What would be the advantage, in Faraday’s experime iuu.r9psuw./3cunqx x/(1 zwnts (Fig. Below), of using coils with many turu. z/(u iwrcxx3/.nus9qp 1u wns?

What is the difference between magnetic n.qfu(ij;ouh*df*1 9y4( ughq jvywb3a,,gxflux and magnetic field?

Suppose you are holding a circular ring of wire and s7q) ofev3hhlzc-o,/ auddenly thrust a magnet, south pole first, away from you toward the center of the circle. Is a current induced in the wire? Is a current induced when the magnet is held steady within the ring? Is a current induced when you withdraw the magnet? In each case, if your answer is yes, specify the direction)7 /l3faooz,-h hce vq.

Two loops of wire are moving in the vicinity of a r/jx ( rw eak:r/t39mks dki1-very long straight wire carrying a steady cur arkr1rmki/sxj - w9 ed:/k3t(rent as shown in (Fig. Below). Find the direction of the induced current in each loop.

Suppose you are looking along a line through th 8t5a qpi.s**s sfyix.e centers of two circular (but separate) wire loops, one behind the other. ipqsati**xf .. 5 8ssyA 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 thea*re*ohs r/q.9 h bijnq4*+-n2xdr vy 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 qolgncpz k -9d,k lw4ae2 --2la distance, a “shielded cable” is used in wg-n2klp d-a,9ok2l l - weq4zchich the signal 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 the two insulated electric wires carrdc6jowi.py*k+ 1apt 2ying ac close together or even twisted aboutd to.w 6k+p*ai1cj2 yp each other?

Explain why, exactly, the lights may dim brih)ptfq.bp31 s efly when a refrigerator motor starts up. When an electric heater is turnefbpp. 1s3 thq)d on, the lights may stay dimmed as long as the heater is on. Explain the difference.

Use (Fig. Below a) and (Fig. Belya n g)wr)uws+h ,m6:k) fhv/:dw2xmq ow b) plus the right-hand rules to show why the counter torq,gr+umw :v6n)w)dh a 2sfm k/xh):wy que in a generator opposes the motion.
a
b

Will an eddy currentw g49-y l3yepq brake (Fig. Below) work on a copper or aluminum wheel, or must the whew 4y3gy-q9pe lel be ferromagnetic? Explain.

It has been proposed that eddy currw d2-ef*o1ud jg vmq9(ents be used to help sort solid waste for recycling. The waste is first gro*wjdmdv1 o- 29(uefgqund into tiny pieces and iron removed with a dc magnet. The waste then is allowed to slide down an incline over permanent magnets. How will this aid in the separation of nonferrous metals (Al, Cu, Pb, brass) from nonmetallic materials?

The pivoted metal bacj;,uri 3bp 8nr with slots in (Fig. Below) falls much more quickly through a magnetic field thrp c ui;n,8bj3an does a solid bar. Explain.

If an aluminum sheet is held between the poles of awi;+9qi s-k,3ez micx ypbfixi u)7-: large bar magnet, it requires some force to pull it out offbzism:wy;ix xkc3i -pu)+i ei7q,-9 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 mz; t7zssx rl2v4t)6btube reaches a terminal velocity even if the tube is evacuated so that there is no air resmv4s;sz lrbz t62 )xt7istance. Explain.

A metal bar, pivoted at one end, oscyc 5rl*v0 ot-tillates freely in the absence of a magnetic field; but in a magnetic field, its oscillations are quickly damped out. Explain. (This magnetic damping is uset* t vyo-r0lc5d in a number of practical devices.)

An enclosed transformer has four)q69cg ,b fulgcf:s1c wire leads coming from it. How could you determine the ratio of turns on the t9qf bu) c,1ccs:6fg lgwo coils without taking the transformer apart? How would you know which wires paired with which?

The use of higher-voltage wq 68ovi auhmp rup+z t5v71s*3n*,*p* pklojlines in homes — say, 600 V or 1200 V — would reduce energy waste. Why ara*op8hnrv pv6i*3**ujlutpq7 s, 5ozw 1pkm+e they not used?

A transformer designed for a 120-V ac input will often “burn out” if connff 9d;g2ehtw c/3wnd(ected to a 120-V dc source. Explain. [Hint: The resistance of the 9hfdg (ndwf/w;e tc23 primary coil is usually very low.]

How would you arrange two flat circular coiw1og+pyz)maz(n; 4u x ls so that their mutual inductance was g;ap(mu)x y41zwn+oz
(a) greatest,
(b) least (without separating them by a great distance)?

Does the emf of the battery in ajqc ,,,r.sh: imy xjc1q5lliy su, 28(Fig. Below) affect the time needed for the LR circuit tyjac,qs. i sm1il u8qcxh j,,r5ly:2,o reach
(a) a given fraction of its maximum possible current,
(b) a given value of current? Explain.

  In an LRC circuit, can the rms voly4 2l4(pa +si ad*o /hrsm,pzctage 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 frequency3vh )jk1 wxo9h,,e:zrhmae 5y of the source emf affects the impedance of
(a) a pure resistance,
(b) a pure capacitance,
(c) a pure inductance,
(d) an LRC circuit near resonance (R small),
(e) an LRC circuit far from resonance (R small).

Describe how to make the impedance)2f8kzfx i)rm in an LRC circuit a minimum.

  The magnetic flux through a coil of wire conti yac(4/ co0sv3q;qiqaining two loops changes from -50Wb to +38 Wb in 0.42 s. What is the / i3vyc(cs a qiqq;o40emf induced in the coil?    V

  The rectangular loop shv2/ 9ilxlu,g/+ld h mnown in (Fig. Below) is pushed into the magnetic field which points inward. In what direction is the indu+i/nldlh9 uxg,2 /vmlced current?  ----待选择----counterclockwiseclockwise 

  The north pole of the magnet in (Fig. Below) is bi9jiqr2c/ .wiz yzu8; eing inserted into the coil. In which direction is thej; 8uiwziyrizc9/q. 2 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 a 1.10-T magne d1p3rgriz 4oo7st. cu0:m 2tgtic field. The loop is removed from the field in 0.15 s 4osggmti.:3 r1 dczo0r7tu p2. What is the average induced emf?    $ \times10^{-2 }\;V$

  A 12.0-cm-diameter loop of wire is initially oriemqivk y(/ek):k5 mr4us;sth 7nted perpendicular to a 1.5-T magnetic field4q kke7: i5mk;u/ yrsm) h(tsv. The loop is rotated so that its plane is parallel to the field direction in 0.20 s. What is the average induced emf in the loop?    $ \times10^{-2 }\;V$

  A 10.2-cm-diameter wire coil is initially oriented so that its plane ic+wxrnt-h zix xi5 47)s 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 the average induced emf in the c 4ihwt5)rc- x7xn+xz ioil?    $ \times10^{ -2}\;V $

  A 15-cm-diameter circular loop of wire is pl(o.6- oy viviuaced in a 0.50-T magnetic field.
(a) When the plane of the loop is perpendicular to the field lines, what is the magnetic flux through the loop?    $ \times10^{-3 }\;Wb$
(b) The plane of the loop is rotated until it makes a 35$^{\circ}\,$ angle with the field lines. What is the angle $\theta$ in Eq. 21–1 for this situation? $\theta$ =    $^{\circ}\,$
(c) What is the magnetic flux through the loop at this angle?    $ \times10^{-3 }\;Wb$

  (a) If the resistance of the resistor in (Fig. Below) 6ew ;mct+; gm9h smn/xis slowly increased, what is the direction of the cumm+e6 hc9g;xn;tsw /m rrent 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 the circular loop due ( e+ek;6ypg ba gq)sp)to the current shown in each part (p+ eggbp)ks; ea)y6q of (Fig. Below)?
a  ----待选择----counterclockwiseclockwise0 
b  ----待选择----counterclockwiseclockwise0 
c  ----待选择----counterclockwiseclockwise0 
d  ----待选择----counterclockwiseclockwise0 

  If the solenoid in (hjq4:e+z vs e*Fig. Below) is being pulled away from the loop shown, in what direction is vs4qee+z :jh*the induced current in the loop?  ----待选择----counterclockwiseclockwise 

  The magnetic field perpendicular to a circular wire loop 12.0 cm in n:(z h ,apgv/xdiameter is changed from +0.52T to -0.45 T in 180 ms, where means tgan, xzv/(:hphe 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 long and is pulled at a speed of 15.0cxgere+5 3 fh:u/,9jrel nh2jsm/s If the mag5r/ee h3e+ sjxjnh uf lgr2:,9netic 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 of the paper l5rt7xa0xd+t s ies in a 0.75-T magnetic field pointing into the paper. If the loosrad0t7 x+tx 5p’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 gen 1 n5* bodja4t9(b id8zun*blaerates an emf of 120 mV while moving in a 0.90-T ma 15a au8(oitzd* b bd9lnbn*4jgnetic 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 rectangudlaf o:t4mc707- zze *ieo5*dktv n8ilar loop of wire with dimensions shown in (Fig. Below) is situated inside a regif*te-okvl7 7znimea4* ciz t 5o0dd8:on of uniform magnetic field of 0.550 T. The total resistance of the loop is $\mathrm{0.230~Ω}$ Calculate the force required to pull the loop from the field (to the right) at a constant velocity of 3.40m/s Neglect gravity.    N

  A 500-turn solenoid, 25 cm long, has a diameter of 2.56fprcj5wmx7i,:i1 ;tzg. z, gi9 occ q cm. A 10-turn coil is wound tightly around the center of the solenoid. If the current mco6 ct9; q15,gzw gf7ii. rci:zpx,j in the solenoid increases uniformly from 0 to 5.0 A in 0.60 s, what will be the induced emf in the short coil during this time?    $ \times10^{-4 }\;V$

  In (Fig. Below), the rod moves with a speedk) z (dze d-llbe+,+kv of 1.6m/s is 30.0 cm long, and has a resis -,vdbzz+ede(lk+)kltance 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/ivrk k5grn+ zt6m-,p of circular copper wire 2.6 mm in diameter. A uniform magnetic field, perpendicular to the plane of the coil, change+-i vpr6k,mrgnt/kz 5 s 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 perpendk bmu.on8 ,i2 :qw)vanicular to a single 13.2-cm-diameter circular loop of copper wire decreases uniformly from 0.bk:u).woaq n,n2 m8v i750 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 out(y-canc7sa2 s f .z;ztput voltage of 24.0 V. The square armature consists of windings that are 6.0 cm on a side and rotat z;.ct2-s cn7ysa(afz es 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 7d jpab,*y qz6V. What will the ou tput 6 dbp*j ya7,qzbe at a rotation speed of 2500 rpm, assuming nothing else changes?    V

Show that the rms output+cu**ead9 w6: zxxv:j w0d auz (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 xurihv c/ lc,s0:es8(square coil 21.0 cm on a side. How fast must it turn in a 0.650-T field to produce a 120-V peak oi,rxc h:sv(c8uel 0s /utput? $f$   rev/s

  A 450-loop circular armature coil witi5zfd,uu-wn4,zl*6 ybjk ijy6w6 ) ohh a diameter of 8.0 cm rotates at 120rev/s in a uniform magnezi)j uw5u y j4wbi,6fyzhd,* 66lo-nktic field of strength 0.55 T.
(a) What is the rms voltage output of the generator? $\approx$    V (Round to the nearest integer)
(b) What would you do to the rotation frequency in order to double the rms voltage output?  ----待选择----oncedoubletriple  the rotation frequency

  A generator rotates at 85 Hz in a magnetic fie*w wxey p49jw9ld of 0.030 T. It has 1000 turns and produces an rms voltage of 150 Ve4wjw*9py wx9 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 resistance ofmtt/s8,g thm/. guxm2 $3.25\Omega.$ 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 whejr(g73l 4f)yn8 o sw t0wz5gqtn operating at 1800 rpm. What would be the back emf at 2500 rpm if the magn g08ly4q 7w 5g rts)tjofwn3(zetic field is unchanged?    V

  The back emf in a motor is 95 V when g uj ;7x0blovlxl/uqj,fyyr53 6n/,j the motor is operating at 1000 rpm. How would you change the motor’s magnetic ,53vl ;o//rqfbu x7y ylln6,jxj0ujg 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 motor of Example 2/ jdo;w ezj 0giz:v0lrd88zq; 1–9 if the load causes it to run at half s j0w;8;zvd/:loqgziej 0zd 8 rpeed?    A

  A transformer is designed to change 120 V into 10,000p*b eu v(cg8f/ V, and there are 164 turns in the primary coil. How many turns are in the secondary coil?e /f8gb*uvp (c $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ $\approx$    turns

  

  A step-up transformer increases 25 V to 120 V. What is the current in the sec5 f5ra ip8u.ycondary coil asy.8r a5 fcpu5i compared to the primary coil?   

  Neon signs require 12 kV for their operation. To operate dv/y-7c6cvfx;dvz1 i 4 ukh.xfrom a 240-V line, what must be the ratio of secondary to pxu;i1 cxk47z y df-v.vh6/ dvcrimary 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 transform o* hptld.a rk5 q+a:5 52aa6iz6gbnryer plugs into 120-V ac and draws 0.35 A while supplying 7.5 A to 5. :r noaaih+6g6b*lka at5dz2y5pq r 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 is 22 A8 6u3d8gl lxfnz 7+tnu.z f3ul86l7du +gxnn 8t
(a) Is this a step-up or a step-down transformer? this is a  ----待选择----step-downstep-up  transformer
(b) By what factor is the voltage multiplied? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ =   

  A transformer has 330 primary turns and 1340 secondary turns. The input voltage p hj- +mr;hn6zis 120 V and the output current is 15.0 A. What are the output; h mn+hjr-zp6 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 town from a generatorxa,m*kk )vj2. 3d,n(slrjlze 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 ri03u d0jv i f5o zb*z1n./gobover two $0.100-\Omega$ lines. Estimate how much power is saved if the voltage is stepped up from 120 V to 1200 V and then down again, rather than simply transmitting at 120 V. Assume the transformers are each 99% efficient.    kW

  If the current in a 180-mH coil changes steadily from 25.0 A to 10.0 A,.hd.bn k2on l in 350 ms, what is thndl h. 2nb.ok,e magnitude of the induced emf?    V

  What is the inductance of a k3d o)jgql /t,coil if the coil produces an emf of 2.50 V when the current in it changes from -28.0mA to +31.0m,3 olj)/tqk dgA in 12.0 ms?    H

  What is the inductance L of a 0.60-m-3)fjqof)hjt 6h :w.w/o.wz b glong air-filled coil 2.9 cm in diameter cont)g:)wt o6 /w wzbh.j f.jofhq3aining 10,000 loops?    H

  How many turns of wire would be required to 4njr )uwi+wo9v,33bom 1 i5x wjkbs5imake a 130-mH inductance out of a 30.0-cm-long air-filled coil with a diameter oj3 1un3wo+iiiv k,sx5b94obwj wrm5 ) f 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 dom ,qg;+vqd d9iameter and 28.;,dgovd qm9+ q2 cm long.
(a) What is its inductance?    $ \times10^{-2 }\;H$
(b) How many turns would you need to generate the same inductance if the core were iron-filled instead? Assume the magnetic permeability of iron is about 1200 times that of free space.

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

A long thin solenoid of length l and cross-sectional alr.,fzaw-rze.2y * o nrea 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 unwound an.f ojo,gibd,ab4ea ),d used to make another tightly wound solenoid of twice the diameter. By what factor does the inducgoeb4jdb),,,o af.i atance change?   

  The magnetic field inside an au7 or2 ahm1s,vnf2o9 1m wsja7ir-filled solenoid 36 cm long and 2.0 cm in diameter is 0.80 T. Approximately how much energy is storeo2s 7 oj2waufnh1r7m9mv1,sa d in this field?    J

  At a given instant the currer;vh4arej.2 v8s vmf;nt through an inductor is 50.0 mA and is increasing at the rate of 115mA/s. What is the initial energy stored in the inductor if the inductance is known to be 60.0 mH, and how long does it take for the energy to increase by a factor of 10 from the initial value?m 8;vv4;fse r 2jvh.ar
U =    $ \times10^{-5}\;J$
$\Delta$t=    s

  Assuming the Earth’s magnetic field averagesaik173jdp*j+,qesv4nd( l yg 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 currento/r qr;)9y gl:1pjkg)gc avl 3 in (Fig. Below) reach within
(a) 10%,    $\tau$
(b) 1.0%,    $\tau$
(c) 0.1% of its maximum value?    $\tau$

  Two tightly wound solenoids have the same length and cirfo/ o*nltd l4 1 j htolj8aref-*)yq-3cular cross-sectional area. But solenoid 1 uses wire that is half l-4 fjl qh oor*f3aj-lney8)1tt/d* oas 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 of yyx6/a q.5yf ka $7.20-\mu F$ 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)req6z b,r ;ep1z8mtp have a reactance of $660 \mathrm{k} \Omega ?$    Hz

  At what frequency will a,d /4vb-muvge+c :,1yfh jbfy $2.40-\mu F$ capacitor have a reactance of $6.70 \mathrm{k} \Omega ?$    Hz

Plot a graph of the reactance oq(i:v)81vl ytwgi l 3pvp*.hi f 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 freqd-t+2 xgf( z./)vq vl-j ymvsh ph(,vruency froz v 2 ,/f(dtmpsh(-jqvvrhy).g x+lv-m 100 to 10,000 Hz.

  Calculate the reactance of, and rms current in, a 160-mH rad2c ,ctse/jfg)nr) gf6io coil connected to a 240-V (rms) 10.0-kHz ac line. Ignore,gf ccf gse j)trn6)2/ resistance.
$X_L$ =    $\Omega$
V =    $ \times10^{-2 }\;A$

  An inductance coil operates at 240 V and 60.0 Hz. It draws 12.8 A. Whatt tm+io2ir+ 1y is the coil’s inducti1y+ m2iort t+ance? $X_L$ =    $ \times10^{-2 }\;H$

  (a) What is the reactance. :j0dri bt.ja of a well-insulated $0.030-\mu F$ capacitor connected to a 2.0-kV (rms) 720-Hz line?    $\Omega$
(b) What will be the peak value of the current?    A

  $\mathrm{A~30-k}\Omega$resistor is in series with a 45-mH inductor and an ac source. Calculate the impedance of the circuit if the source frequency is
(a) 50 Hz,    $ \times10^{4 }\;\Omega$
(b) $3.0\times10^4\mathrm{~Hz}.$    $ \times10^{4 }\;\Omega$

  $\mathrm{A~3.5-k}\Omega$ resistor and a $4.0-\mu F$ capacitor are connected in series to an ac source. Calculate the impedance of the circuit if the source frequency is
(a) 60 Hz,    $ \times10^{3 }\;\Omega$
(b) 60,000 Hz.    $ \times10^{3 }\;\Omega$

  For a 120-V rms 60-Hz voltage, an rms current o98x flb-nv q-jf)fhky- +z g3ypt4k. rf 70 mA passing through the human body for 1.0 s coulk3 rnthq-g-jk.py-+vl84 f bx )y 9zffd 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 impedawqp,lgee 0 e-7 xyia* 4pf53rwnce is $\mathrm{235~Ω}$ and its reactance is $\mathrm{135~Ω}$    $\Omega$

  What are the total impedanceuy6m 1/hs1ve e, phase angle, and rms current in an LRC circuit connected to a 10.0-kHz, 725sv1m y6euh1e/-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 w e9k qoum*e65jdkx 2u-ith a 420-mH inductor is driven by an ac power supply. At what frequency is the impedance double that of the impedance at 60 H*-5q u e92kekj domu6xz?    Hz

  (a) What is the rms cu7q+ou6i8 l;ncwg-t. e1 yzzn lrrent in an RL circuit when a 60.0-Hz 120-V rms ac voltage is appoiezw8n +yt 1cugz-ll76 .n; qlied, 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 rd sor0jk2t eq+ic.o /mx8(j 8an RC circuit if $R=8.80\mathrm{k}\Omega,C=1.80\mu\mathrm{F},$ and the rms applied voltage is 120 V at 60.0 Hz?    $ \times10^{-2}\;A$
(b) What is the phase angle between voltage and current? $\phi$ =    $^{\circ}\,$
(c) What are the voltmeter readings across R and C?
$V_{rms\,R}$   V
$V_{rms\,C}$    V

  A 3500-pF capacitor is connecte-l-4tyz3(fgl c,o(0uh5pf f t efzm,5qka e-wd 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 of 280x *2ui wx :(hdy+k-ovs0 pF when the radio is tuned to a statioyv2 swi*(k +-:xduox hn 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 = 2.8q3clqkl, r k4d8gkhv xzq414.8 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 di;gk5 9m 6j)gui mdu3current loops in the plane of the page as shown in (Fig. Below). When switch S is thrown in the left-hand coil,j)im;35 gmiugd9 u kd6
(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 sido8o,p6byh/ecme yz 3e1llx7,e has 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 tm-1i )wjah9 d45 W but requires only 12 V. It contains a transformer tha1-a dhi9wm)j tt 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 atnqbl t7 f07*jq 24 kV at a generating plant located 118 km from a town that requires 50 MW of power at 12 kV. Two transmission lines from the plant to the fj*qb q7nlt0 7town 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 has1ar2c(j9 9j:uzxt yc p an 80% efficiency are connected to 110-V ac. The secy 9 t2ja1cz9: ux(jprcondary 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 3/l6vd/mic3 j+j a. 2yvgvfkneach have a $0.80-\Omega$ resistance and carry 740 A over 9.0 km. If the rms input voltage is 42 kV, calculate
(a) the voltage at the other end, $\approx$    kV
(b) the power input, $\approx$    $ \times10^{7 }\;W$
(c) power loss in the lines, $\approx$   $ \times10^{5 }\;$W
(d) the power output. $P_{out}$ $\approx$    $ \times10^{7 }\;W$

  Two resistanceless rails rest 32 cm apzjj*: kh8ad0:v phg/qav4a1b art 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 transmissi qd n::q;xun;pon 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, an+ n 6/a/dgqfyod 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 deviry14)uog2ln4q sjoq.4p byi1 ce needs to be protected against sudden surges in current. In particular, after the power is turned on the current shouyoq124up)14 og4 sbqlj i.yrn ld 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 isl3tom8+ za3v q placed between the pole pieces of an electromagnet. When the magnet is turned on, the flux through the coil changes, inducing an emf. At what rate (in T/s) must the field produced by the magnet change if the +m8tv3 lo3qaz emf is to be 120 V? $|\varepsilon|$    T/s

  Calculate the peak output voltage of a simple generator whose square ai xx6y j+cs ,/iw:cp5zrmature windings are 6.60 cm on a side; the armature contains cxxc+i5js/ z,iypw:6 155 loops and rotates in a field of 0.200 T at a rate of 120rev/s. $\varepsilon_{peak}$ =    V

  Typical large values for electric and magnetic fields attainedr uch1(cc0q3cw1)ndn in laboratories are ab1)(cw3cnd0nc ch1uq rout $1.0\times10^4\mathrm{~V/m}$ 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 tran3 m*tb8phicp.t bjqzku,/fdh8j7 e(-sformer whose input is 220 V at 60.0 Hz if the current drawn is 5.8 A? Assume no currentbf7mejq.(pj bcpuk zt3t, -8h8d* / hi in the secondary.    H

  A 130-mH coil whose resi* ydo r2fnb-g3( ldlt-stance 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 c xs*;/rgxqx xjub a ja79ebq 1j*4yz9*onnected to a 36-V battery. When connected to a er*x u7x ;qg*xxb/jj*bsaq 4 a9j1 9yz60-Hz 120-V (rms) source, the current drawn is 3.8 A (rms). Determine the inductance and resistance of the coil.
$V_{dc}$ $\approx$    $\Omega$
L $\approx$   $ \times10^{-2 }\;H$

  A 135-mH inductor with 1;dyib- n-olsi9hgvr0 n s/1n $2.0-\Omega$ 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 circui wpi qr3bz:4:st can be defined as the ratio of the voltage across the capacitor (or inductor) to the voltage acrbs 3pqi4r w::zoss 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$