in (Fig. Below) isu az8 1whjl:c( 12.0 cm long and is pulled at a speed of 15.0cm/s Ifja1ulhz8: wc ( the magnetic 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 the plane ofr5 m qr3,vf) 3*pdx;vsv1;*n e aabgsw the paper lies in a 0.75-T magnetic field pointing into the paper. If the loop’s diameter chanfv * vrsw5xdmqane,)as1p3;;b grv *3ges 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 generathgzp)jw2 22fvl qb5l ,es an emf of 120 mV while moving in a 0.90-T maql)5lg ,2jwzfbh v 22pgnetic 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 rectangvys*p 7lq8 9o kufiaa1 s428mnular loop of wire with dimensions shown in (Fig. Below) is situated inside a region of uniform 18v82 nsa m* posyl974quifak 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-turn codv*ggzg r :( o+gwb+c)il 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 iro*):g gb+d +(wcgvgznduced 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 lonw/wls;:f-l v06 s vfpsg, and has a resistancesw s:wffv vlp0s/l-;6 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 shu, 4vaw 76srconsists of 20 turns of circular copper wire 2.6 mm in diameter. , r4h7s6 swuvaA uniform magnetic field, perpendicular 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-diameter circular loop of cr*ml/uq q +x: dy xs5l(2i;mjjopper 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 duriji2+*r y;5qm xllm(uj:xd s/qng this operation?    C

  A simple generator is used to generate a peak output voltagp,astj0s * wpby2 yg)3e of 24.0 V. The square armature consists of windings that are 6.0 cm on a side and rotates in a field of 0.420 T ,sp bay20jyp w*g)s3tat a rate of 60.0rev/s How many loops of wire should be wound on the square armature? $\approx$    loops(Round to the nearest integer)

  The generator of a car idling at 1100 rpm produces 12.4 V. What will 4t*6uiezffuo9gn t6. the ou tput be at a rotation speed of 2500 rpm, assuming nothing else changeuieg.*9tn4z 6ut 6 ffos?    V

Show that the rms output (Section . c *s-mr3bn/rjbp3fp 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. How fast must6-orr3 pbsm 9gv+sse4 it turn i+pms-vs4rrb o6 s3ge9n a 0.650-T field to produce a 120-V peak output? $f$   rev/s

  A 450-loop circular armature coilkew(2 m6c+jyn with a diameter of 8.0 cm rotates at 120rev/s in a uniform magnetic field of streng26 c+ enmyjkw(th 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. nuoo i(t 5x:3z.+mquc*bpr.7z q3tk sIt has 1000 turns and produces an rms voltage of 150 V az p73ouc (xonz. siuk5+mtr : qb.t*q3nd 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 resistance 2*xsc s qq28 itrxu/x1of $3.25\Omega.$ 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 whcvs hh;u 3,-hmen operating at 1800 rpm. What would be the back emf atu,h3s; mh v-ch 2500 rpm if the magnetic field is unchanged?    V

  The back emf in a motor is 95 V when thohp /aj :g 5hyl-k-0mz;iwc. lv7qk p3e motor is operating at 1000 rpm. How would you change the motor’s magnetio mgvp -:zhc 0wlj7 p.kl/k3qi- ah;y5c field if you wanted to reduce the back emf to 65 V when the motor was running at 2500 rpm? reduce the magnetic field to    % of its original value

  What will be the current in the mo i1w30w y 5tt5x.cg d:oet-dlqrw 4j5etor of Example 21–9 if the load causes it to run at 4-dw t g5xictyd. :w10wer5otjlq5 3e half speed?    A

  A transformer is designed to change 120 V into 10,000 V, and there are 164 toaz (5hu)0b vjurns in the primaryuv0bj h5ao)z ( 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 currek./ lq as*znq+2zuow 6nt in the secondary coil as compare anu+ o/ kzl2wsz*q6.qd to the primary coil?   

  Neon signs require 12 kV for their obet jmxb3tzw89(d6 8rperation. To operate from a 240-V line, what must be the ratio of secondary tb8 zxdejwbr38(9mt t6o primary turns of the transformer? What would the voltage output be if the transformer were connected backward?
$\frac{N_\mathrm{s}}{N_\mathrm{p}}$ =   
$V_s$ =    V

  A model-train transformer plugs into 120-V ac and draws 0.35 A while , -tq+m-kskay/ 7hdn nhw;h0osupplying 7.5 A to the tra o -k7;khw/yq-a t+,dn0mhhnsin.
(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 (;ahszle+n p:r )a.qiinput current is 22 A.naha)+r :e .q;p is(zl
(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 4u5 1 :t,qtp0ctzcpc nprimary turns and 1340 secondary turns. The input voltage is 120 V and the output current is 15.0 A. What are the output voltptup,t q4ct 1c:0cn5 zage 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 town from a generaug ff7umdd; q :5xc*ggvq02b9 tor 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 t1q yiw, jq3* sham3cb-,8uvcbwo $0.100-\Omega$ 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 18e:qw6,j9n + szmceq h(v:9jbe0-mH coil changes steadily from 25.0 A to 10.0 A in 350 ms, what is the magn:jcmezqn9, j vsq9(hwb:e +6eitude of the induced emf?    V

  What is the inductance of a coil if the coil produces an emf of 2si m za7fq5:rlpe6(3l.50 V when the current in it change3li qpf7r(e 5lm sa:6zs from -28.0mA to +31.0mA in 12.0 ms?    H

  What is the inductance L of a 0.60-m-long air-filled coil 2.9 cm in diameter con x6lty1p3.d**yq.panvvp w, htaining 10,000 loops? .3 ppyy6lp h.*w v,dtxqnv*1a    H

  How many turns of wire would be requirs -+)d(oj58g2q d+ vyon3ub g8oseevm d/fv;h ed to make a 130-mH inductance out of a 30.0-cm-loh8vddq ;2v8o5gm ob s+jn eo/ -ufs+dyvg3() eng air-filled coil with a diameter of 5.2 cm? L$\approx$    turns (Round to the nearest integer)

  An air-filled cylindrical inductor has 2800 turns, and it is 2.5 cm in dia+rf*vi*h0c(qvny us1 lezl ,) meter and 28.2 cm long. zv,usr1c0l * ln)(ev qh *y+fi
(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 crossz/r6evl5j2c z-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 solenoid is u k,q(y 9zc5nrynwound and used to make another tightly wound solenoid of twice the diameter. By what , zk5qy(cr 9nyfactor does the inductance change?   

  The magnetic field inside an air-filled solenoid 36 cm long and 2.0 cm in diameztld q 5a0/u3a a:ypf wuag45l)7g+aater is 0.80 T. Approximateya3a 45ada5/: g7p)qfzl auua wt0lg+ly how much energy is stored in this field?    J

  At a given instant the current through an inductorh1n ) eez* +)t.miocu fgc3/hk 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 inkczf+*it .e/)mhe hnuo g 1)c3crease by a factor of 10 from the initial value?
U =    $ \times10^{-5}\;J$
$\Delta$t=    s

  Assuming the Earth’s magnetic field averages aboutsxyv (a6pmg; 1m s9q7n $0.50\times10^{-4}\mathrm{~T}$ 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) reachj4 3akbl+fx f5du:l4l 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 circular cross-be9mu-r8 j:y s:9*xece dv s/:t-zujs sectional area. But solenoid 1 uses wi *mj8:-uuj9z eyb-:trss/ :scex v e9dre 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 reactanceo oe+;hom5hv5jg/ d fx n6.qv6 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 reactanct6bjat )rjerz t4 4tn/9yb*h6 e of $660 \mathrm{k} \Omega ?$    Hz

  At what frequency will a z3lnv htx)y4 7s-3yh w$2.40-\mu F$ capacitor have a reactance of $6.70 \mathrm{k} \Omega ?$    Hz

Plot a graph of the reactance of z;axd.ds6u f/a $1.0-\mu F$ capacitor as a function of frequency from 10 to 1000 Hz.

Plot a graph of the reactance ss8wu/( lxo4hof a 1.0-mH inductor as a function of frequency from 100 to 10,0(s 8uxlsh4 o/w00 Hz.

  Calculate the reactance of, and rms current in, au b f w2/e1gs07tyd70uaansl 2 160-mH radio coil connected to a 240-V (rms)7f /w e0l72 dsa02nbast ugyu1 10.0-kHz ac line. Ignore resistance.
$X_L$ =    $\Omega$
V =    $ \times10^{-2 }\;A$

  An inductance coil operates at 240 V an +ut7crj . vxv:c. ,:jz1pxgssd 60.0 Hz. It draws 12.8 A. What is the coil’s inductanjgv+1:cux 7.j r pvt cx,ss:.zce? $X_L$ =    $ \times10^{-2 }\;H$

  (a) What is the reactav 0 x(rnrdn0bi ,v.hau5xx9)gnce 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 rmyq9- z*nr 2wwas current of 70 mA passing through the human body for 1.0 s could be lethal. What must be the impedance of the body forwqawy-2n*r9z this to occur?    $ \times10^{3 }\;\Omega$

  What is the resistance of a coil if its impedance i1 +/g :6annzgme1x plc3 0jxhfs $\mathrm{235~Ω}$ and its reactance is $\mathrm{135~Ω}$    $\Omega$

  What are the total impedance, phase an2x 4k)m koj6kagle, and rms current in an LRC circuit connected to a 10.0-kHz, 725xko )mk 62jka4-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 inductor is driven by an ac pow h3n-r;(vk bbbxznt (b:ys: 7rer supply. At what freque :ny 3bbtrs((b- h:rkb xznv;7ncy is the impedance double that 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 vsuh jkf077 h:/+xahc : rjzf/zoltage is applied, wc:jrakuj x77/s:hzhhf fz0/+ here $R=1.80\mathrm{~k}\Omega,$ 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 if8 ..dzk03gym+ wd laov $R=8.80\mathrm{k}\Omega,C=1.80\mu\mathrm{F},$ 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 con/v/y+ b2v)i wrxbca1 vrc :s 6glb)7bnnected 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 of9xpihr)uu v5 5 2800 pF when the radio is tuned to a9v uhrp)5 x5ui 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 vzsub** 90l je iznjurla:5 /,mH and $R=4.40\Omega$.
(a) What value must C have to produce resonance at 3600 Hz?    $ \times10^{ -7}\;F$
(b) What will be the maximum current at resonance if the peak external voltage is 150 V?    A

  Suppose you are looking at two current lyk:-;w 5 tda vzn4 /mr/rww6mnoops in the plane of the page as shown in (Fig. Below). When switch S is thrown in the le m5ay6z;: wtm-w n/wrdv /nr4kft-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 resisrajlprnpks(5 ,h/ ei 2pf47g4tance of $5.20\Omega.$It is initially in a 0.665-T magnetic field, with its plane perpendicular to $\vec{\mathbf{B}},$ but is removed from the field in 40.0 ms. Calculate the electric energy dissipated in this process.    $ \times10^{-3 }\;J$

  A high-intensity desk lamp is rated at 45 W but requires only 12 V. It contaf zjam c/r/3r:ins a trarfca: m rz3j//nsformer that converts 120-V household 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(rjg sh6i. 03oyfuhhb:j, u: fdk x8+u plant located 118 km from a town that requires 50 MW of power at 12 kV. Two transmissi y8i0h h: d k6g3:.hb+uuo,uf(rfsj jxon 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 td rlr:oqi9ud y 9jak7;e r+9qy.y/t:xransformer which has an 80% efficiency are connected to 110-V ac. The secondar:ad.9y9xrkjyteqi9y/; :7ro l d r qu+y 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 transmission lines each ha(myrj. xkd lr+ j113x0c9cj auuvl,v; ve 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 32z28tt1jbdek3mnz,7ul ,sz fjh m. 7 c) 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 transmission linesdfxelgv* in5s; m1;3t yk1k. s t3o;lr, $R_L$ 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 k; kf- ;ktoe6-:scm ewcm, 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 desiiqej ck-gm5hh(n. s(- i7r5vice needs to be protected against sudden surges in current. Iniih5-chn(s-esk(iqm. 5jrg 7 particular, 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 el502h9,ir d3ai gx+;jhlfgs lsectromagnet. When the magnet is turned on, the flux through trlg i a,+h slgxf j35dh09;2ishe coil changes, inducing an emf. At what rate (in T/s) must the field produced by the magnet change if the emf is to be 120 V? $|\varepsilon|$    T/s

  Calculate the peak output voltagy cv) e(v os-r8frkqb/*,9 mbde of a simple generator whose square armature windings are 6.60 cm on a side; the armature contains 155 loops and rotates in a field of 0.200 T at a/ko be*(cf vr), 9qbm8vy srd- rate of 120rev/s. $\varepsilon_{peak}$ =    V

  Typical large values for electric and magnetic fields attained inht* h :pu6uq6i laboratories a:hpu66 ihq ut*re about $1.0\times10^4\mathrm{~V/m}$ 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 ofoy +ru f+/ pf wj2kkx*fa9)3zf a transformer whose input is 220 V at 60.0 Hz ifff 9y2) auko+pf jfw*z+3kx/r the current drawn is 5.8 A? Assume no current in the secondary.    H

  A 130-mH coil whose resistance-t6fjqe ,ow,a)ksm:z 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-Votp zq ; x.xi/8ct:aj+ battery. When connected to a 60-Hz 120-V (rms) source, the current draw:o ct;xzqaj.pi/ x8t+n 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 wil9:k *w;j*a w5 hatrthth $2.0-\Omega$ 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 ic-k4+) mqre7zjzqm,j5qae 6 the voltage across the capacitor (or inductor) to the voltage across the resistor, at resonance. The larger the Q factor, the sharper the resonance curve will be and the sharper the tun,q567 e j 4 aqkmqimzr-jc)+zeing.
(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$