What would be the advantage, in Faraday’s experiments (Fig. Below), of usirx +bo-w(c f :m80zzmwng coils with mzxm(8:wfz0 oc -m+rwb any turns?

What is the difference between magnetic fluxd(agc80th3jt+edc a6z7 9x hk and magnetic field?

Suppose you are holding a circular ring of wd. c v ns1 sz3fzo.knbi-o,3f4ire and suddenly thrust a magnet, south pole first, away from you bz k,nn31.fscio 4v- f.d3szo 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.

Two loops of wire are moving in theeqzb; t *-edv( vicinity of a very long straight wire carrying a steady current as shown in (Fig. Below)t- bz d;*(veqe. Find the direction of the induced current in each loop.

Suppose you are looking along a line through the centeu hjl* p0x/zz2rs of two circular (but separate) wire loops, one behind the other. A battery is suddenly connected to the front loop, establisx2j0lhp/z* zuhing 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 curre2c fr7j+sp-dj nt 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 si02 4xsd9oocwpzo u.v-gnal must travel over a distance, a “shielded cable” is used in which the signal wire is surrounded by an insulator and then enclosed by.90swzov -p2 oxcu4d o a cylindrical conductor carrying the return current. Why is a “shield” necessary?

What is the advantage of placing the two insulated electric wires carrying ac cli8ngo cmr:t jm)w /y7nm; c+9 0qknc-0.lt ctuose togem-/y gjc+lwtrt0kcqm m;)u c: in8nn70c9o .tther or even twisted about each other?

Explain why, exactly, the lights may d5p/ri3s5 we fiim briefly when a refrigerator motor starts up. Wheer i/pwis3f55 n an electric heater is turned on, the lights may stay dimmed as long as the heater is on. Explain the difference.

Use (Fig. Below a) and (Fig. Below b) plus the right-hand rules to show whyssjb,g fn 0s gs589;ko the counter torque in a generator opposes89ofns 0gsjks5g, b;s the motion.
a
b

Will an eddy current brake (Fig. Below) work on a copper or alu: w 6wvze jeu)c:4sye 9ix:u:xminum wheel, or must the whee:xw: jc6i:yuezx e 4w) uv9:sel be ferromagnetic? Explain.

It has been proposed that eddy currents be used to help sort solid waste for r93r egny 0(nmwprgy10ecycling. The waste is first ground into tiny pieces and iron 1ygrrgmn9030n peyw( 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 quic xxz-oi2v*nybw. uqjn; bb3 01kly through a magnetic field than does a solid bar. Explain.-i*vwy 13 nxqb2n;u. bxzojb0

If an aluminum sheet is held between the poles of a large /0zlo/v)4fk4 tcxf,figwx; b bar magnet, it requires some force to pull it out of the magnetic field even though the sheet is not ferromagnetic /f ,0l /x wgfxt4if4czkb);ov and does not touch the pole faces. Explain.

A bar magnet falling inside a vertical metal tub igmps/vc(s.4ie,y :hj 5 s:ple reaches a terminal velocity even if the tube is evipsve gs ,yplhic: s/(4:.5jmacuated so that there is no air resistance. Explain.

A metal bar, pivoted at one end, oscillates freely in the absence of a magneewdsxc*z n)077y 3 gentic field; but in a magnetic field, its oscillations are )snn e3wz*7excg0yd7quickly damped out. Explain. (This magnetic damping is used in a number of practical devices.)

An enclosed transformer has 4jh 5d)evm)f i*zslu9four wire leads coming from it. How could you determine the ratio of turns on the two coils without taking the trzjdimsf4*) vlhe9u5 )ansformer apart? How would you know which wires paired with which?

The use of higher-voltage li0sldlqh) ugxj7(- 1c enes in homes — say, 600 V or 1200 V — would reduce energy waste. Why are they nod )eu-xj s1ghq(7l0 lct used?

A transformer designed for a 120-V ac input will often “burn out” wm0 o8 hd;il a ;7ch;c w04:l(xxaxgjdif connected to a 120-V dc source. Explain. [Hint: The resistance of the prix:o;0hwg 4dj lcxd8 ;caam( h;x0iw 7lmary coil is usually very low.]

How would you arrange two flat circular coils so that their mye ylz5b*i6c9slemihm 8 1:2h utual inductance was1byllh yem:mc*ii9h 56 s28ez
(a) greatest,
(b) least (without separating them by a great distance)?

Does the emf of the battery in (Fig. Below) affect the time needed forc8d wbw1ll*+a the LR circuit to rea d+aw8c *1wllbch
(a) a given fraction of its maximum possible current,
(b) a given value of current? Explain.

  In an LRC circuit, can the t,)4uouu .ovnrms 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 f qhd32-/bbvrp requency 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 in an LRC circuit a minimumon(i3 et r4:/zxrj2 a,ws0fxf.

  The magnetic flux through a coil of wire containing two loops chan vxtd(l/)u f 7vqhvad-:y,r8 wges from -50Wb to +38 Wb in 0.42 s. What is the emf induced in the coil?fud:tvdvwr,hav7x/q-y (l 8)    V

  The rectangular loop shown in (Fig. Below) is pushed into4ym/m 8d6)s) qv7rvipfp wj0 q the magnetic field which points inward. In what direction is the induced currenm) ifmr)jpp846 y7q sq wv0v/dt?  ----待选择----counterclockwiseclockwise 

  The north pole of the magnet in (Fig. Below) is being in pdblu -+db878y.wxrhserted into the coil. In which direction is the indb. d y-d7wh8x8+pbulruced 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 magnetic field. The sy74oh9s1 flsloop is removed from the field in 0.15 s. Whash49 1so7lfsy t is the average induced emf?    $ \times10^{-2 }\;V$

  A 12.0-cm-diameter loop of wire is initially oriented perpendicular to a 1.5-T ry4rr: ue)mr; magnetic field. The loop is rotated so that its plane is parallel to the field direction in 0.20 s. What is the average induced emf in th)rre u :ry;rm4e loop?    $ \times10^{-2 }\;V$

  A 10.2-cm-diameter wire coil is initially oriented so that it ).so8.ehx xfis plane is perpendicular to a magnetic field of 0.63 T pointing up. During the course of 0.15 s.efo) x.h8x is, the field is changed to one of 0.25 T pointing down. What is the average induced emf in the coil?    $ \times10^{ -2}\;V $

  A 15-cm-diameter circular loop of wire is placed in a 0.50-T m5 u( b zdxriu/c1pvsb(3:c.r4gl k* slagnetic 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) is s/ .odk9.c3bqt m*nfeg9y bm y9lowly increased, what is the direction of the current induced in the small circular loop inside the larg/9.dgey9.3* tof kcbn9 bmyqmer 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 circ5kn; zrzo0-nf ular loop due to the current shown in each part of (Figko nzz;r 0fn5-. Below)?
a  ----待选择----counterclockwiseclockwise0 
b  ----待选择----counterclockwiseclockwise0 
c  ----待选择----counterclockwiseclockwise0 
d  ----待选择----counterclockwiseclockwise0 

  If the solenoid in (Fig. Below) is being pulled away from srrc *2f9vi, ethe loop shown, in what directiosvrfrc,9 i2 *en is the induced current in the loop?  ----待选择----counterclockwiseclockwise 

  The magnetic field perpendicular to evd ,5b(+tp; 1e df*fk/bxz0i;y sm rda circular wire loop 12.0 cm in diameter is changed from +0.52T to -0.45 T in 180 ms, w xdf,bk0mee5;;t /did*yrf(v1 zbs p+here means the field points away from an observer the observer.
(a) Calculate the induced emf.    $ \times10^{-2 }\;V$
(b) In what direction does the induced current flow?  ----待选择----counterclockwiseclockwise 

  The moving rod in (Fig. Below) is 12.0 cm long and is pulled at a spep-ty lnm2h499xl crdu4*gb9 7 3cpe fre*n e,qed of 15.0cm/s If the magnetic field isq fyt-gn e,neprl*clc49e*b97 pmrx3du 2h 94 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 lies in a 0.75-T m3 w. g:5iiiqnkagnetic field pointing into the papiq.5gik wi n3:er. If the loop’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 0laegq1q(2m8kw n7 pkof 120 mV while moving 28p mkg01kweqnq7(al 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 dimenoz6 1*)ym glgrsions shown in (Fig. Below) is situated inside a region of uniform magnetic field*l) y6gr1mgo z 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, 2l5qp+:bjm)ecjlanr6o9g d;8p4 tod has a diameter of 2.5 cm. A 10-turn coil is wound tightly around the center of the solenoid. If the current in the solenoid increases uniformly from 0 to 5.0 A in 0.60+c6g e2p5dr4qt naj)jldl :o9b8mo; p 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 speed of 1.6m/s is 30.0 cm long, and ha37rvmml dbn67q 83vpwz or1y- s a resistancr7rz63pmy1378o nmwldvqb- v e 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 u +iu+-)a w+9vtqhrqb wire 2.6 mm in diameter. A uniform magnetic field, perpendic +9butw+qvq+hur- a)i ular 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 loo2-n 4yp 3zw.or8mvx7e.a e4cbl1i pyop of copper wire decreases uniformly from 0.750 T to zero. If the wire is 2.25 mm in diameter, how much charge moves past a point in the coil during tvye w3plym e.oo 7z8in-p1a4b x .r42chis operation?    C

  A simple generator is used to generate a peak ouwng95jsa v)pp c 4qstd*5b,a a40hhg; s4:oiwtput voltage of 24.0 V. The square armature consists of windings that are 6.0 cm on a side and rotates in a field of 0.4 ch an5osg 4;jg0a)d*swh4v 5,9wa ispbtqp4:20 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.pwn;5p +gxr1o j r7nb7 What will the ou tput b75bn prw1no 7pj+gx;re at a rotation speed of 2500 rpm, assuming nothing else changes?    V

Show that the rms output (Section 18–7) of an ac genez2me )m 8(ze2g u/)cgf 3zgknbrator 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 oxk n0 fu)9ropc+oq3(mn a side. How fast must it turcx) u+q39(0 omk noprfn in a 0.650-T field to produce a 120-V peak output? $f$   rev/s

  A 450-loop circular armature coil with a dia/pwkyr; gtr56,d p m;hmeter of 8.0 cm rotates at 120rev/s in a uniform magne/r ;rpdkwhy;6 tg,5mptic 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 man )a r4b5joyl52sys 9ngnetic field of 0.030 T. It has 1000 turns and produces an rms volb )9y2nj oasy 4lrns55tage of 150 V and an rms current of 70.0 A.
(a) What is the peak current produced?    V
(b) What is the area of each turn of the coil?    $ \times10^{-2 }\;m^2$

  A motor has an armature r7juft j6mjk)syxb/os4ev :( ) pxnd-/esistance of $3.25\Omega.$ If it draws 8.20 A when running at full speed and connected to a 120-V line, how large is the back emf?    V

  The back emf in a motor is 72 V when o rc59hi( y.uddperating at 1800 rpm. What would be the back emri 5c.(y9du dhf at 2500 rpm if the magnetic field is unchanged?    V

  The back emf in a motor is 95 V when the motor is operating at 1000 rpm. How oj9 : 5oyad:njn 2b-gewould 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? reduye2on- a ogjn:d5: bj9ce the magnetic field to    % of its original value

  What will be the current in the motor of Example 21–9 if the9h 0f*5otgqm*pwt10r / xprg o load causes it to run at half speed? pxm5 /gog*qt9prt1 h0f w* 0ro   A

  A transformer is designed to change 120 V into 10,000 V, ando6 6 qcdh1zd3u there are 164 turns in the primaroc63z61u hdqd y 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 current in j6pr,ckq*dtq6ox (n ;1vwy*v the secondary coil as compared to *t,6 q6y jx;n (k*cwrd1qpvvothe primary coil?   

  Neon signs require 12 kV for their operation. To operate from a 24:qhkty )9pa4(mopt6 ,ercv 5t0-V line, what must be the ratio of secondary to primary turns of the transformer? What would the tv(r6 ytc 4 ohp 5,pqem)a9:tkvoltage output be if the transformer were connected backward?
$\frac{N_\mathrm{s}}{N_\mathrm{p}}$ =   
$V_s$ =    V

  A model-train transfoyoz+oz b 9zumop,-o*y(16m hwrmer plugs into 120-V ac and draws 0.35 A while supplying 7.5 A to the train. mz6pz(y uzmo*w -,ooyh o 9+b1
(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 iysztqndf y x*05b 4(h-nput current is 22 A. xt 0 qf (5b4yydz*n-sh
(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 t8+tm2c)3c *yzw. (rvp zfempmurns and 1340 secondary turns. The input voltage is+2c(p e *fmwzmtc.ry)v 3p8z m 120 V and the output current is 15.0 A. What are the output voltage and input current? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ =    V
$\frac{I_\mathrm{s}}{I_\mathrm{p}}$ =    A

  If 30 MW of power at 45 kV (rms) arrives at a town from a genm o2r jxpnk4e5z2/d.t erator 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 town6bt(ab4 *1tjdp0tnlc 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 coil changes steadily from 25.0 A to 10.0 A in 350epnk97 67np jr ms, what is the magnitude of the induced emf?pnne6 7prkj97    V

  What is the inductance of a coil if the coil produces an e8 9f9(qlv qoabunkntza;63 u+mf of 2.50 V when the curref9b a9+ 6nqzlokua8 ;3unq(vtnt in it changes from -28.0mA to +31.0mA in 12.0 ms?    H

  What is the inductance L of a 0.60-m-long air-filled coil 2.9 cm in diam lstvak*/ o*1jh:d 5fra4 6fmmeter containing 10r:ha4 6alfmmf* ov/k1*jdts 5,000 loops?    H

  How many turns of wire would be required to make a 130-mH inductanhy57 d n8oj(inoj v:8uce out of a 30.0-cvjn:8( u5 odo h8yjni7m-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 2-euzw o3cd9xkweyq +5 x1 *lq0800 turns, and it is 2.5 cm in diameter and 28.2 cm lonw5*1o +0qy 3q k9xdelw-x zuecg.
(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 apr/b2+t gr1i -etn3-gkm gb)jrea 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 woj1cnk.kc/ c1 v4e:ysmusuh2z,s .w1bund solenoid is unwound and used to make another tightly wound solenoid of twice zumhyc s2, j eub cc/v.ks11:sk4 n1w.the diameter. By what factor does the inductance change?   

  The magnetic field inside an air-filled solenoid 36 cm long and 2.0 z 8m0gn(mzi uecjd/)u3a8(h*qppr s,cm in diameter is 0.80 T. Approximately how much energy is stored i *s8i)(,rz gazu80cmm(uneh/3 pdpqjn this field?    J

  At a given instant the current th u94yey dvx)-nrough an inductor is 50.0 mA and is increasing at the rate of 115mA/s. What is the initial energy s-y4y eux9 )dnvtored 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?
U =    $ \times10^{-5}\;J$
$\Delta$t=    s

  Assuming the Earth’s magnetic field avere8z:c 7-c0ewmsgi u* yages 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 i52 ;in4 jdnienn (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 circular cow wqv*c wgh s195wtp+-9y 4kvross-sectional area. But solenoid 1 uses wire that is hal*9oy tww9vcp ksw1vw hg4+5- qf 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 of a9x.*yl mubvia+q od 72 $7.20-\mu F$ 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 h/ x:d3is +6v w2kglqq s-kp+osave a reactance of $660 \mathrm{k} \Omega ?$    Hz

  At what frequency will a e tql)4yokenr0/* 8 qy$2.40-\mu F$ capacitor have a reactance of $6.70 \mathrm{k} \Omega ?$    Hz

Plot a graph of the reactanjj myh/3iwo.*.xv+) iwrs38ign+ fl sce of a $1.0-\mu F$ capacitor as a function of frequency from 10 to 1000 Hz.

Plot a graph of the reactancmwl 3u6kdi6hpat/o-(x3 d2*gzly 6 cpe of a 1.0-mH inductor as a function of frequency from 100 to 10,ci6 dup2lod/*lh3-y6 6 t3w a gxp(mkz000 Hz.

  Calculate the reactance of, a ;)x fn2r9fqr nrr y*4:spuxp*nd rms current in, a 160-mH radio coil connected to a 240-V (rms) 10.0-kHz ac lr92 *)xp*yr s quff;nprn: 4xrine. Ignore resistance.
$X_L$ =    $\Omega$
V =    $ \times10^{-2 }\;A$

  An inductance coil operates at 240 V and 60.0 H*t pi 00 5q9ra5gubvsdz. It draws 12.8 A. What is the co*rs5 ga t50b d9vpu0iqil’s inductance? $X_L$ =    $ \times10^{-2 }\;H$

  (a) What is the reactance of a -,bmp,kn 2 d +vhy,nxmwell-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 of 70 mA pass.bbn6 c;)hh6hf )pg ading through the human body for 1.0 s could be lethal. What must be the impedance of the body for this to occu;d6 .)ghf6 ch bpnbah)r?    $ \times10^{3 }\;\Omega$

  What is the resistance of a coil if its impedance +tg*;jwwm,ui4 79, c.dlvuphp 2rnjnis $\mathrm{235~Ω}$ and its reactance is $\mathrm{135~Ω}$    $\Omega$

  What are the total impedance, phase angle, and rms current in an LRC circuit 8+r a(tgyigrt */z/hoconnected to a 10.0-kHz, 725-V (rrg8r/h(o/ atgt zi+y* ms) 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)(jpjme5jnt qfy9 2qnvq,) 0q -mH inductor is driven by an ac power supply. At what frequency is the impedance double that of the impedance q2eynmq59)qvj t j,pq0n (jf) at 60 Hz?    Hz

  (a) What is the rms current in an RL circuit when a 60.0-Hz 1h5o p/. euzwb 56b)fng20-V rms ac voltage b5p/ 5nzu eg6h.)fwobis applied, where $R=1.80\mathrm{~k}\Omega,$ and $L=350\mathrm{~mH}?$    $ \times10^{ -2}\;A$
(b) What is the phase angle between voltage and current?    $^{\circ}\,$
(c) What are the rms voltage readings across R and L?
$V_{rms \,R}$ $\approx$    V (Round to the nearest integer)
$V_{rms\,L}$ =    V

  (a) What is the rms current in an RC circuit is )xll ,x+ri9bo1tdc;p- xf mt4-78kl,n uzxtf $R=8.80\mathrm{k}\Omega,C=1.80\mu\mathrm{F},$ 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 connec a+7.tcc/vvhhted 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 tqtryj86f,)t AM radio has a capacitance of 2800 pF when the radio ij6qy ,8)t ttfrs tuned to a station at 580 kHz.
(a) What must be the capacitance for a station at 1600 kHz? $C_{1600\mathrm{~kHz}}$ $\approx$    pF(Round to the nearest integer)
(b) What is the inductance (assumed constant)?    $ \times10^{ -5}\;H$

  An LRC circuit has L = 14.8 -dk ubzd v(dn/w; ,*g(gv::whnt1k9fyd 5 wlgmH 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 lookingotztrne3 yba-cc b) 8q; b0*-m at two current loops in the plane of the page as shown in (Fig. Below). When switch S is throwntb;3yb0c-zone)q*mc8 a tb - r 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 resistj.k- 9 iwb7 vdq(e5mnzb)bm-h ance 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 lampr7 yy l02wkvp+ is rated at 45 W but requires only 12 V. It contains a transformer that converts 120-V househov0r7l +wp y2ykld 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 xv1z*6e1.go-ioi blsa generating plant located 118 km from a town that requires 50 MW of power at 12 ix1*sv .-zo i lgebo61kV. 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% el)j,(g ke wyg4fficiency are connected to 110-V ac. The secondary winde()jg4gkl yw ,ings 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 eaxa c(* uuldl*2ch 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 apart on a 6celg*.1zgdv 1.0$^{\circ}\,$ 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 t* ft g-y+jgyc9aelg* rx4 u17eransmission 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, and a :uk;hp.u e2halks) /c onl-w6resistance 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 devicey-4o 0 rsw( gjvsz d6ggpcq78- needs to be protected against sudden surges in current. In particular, after the power is turned on the current should riser-qogszgy w(-06dcj pgs874 v 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 jr,3v*mos:4l 1mc.tp d w o*yc/pz3 wdbetween 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 emf is to be 120 Vd,v c13ldozjc 3/ypmr:w4 w**om.pt s? $|\varepsilon|$    T/s

  Calculate the peak output voltage of a sim1ityhj(z kf5 d5 d3-cbple generator whose square armature windings are 6.60 cm on a side; the armature contains 155 loops and rotates in a field of 0.2003ztf bkh515y ddc(ji- T at a rate of 120rev/s. $\varepsilon_{peak}$ =    V

  Typical large values for electric and magnetic fieldstj* o23cxt4x) 4daf)jnq lbb, attained in laboratories are abou)ba,)t4j* n2lb ofxd3j qtx4ct $1.0\times10^4\mathrm{~V/m}$ 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 transforme rf2x; vui3.y h6r:thwr whose input is 220 V at 60.0 Hz ifty6h3;u2. fvr hr:w xi the current drawn is 5.8 A? Assume no current in the secondary.    H

  A 130-mH coil whose resiszf96so 7*c2heieq4u*sv t *sstance is $\mathrm{18.5~Ω}$ is connected to a capacitor C and a 1360-Hz source voltage. If the current and voltage are to be in phase, what value must C have?    $ \times10^{-7 }\;F$

  An inductance coil draws 2.5-A dc when connected to a 36-V ba; .f+ *eruemp fiwm-.) vaj-rdttery. When connected to a 60-Hz 120-V (rms) source, the current )fm +p ved-rm u.w-*.jif er;adrawn 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 wite kh45oe4bbi3q5jeay* k0v + s)6dmu lh $2.0-\Omega$ 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 resonanvy i+cmx +f*-t /cqxwzn50ix*ce circuit can be defined as the ratio of 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 txvq5n i*x c0c+xtfm+ *-/ ywziuning.
(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$