What would be the advantage, in Faraday’s experi.rf6arx1ab em-iuy* +c8ypk -ments (Fig. Below), of using coils with manyxy8fa1y. p+ieu *bmr-ak6-rc turns?

What is the difference between magnetic flux and magltyud+ hb ahc9w*a27yftq08i 8p ,z( wnetic field?

Suppose you are holding a circular ring of wire and suddenly thrust a m siy/9siuwrb: 3)ix.mo+ w:*cv3r muzagnet, south pole first, away from yioum:3m+)wir v:./i xuwbr9 zs3cs*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.

Two loops of wire are moving in the vicinity of a*wuxt) 5ko,hb very long straight wire carrying a steady current as shown in (Fig. Below). Find the direction of the induced current in each loo tw, u)bo*xkh5p.

Suppose you are looking along a line through co:3q8c rhxq0 ql0):nzic7 ph the centers of two circular (but separate) wire loops, one behind the ot0:oc7:pqx0zn hql r hc cq8i)3her. A battery is suddenly connected to the front loop, establishing a clockwise current.
(a) Will a current be induced in the second loop?
(b) If so, when does this current start?
(c) When does it stop?
(d) In what direction is this current?
(e) Is there a force between the two loops?
(f) If so, in what direction?

  In (Fig. Below), determine the direction of the induced current in re71vx . 4jzun6 rjx*ppjsistor $R_A$ when
(a) coil B is moved toward coil A, ----待选择----increasedecrease 
(b) when coil B is moved away from A, ----待选择----increasedecrease 
(c) when the resistance $R_B$ is increased. ----待选择----increasedecrease 

In situations where a small signal must travel over a dista-t qm b(t)4ds,:i8fif .vnf7a6jg i avnce, a “shielded cable” is used -a vg:sji8afvi6d i)47fqf .(bnmtt,in which 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 carryingxi6qtwtx h/)/sh+o3v ac close toget/wh)3qth /xxsi 6+t ovher or even twisted about each other?

Explain why, exactly, thwbmv 2(w9 n3yre lights may dim briefly when a refrigerator motor starts up. When an electric heater is turned on, the lights may stay dimm3(mryv 92nwwb ed as long as the heater is on. Explain the difference.

Use (Fig. Below a) and (wd hn jvvqm5oi6 1jfdxak d1/t( 29h91Fig. Below b) plus the right-hand rules to show why the counter torque in a generator opposes the mohvk9dvn mj6(a tjofwd 5i 9xq1 12/h1dtion.
a
b

Will an eddy current brake (Fig. Below);gvkl 9vd q *5f.upht1- hz(as work on a copper or aluminum wheel, or must the wheel be ferromagnetic? Explain .ufsd1 9qv(alg5kptv *h h-z;.

It has been proposed that eddy curre /bqyhg+ul0o5 t, ma9vddio30nts be used to 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 b+ tih v9uqgdoy 50la,o30m/dmagnets. 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 quickly t8 m4gp 7mxbe,phrough a magnetic pg4mp8, mxb7e field than does a solid bar. Explain.

If an aluminum sheet is held between the poles of a large bar magne;1wxeko/f z5pt, it requires some force to pull it out of the magnetic field ewf/px oe51;kzven though the sheet is not ferromagnetic and does not touch the pole faces. Explain.

A bar magnet falling inside a vertical metal tube reaches a termw-* (vtkrn j2cinal velocity even if the tube is evacuated so that there is no wk- rj*( 2tncvair resistance. Explain.

A metal bar, pivoted + 1llrg1j, :(tc f uv-tj6jhhgat one end, oscillates freely in the absence of a magnetic field; but in a magnetic field, its oscillations are quickly damped out. Explain. (This magnetic dampgtj(ruhtc1 +v :,-l1jfg l6hjing is used in a number of practical devices.)

An enclosed transformer has four wire leads coming from it. How could you detxp-y0k(ttjp / ermine the ra0/kt-ppxt jy( tio of turns on the two coils without taking the transformer apart? How would you know which wires paired with which?

The use of higher-voltage lines in homes — say, 600 V or 12dv(op *31fbcweg/a 3vnbg sft30 g:9g00 V — would reduce ener cfw*gva 0:9 (sb3 13gt /dgvopbgefn3gy waste. Why are they not used?

A transformer designed for a 120-V ac input will often “burn vx:t gvh.)a( fout” if connected to a 120-V dc source. Explainvh( fa.:t)vgx. [Hint: The resistance of the primary coil is usually very low.]

How would you arrange two fgys301 wc(fx;mnbp1tlat circular coils so that their mutual inductance wa f0tp xcyn1bgs;31w( ms
(a) greatest,
(b) least (without separating them by a great distance)?

Does the emf of the battery in (Fig. Below) affect the time n m; wo5uv-p.dfeeded for the LR circuit to reap ;o.d5f m-vuwch
(a) a given fraction of its maximum possible current,
(b) a given value of current? Explain.

  In an LRC circuit, can the n)r;*mqw b86svy) n vvrms voltage across
(a) an inductor, ----待选择----yesno 
(b) a capacitor, be greater than the rms voltage of the ac source? Explain. ----待选择----yesno 

Describe briefly how the frequency of the source emf affects the implabmprredp5z.,(9(b edance 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 impedanceqy eowb4k56)t in an LRC circuit a minimum.

  The magnetic flux through a coil of wire containing two loops changes from -50t j,fnfta:+ :lWb to +38 Wb in 0.42 s. What is the emf induced in the n:lt ,at:j+ ffcoil?    V

  The rectangular loop shown in (Fig. Belx g c5,tg,x7viow) is pushed into the magnetic field whicc,i gv txx7g,5h points inward. In what direction is the induced current?  ----待选择----counterclockwiseclockwise 

  The north pole of the magnet in (Fig. Below) is being insertedk pk ao :4u6gwxik x8ltcj9/ *d9g,0ke into the coil. In which direction is the induced current flo 60j *k8taexgig k4x9u,kop 9l/dwk c:wing 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 fi0se;rpyc- ex8xn.6 g ield. The loop is removed from the field in 0.15 s. Whagpy8snrc0 - x;e6x.e it is the average induced emf?    $ \times10^{-2 }\;V$

  A 12.0-cm-diameter loop of wire is initially o wq-i:)jp*ct nriented 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 induced emf in the loow*j:) ptn -qicp?    $ \times10^{-2 }\;V$

  A 10.2-cm-diameter wire coil is initially orientz3//onojz4jxsyf4 hv8a8s o09 0kmru ed so that its plane is perpendicular to a magnetic field of 0.63 T pointing up. During the course of 0.15 s, the field is changed to one of 0.25 T pointing down. What is the average induced emf in t/r 4yz8zj/4x au8 jsvomk39s f0on0h ohe coil?    $ \times10^{ -2}\;V $

  A 15-cm-diameter circular loqqje6b;ql2ghl0 o/r0m4) z l iop of wire is placed 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 -os7 ezg112oicsr w6ynewi lh7tc 2 ()of the resistor in (Fig. Below) is slowly increased, what is the direction of the current induced in the wneho 77-os12c1)2er t ils( 6ycigzwsmall 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 cj ue; l-vmtq;sr/,:smurrent in the circular loop due to the current shown in each part of (Fig. Below)?/;l,me r ;uv -sqmjt:s
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 pulledm2c 3) a+rjfao away from the loop shown, in what direction is the induced curre oma+2jca3r)f nt in the loop?  ----待选择----counterclockwiseclockwise 

  The magnetic field perpendicular to27qq+ym opuva9fbw2 e ;9;e ju a circular wire loop 12.0 cm in diameter is changed from +0.52T to -0.45 T o fb e+u;e792mvw;yq9j2 qpua in 180 ms, where means the field points away from an observer the observer.
(a) Calculate the induced emf.    $ \times10^{-2 }\;V$
(b) In what direction does the induced current flow?  ----待选择----counterclockwiseclockwise 

  The moving rod in (Fig. Belanxt m * r8.oc4qtuz m:9/ujm)ow) is 12.0 cm long and is pulled at a speed of 15.0cm/s If the magneticux mm8 )/4uqj.toram* : nzt9c 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 p /mt9fal ty a 1 bxha2es8lp(vc+h0wvh5k65 p3lane of the paper lies in a 0.75-T magnetic field pointing into the paper+25s t/ha1 p5(w3vma h0alblefhv 8yx69pkc t. 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 cmv*pg5 t6 yt1p2vopyn3 -kb+ho long and generates an emf of 120 mV while moving in a 0.90-T magne+t -n t5pb vp6*y2h31pgy kovotic field.
(a) What is its speed?    m/s
(b) What is the electric field in the rod?    V/m  ----待选择----updown 

  Part of a single rectangular loop of wire with dimensions shown in (Fig. B7+wt+nhlr c0 celow) is situated inside a region of uniform magnetic fielncwcr0h l++ 7td of 0.550 T. The total resistance of the loop is $\mathrm{0.230~Ω}$ Calculate the force required to pull the loop from the field (to the right) at a constant velocity of 3.40m/s Neglect gravity.    N

  A 500-turn solenoid, 25 cm long, has a diameter of 2.5 cm. A+e frwl9 pc55tjm eb42 10-turn coil is wound tightly around the center of the solenoid. If the current in the soebf w9r5lmetj 5+24pclenoid 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 sd-rgn6rs g /j8peed of 1.6m/s is 30.0 cm long, and has aj8nd/gs-rr g6 resistance 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 mm inrhd, );c op:uw diameter. A uniform magnetic field, perpendicular to the plane of the coil, chang)o;,hr up:dwces 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 perpendagi9*n wl5kfr lsol7ps0sj2, 9mxk2 6icular to a single 13.2-cm-diameter circular loop of copper wire decreases uniformly from 0.750 T to zero. If theik* 02plj65lra 7o29nswkls gf, ms9 x 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 oui9 av 3ynwae (4t.fbjv. :)djhtput voltage of 24.0 V. The square armature consists of windings that are 6.0 cm on a side and rot4hj:)aw.vy e9(d. 3ntj v ifabates in a field of 0.420 T at a rate of 60.0rev/s How many loops of wire should be wound on the square armature? $\approx$    loops(Round to the nearest integer)

  The generator of a car idling at 1100 rpm produces 12.4 V. What s.eivg8j- u l5will the ou tput be at a rotation speed of 2500 rpm, assuming nothingg sl5vue ji8.- else changes?    V

Show that the rms output (Sectio p/db9l9d hfv,n 18–7) of an ac generator is $V_\mathrm{rms}=NAB\omega/\sqrt{2}$, where $\omega=2\pi f.$

  A simple generator has a 320-loop square coil 21.0 cm on a sid-, e y xr-hiswv21.lize. How fast must it turn in a 0.650-T v 1izsy2ex i,h .wr--lfield to produce a 120-V peak output? $f$   rev/s

  A 450-loop circular armature coil wmr*fhv n (9(veith a diameter of 8.0 cm rotates at 120rev/s in a uniform magnetic field ofh*n((9 v mrfev 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 magnet0rpzx.ddpmd -f9ez. b0pgob er5t +:(ic field of 0.030 T. It has 1000 turns and produces an rms voltage of 150 V and an z .: oex grpzm5.0pr+ (-f9d0tebdbdp 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 resistanckt 2f(xbj ax2i9dt,w6 e 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 / dwkg9 3fj4e4n /j6chpr uz8x72 V when operating at 1800 rpm. What would be the back rku3/4g6 hjpfd 4wxj 89 cne/zemf 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. Hb +;a( t1wzyeiow would you change i+y1( tbew;azthe motor’s magnetic field if you wanted to reduce the back emf to 65 V when the motor was running at 2500 rpm? reduce the magnetic field to    % of its original value

  What will be the current in the motor of Example 21–9 if the loa+hwic7v 4;m2rz 9o bazd causes it to run at half s wb;+ocv7hi2zm r9za 4peed?    A

  A transformer is designed to change 120 V i3 zaolae) 06;n)akxrbnto 10,000 V, and there are 164 turns in the primary coil. How many turns aanobzx0a3 6;ea)r k)l re in the secondary coil? $\frac{V_\mathrm{s}}{V_\mathrm{p}}$ $\approx$    turns

  

  A step-up transformer inc4jtsr70fep i1s4x jv3 reases 25 V to 120 V. What is the current in the secondary coil as 13 40psj tsjie 7vrfx4compared to the primary coil?   

  Neon signs require 12 kV for t6ecc*njv kb fsrfq*d8zo-vu2k/g ,4) heir operation. To operate from a 240-V line, what must be the ratio of secondary to primary turns kd qs*k)cc/e -fvz fv624jb,n *ougr8of the transformer? What would the voltage output be if the transformer were connected backward?
$\frac{N_\mathrm{s}}{N_\mathrm{p}}$ =   
$V_s$ =    V

  A model-train transformer plugs into 120-y n**,l2s *jjmuy(s bp,bsg/lV ac and draws 0.35 A while supplying 7.5 A to the train. / bsu p n yj(s,llsjb*m,gy*2*
(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 cur xbx zb7epke4q .p5.k+rent is 22 A. px47e. zxq .5bke+bpk
(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 turngekv p955 d6cp.mkzebaq89 v2 s. The input voltage is9ea9gk q c8mb.5vdp52ke6zvp 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 generatoa- g3cg4)oqak r 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 2d1tkoc *j+ o55t9ghpv+kbquover 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 coilv6r jca d;0m0k changes steadily from 25.0 A to 10.0 A in 350 ms, what is the magnitude of the ind6m;arjk 00d cvuced emf?    V

  What is the inductance onlcqau4,23gx cf,a. sf a coil if the coil produces an emf of 2.50 V when the currentf, 4 ca cau,gnslx23.q 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-ilgmcm37 zub.y6 b4*xw9+ wmnf ;xe2ifilled coil 2.9 cm in diameter containing 10,000 2b*i.nwwc3yxmei; +b mz 649ux flg7m loops?    H

  How many turns of wire would be required to make a 130-mH inductance o,e/u wv 657dam c1uaqout of a 30.0-cm-acwuuvem 5/a7d6q1 ,olong air-filled coil with a diameter of 5.2 cm? L$\approx$    turns (Round to the nearest integer)

  An air-filled cylindrical induam/m (ub6d*g fctor has 2800 turns, and it is 2.5 cm in diameter and 28.2 c(bm6f/ dmg *uam 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 wz c nmn;f/90gth.;b*qtenw :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 and used to make another tightomv6u5 /cxrk9:+qg ;mfm ad f1ly wound solenoid of twice the diameter. By what factor does the ind 6m;:ac qd9m1k5r oxgmu/f+vf uctance change?   

  The magnetic field inside38 f-h4wcj+ rx s2 vfbt((rxze an air-filled solenoid 36 cm long and 2.0 cm in diameter is 0.80 T. Approb+f z2(s3 rvtw8hxfj (rc x4e-ximately how much energy is stored in this field?    J

  At a given instant tdve06*sl h av2- au)owhe current 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 i)wsah* a0 uo6l2vv-ed f 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 averag)k1+;pn:-c hk gu pwlaes 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 thq/ve3 :u zgc7qp 1yw5he current 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 lengt s:;9z n1u (ezpfw,qhfh and circular cross-sectional area. But solenoid 1 uses wire that is q9e, zzfn:fh w psu(1;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 of a u*;2v94y4ny pztvb np$7.20-\mu F$ 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 hab1nrz*l 9 7rqrve a reactance of $660 \mathrm{k} \Omega ?$    Hz

  At what frequency will a p r93q+. r+nlfd-1v3-z4 b8 dy gbx+tdmlyahl $2.40-\mu F$ capacitor have a reactance of $6.70 \mathrm{k} \Omega ?$    Hz

Plot a graph of the r*s(c 7gyyx.bjl6 cou /eactance of a $1.0-\mu F$ capacitor as a function of frequency from 10 to 1000 Hz.

Plot a graph of the reactance of a 1.0-mH inductor as a function of frequency for6apxkcj9a7e g t2 00rom 27ax jt0 r096p eogakc100 to 10,000 Hz.

  Calculate the reactance of, and rms z f8mk xjy4 swz++ wvbiqh/-6-current in, a 160-mH radio coil connected to a 240-V (rm svmh f q- w/+xzkjzb4+-6ywi8s) 10.0-kHz ac 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. What is the s 6ls;7inr/tsg i0n*scoil’s iinst6 r*;l ins0 ss/g7nductance? $X_L$ =    $ \times10^{-2 }\;H$

  (a) What is the reactance of a qpu29-d grs ze g1.:l59oigp vwell-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 ww 5qt)9dv4w plpb,+f passing through the human body for 1.0 s could be lethal. What must be the impedance of the body for this to occur?wdpt)+bq 5w,vw4 fp9l    $ \times10^{3 }\;\Omega$

  What is the resistance of a coil if its impedance i )r/lkubrn92m yk a y9*v *+mvi0sztf6s $\mathrm{235~Ω}$ and its reactance is $\mathrm{135~Ω}$    $\Omega$

  What are the total impedance, phase angle, and rms current in an )d90ixlp jwj ,LRC circuit connected to a 10.0-kHz, 725-V 0 xid)jlwj9p ,(rms) source if $L=22.0\mathrm{~mH},R=8.70\mathrm{~k}\Omega,$ and
Z $\approx$    k$\Omega$
$\phi$ =    $^{\circ}\,$
$I_{rms}$ =    $ \times10^{ -2}\;A$

  A resistor in series with a 420-mH inductk*,)6: jv j xzgdsg*x7muk8 td7dw7ypor is driven by an ac power supply. At what frequency is the impedance double that of the impedance at 60 H7*wd:y,dzk7*67dgv ps tj)m jkxgx8u z?    Hz

  (a) What is the rms cu6cbfph b0thy lb8y) lh3.c(-mrrent in an RL circuit when a 60.0-Hz 120-V rms ac voltage is appli3m(6tl0-p hbhlf. bh8y)c bcy ed, 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 iwwnl8 f 8ru*t,1rqyn5 f $R=8.80\mathrm{k}\Omega,C=1.80\mu\mathrm{F},$ and the rms applied voltage is 120 V at 60.0 Hz?    $ \times10^{-2}\;A$
(b) What is the phase angle between voltage and current? $\phi$ =    $^{\circ}\,$
(c) What are the voltmeter readings across R and C?
$V_{rms\,R}$   V
$V_{rms\,C}$    V

  A 3500-pF capacitor isl*-k0q8ecnxgeko - i*0fhg d. connected 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 tuo06m37y/ ie/bk --js pp. xl+a gjk-mzrxzo;uner of an AM radio has a capacitance of 2800 pF when tlrebk;jx/u-/m7i0yo6ap.pmx s+ 3jo z - -kzghe radio 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 mH and * s*siwd-u;xq ta(ih)$R=4.40\Omega$.
(a) What value must C have to produce resonance at 3600 Hz?    $ \times10^{ -7}\;F$
(b) What will be the maximum current at resonance if the peak external voltage is 150 V?    A

  Suppose you are looking at two current loops in the plane of tfx3o:uwtzb 2v c v4z9gk*/ ua/he page as shown in (Fig. Beloo fub9 g/ u2ca:w/3 zx*z4vtvkw). When switch S is thrown in the left-hand coil,
(a) what is the direction of the induced current in the other loop?  ----待选择----counterclockwiseclockwise 
(b) What is the situation after a “long” time?
(c) What is the direction of the induced current in the right-hand loop if that loop is quickly pulled horizontally to the right?  ----待选择----counterclockwiseclockwise 

  A square loop 24.0 cm on a side has a resistanuq,h n0dy)g,.y vn3 hjar-l 4oce 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 y asczvsk/h*pj *u7* d. 1s)rrV. It contains a tranvd j7r*syz/*sauc1hks p *)r.sformer that converts 120-V household voltage.
(a) Is the transformer step-up or step-down? this is a  ----待选择----step-downstep-up  transformer
(b) What is the current in the secondary coil when the lamp is on?    A
(c) What is the current in the primary coil?    A
(d) What is the resistance of the bulb when on?    $\Omega$

  Power is generated at 24 kV at a generati*b4zy(gsb0xb90 wb cpqq4rt0ng plant located 118 km from a town that requires 50 MW of power at 12 kV. Two transmission0zyrsc*qbb g 4 94b0px(w0qbt 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% efficiency are conlk x4*p0m5k) -jvxl jznected to 110-V ac. The seconda*j-4mljxzk 0)plv k5xry 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 eacbhg 4yxaqlh*t p3 k,.)vcs1 0ah 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 uknns t1r gm2i6,hp6 (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,gjni390tq 2):w9 xf d nqhiuton 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, ando-vd5xqsbdp 4s5 ,s8b 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 devic846ygl;aq mx v 9wvz/te needs to be protected against sudden surges in current. In/al 6qw8mvt xv;y9 zg4 particular, after the power is turned on the current should rise no more than 7.5 mA in the first $120\mu s$ The device has resistance $\mathrm{150~Ω}$ and is designed to operate at 55 mA. How would you protect this device? L $\approx$    in series(retain two decimal places)

  A 25-turn 12.5-cm-diameter coil is placed between the pole pi02tqy7hvb, vwfets q5vq 06s1eces of an electromagnet5y1qvshe06 bwt s0f7q q vv,2t. 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 V? $|\varepsilon|$    T/s

  Calculate the peak output voltage of a simple generm t61rhgpb7az+( 1) gppg3wfl r1lv6rator whose square armature windings l mg)+(at7zgr11rb16p pw rf6hlg3 v pare 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 electric and magnetic fields attained shp/d/ gxj8sg(m;xyw/8l g*fin laboratories are aboutd8gwys /g mj;lsp/( 8 gf/xx*h $1.0\times10^4\mathrm{~V/m}$ 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 v+acr u/*y i itn:5v1kqs9vazr; )r4v a transformer whose input is 220 V at 60.0 Hz usvvri t1 +k a9aiy cr;5/z):4rn*vqvif the current drawn is 5.8 A? Assume no current in the secondary.    H

  A 130-mH coil whose relt9 ckk1b) nn7fs 7wn5sistance 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 3h qxzj4g(z p+a-0 sd,q6-V battery. When connected to a 60-Hz 120-V (rms) source, the current drawn is 4djzz s( -q qhga,px+03.8 A (rms). Determine the inductance and resistance of the coil.
$V_{dc}$ $\approx$    $\Omega$
L $\approx$   $ \times10^{-2 }\;H$

  A 135-mH inductor with be:j1w( je uskx.wuprmj +s-6vi; /r8$2.0-\Omega$ resistance is connected in series to a $20-\mu\mathrm{F}$ capacitor and a 60-Hz, 45-V source. Calculate
(a) the rms current, $I_{rms}$ =    A
(b) the phase angle. $\phi$ =    $^{\circ}\,$

  The Q factor of a resonance circuit can be defined as the rativhw8/ vbz kvs.dj nzvxbm ngdg23()1 +q.,f3ko 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 shar/bvq(k8k gdzdsfvm,+b x 2 h3v.zvjg. n1w3n)per 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$