What would be the advi +oh 46bxisa51o t8 buogc45qantage, in Faraday’s experiments (Fig. Below), of using coils with maii65ha4b5 b 8tx+ uoqcs1o go4ny turns?

What is the difference between magnz27h wy2nfxy)plynu+ /l(hr, ha: x9 qetic flux and magnetic field?

Suppose you are holding a circular ring of wire and suddenly thrusuz/upm-c*xdp*0m:1:eh coikh s+vc0 j nu u 25t a magnet, south pole first, away from you toward 5z1 hj02 +ppcchuv/xi*m *: mons:u0-uc ekudthe center of the circle. Is a current induced in the wire? Is a current induced when the magnet is held steady within the ring? Is a current induced when you withdraw the magnet? In each case, if your answer is yes, specify the direction.

Two loops of wire are moving in the vicinity of a very long straight wirs sc-rd.d8l45rb7t :jojsiw ) e carrying a steady current 4jos8sls7c tb-d r ).:wrji5das shown in (Fig. Below). Find the direction of the induced current in each loop.

Suppose you are looking along a line th(u/y8di( xdfzq pkd3** om s4su u;nf-rough the centers of two circular (but separate) wire loops, one behind the other. A battery is suddenly connected to the front loop, es8sd ; umpd i-uf /43ox( qf*d*uynz(kstablishing 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 )63 s,vnkoy 3 e,8lcepamt9sbof 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 “shielded l hz,hx3(9qb kcable” is used in which the signal wire is surrounded by an insulator and then enclosed by a cylindrical ck hqhl9,3 bz(xonductor carrying the return current. Why is a “shield” necessary?

What is the advantage of placing the two insulated eln cz8ej9 r*v4hectric wires carrying ac close together or even twisted about each z9c*v 8 4jrhenother?

Explain why, exactly, the lights may dim briefly when a refrigerator motor stq( g7ve8eiezz(pwk2 - arts up. When an electric heater is turned on, the l(i7z e epq(k2-vwzeg 8ights may stay dimmed as long as the heater is on. Explain the difference.

Use (Fig. Below a) and (Fig. Below b) plus the right-gyf wi6g xe-xa 1f44-phand rules to show why the counter 4y -g6-pxia1gffex w4 torque in a generator opposes the motion.
a
b

Will an eddy current bra etn) 15yg2i;fuji+ apke (Fig. Below) work on a copper or aluminum wheel, or must the wheel be ferromagnetic? Expla)+fegi tnpu j5i2 1a;yin.

It has been proposed that eddf6b:)g+tt/kga c*rk 0:px;ll :pwfduy currents be used to help sort solid waste for recycling. The waste is first ground into tiny puk/+x lg kl g0f:*a)p::bt t;c pfwdr6ieces 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. Below) falls much more quifqv q2ln-x c0j+9z9*ucafn k5dhs3v .ckly through a magnetic field than does a solid bas+*q.9u 3 5l9vnkhncdc02 -jx fvzqf ar. Explain.

If an aluminum sheet is held between the poles of a large bar magnet,((xtj z;ysxcc+e rq- ,q vx)r; it requires some force to pull it out of the (tcr xjx)cv;q,(+ eq -; yxszrmagnetic field even though the sheet is not ferromagnetic and does not touch the pole faces. Explain.

A bar magnet falling inside a vertical metwr .3)efg,/mt/t(f2vfnpv utal tube reaches a terminal velocity even if the tube is evacuated so that there is no aif/ gv2v mtp 3,f() ttwu.fenr/r resistance. Explain.

A metal bar, pivoted at one end, oscillates frqm(drwny-5flzd7yjh 9 +6)j ()r, hoo ngzh.feely in the absence of a magnetic field; but in a magnetic field, its oscillations are quickly damped out. Explain. (This magnetic dampi7n lhfom5y.(hddjrhgr ,w6-z +jfozny () 9)qng is used in a number of practical devices.)

An enclosed transformer h5)1b+v4fur1 cj u wuxpas four wire leads 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 wires paired with whichxcuv 4u1 bwfj5pu+r )1?

The use of higher-voltage lines in homes — say, 600 V or6c 1- q i*blp, y,r9r6fzwhnis 1200 V — would reduce ener6b,r q6wc 1nz,si-y phf9rl *igy waste. Why are they not used?

A transformer designed for a 120-V ac input will often “burnvoz(xgpw 5 vp. /x/0mg out” if connected to a 120-V dc source. Expg0o (zpwm/xg vp.5x/ vlain. [Hint: The resistance of the primary coil is usually very low.]

How would you arrange two flat circular c( ysm/ /1t+zj absvbbe2.msyok .1 a6uoils so that their mutual inductance wajs2tsy6sm ay/v /.bou bm1(ae+1.zk bs
(a) greatest,
(b) least (without separating them by a great distance)?

Does the emf of the battery in (Fig. 8paa d3n8h/ j.; wdplhi/9vkny he. g0Below) affect the time needed for the LR circuit to reilahg;3dp0/ k 9 8jeh.dvhyna 8.pwn/ach
(a) a given fraction of its maximum possible current,
(b) a given value of current? Explain.

  In an LRC circuit, can 4q8a jv-e9xel1ic+/u x0t djithe 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 s/3sxj v k22kfsakgz18 ource emf affects the impedance of
(a) a pure resistance,
(b) a pure capacitance,
(c) a pure inductance,
(d) an LRC circuit near resonance (R small),
(e) an LRC circuit far from resonance (R small).

Describe how to make the impedance in an LRC circuit a min d z511ddw+7m sevu-vcimum.

  The magnetic flux through a coil of wire containing two loops changes from -50Wyiq : rvg48ceq:mfs9/) vd( beb to +38 Wb in 0.42 s. What is the emf inducedi/ 9g :8qscer)yv :dfm4(bve q in the coil?    V

  The rectangular loop shown inb4a8 wuy(f 1yt (Fig. Below) is pushed into the magnetic field which poif twy1a 4(u8bynts inward. In what direction is the induced current?  ----待选择----counterclockwiseclockwise 

  The north pole of the magnet in (Fig. Below) is being inser: s5s6wz7rq kq1gdk53f l* u/ 4u9lqatni 8lowted into the coil. In which dko 79tql*w53gw5uazq :rdfs ui qn s86k/l1 4lirection is the induced current flowing through the resistor R?  ----待选择----from right to leftfrom left to right 

  A 9.6-cm-diameter circular loop of wire is in 7jx (qk58q xk+tcc *rda 1.10-T magnetic field. The loop is rx5cx*k kcqjt8(dq7+r emoved from the field in 0.15 s. What is the average induced emf?    $ \times10^{-2 }\;V$

  A 12.0-cm-diameter loop of wire is initially orienupizqsv/8)mkr6 71qepdw 6 :c1r8htkted perpendicular to a 1.5-T magnetic field. The loop is rotated so that its planeq 71ue6ptci 1hkr / zdrqkvmp8:6s )8w is parallel to the field direction in 0.20 s. What is the average induced emf in the loop?    $ \times10^{-2 }\;V$

  A 10.2-cm-diameter wire coil is initially oriented so that i.jcjwl j*qej dwc0vca/57x. pt+9f2 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 qejd./ 0 57xc+ijp jt v*l9wjwcfca2. of 0.25 T pointing down. What is the average induced emf in the coil?    $ \times10^{ -2}\;V $

  A 15-cm-diameter circular loop of wire is placed in a 0.50-T magnetic field. / 4yy9si s7tc*:ct:inqxdo7g
(a) When the plane of the loop is perpendicular to the field lines, what is the magnetic flux through the loop?    $ \times10^{-3 }\;Wb$
(b) The plane of the loop is rotated until it makes a 35$^{\circ}\,$ angle with the field lines. What is the angle $\theta$ in Eq. 21–1 for this situation? $\theta$ =    $^{\circ}\,$
(c) What is the magnetic flux through the loop at this angle?    $ \times10^{-3 }\;Wb$

  (a) If the resistance of the resistor in (Fig. Below) is h:pjhjn)/uikhd *1 ;e0 x8 pxn)iri i-slowly increased, what is the direction of the current induced in the small circular loop inside jrn *phih8ik:xnix0/i1)p hjd-ue; ) the larger loop?  ----待选择----counterclockwiseclockwise 
(b) What would it be if the small loop were placed outside the larger one, to the left?  ----待选择----counterclockwiseclockwise 

  What is the direction of the induced current in the circular lol s3, bvr.v5gyop due to the current shown in each part of (Fig. Bvsr. gbyl3 ,5velow)?
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) i-h)nv3f l9 ngls being pulled away from the loop shown, in what direction is the induced cu3-n lhg f)lnv9rrent in the loop?  ----待选择----counterclockwiseclockwise 

  The magnetic field perpendicul , -zl qp7(w9i0knqcriar to a circular wire loop 12.0 cm in diameter is changed from +0.52T to -0.45 T in 180 ms, where means th( r kq0nq,lp9i-7wzice 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 lo,lj, bc5d np.z* 5eq 7wf;-7 rf- vfihirag.12.0 cm long and is pulled at a speed of 15.0cm/s If the magnetic field is 0.800 T, ;5rgeawnffo 5.ldhpzqvj.l7 , ,-ricibf* - 7calculate
(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 thj1 nlhwz*5pr, e plane of the paper lies in a 0.75-T magnetic field pointing into the paper. If the lor1* 5lhn jwzp,op’s diameter changes from 20.0 cm to 6.0 cm in 0.50 s,
(a) what is the direction of the induced current,  ----待选择----counterclockwiseclockwise 
(b) what is the magnitude of the average induced emf, $|\varepsilon|$ $\approx$    $ \times10^{-2 }\;V$ (retain one decimal places)
(c) if the coil resistance is 2.5$\Omega$ what is the average induced current?    $ \times10^{-2 }\;A$

  The moving rod in (Fig. Below)is 13.2 cm long and generates an emf of 120 mV wh5:xql:kh vjk0ile k:q5h0l k: jxvmoving 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 shr kr yp 9tlzo9p z.9+y)*ng3vm2oi.,p5 ohip down in (Fig. Below) is situated inside a region of uniform magnetic field p5opoipd+rly,ontkhig9 yzpv r9 .9z m2. )3* 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-tur-i d-h 2bqic/tja2l6ln 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 co/j ldc 2a-lhbi2tq 6-iil during this time?    $ \times10^{-4 }\;V$

  In (Fig. Below), the lx /8r.cvs: 6iaz(zesrod moves with a speed of 1.6m/s is 30.0 cm long, and has a res( z 6xr.elcv/:8sz siaistance of $\mathrm{2.5~Ω}$ The magnetic field is 0.35 T, and the resistance of the U-shaped conductor is $\mathrm{25.0~Ω}$ at a given instant. Calculate
(a) the induced emf, $\varepsilon$ $\approx$    V(retain two decimal places)
(b) the current in the U-shaped conductor, $I\approx$    $ \times10^{-3 }\;A$ (retain one decimal places)
(c) the external force needed to keep the rod’s velocity constant at that instant. $F\approx$    $ \times10^{- 4}\;N$ (retain one decimal places)

  A 22.0-cm-diameter coil consists of 20 turns of circular copper wire 2.6 m;jxez 7:me2n dp/ /u5idtx/d pm in diameter. A uniform ma mipn2eu5/dp ejdd/: /7xz;x tgnetic 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 perpendicular3r 0f ijluevv*cv6 +5q to a single 13.2-cm-diameter circular loop of copper wire decreases uniformly from 0.750 T to zfjr6v03c +qiulv *e5vero. 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. Thev1yd ft*e*gllsjua* 0k. 4- ch square armature consists of windings that are 6.0cl*d vsyu**lkh ft 4-.g1a0ej 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 12.4 V. What will the ou tpu6u 386h9 hg; sqsnedqzomg) .wt be at a rotation speed of 2500 rpm, assuming nothing else cha93 hgqow eszhs)nudm;.qg 866 nges?    V

Show that the rms output (Section 18–7) o u*z: ltynl-e u6)p4tff 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. ktj3t6 co.l56:fgqm g0 cm on a side. How fast must it turn in a 0.650-T field to pl53f6 o.:g6jqtk gmtc roduce a 120-V peak output? $f$   rev/s

  A 450-loop circular aenmp:jl ;ml9dl pwm0,p;k;l5 rmature coil with a diameter of 8.0 cm rotates at 120rev/s in a uniform magnetic;jm lwnll9:m ,l05;ep dm;pk p field of strength 0.55 T.
(a) What is the rms voltage output of the generator? $\approx$    V (Round to the nearest integer)
(b) What would you do to the rotation frequency in order to double the rms voltage output?  ----待选择----oncedoubletriple  the rotation frequency

  A generator rotates at9/iqkjb- 46v c-asexy 85 Hz in a magnetic field of 0.030 T. It has 1000 turns and produces an rms voltage of 150 V aa ekc iq9b /-6j4sv-xynd 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 resist8fdki0o k v6/nance 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 k2jg+ s-i-) r sh*qguhthe back emf at 2500 rpm if the i*-s2k ju+hs gq g-rh)magnetic field is unchanged?    V

  The back emf in a motor is 95 V when the motor is operating at 100-- zmwh y -*s *kb:y0gikoz9wu0 rpm. How would you change the motor’s magnetic field if you wanted to reduce the back emf to 65 V when the motor was running at 2500 rpm? reduce the ma o- z yg*-yzkhmkib09sww*-: ugnetic field to    % of its original value

  What will be the current in thopgzc 2caga+5p1) : m.c r;mf9vf4wlwe motor of Example 21–9 if the load causes it to run at half sf ;5)momzc rgwf 4.+pca1c wa2vg9 p:lpeed?    A

  A transformer is designed to change 120 V into 10,000 (/bqss4t 1kdah)m x 87flx+j k* jrc6l4q ccx0V, and there are 164 turns in the primary coil. How many turns are in tc7 s4/h*6m4a+ qkb1tj0k slxj xc8) fqd(xlcrhe secondary coil? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ $\approx$    turns

  

  A step-up transformer increases 25 V to 120 V. What iamwb0 u7t awx)1yji..s the current in the secondary coil a7ubt1mijw.ax)awy 0 .s compared to the primary coil?   

  Neon signs require 12 kV for their operation. To operat(8+6ieor +t pj , scg6,q (bmw;sysjzce from a 240-V line, what e ,+zs, roysp6cq8ci bwjtm6g(+ (sj;must be the ratio of secondary to 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.l*d e s2:moz8 *rjkyc;35 A while supplying 7kzl oec:sj8 m**2ry d;.5 A 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 the input current iszq w9g(2p /:pef4v dny 22 A. wvgn29/yqp df4p:ze(
(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 33r:u. 5+hvyg ej0 primary turns and 1340 secondary turns. The input voltage is 120 V and the output current is 15.0 A. What are the output voltage and input curr.5ehg+j :vy ruent? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ =    V
$\frac{I_\mathrm{s}}{I_\mathrm{p}}$ =    A

  If 30 MW of power at 45 kV (rq598naxwc.sy 7; jzokms) arrives at a town from a generator via $\mathrm{4.0-Ω}$ transmission lines, calculate
(a) the emf at the generator end of the lines, $\varepsilon$    V
(b) the fraction of the power generated that is wasted in the lines. fraction wasted   

  65 kW is to arrive at*tn y -1nz(ab*hr4 jps a town over 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 bl0nrx80b ht;coil changes steadily from 25.0 A to 10.0 A in 350 ms, what is the magnitude of the inxn0l; 8r0tbhbduced emf?    V

  What is the inductance of a coilsm,;u9h gw )wqhxb;x. if the coil produces an emf of 2.50 V when the current in it changes from -2s;wxx wuhgb m,.)9h;q 8.0mA to +31.0mA in 12.0 ms?    H

  What is the inductance L of a 0.60-m-long air-fil7xl,9;ux hxta led coil 2.9 cm in diameter containi9u hxx;l x7,atng 10,000 loops?    H

  How many turns of wire would be requirxk:nd vkc+3r)ed to make a 130-mH inductance out of a 30.0k)3 rn:xc +kdv-cm-long 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 i96zz j xk-i/ma nkd w1)wrf65rs 2.5 cm in diameter and 28.2 cm long. 6k9a1i-kj drwx)rzz/56 nmwf
(a) What is its inductance?    $ \times10^{-2 }\;H$
(b) How many turns would you need to generate the same inductance if the core were iron-filled instead? Assume the magnetic permeability of iron is about 1200 times that of free space.

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

A long thin solenoid of length l and cross-sectional aa3se .m;4kw eerea 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 tightlyt5h ltk,w7usxflxu.r az(hh 0jh 8,- 4 wound solenoid is unwound and used to make another tightly wound solenoid of twice the diameter. By what factor does the inductance change? j40(8al.hrhf-xkl,hx7,s5zhtutwu  

  The magnetic field inside049 t rojpwb.f an air-filled solenoid 36 cm long and 2.0 cm in diameter isr9tf4w jp0ob. 0.80 T. Approximately how much energy is stored in this field?    J

  At a given instant the current through an inductor iud 1:+ped;( sc-rmz lsyfcgg3 (p0y9 us 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 tacul ; (d(f:9esmyygr 1pdp s 0ug+cz3-ke for the energy to increase by a factor of 10 from the initial value?
U =    $ \times10^{-5}\;J$
$\Delta$t=    s

  Assuming the Earth’s magnetic field averagenc1kw1chm /pbt+ s s:).ogyv9s 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. Below) reach wihh9r/m5e2v kqr6 i dkwg13-qothin
(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 (db cwl3ar * sqdty84-9fjctw 4fm 5(scross-sectional area. (ytm ( csw5qsd-bcj l3 a 4w9drt4f8*fBut 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 -1up:/ 6mkwz4episna av(* gvof 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 rzc-nwn p9;d)r f:c8 a8i*nfepeactance of $660 \mathrm{k} \Omega ?$    Hz

  At what frequency wi ;or. b8 /w7ve:m,xu uugu qh4c8hc7jqll a $2.40-\mu F$ capacitor have a reactance of $6.70 \mathrm{k} \Omega ?$    Hz

Plot a graph of the -s4fmad-pr / jreactance 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 frequxx gctg(c6rh(zl + (0fm0/p lharc9 +nency from 100 to g+c(n09rat/l6 xgh0f(z h(l+x c rmcp10,000 Hz.

  Calculate the reactance ovk1(ep(u og 1lf, and rms current in, a 160-mH radio coil connected to a 240-V (rms) 1(e11lkg uo (vp0.0-kHz ac line. Ignore resistance.
$X_L$ =    $\Omega$
V =    $ \times10^{-2 }\;A$

  An inductance coil operates at 2407. d;u r7msnnub(4i ko V and 60.0 Hz. It draws 12.8 A. What is the coil’s ikdso.4rnbu;(7m n7 iunductance? $X_L$ =    $ \times10^{-2 }\;H$

  (a) What is the reactance of n/alp6g-)jjbzexgzdb9 75b1+ug +l ta 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 rms6)5 dnftth1uns4 w um2m3qnby 9ynr:3 current of 70 mA passing through the human body for 1.0 s could be lethal. What must be the impedance of the bod)wh ym2s 1my4t5t393qfdn b 6n: ruunny for this to occur?    $ \times10^{3 }\;\Omega$

  What is the resistance of a coil if its imqu4 jub-;gp( kpedance is $\mathrm{235~Ω}$ and its reactance is $\mathrm{135~Ω}$    $\Omega$

  What are the total impedance, phase angle, and rms current f d1ja)+zm/x9 uex) vcin an LRC circuit connected to a 10.0dfaxj1+e uv/x9zm)c)-kHz, 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 avxc 0 8d+0roti2xg fz9 420-mH inductor is driven by an ac power supply. At what frequency is the impedance double that of the g0x+ic 2fvt0zxd 9o8rimpedance at 60 Hz?    Hz

  (a) What is the rms current in an RL circuit when a 60.0-Hz 12reb8;w*tby 1lq2uytw p;. u u/ vt/rr80-V rms ac voltage is applied, wher e*8tr br.uryuq8ulw1vpt2;/;/ w btye $R=1.80\mathrm{~k}\Omega,$ 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 iah+ug6w*0 iwn f $R=8.80\mathrm{k}\Omega,C=1.80\mu\mathrm{F},$ 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 connected to a 1b3jcy,y,n le$55.0-\mu H$ 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 capacit-q9jpx3v1oww/exgk8 vyn 7 4 yance of 2800 pF when the radio is tuned to a station at 580 kHznvy x7wy4 /1kqjv 8gep-3w9xo .
(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 8q se-hq8 jy.t r7czfzmbf).)juap51 = 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 current loops in the plane of the pak/ 6)oet ajdbmvo+t );ge as shown in (Fig. Below). When skm/;a bo6oetj t+) v)dwitch 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 resi,izn ; pc: h.rwywm2v7stance 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 4lghiiaoc22 h,( ;bi-f.nwe0u 5 W but requires only 12 V. It contains a transformer tho2i2 e.fi, (0gain bhuwc;h-l at 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 plant located g+.ky8,z1v f 1hz3x0ds)a 4upwua5bnz)ytxk 118 km from a town that requires 50 MW +5n4z,dvpy)3g k b1z8sa zkwu1y )x0.htaufxof power at 12 kV. Two transmission lines from the plant to the town each have a resistance of $0.10\mathrm{~}\Omega/\mathrm{km~}.$ What should the output voltage of the transformer at the generating plant be for an overall transmission efficiency of 98.5%, assuming a perfect transformer? V $\approx$    kV

  The primary windings of a transformer which has an 80% effe,*r g*43r61 jveenb1 q3vey j 8hbykqiciency are connected to 110-V ac. The secondary windings eqv*1ejvr nryjqbky3eg 61* 3b8,4e hare 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 l m0r4+2*ckdizxrx8*/k .ab2m vqa n nqines each have a $0.80-\Omega$ resistance and carry 740 A over 9.0 km. If the rms input voltage is 42 kV, calculate
(a) the voltage at the other end, $\approx$    kV
(b) the power input, $\approx$    $ \times10^{7 }\;W$
(c) power loss in the lines, $\approx$   $ \times10^{5 }\;$W
(d) the power output. $P_{out}$ $\approx$    $ \times10^{7 }\;W$

  Two resistanceless rails restg/j-c kh8vufp7u c*b - 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 transmissiootw.9 u i(3vu dn8g:jei5b9ayn 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,ry: jetm*-ij0++-lko8 kldj-ptjo0 l a radius of 5.0 cm, and a resistance of $\mathrm{12~Ω}$ surrounds a solenoid with $230\mathrm{~turns/cm}$ and a radius of 4.5 cm; see (Fig. Below). The current in the solenoid changes at a constant rate from 0 to 2.0 A in 0.10 s. Calculate the magnitude and direction of the induced current in the coil.
I =    $ \times10^{-2 }\;A$
 ----待选择----left to rightright to left 

  A certain electronic device needs to be .fl2q t6s6j* bcm .uyzh2j3ro protected against sudden surges in current. In particular, after the power is turned on the current shoul m6h6f.b j jqz*co2us .t2rl3yd 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 elect;gltp bnrd-b, h+7 vf;/pal y*romagnet. When the magnet is turned on, the flux through the coil changes, inducing an emf. A-/l ;ra;vlnp7tyhbf +*bg pd,t 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 simplejhb;t i9yr6ay jxz1+. generator whose square armature windings are 6.60 cm on a side; the armature contains 155 loops and rotates in ajjhy6x;9ba tr1. z+yi field of 0.200 T at a rate of 120rev/s. $\varepsilon_{peak}$ =    V

  Typical large values for electric and magnetic fields attained in laboratorr )5iut7pyidfl / d7)qies are abouy7lt iu)p5rdq) 7df/ it $1.0\times10^4\mathrm{~V/m}$ 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 220 V 9ccs5 p,vo w;nxez1p;dmpk*4 at 60.0 Hz if the current drawn is 5.8 ozsxp;cmwv e p915dp,4kc;*n A? Assume no current in the secondary.    H

  A 130-mH coil whose resistance istkpw wmd37h- 7 $\mathrm{18.5~Ω}$ 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 wh0jh*to1gc(/ o zd4xix ft* /fren connected to a 36-V battery. When connected to a 60-Hz 120-V (rms) source, the current drawn is 3.8 A (rms). Determine the inductance and rx*iozt /ofx*h01td/gf (4c rjesistance of the coil.
$V_{dc}$ $\approx$    $\Omega$
L $\approx$   $ \times10^{-2 }\;H$

  A 135-mH inductor wit f7klm5 gny;o jkwhj;r(,,mm3h $2.0-\Omega$ 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 r2ymg.,e (5skdon6+ef;klhq*p cy y m0x de94eatio of the voltage across the capacitor (or inductor) to the voltage across the resistor, at resonance. The larger the Q factor, the sh0lk; ee,x 4(d2y.eks 9phyqfdomcey5m 6 g+n*arper 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$