What would be the advantage, in Faraday’s expx+8:)qzmn k2 nxkk *kieriments (Fig. Below), of using coils with many kkm zi2nn+*:xxk q8 k)turns?

What is the differen /ewsj/dlrz:u.9 y,hs,udk a4ce between magnetic flux and magnetic field?

Suppose you are holding a circular ring of wire and suddenly thrust ac;zszeh hu,yubqblfi:ey7x7*c0 8 v. 6pof )- magnet, south pole first, away from you toward the center of the circle. Is a current induced 8su *;:.z iyxebc,lu 6)yp0-vochffzq7b 7 ehin 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 oz( m( 7mwr .fj,o /6ns(zdsqjmoving in the vicinity of a very long straight wire carrying a steady current as shown in (Fig. Below). Find the direction of the induced current in each loop.osd(67(/mjmw s.j zfon(,q zr

Suppose you are looking along a line through the lptex1m:v2.,rhmqfp/;-zfr m (dyu8 /j u2 gv centers of two circular (but separate) wire loops, one behind the other. A battery is suddenly connected to the front loop, establishr 2.v /:gue1v,h2 yf;/md mm(fu8jlpx-ztqr ping a clockwise current.
(a) Will a current be induced in the second loop?
(b) If so, when does this current start?
(c) When does it stop?
(d) In what direction is this current?
(e) Is there a force between the two loops?
(f) If so, in what direction?

  In (Fig. Below), determine the direction of the induced current in resv5 ffcwast c+(zi zm6s5 e9b35istor $R_A$ 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 trapo0jj; 0ufq6.+ gw2 ujf1bezfvel over a distance, a “shielded cable” is used in which the signal wire is surrounded by an insulator and then enclosed by a cylindrical conductor carryie j6;.gz o02f1pqb0uu+f jfjwng the return current. Why is a “shield” necessary?

What is the advantage of placing the two i8: xn jii.a6weidl :.4cd)j*q dtoxq /nsulated electric wires carrying ac close together or even twisted about each ot.dwnj/ ) dx6ijicte:ql a. 84:iqdo* xher?

Explain why, exactly, the yt2cq.s30 prbh3gtgylq,/ z-lights may dim briefly when a refrigerator motor starts up. When an electric heater t3 h0. 2,glyr bpzs- tyqgq3/cis 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)a)y5xiik:vp2 gxil i7lp 9q/3 plus the right-hand rules to show why the counter torque in a generay iaqp25kg39i )px l /v:7ilxitor opposes the motion.
a
b

Will an eddy current brake (Fig. Below) work on a copper dq3rss5i7,ths2 t p2-avqs43j:vi dq dmwp-, or aluminum wheel, or must the wheel be ferro,d sdp2j, s vt4-q2sswti37ard:5q q mpih3-vmagnetic? Explain.

It has been proposed that eddy currents be used tyk,- 0p9 ocsin: yt ,.bn)ybmfo help sort solid waste for recycling. The waste is first ground 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 nonfef9c)m-,in :,ptk y0bs onyy. brrous metals (Al, Cu, Pb, brass) from nonmetallic materials?

The pivoted metal bar with slotsk1 dhfhv:qv.1-x u sp: in (Fig. Below) falls much more quickly through a magnhvp: dvsux1:1k.h- qfetic field than does a solid bar. Explain.

If an aluminum sheet is held between the poles of a large barhqrq e -otm jz,:6f6o2a,*yhe magnet, it requires some force to pull it out of the magnetic fizq,q y6* 6toe,2hhfer am:-ojeld even though the sheet is not ferromagnetic and does not touch the pole faces. Explain.

A bar magnet falling in/h-kxvag4z+9k qc.+b h u(qxzside a vertical metal tube reaches a terminal velocity even if the tube is evacuated so that there is no air resistance. Expla4x-+9u( kqzkqhzvgbh+ .cax /in.

A metal bar, pivoted at one end, oscillates freely in the 1j9j an/ 2wcbfabsence of a magnetic field; but in a magnetic field, its oscillations are quickly damped out. Explain. (This magnetic damping is used in a number of pawjb 1 j92f/cnractical devices.)

An enclosed transformer has four wire leads coming from it. How could socp tdx rw.rqv /z.*hec;.h7(-k ys-you determine the ratio of turns on the two coils without taking theqs r*c;(d7 .vhwy-te zo.-rhc x/.skp transformer apart? How would you know which wires paired with which?

The use of higher-voltage lines in ho7 qkl )r k7aqma 7ij+n11lx.;kclhwc3mes — say, 600 V or 1200 V — would reduce energy waste. Why are they 7qi1+ 3l ncqmr;j)aw7 7kkkh.l1 x lacnot used?

A transformer designed for a 120-V :/wxkq0 y:yxij ljk3o,n(w:u ac input will often “burn out” if connected to a (qn:/jy ,: xjkyl:i3uwwkox0120-V dc source. Explain. [Hint: The resistance of the primary coil is usually very low.]

How would you arrange two flat circular coils so that their mutj(b-7 dmc. l;n+xke yzual inductance was ; k mn(zx7jcb +yle-.d
(a) greatest,
(b) least (without separating them by a great distance)?

Does the emf of the battery i6 - u )tky1y xbdz2ke)fygn*z6zqsw+4n (Fig. Below) affect the time needed for the LR circuiwg-kxz qs46zy)2 bk+eyd1nf )6 u*ty zt to reach
(a) a given fraction of its maximum possible current,
(b) a given value of current? Explain.

  In an LRC circuit, can the rms voltage acrosj76mv pxl/m-s6t+d 6d yyqrv -p)x1jws
(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 frequencyil- *t f+uu*qk 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 mink9/hqwy6njfn,pw q 0 .imum.

  The magnetic flux through a coil of wire containing two loops changk3*)j:kwl j -l+vr g6gadrrh 0es from -50Wb to +38 Wb in 0.42 s. What is thgk j*6a0 jrrl3vdwkl:r +)gh-e emf induced in the coil?    V

  The rectangular loop shown in (Fig. Below) is pushed into the magnetic field(uklrxe/ex)*cp; wt,;ygj*k which points icypeeuk)r/x ,;lgw(*kx ;j *tnward. In what direction is the induced current?  ----待选择----counterclockwiseclockwise 

  The north pole of the magnet in (Fig. Below) is being inserted into the coil.n96h do lo0ky, In which direction is tkodoh6,n y9l 0he 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 ixf4wh:b71tu(e *q dz a 1.10-T magnetic field. The loop is removed from the field in 0.15 s. What is the average inducw:h fi1 tuzx4qd7*e(bed emf?    $ \times10^{-2 }\;V$

  A 12.0-cm-diameter loop of wire i2lzu8obni b8 uk: 3bfp;-e 4lwix :mm-s initially oriented perpendicular to a 1.5-T magnetic field. The loop is rotated so that its plane is parallel to the field direction in 0.20 s. What is the average induceu:i3pboe 8bfbn; mw-m -klzx8:u li24d emf in the loop?    $ \times10^{-2 }\;V$

  A 10.2-cm-diameter wire coil is initially oriented so that its plape*vd( zz :7mfne is perpendicular to a magnetic field of 0.63 T pointing up. During the course of 0.15 s, the field is changed to one of 0.25 T pointing down. What is the average induced emf id pv:e7 zmf*z(n the coil?    $ \times10^{ -2}\;V $

  A 15-cm-diameter circular loop of wire is placed 0 xng +w.szn7wqs*:k gm 8fux8in 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.smyi+3 cjxqn2frj8+f9qu1 f 1 Below) is slowly increased, what is the direction of the current induced in the small circular looq2 q+r1fjcny1+i8f3 sxjf9 mu p 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 thevf(kqb3) tvhb; n8- zp induced current in the circular loop due to the current shown in each 8k -(h ft;v )bpb3znvqpart 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 (Fig. Beloa1 v95s3tk2v)wi g kufw) is being pulled away from the loop shown, in what direction 13ti9kv5k gw)u s2avfis the induced current in the loop?  ----待选择----counterclockwiseclockwise 

  The magnetic field perpendicuset z: byw l/f i:/)0inb93z+h bgj(dzlar to a circular wire loop 12.0 cm in diameter is changed from +0.52T to -0.45 T in 180 ms, where means the field points away from an observew3li /e ytzj :/0i+)z(bdb g bns:zf9hr 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 p14viqmy;t6rw 07+nrtweoi ,speed of 15.0cm/s If the magnetic field owptqmwiyi e+t6,n74v 0r; r1 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 lies in a 0.75-T magnetic fi;0ewk e)1gabg)z ro z-rnup2. eld pointing into the paper. If the loop’k.r neeg)0 r gp21;aw-zo bu)zs 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. Beloo-3g5dc(jkbr i*fo f4oyin/7w)is 13.2 cm long and generates an emf of 120 mV while movinoi5i(kgorc *ffd3o7 j4/ybn -g 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 loop2mwpa3jw1 ine* s+5gl of wire with dimensions shown in (Fig. Below) is situated inside a ij np2+3 a1*wmelw5gsregion 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 diameteri z *oqa/+qd;z 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 s, what will iz q*ao/qdz;+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 sceo+psoh79hn9urov;(dk 3 4is 30.0 cm long, and has a r9o(epo +9sn;vsro u7ch3h 4dkesistance 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 m1tibtzu9. b,jdj e*m4 m in diameter. A uniform magnetic field, perpendicular to the plan b. 1*,tib9dj4e zujtme 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-dolq 8, g.w8q87tx1mbw:sk ya2bwd 2lf iameter circular loop of copper wire decreases uniformly from 0.750 T to zero. If the wire is 2.25 mm in diameter, how much charge 2 wk b8: sow1lq wdt8.fab m,7qxl8y2gmoves past a point in the coil during this operation?    C

  A simple generator is used to generate a pe)bba b1:blufj)-. czg5br dd7ak output voltage of 24.0 V. The squareulb gjb-7:db 5 d1zafcbb).)r armature consists of windings that are 6.0 cm on a side and rotates in a field of 0.420 T at a rate of 60.0rev/s How many loops of wire should be wound on the square armature? $\approx$    loops(Round to the nearest integer)

  The generator of a car idling at 1100 r3if94mfx.dc0y; cre a.i m ;empm produces 12.4 V. What will the ou tput d3.ei 4fyafcxe ri0m; mmc.9;be at a rotation speed of 2500 rpm, assuming nothing else changes?    V

Show that the rms output (Section 18–7su8vg4 wr i.*3.y+k oi nojl/q) of an ac generator is $V_\mathrm{rms}=NAB\omega/\sqrt{2}$, where $\omega=2\pi f.$

  A simple generator has a 320-loop square coil 21.0 cm- mvt9vf:j*(0fbcr shv ).qql on a side. How fast must it turn in aff -t( bv0r:s9)jc*qvlmvq . h 0.650-T field to produce a 120-V peak output? $f$   rev/s

  A 450-loop circular shfjxg4 v)r1(armature coil with a diameter of 8.0 cm rotates at 120rev/s ij)x1 rs(vh4f gn a uniform magnetic 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 field of 0.030 T. It has 1000d0slwk h46otqaf8 -gzm6 6zf) f1jrf+ turns and produces an rms voltage of 150 V and an rms current of 6j6wm-a4 0z+rf8 )g1qzltfo hsf6dfk70.0 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 o8ukmg(vd*j7 m5gcd c ,f $3.25\Omega.$ 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 woulh3qdif*.xpddc)hbu* v(bv6 0 i9m*dx:n xa 9ed be the back emf at 259vbhd.dd 9nv ui*:mex*0c6bh *xdx (apfq)i300 rpm if the magnetic field is unchanged?    V

  The back emf in a motor i 99s(gvpfqc+ m.4 jwcjs 95 V when the motor is operating at 1000 rpm. How would you change the motor’s magnetic field if you wanted to reduce the bacsg.cw(q9j 4fcmvj + 9pk 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 21–9 if the load causes it l/ 7y6l v,u5tudd n3lvto run at half sp5d/uvldl3t, u 67l yvneed?    A

  A transformer is designczc7w 16t wcc 4vd2o)fed to change 120 V into 10,000 V, and there are 164 turns tzwc 62occ1 w7) vcdf4in the primary 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 cur:*hr0)iof/zlp awj 0drent in the secondary coihzfd/ jo*)ipl0a:0 w rl as compared to the primary coil?   

  Neon signs require 12 kV for their operation. To operatf. pglr(a+b f0e from a 240-V line, what must be the ratio of secondary to primary turns of the transformer? What would the voltage output be ifb.l(gfr 0af+ p 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 dd:;/j)wo tm ld6x9 :t xy4eoviraws 0.35 A while supplying 7.5 A to the trai:t od 4)om:6/ixyw l9jex; tvdn.
(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 22q,pl9s ocl gr 4*.ad.z9eiiy. A.l . pq 4i*aldr9igs,z9 yoc.e.
(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 turn 0 7 qrlj+zbm+ooqp:z3s and 1340 secondary turns. The input voltage is 120 V and the outp7rlz z o:3q0+mop+qjbut 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 towu+4 boi(y-lg 4f(m, qk8iwxgd n from a generator via $\mathrm{4.0-Ω}$ transmission lines, calculate
(a) the emf at the generator end of the lines, $\varepsilon$    V
(b) the fraction of the power generated that is wasted in the lines. fraction wasted   

  65 kW is to arrive at a towc n*v:w5np 3et:ygn ev(:m na:n 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 llzgwnchb- ((6px2 3x180-mH coil changes steadily from 25.0 A to 10.0 A in 350 ms, what(gw2h-cblp (x zlx6n3 is the magnitude of the induced emf?    V

  What is the inductance of dj sj 2x2+6toua coil if the coil produces an emf of 2.50 V when the current in it changes from -28.0mA to +j 2j2s6ox+tud 31.0mA in 12.0 ms?    H

  What is the inductance L of a 0.60-m-long air-fille: rwl4 cyjy3 8cu.rb4awnl-.ed coil 2.9 cm in diameter containing 10,0j4le4 c.bn ayrw.wc- 3 u8r:ly00 loops?    H

  How many turns of wire would be required to maac8up* 27mcc0cvtoh: -h fgp5 ke a 130-mH inductance out of a 30.0-cm-long ahmcvhuc-p* c25g p7f 0tc8:oair-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 isq2,9l2pt n8ekfgdv+zr6qw h3 2.5 cm in diameter a ne 2gkq3 d+ 6z92l,wrhqtfpv8nd 28.2 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 area k4 rbdko *9lc-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 80- ly9 jh wkj+9yq lqb2ovm(t(au3qtunwound and used to make another tightly wound solenoid of twice the diameter. By what factor does the inductaw-t3jb j(l+l vk9t9 q2yhm( oq80 auqynce change?   

  The magnetic field inside an air-filled solenoid 36 cm lonylpy lzm y zt:,fv. ;-0 (uzy*cp7p6bqg and 2.0 cm in diameter is 0.8lt.uzy b* (z 7z 0:pfpyl6cm-y y;pq,v0 T. Approximately how much energy is stored in this field?    J

  At a given instant the current through an inductor is 50.0 m t2 fgz3.8fj cd-lr0h1depg2r8 g: qlqcpcr* ;A and is increasing at thez.ct e-p;r1dg: 2jh q2f8c rqrcg*803 ll gdfp 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?
U =    $ \times10^{-5}\;J$
$\Delta$t=    s

  Assuming the Earth’s magnetic fixud8x0x; +hbkeld averages about $0.50\times10^{-4}\mathrm{~T}$ near the surface of the Earth, estimate the total energy stored in this field in the first 10 km above the Earth’s surface.    $ \times10^{15 }\;J$

Determine $\Delta I/\Delta t$ at t = 0 (when the battery is connected) for the LR circuit of (Fig. Below) and show that if I continued to increase at this rate, it would reach its maximum value in one time constant.

  After how many time constants does the current in (Fig. Below) reach witm5dg- n;0x gz3rv (cbohin
(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 crossrp-jjc c v .m;7)ukt-f-sectional area. But solenoid 1 uses wire that is-m-c7)jptfkr; u cv .j 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 ofaa7qz+mqou1vv2 vr l:,j/ 9p:y.cyn h 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 inc/1)vdk/z z+ ivmaq+ jductor have a reactance of $660 \mathrm{k} \Omega ?$    Hz

  At what frequency wiw3rv 0d+vx/-m/ne/ uu e4tgyp5/wz ohll a $2.40-\mu F$ capacitor have a reactance of $6.70 \mathrm{k} \Omega ?$    Hz

Plot a graph of the reactancetvql.8. s mha( 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*534m gbh:jp6ib7vz g*4c xu b6ivgi r function of frequency fror4viu*hm cxbig:6zb*i5jg 7b4p 6g3v m 100 to 10,000 Hz.

  Calculate the reactance of, and rms current in, ar,mo3+mjj r w: 160-mH radio coil connected to a 240-V (rms) 10.0-kHz ac +:mjrr3w o,mj line. Ignore resistance.
$X_L$ =    $\Omega$
V =    $ \times10^{-2 }\;A$

  An inductance coil operates at 240 V and 60.0 Hz. It draws 12.8 A. Whatn0l --yptmsr7-nb3vr is the coil’s i -slt0y7nn--vbp m3rrnductance? $X_L$ =    $ \times10^{-2 }\;H$

  (a) What is the reactance of a well-insulated skq*f 0y (iq8tvb/2yu$0.030-\mu F$ 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)*ira 75pyl *tigtrd. of 70 mA passing through the human body for 1.0 s could be lethal. What must be the impedance of the body for this to oc7t i.5arr )dgp**tyli cur?    $ \times10^{3 }\;\Omega$

  What is the resistance of a coillm :9mi.a 4einpn(t3jcqvk5 6 if its impedance is $\mathrm{235~Ω}$ and its reactance is $\mathrm{135~Ω}$    $\Omega$

  What are the total impedance, phase angle, and rms current in an LR* k -fevm 1w t agutg y,/59y4ai6:ye1ceferk;C circuit connected to a 10.0-kHz, 725-V (rms) sourg ge9a4;:aevt1i1tfe uwk c ym-y, eryk/f56*ce if $L=22.0\mathrm{~mH},R=8.70\mathrm{~k}\Omega,$ and
Z $\approx$    k$\Omega$
$\phi$ =    $^{\circ}\,$
$I_{rms}$ =    $ \times10^{ -2}\;A$

  A resistor in series with a 420-mH indqn-,u 6g wv89awp*kno yui 8+luctor is driven by an ac power supply. At what frequency is the impedance double that of the impy-aiv w uo9n6q+,8g*8lwuknpedance at 60 Hz?    Hz

  (a) What is the rms cuoq:j qphxn(tu 3-1cv-rrent in an RL circuit when a 60.0-Hz 120-V rms ac voltage is applied, where1 upnvtoq-(:j xhcq3- $R=1.80\mathrm{~k}\Omega,$ 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 ci 7vc ggp22gcssnf)//vrcuit 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 connecteden * sk).wy9 4u;7j kmsmne7kt 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 rziotch.j2* b .adio has a capacitance of 2800 pF when the z htbj. ci2*.oradio is 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 8 n6q( bopv+obmH 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 curdrfd 8la2/y eb1,cxa+ rent loops in the plane of the page as shown in (Fig. Below). When switch S is thrown in the left-hand c/xdyd c raf81bl +,a2eoil,
(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 q7wk imw59grf l4ok6( a side 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 45 W but requires only 12)he jmk0.(ta n m;hh,n V. It contains a transformer that converts 120-V householhen)tkj .,mn ;0ahh(md 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 118 ;:dc8 bsfuns/km from a town that requires 50 MW sn /cd usb8;:fof 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 transformuc+f45rtm4msfl ,5nx y k9 9rler which has an 80% efficiency are connected to 110-V ac. The secondary windings are conne4lxf 594m tyr,s +m nr9cflku5cted 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 linydmen0-et6)1 1 ei*u;cqsy utes 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 rest 32 cm apart onk+c)y9.skr n. es:ewb 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 transmidr 8se-ijyk 1n942q kwssion 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 d9i s9rk bw/wqvalpm0g/20, aa resistance of $\mathrm{12~Ω}$ surrounds a solenoid with $230\mathrm{~turns/cm}$ and a radius of 4.5 cm; see (Fig. Below). The current in the solenoid changes at a constant rate from 0 to 2.0 A in 0.10 s. Calculate the magnitude and direction of the induced current in the coil.
I =    $ \times10^{-2 }\;A$
 ----待选择----left to rightright to left 

  A certain electronic device needs to be protected against sudden surges in cn 4*/ ihuhaz+zurrent. In particular, afuazz +*4ni/hh ter the power is turned on the current should rise no more than 7.5 mA in the first $120\mu s$ The device has resistance $\mathrm{150~Ω}$ and is designed to operate at 55 mA. How would you protect this device? L $\approx$    in series(retain two decimal places)

  A 25-turn 12.5-cm-diameter coil is placed between the pole pieces of an ele+, a:rzgx8jn;r,l)v4f hln 5vu xm 2jxctromagnet. 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 e 5vxjf,x m4g;lvnrxh +a):rzu, jln28mf is to be 120 V? $|\varepsilon|$    T/s

  Calculate the peak output voez*lh g twc.pseck7e * aw01,(ltage of a simple generator whose square armature windin(e c z1ewge*tsca7.k,lp0 wh*gs are 6.60 cm on a side; the armature contains 155 loops and rotates in a field of 0.200 T at a rate of 120rev/s. $\varepsilon_{peak}$ =    V

  Typical large values for electric3swlt,t9wn;1 ,g ktsxn 3zo x.eqmu 43 and magnetic fields attained in laboratories are abot nsex3mwnskt u.o,q3 ; wx419 ,gz3tlut $1.0\times10^4\mathrm{~V/m}$ 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 transformeo c+5l3 m2k;:nwxksv 5o m4acwr whose input is 220 V at 60.0 Hz if the cur nkw+c;34 wmav 5m5:cl2oksox rent drawn is 5.8 A? Assume no current in the secondary.    H

  A 130-mH coil whose resistance imi; w:pvcjfxgedl .9;11q f n+yx-o+ ms $\mathrm{18.5~Ω}$ 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 y/m-kbzpxzr8 )a -qq0 kd(n z2when connected to a 36-V battery. When connected to a 60-Hz 120-Vydz-/20a kq(z qp)mrn x8-kzb (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 wi9h5k3a3mfa( l ofstiyq ,,vg7 th $2.0-\Omega$ 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 asj vlt:y3r /yttel9n4+ the ratio of the voltage across the capacitor (or inductor) to the voltage across the resistor, at resonance. The larger the Q fac lj3 yttlr+/ e49:yvtntor, 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$