What would be the advantage, in Faraday’s eq3;vw;vd l :js*r az 7xy6i(wsxperiments (Fig. Below), of using coilsaq*r ws;l6wy x(d ;s:37zjivv with many turns?

What is the difference between magnetic flux and mag p4hef(.;.smpi ridp6 netic field?

Suppose you are holding a circular ring o vvdai9 77apx5f wire and suddenly thrust a magnet, south pole first, away from you toward the center of the circle. Is a current induced in the wire? Is a current induced when the magnet is held steady within the ring? Is a xva97vdi5ap7 current induced when you withdraw the magnet? In each case, if your answer is yes, specify the direction.

Two loops of wire are movi.nasd-:oefo z1 lhu5 (ng 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 enz .ua(shoefdo-:15 lach loop.

Suppose you are looking along a line through the centers of two circue-bvju.rd61:x r+u7ktc h pj/ g4n8 fglar (but separate) wire loops, one behind the other. A battery is suddenly connected to t tpv.+ r1:n8jux7 rg b4/cdjge6khf u-he 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 currentai xgrlme;,51 in resistor $R_A$ when
(a) coil B is moved toward coil A, ----待选择----increasedecrease 
(b) when coil B is moved away from A, ----待选择----increasedecrease 
(c) when the resistance $R_B$ is increased. ----待选择----increasedecrease 

In situations where a small signal must travel over a distance9pp (8uap3 :ue0n)4hktv 0 u r91fxoevd ni(je, a “shielded cable” is used in which the signal wire is surrounded by an insulator and then enclosed by a cylindrical conductor cj:norate4 v i )ne1 uu(3 vfux0pp dkh089(9eparrying the return current. Why is a “shield” necessary?

What is the advantage of pla (msxx(m mifmxah1 3/9cing the two insulated electric wires carrying ac closxmm1x( m/9hmfaix3 s(e together or even twisted about each other?

Explain why, exactly, the li-g gxdxkjrz5 15x3 *yl m2bn+jghts may dim briefly when a refrigerator motor starts up. When an electric heater is turned on, the lights may stay dim2 l-g+r5 y 51j3 gxzxndxmb*jkmed as long as the heater is on. Explain the difference.

Use (Fig. Below a) and (Fig. Below b) yt1rh 4f 6y1to ((spueplus the right-hand rules to show why the counter torque in a generator opposeso t1frp s6y(hy4tu e1( the motion.
a
b

Will an eddy current brake (Frik iv2 ub6 ykm r*28wvz13x.fig. Below) work on a copper or aluminum wheel, or must the wheel be ferromagnetic1. i2k2 krxvu8v6wzy*r b3f mi? Explain.

It has been proposed that eddyp-rp51 r(nalg(trzd8 currents 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 magnets. How will this aid in the separation of nonferrous metals (Al, Cu, Pb, brass) from nonmgd5(pa -t1pn lr8r (rzetallic materials?

The pivoted metal bar with slots in (dixfnz:blm2* h :90v) sw-a+qj yj y8e3tr)udFig. Below) falls much more quickly through a magnetic field than does a solid bar. Exp:tb2ly8n0: qjm)hyrwzu *sd3fa x- 9d )ve+i jlain.

If an aluminum sheet is held between wki b)c.ki7sjge )3 7a9r0pxmthe poles of a large bar magnet, it requires some force to pull it out of the magnetic field even though the sheet is not ferromagnetic and does7a ikmbes7p9r3jk)g ci 0.)wx not touch the pole faces. Explain.

A bar magnet falling inside a vertical metal tube reaches a terminal velocc6mcle.8 q-vuity even if-8cvlqceu6m. the tube is evacuated so that there is no air resistance. Explain.

A metal bar, pivoted at one end, oscillatesdi 8u4ie zn-fl/ oime/*u(am. freely in the absence of a magnetic field; but in a magnetic field, its oscillatmie i(ua*n/zmdf4e.8- /uiloions are quickly damped out. Explain. (This magnetic damping is used in a number of practical devices.)

An enclosed transformer has four wire leads coming from it. How coul s.xqohk26c5t d you determine the ratio of turns on the two coils without taking the transformer apart? How would you know which wires paired 2khxc.q5 6 tsowith which?

The use of higher-voltage lines in )o0 1mgxrxd abaa:2z) homes — say, 600 V or 1200 V — would reduce energy waste. Why are :rxdab)ao m0z1a2 g)x they not used?

A transformer designed for a 120-V ac inputc6.p f rj; 6w mg.wv2rcy,x-fi will often “burn out” if connected to a 120-V .p-wgcfw v,iy;c. 2j 66fxmrr dc source. Explain. [Hint: The resistance of the primary coil is usually very low.]

How would you arrange two flat circular coils so thal 8 /-udviyo6ee8te*at their mutual inductance wa/teld* 6e y-aeo8 v8uis
(a) greatest,
(b) least (without separating them by a great distance)?

Does the emf of the battery in (Fig. Below) affect thc ysdb3)ew 6ct-3ai/ifdo -* ae time needed for the LR circubca i/y)st wcf3aod-3d *-e i6it 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 volthwz2 nb57h;e ,wii 99vl+f9ai sh bi9mage 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 thektiu;15 7u hkiq;4da q 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 (bqv1- la5ba ukw.eg -2myu,evb6oo1minimum.

  The magnetic flux through a coil of wire containing two loops changes frokpnyg k*4o + os3m2,wlm -50Wb to +38 Wb in 0.42 s. What is the emf induced in the coil? l n2o ,wk4k*g3om+sp y   V

  The rectangular loop shown in (Fig. Below) is 1l)va1n jb6bs7.f rwlbi;fw+ pushed into the magnetic field which points inward. In what direction is the induced current? .s1 nbf a+;rww vl)lbi1bf7 j6 ----待选择----counterclockwiseclockwise 

  The north pole of the magnet in (Fig. Below) is (i0w - puddqmf s(:o;obeing inserted into the coil. In which direction is the induced current flowing through the resistor R? ow-sq ofmp u:0(i d(d; ----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. T 5a rjpt8k lz.qav+ xst12ng99he loop a 2gxj58qvklprtst9+a .9 zn1 is removed from the field in 0.15 s. What is the average induced emf?    $ \times10^{-2 }\;V$

  A 12.0-cm-diameter loop okur1 h2 .df.fgf wire is 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 0.20kf ..gr1duh2f s. What is the average induced emf in the loop?    $ \times10^{-2 }\;V$

  A 10.2-cm-diameter wire coil is initial* ocp:nuwtn ) cp-p 6u8m2+urfly oriented 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 the c*ou-tu pc+2)8cf nnp:pu6 wmroil?    $ \times10^{ -2}\;V $

  A 15-cm-diameter circular loop of wire is placed in a 0.50-T magnetic field. iv,n;pg b /boel;gs49
(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 slowly *8: axy c1lvh2m. vwcwincreased, what is the direction of the current induced in the small circular loop inside the larg*w lav1hwc2: vymx.c8 er 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 inux3f yegt5g/5 t13ry lm03dju the circular loop due to the current shown in each part of (Fig. Belo1y3tyf g5u3mj/3r dlg50 xetuw)?
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 w0*uz;s:o a lioh7pr2 from the loop shown, in what direction is the induced cu*lwphr7 o suz2a:o ;0irrent in the loop?  ----待选择----counterclockwiseclockwise 

  The magnetic field perpendicular to a circularuy z/itu l sjnh rk(9rn2+:/+h wire loop 12.0 cm in diameter is changed from +0.52Tj/u2hrk (tru l+ n/zn+si9:y h to -0.45 T 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. Belo/p;mc4kgob p9h1d ay/zi/ -k bw) is 12.0 cm long and is pulled at a speed of 15.0cm/s If the magnetic field is 0.800 T, calc kcz/4dpgb/k 91a- py; hbomi/ulate
(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 field pointi t 9j7zp ouu2,mep:xg-ng into the paper. If th:uepz gj 2t97-pu x,moe 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 aads 4 ms6svgqxsf27, 3n emf of 120 mV while movs2d fs43x6ssq7, mvgaing in a 0.90-T magnetic field.
(a) What is its speed?    m/s
(b) What is the electric field in the rod?    V/m  ----待选择----updown 

  Part of a single rectangular loop of wire with dimensions shown in (Fig. Bel ur3pq/7;q- 4ce-hh pp hw1qthow) is situated inside a region of uniforc1h- qwqe 4/hh3ppr put- h7q;m magnetic field of 0.550 T. The total resistance of the loop is $\mathrm{0.230~Ω}$ Calculate the force required to pull the loop from the field (to the right) at a constant velocity of 3.40m/s Neglect gravity.    N

  A 500-turn solenoid, 25 cm long, has a diameter of 2.5 cm. A 10-turn crr .mr1 p0imh-oil is wound tightly around the center of the solenoid. If 0rm-mrpih 1r. the current in the solenoid increases uniformly from 0 to 5.0 A in 0.60 s, what will be the induced emf in the short 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, u3t4 vpv3+ziv and has a resistance +iz 43vvvut3pof $\mathrm{2.5~Ω}$ 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 yudvn ,; ln7d)turns of circular copper wire 2.6 mm in diameter. A uniform magnetic field, perpendicular to the plane oy d)d7 l;nnu,vf 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 fv)qe 5y h;w74g4bctc circular loop of copper wire decreae thbvf 4y7c4;g5c w)qses 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 this operation?    C

  A simple generator is used to generate a peak output voltage of 24.0 V. T2 v94-,c vov viqyo-ykhe square armature consists of windings that are 6.0 cm on a side and rotates in a field of 0.42 4vvkv9i,ycq --vooy20 T at a rate of 60.0rev/s How many loops of wire should be wound on the square armature? $\approx$    loops(Round to the nearest integer)

  The generator of a car idling at 1100 rpm produces 12.4 V. What will the ou tlhq8k4 t( x6hw (ejnu*put be at a rotation speed of 2500 rpm, assun6x4t e(hk* jhulq(w 8ming nothing else changes?    V

Show that the rms outpukz rq1vuj( +5h) wur:tt (Section 18–7) of an ac generator is $V_\mathrm{rms}=NAB\omega/\sqrt{2}$, where $\omega=2\pi f.$

  A simple generator has a 320-loop square coil 21.0 cm on a side. Hofbk8rq3v,vzi gt mvlvg* f-i3o9+ v.pc 1)u8a w fast must it turn in a 0.650-T field to produce fblmi.v p8r-+1t3c*8vzgvu9vq,k f avgi )o3a 120-V peak output? $f$   rev/s

  A 450-loop circular armature coil with a diameter of 8.0 cm rotrsz oge m.rxl8) ml,:2ates at 120rev/s in a uniform magnetic field of strength 0.55 T. mse .mr gx:o2l,rlz 8)
(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 0.03cr3:bycwhe ytx/)4koeng r 92 r8*4:)akvxpz0 T. It has 1000 turns and produces y:tnrg z4 )rw*yh/bapo:e exxv 3c9r 2)84ckkan rms voltage 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 resista* rbh(q h1c 5(yhtkue)nce of $3.25\Omega.$ If it draws 8.20 A when running at full speed and connected to a 120-V line, how large is the back emf?    V

  The back emf in a motor is 72 V when operating at 1800 rpm. What would b5 )5 lt;mewzone the back emf at 2500 rpm if the magnetic field w l )5t;enzom5is unchanged?    V

  The back emf in a motor is 95 V when the motor is o)q ,rg/ k om60ttuqo )mxm+y-zperating at 1000 rpm. How would you change the motor’s magu+txqm))m,0otyz o -6m / qrkgnetic 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 currentfq kuq6t,,jo7u1xn6v in the motor of Example 21–9 if the load causes it to run at half speed? o17 ,ku u,q xnvf66tjq   A

  A transformer is designed to change 120 V into 10, :*/:k n9gy5v d /f qqsj+p;,calbmnml000 V, and there are 164 turns in the primary coil. Hf5qml : n+agq:ymkp*jn,/cbvl 9/s;dow 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 the se.gb.ecao,(p txc d+: econdart :a.pgcx+ cd.b(eeo, y coil as compared to the primary coil?   

  Neon signs require 12 kV for their operation. To operate from a 240-V li h3y krqnh6r8)ne, what must be the ratio of secondary to primary turns of the transformer? What would the voltage output be i )rhh6 8qn3rykf 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 doggcqp;det;2 2 9 u/ioraws 0.35 A while supplying 7/od2p9;tu eic;g q2 og.5 A to the train.
(a) What voltage is present across the tracks?    V
(b) Is the transformer step-up or step-down? this is a  ----待选择----step-downstep-up  transformer

  The output voltage of a 95-W transformer is 12u.ecw5x37-h5u h qdu (qxa6 zi V, and the input current is 22 A. z5- .eq x(7uw5h6xuqu3aic dh
(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 primaxfazs6 3r0+j xry turns and 1340 secondary turns. The input voltage is 120 V and the output current is 15.0 A. Whaaz6r fxx+s03jt 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 2 9p/rd3/n4nob 8svogf 6ibebf- ik 3oa 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 tlxo.: ns;yrim 1yrl).own 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 change fj5sn 8)gndfl vy2:kp /1dq*js steadily from 25.0 A to 10.0 A in 350 ms, what is thfky:1lv jn5d2)pqngf/8s* d je magnitude of the induced emf?    V

  What is the inductance of a coil if the coil ;m:v sz6t/0njc q h95ap:ykj xproduces an emf of 2.50 V when the current in mv:5xcqh 6jaykt:/jsn0zp9 ; it changes from -28.0mA to +31.0mA in 12.0 ms?    H

  What is the inductance L of a krcab1 4akrsj i6) 19b0.60-m-long air-filled coil 2.9 cm in diameter contain c1jaai )r6rskbb194 king 10,000 loops?    H

  How many turns of wire would be required tf23vrt, (0: ol f vowgjhmgj5 ud/p2s*o make a 130-mH inductance out of a 30.0-cm-long g/2fv0ordl3j(sjw fgmp5: thv , 2*ou air-filled coil with a diameter of 5.2 cm? L$\approx$    turns (Round to the nearest integer)

  An air-filled cylindrical induc 9r3b- /hxkohwtor has 2800 turns, and it is 2.5 cm in diameter wo r3/x-hbh9kand 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 crosa)s mt8 uui,7j w-r2pts-sectional area 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 tighttjf7w ) oy7wyo/l1ui6 x,8d duly wound solenoid o7d8do ,wli6w1 of/ y)uj7xtuy f twice the diameter. By what factor does the inductance change?   

  The magnetic field inside an air-filled solenoid 36 l,p- 5f9ge an9 rgmnr/cm long and 2.0 cm in diameter is 0.80 T. Appm 5nrenf rg9p9-g a,l/roximately how much energy is stored in this field?    J

  At a given instant the current throu6tonl 4ug a6-tv:0 i0diur)fqgh an inductor is 50.0 mA and is increasing at the rate of 115mA/s. What is the initial energy stored in the inductor if the q0 iiv 4ao-gdt n)t0uur:66f linductance 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 m, t01zthtelgumz (,h i8ll,kwy2.s ;xagnetic field 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. o 2x0yn6;iuwo Below) reach within
(a) 10%,    $\tau$
(b) 1.0%,    $\tau$
(c) 0.1% of its maximum value?    $\tau$

  Two tightly wound soleno/k ltgm8 t:z*er+m(trtz w4-u ids have the same length and circular cross-sectional area. But solenoid 1 uses wire that is half as thick as s( t * k trt+:8tzgwmu4-/lzmerolenoid 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 mt / eu4a)r0mda $7.20-\mu F$ capacitor at a frequency of
(a) 60.0 Hz,    $\Omega$
(b) 1.00 MHz?    $ \times10^{ -2}\;\Omega$

  At what frequency will a 22.0-mH inductor have aw9g45sa kwr 2k reactance of $660 \mathrm{k} \Omega ?$    Hz

  At what frequency wil , mwp:vq 0v3hj2kj2m+en7vm.ru4 omyl a $2.40-\mu F$ capacitor have a reactance of $6.70 \mathrm{k} \Omega ?$    Hz

Plot a graph of the rea1v:a6bi,n;t4c7p , vwfo opjwctance 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 frwvv(o(j(m01 7 epv uxpequency from 100 to 10,000 H1 o( (vup(xj7vepwv0mz.

  Calculate the reactance of, and rms current in, a 160-mH radio coil connuwa(wq 0 zh8 ips rsez+q4xb6sa;4q44ected to a 240-V (rms) 10.0-kHz ac line. Ign bqh 8s 4+s zx4ur;6i qwza4wqs(aep40ore resistance.
$X_L$ =    $\Omega$
V =    $ \times10^{-2 }\;A$

  An inductance coil operates at 240 V and 60.0 Hz. It draws 12.8xz *4nm vfgo(wtd+9-:,yljt h A. What is the coi*tvmn4jo+( fwd:-th g9l,y zxl’s inductance? $X_L$ =    $ \times10^{-2 }\;H$

  (a) What is the reactance emjhf q z+1ga+cs5y:(of a well-insulated $0.030-\mu F$ capacitor connected to a 2.0-kV (rms) 720-Hz line?    $\Omega$
(b) What will be the peak value of the current?    A

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

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

  For a 120-V rms 60-Hz voltage, an rms currenj3(nm b v+k bbao:*nv2t of 70 mA passing through the human body b+n*nkjbbv:2moa v(3for 1.0 s could be lethal. What must be the impedance of the body for this to occur?    $ \times10^{3 }\;\Omega$

  What is the resistance of a coil if its im k0vl wqkmzhh0e0,8c9pedance is $\mathrm{235~Ω}$ and its reactance is $\mathrm{135~Ω}$    $\Omega$

  What are the total impedance, phase angle, and rms nd;2xj xscr. 8current in an LRC circuit connected dx.j ;x sn2r8cto a 10.0-kHz, 725-V (rms) source if $L=22.0\mathrm{~mH},R=8.70\mathrm{~k}\Omega,$ and
Z $\approx$    k$\Omega$
$\phi$ =    $^{\circ}\,$
$I_{rms}$ =    $ \times10^{ -2}\;A$

  A resistor in serik977xunv1zo dxi/wa2 nd+l 0ies with a 420-mH inductor is driven by an ac power supply. At what frequency is the xia7n u01kv/ x2dz+n7d wlo9iimpedance double that of the impedance at 60 Hz?    Hz

  (a) What is the rms current in an RL circuit when a 60.0-Hz 120-V rm -4div- bjx9+ 4bwpyaps ac voltage is applied, wj4yx -9iw -a+ pb4vdbphere $R=1.80\mathrm{~k}\Omega,$ 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 inky/6kbi( l. a6sxud)m1zc7 hsc ;pbn/ an RC circuit if $R=8.80\mathrm{k}\Omega,C=1.80\mu\mathrm{F},$ and the rms applied voltage is 120 V at 60.0 Hz?    $ \times10^{-2}\;A$
(b) What is the phase angle between voltage and current? $\phi$ =    $^{\circ}\,$
(c) What are the voltmeter readings across R and C?
$V_{rms\,R}$   V
$V_{rms\,C}$    V

  A 3500-pF capacitor is connectedpms ++ 6o1y* zpf4k7diam1l ni to a $55.0-\mu H$ coil of resistance $3.00\Omega.$ What is the resonant frequency of this circuit?    $ \times10^{5 }\;Hz$

  The variable capacitor in the tuner of an AM radio h:zsxik qbse7 1xg; q:*as a capacitance of 2800 pF when the radio is tuned to a statiogxzbse :q*qik;x :s71 n 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 any7jevt yyl6/c2b pq25d $R=4.40\Omega$.
(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 g)ah8no g(;r nof the page as shown in (Fig. Below). When switch S is thrown in the left-hand coil, rnnha8(g g);o
(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 resistanpz 7qxug s)asvwc,r+ 3mh70 lw6 /y6nnce 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 bggycbp,+ +)vgx i.k n0ut requires only 12 V. It contains a transformer ti+) g, cxykng g.0pvb+hat 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 gendq4 c0i.fnqbh)+- v6 zn3 fz5l jiw8lherating plant located 118 km from a town that requires 50 MW of power at 12 kV. Two transmission lines from thflhq08zhfc4windv+ -) 5 3l.bijq 6zne 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 hbr- /9e ol1-cyjx5gean 80% efficiency are connected to 110-V ac. Thecjxbo95hl -y-g 1/ ree secondary 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 tranzlt14mv4hp8 9 oxoy1jd mjdw. l(w ,)dsmission lines 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 yaa m .4x.1y:mdqegoo2q+t z* rest 32 cm apart on a 6.0$^{\circ}\,$ ramp. They are joined at the bottom by a $0.60-\Omega$ resistor, and at the top by a copper bar of mass 0.040 kg (ignore its resistance) is laid across the rails. The whole apparatus is immersed in a vertical 0.55-T field. What is the terminal (steady) velocity of the bar as it slides frictionlessly down the rails? v =    m/s

Show that the power loss i5 ug/d z ,e5o0qm1acmyn transmission 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 res fev(0co2om l6xm y9tcv0 go/9istance 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 wbx8n+ -ga baof10nwziyz 7xn/*5ee;to be protected against sudden surges in current. In paw n;5gen0 z+z yboni1*wf aa7x/ e8x-brticular, 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 pieces of an et4 5iin2)ekple.m ,km7sq0vhb ( 2pkxlectromagnet. When the magnet is turned on, the flux through the coil changes, inducing an emf. At whavt. 0bnmphke45(imkqxk2e 2l ) p7si,t 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 generator whose sqf,(9/fu gz sel8o6 laquare armature windings are 6.60 cm on a side; the armature contains 155 loops and r,fso9 /el6 (8 azqfuglotates 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 in laboratories *ezz9,6gqrt:gk qt8 y a :zt9k,8g zeq*qyr6tgre about $1.0\times10^4\mathrm{~V/m}$ and 2.0 T.
(a) Determine the energy density for each field and compare.
$u_E$ $\approx$    $ \times10^{-4 }\;J/m^3$
$u_B$ $\approx$    $ \times10^{6 }\;J/m^3$
$\frac{u_B}{u_E}$ =   $ \times10^{9 }\;$
(b) What magnitude electric field would be needed to produce the same energy density as the 2.0-T magnetic field?    $ \times10^{8 }\;V/m$

  What is the inductance L of the primary of a transformer whose input is*; * ba1obfjf;z gq(a t;ihg7v 220 V at 60.0 Hz if the current drawn is 5.8;1ovf *h*;j aaqb7g; bgzt(fi A? Assume no current in the secondary.    H

  A 130-mH coil whose resista eh3mj+yfmmz jv. ./+5nhhq1ynce 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 conn mc.*+qeuha:p*rp+fuected to a 36-V battery. When connected to a 60-Hz 120-V (rms) source, the current drawn is 3.8 A (rp fuu+:rp*.a +mch*eqms). Determine the inductance and resistance of the coil.
$V_{dc}$ $\approx$    $\Omega$
L $\approx$   $ \times10^{-2 }\;H$

  A 135-mH inductor witqa;l u w4q bnh2*7(vuth $2.0-\Omega$ 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 rajzv /fz8-la/0 ao7yeztio of the voltage across the capacitor (or inductor) to the voltage across the resistor, at resonance. The large/flja8z /vzy0oea7z -r the Q factor, the sharper the resonance curve will be and the sharper the tuning.
(a) Show that the Q factor is given by the equation $Q=(1/R)\sqrt{L/C}.$
(b) At a resonant frequency $f_0=1.0\mathrm{~MHz},$ what must be the values of L and R to produce a Q factor of 550? Assume that $C=0.010\mu\mathrm{F}.$ L $\approx$    $ \times10^{-6 }\;H$(retain one decimal places) Q =    $ \times10^{-2 }\;\Omega$