Explain why birds can sit on powed77f,piww au )f1a;f-ik*ti br lines safely, whereas leaning a metal ladder up against a power line to fetch a stuck kite is extremely aaf dii i)wtb 77pf;fk*w1-u,dangerous.

Discuss the advantages and disadvantages of Christmas treey/pbb hwecs/ce8l2:as1 k 0 6x lights connected in parallel versus those con/0bae xh2c :bp l6w/cs8ek s1ynected in series.

If all you have is a 120-V line, would it26(/:oeb n6mqe eupm mu,p8 yaf9lyq4 be possible to light several 6-V lamps without burning them out? How(ablp/u,e me9feq 4 ny:6q8 uy o6pm2m?

Two lightbulbs of resistan4rgu f s(fd5w/ce $R_1$ and $R_2(R_2>R_1)$ are connected in series. Which is brighter? What if they are connected in parallel? Explain.

Household outlets are often double outlets. Are these connected in se9*il0nj93 k, om f)fsipqzo;u ries or parallel;fsoii3 qk z 0jpmfo) 9,9nl*u? How do you know?

With two identical lightbulbs ao6*mx0j .e;n7p-/,spjitj *b j wwxdmnd two identical batteries, how would you arrange the bulbs and batteries in a circuit to get the maximum possible total power out? (Assume the batteries have negligible injm-po* j.imnx;p*ej sdbw/x0, tw7 6jternal resistance.)

If two identical resistors are connected in series to a battery, does the bato ;d/ uv2yvg b/jr 9*ohzr- (/i)bv)zssxzr/atery have to supply more power or less power than when only one of the resistors is connectez ;ua* sy(vd i/o s2r)v9j/hxob/r/zgvbz-)r d? Explain.

You have a single 60-W bulb on in your room. How does the overall -* -4myt*1cpm5voap2tx o:hd9vddb j resistance of your roo1vc* p m:y2adv-opjdtdhm-* 4to bx 59m’s electric circuit change when you turn on an additional 100-W bulb?

When applying Kirchhoff’s looj39 b8bxe 3jnhp rule (such as in Fig. Below), does the sign (or direction) of a battery’s emf depend on the direction of current through the battery? What abhbjneb8 j33x9 out the terminal voltage?

  Given the circuit shown in Fig. 19–36, bec-t2bpt 72 duse the words “increases,” “decreases,” or “stays the e2dt 72bpcb-tsame” to complete the following statements:
(a) If $R_7$ increases, the potential difference between A and E  ----待选择----stays in samedecreaseincrease . Assume no resistance in Ann meter and power supply.
(b) If $R_7$ increases, the potential difference between A and E  ----待选择----stays in samedecreaseincrease . Assume Ann meter and power supply have resistance.
(c) If $R_7$ increases, the voltage drop across $R_4$  ----待选择----stays in samedecreaseincrease .
(d) If $R_2$ decreases, the current through $R_1$  ----待选择----stays in samedecreaseincrease .
(e) If $R_2$ decreases, the current through $R_6$  ----待选择----stays in samedecreaseincrease .
(f) If $R_2$ decreases, the current through $R_3$  ----待选择----stays in samedecreaseincrease .
(g) If $R_5$ increases, the voltage drop across $R_2$  ----待选择----stays in samedecreaseincrease .
(h) If $R_5$ increases, the voltage drop across $R_4$  ----待选择----stays in samedecreaseincrease .
(i) If $R_2$,$R_5$, and $R_7$ increase, power supply (r = 0)  ----待选择----stays in samedecreaseincrease .

For what use are batteries connected in series? For what u1 o 9h0e9m-*rrysufg fse are they connected in parallel? Does it matter if the batteries are nea0 fgo*fyr u19-shm9errly identical or not in either case?

Can the terminal voltage of a battery ever exceed its emf? qexgpbo2i :0 (8wfv;r Explain.

Explain in detail how you could me9a3.ce(vi r kfasure the internal resistance of a battery.

Compare and discuss the formulas for resistors and for capacitors when cgu1: *u0sg5a kob an/qonnected in series and in p* ao0 1 ngb5:uqug/sakarallel.

Suppose that three identical capacitors are connectej .nqok q:m3:g0z,6guvw mv9 hd to a battery. Will they store mor 0mhqvqz:9mg3,unk6.go j v: we energy if connected in series or in parallel?

Why is it more dangerous to turn on an electric appliance when you are standimr c -d:0(6bo,tr; ib lt6vgo-s+ejyz ng outside in bare feet than when you are inside wearing shoeo dsr:t,tb -eg0(j+cizm6r l bo 6-;yvs with thick soles?

(Fig. Below) is a diagram of a capacitor (or ct)vk2:zjtb yq/wa- /kondenser) microphone. The changing air pressure in a sound wave causes one plate of the capacitor C to move back and forth. Expt-jk wktaq)v/yz/:b 2lain how a current of the same frequency as the sound wave is produced.

Design a circuit in which two ysmz,mllh)r fp 5f.;c. key. ty+s/ u(different switches of the type shown in (Fig. Below) can be used to operate th/r yl5z ;tcflm)+es p,km..yhfus .(y e same lightbulb from opposite sides of a room.

In an RC circuit, current flows from the ,g g*75y5 zlj4zsamy ld56bus be ;p;obattery until the capacitor is completely charged. Is the total energy supplied by the battery y m b,5js;g75lzpe4az5*so6g dy;ub lequal to the total energy stored by the capacitor? If not, where does the extra energy go?

What is the main difference betweens(h + x3g8ykys ze5: asdbr,c: an analog voltmeter and an analog ammeter?

What would happen if you mistakenly used an ammeter where you n- e5/ s)pc ws nzryfz*u()x9nyeeded to use a voltm5 e s)n9y -(c/xr wzu)snypzf*eter?

Explain why an ideal a0ck6pl hnib ,dt7: w9fmmeter would have zero resistance and an ideal voltmeter infht w lp,7:k9d0 bnic6finite resistance.

A voltmeter connected across a rezan8oyl 56k u cq3hridi(5 p5;sistor always reads less than the actual voltage across the resistor when the meter isz 5ucra85y6 i(ldpo5h ik;q3n not present. Explain.

A small battery-operated flashlight requires a single 1.5-V bah oltaner 82b6) +*zkfttery. The bulb is barely glowing, but when you take the battery out and ct 6aekb *o)hn2zrfl8 +heck it with a voltmeter, it registers 1.5 V. How would you explain this?

  Calculate the terminal voltage for a battery with an internal res bhb e9dw4 wopb-0k-t-p .yz6tistance of $0.900\Omega$ and an emf of $8.50\,V$ when the battery is connected in series with
(a) an $81.0-\Omega$ resistor,    V
(b) an $810-\Omega$ resistor.    V

  Four $1.5-V$ cells are connected in series to a $12-\Omega$ lightbulb. If the resulting current is $0.45\,A$, what is the internal resistance of each cell, assuming they are identical and neglecting the wires?    $\Omega$

  What is the internal(e y,q6:aooom resistance of a $12.0-V$ car battery whose terminal voltage drops to $8.4\,V$
when the starter draws $75\,A$?    $\Omega$
What is the resistance of the starter?    $\Omega$

  A $1.5-V$ dry cell can be tested by connecting it to a low-resistance ammeter. It should be able to supply at least $22\,A$. What is the internal resistance of the cell in this case, assuming it is much greater than that of the ammeter?    $\Omega$

  Four $240-\Omega$ lightbulbs are connected in series.
What is the total resistance of the circuit?    $\Omega$
What is their resistance if they are connected in parallel?    $\Omega$

  Three $45-\Omega$ lightbulbs and three $75-\Omega$ lightbulbs are connected in series.
(a) What is the total resistance of the circuit?    $\Omega$
(b) What is their resistance if all six are wired in parallel?    $\Omega$

  A $650-\Omega$ and a $2200-\Omega$ resistor are connected in series with a $12-V$ battery. What is the voltage across the $2200-\Omega$ resistor?    V

  Given only one $25-\Omega$ and one $35-\Omega$ resistor, list all possible values of resistance that can be obtained.    $\Omega$    $\Omega$    $\Omega$    $\Omega$

  Suppose that you have a e eahpw ut8 mt 6z+*7:2; ybyf:uvnle;$680-\Omega$, a $940-\Omega$ and a $1.20-k\Omega$ resistor. What is
(a) the maximum,    $\Omega$
(b) the minimum resistance you can obtain by combining these?    $\Omega$

Suppose that you have+jsv,3 mwtjapd*9aw l 4,tv3cb+6 fkh a $6.0-V$ battery and you wish to apply a voltage of only $4.0\,V$. Given an unlimited supply of $1.0-\Omega$ resistors, how could you connect them so as to make a “voltage divider” that produces a $4.0-V$ output for a $6.0-V$ input?

  Three $240-\Omega$ resistors can be connected together in four different ways, making combinations of series and/or parallel circuits. What are these four ways, and what is the net resistance in each case?
The resistors can all be connected in series   $\Omega$
The resistors can all be connected in parallel.   $\Omega$
Two resistors in series can be placed in parallel with the third.   $\Omega$
Two resistors in parallel can be placed in series with the third.    $\Omega$

  A battery with an emf of31 s-tl2b 6ea1 ywo(fq mqdr6o zvb91c $12.0\,V$ shows a terminal voltage of $11.8\,V$ when operating in a circuit with two lightbulbs rated at $3.0\,W$ (at $12.0\,V$) which are connected in parallel. What is the battery’s internal resistance?    $\Omega$

  Eight identical lights are conned0e40chea:n p;ivtx +cted in series across a $110-V$ line.
(a) What is the voltage across each bulb? V$\approx$    V(Round to the nearest integer)
(b) If the current is $0.50\,A$, what is the resistance of each bulb, and what is the power dissipated in each?
R $\approx$    $\Omega$(Round to the nearest integer)
P $\approx$    W(retain one decimal places)

  Eight lights are connected i fj5 6o:2pyvvin parallel to a $110-V$ source by two long leads of total resistance $1.6-\Omega$. If $240\,mA$ flows through each bulb, what is the resistance of each, and what fraction of the total power is wasted in the leads?
$V_R $ =    $\Omega$
firaction wasted =   

  Eight $7.0-W$ Christmas tree lights are connected in series to each other and to a $110-V$ source. What is the resistance of each bulb?    $ \Omega$

  A close inspection of an electric c.noz1 ob;:yh1o;t1c qmjj hg,ircuit reveals that a $480-\Omega$ resistor was inadvertently soldered in the place where a $320-\Omega$ resistor is needed. How can this be fixed without removing anything from the existing circuit?    $\Omega$

  Determine
(a) the equivalent resistance of the circuit shown in (Fig. Below),
$R_{eq}$ =   $\Omega$
$V_{470}$ =    V
(b) the voltage across each resistor. $V_{parallel}$    V

  A $75-W$, $110-V$ bulb is connected in parallel with a 40-W, 110-V bulb. What is the net resistance?    $\Omega$(Round to the nearest integer)

  Consider the network of resistoxtt6b kxgn:61 rs shown in (Fig. Below). Answer qualitatively: :1x6btgkx6tn
(a) What happens to the voltage across each resistor when the switch S is closed? $V_1$  ----待选择----increasedecrease  $V_2$  ----待选择----increasedecrease  $V_3$  ----待选择----increasedecrease  $V_4$  ----待选择----increasedecrease 
(b) What happens to the current through each when the switch is closed? $V_1$  ----待选择----increasedecrease  $V_2$  ----待选择----increasedecrease  $V_3$  ----待选择----increasedecrease  $V_4$  ----待选择----increasedecrease 
(c) What happens to the power output of the battery when the switch is closed?  ----待选择----increasedecrease 
(d) Let $R_1=R_2=R_3=R_4=125\Omega$ and $V\,=\,22.0\,V$. Determine the current through each resistor before and after closing the switch. Are your qualitative predictions confirmed? Notice that the current through each of the parallel resistors is half of the total current, within the limits of significant figures. $I_1$ =    A $I_3$ =    A $I_4$    A Notice that the current through each of the parallel resistors is one third of the total current, within the limits of significant figures.$I_1$ =    A $I_2$ =    A $I_3$ =    A $I_4$ =    A  ----待选择----YesNo 

  What is the net resistance of the circuit connected to the bat wii yfvypzlz266 xt03z6s)ba4wnm m7p 1*jw7 tery in (Fig. Below)? Ev6tm ipyn176ly) pzf2wx mjwz3si b0z *4w67a ach resistance has $R\,=\,2.8K\Omega$.   k$\Omega$(retain one decimal places)

  Three equal resistorsda0i0 kx1 7;8fyeebp, al+bmh (R) are connected to a battery as shown in (Fig. Below). Qualit8af1, dix +l 0kbe07pbhy mae;atively, what happens to
(a) the voltage drop across each of these resistors, $V_{left}$  ----待选择----decreaseincrease0  $V_{right}$  ----待选择----decreaseincrease0  $V_{right}$  ----待选择----decreaseincrease0 
(b) the current flow through each, $I_{left}$  ----待选择----decreaseincrease0  $I_{right}$  ----待选择----decreaseincrease0  $I_{right}$  ----待选择----decreaseincrease0 
(c) the terminal voltage of the battery, when the switch S is opened, after having been closed for a long time? terminal voltage  ----待选择----decreaseincrease0 
(d) If the emf of the battery is 15.0 V, what is its terminal voltage when the switch is closed if the internal resistance is $0.50\Omega$ and $R\,=\,5.5\Omega$?
$V_{terminal\,closed}$ =    V
(e) What is the terminal voltage when the switch is open? $V_{terminal\,closed}$ =    V

  A $2.8-k\Omega$ and a $2.1-k\Omega$ resistor are connected in parallel; this combination is connected in series with a $1.8-k\Omega$ resistor. If each resistor is rated at $\frac{1}{2}W$ (maximum without overheating), what is the maximum voltage that can be applied across the whole network?    V

  Calculate the current in the ci/5djent 1:2delpaj v0rcuit of (Fig. Below) and show that the sum of all the vot de /05j j:d2pea1lnvltage changes around the circuit is zero.
I $\approx$    A(retain two decimal places)
$\sum$ =    V

  Determine the terminal voltage of each battery in (Fig. Below).e p r:nw.+slm .yrnk-;f4n+dtfki9 4f 18V battery =    V 12V battery =    V

  (a) What is the potenti0fmz7;eftzacr:l9m ; al difference between points a and d in (Fig. Below a) (same circuit as Fig. aeczf :m9tflm07;; zrBelow b, ), $V_{ad}$    V
(b) what is the terminal voltage of each battery?
80V battery =    V
45V battery =    V

a
b

  For the circuit shown in (Fig. Below), findv xt+2w( bsnk, the potential difference between points a and b. Each ks,wv xt (2nb+resistor has $R\,=\,75\Omega$ and each battery is 1.5 V.    V

  Determine the magnitudes and directionsznkn09 hes:c0, ywdl: of the currents through $R_1$ and $R_2$ in (Fig. Below). $I_1$    A  ----待选择----leftright  $I_2$    A  ----待选择----leftright 

  Repeat Problem 27, now k)w p3:1ne/d,q lx i jv/fhx7da0gae(assuming that each battery has an internal resistance $r\,=\,1.2\Omega$.
$I_1$ $\approx$    A  ----待选择----leftright (retain two decimal places)
$I_2$ $\approx$    A  ----待选择----leftright  (retain two decimal places)
$I_3$ $\approx$    A  ----待选择----leftright  (retain two decimal places)

  Determine the magnitudes1t;l (8:l7xqzmye kth and directions of the currents in each resistor shown in (Fig. Below). The batter1x( ;:kllty qzmt7he 8ies have emfs of $E_1\,=\,9.0V$ and $E_2\,=\,12.0V$ and the resistors have values of $R_1\,=\,25\Omega$,$R_2\,=\,18\Omega$, and $R_3\,=\,35\Omega$
$I_1$ $\approx$    A  ----待选择----leftrightup (retain two decimal places)
$I_2$ $\approx$    A  ----待选择----leftrightup  (retain two decimal places)
$I_3$ $\approx$    A  ----待选择----leftrightup  (retain two decimal places)

  Repeat Problem 29, assuming eaci68hy9 wd8u*qb.d qxs h battery has internal resistance $r\,=\,1.0\Omega$.
$I_1$ $\approx$    A  ----待选择----leftrightup (retain two decimal places)
$I_2$ $\approx$    A  ----待选择----leftrightup  (retain two decimal places)
$I_3$ $\approx$    A  ----待选择----leftrightup  (retain two decimal places)

  Calculate the currents in each resistor of (F3 s(h2 twkmq bk.s6j)oig. Below).
$2\Omega$    A
$6\Omega$    A
$8\Omega$    A
$10\Omega$    A
$12\Omega$    A

  (a) Determine the curren7ksbl s6) m;nats $I_1$,$I_2$, and $I_3$ in (Fig. Below). Assume the internal resistance of each battery is $r\,=\,1.0\Omega$$I_1$ $\approx$    A(retain two decimal places)
$I_2$ $\approx$    A (retain two decimal places)
$I_3$ $\approx$    A (retain three decimal places)
(b) What is the terminal voltage of the 6.0-V battery? $V_{terminal}$    V

  What would the current x7;sm5is rg*.t gop w0$I_1$ be in (Fig. Below) if the $12-\Omega$ resistor is shorted out? Let $r\,=\,1.0\Omega$. $I_1$    A

  Suppose two batteries, with unequal emfs of 2.00 V and 3.00 V, xc961ro- ytop are connected as shown in (Fig. Below). If each internal resistarc1 oo69p-ty xnce is $r\,=\,0.100\Omega$ and $R\,=\,4.00\Omega$, what is the voltage across the resistor R? $V_R$ $\approx$    V (retain two decimal places)

  (a) Six $4.7-\mu F$ capacitors are connected in parallel. What is the equivalent capacitance? $C_{eq}$ =    $\mu F$
(b) What is their equivalent capacitance if connected in series? $C_{eq}$ =    $\mu F$

  You have three capacitzne ff,rcor ,z/:j3-rors, of capacitance 3200 pF, 7500 pF, and $0.0100\mu F$ . What maximum and minimum capacitance can you form from these? How do you make the connection in each case?
$C_{max}$ =    $ \times10^{-8 }\;F$ in  ----待选择----parallelseries 
$C_{min}$ =    $ \times10^{-9 }\;F$ in  ----待选择----parallelseries 

  A $3.00-\mu F$ and a $4.00-\mu F$ capacitor are connected in series, and this combination is connected in parallel with a $2.00-\mu F$ capacitor (see Fig. Below). What is the net capacitance? $C_{eq}$ =    $\mu F$

  If 26.0 V is applied acr5 u-e *wut:rior :rg(poss the whole network of (Fig. Below), calculate the voltage r:ut*pi(o5: e wru-rg across each capacitor.
$V_{2.00}$ =    V
$V_{3.00}$ =    V
$V_{4.00}$ =    V

  The capacitance of a portion of a circuit r,5ck qe3agkc :;hn1his to be reduced from 4800 pF to 2900 pk;rg,n:ehac h5 13kqcF.
What capacitance can be added to the circuit to produce this effect without removing existing circuit elements?    $ \times10^{ -9}\;F$
Must any existing connections be broken in the process?  ----待选择----YesNo 

  An electric circuit was accidentally construct xmdj1c: - qn /uqt8u)as))evoed using a $5.0-\mu F$ capacitor instead of the required $16-\mu F$ value. Without removing the $5.0-\mu F$ capacitor, what can a technician add to correct this circuit?
   $\mu F$
conneected in  ----待选择----parallelseries 

Determine the equivalent ca a p/wi1uel:y35zpf59h e+r:r y9zpc ipacitance of the circuit shown in (Fig. Below).

  In (Fig. Below), if 4z(el3.nx+c8ky16tnh zq v xp$C_1=C_2=2C_3=22.6\mu F$, how much charge is stored on each capacitor when $V\,=\,45.0V$?
$Q_1$   $ \times10^{-3 }\;C$
$Q_2$   $ \times10^{-4 }\;C$
$Q_3$   $ \times10^{-4 }\;C$

  In (Fig. Below), supprp i3ykqe);is7 ;c k2tv4ft ;yose $C_1=C_2=2C_3=16.0\mu F$, If the charge on $C_2$ is $Q_2\,=\,24.0\,\mu C$, determine the charge on each of the other capacitors, the voltage across each capacitor, and the voltage V across the entire combination.
$ Q_{1}$ =    $\mu C$, $V_{1}$=   V
$ Q_{2}$ =    $\mu C$, $ V_{2}$=    V
$ Q_{3}$ =   $\mu C$, $ V_{3}$=    V
V=    V

  In (Fig. Below), letbt 5 *.p6 mmiu:*phkj;2jabzd $V\,=\,78V$ and $C_1=C_2=2C_3=7.2\mu F$. How much energy is stored in the capacitor network?    $ \times10^{-2 }\;J$

  A $0.40-\mu F$ and a $0.60-\mu F$ capacitor are connected in series to a 9.0-V battery. Calculate
(a) the potential difference across each capacitor,
$V_1$ =    V
$V_2$ =    V
(b) the charge on each. $Q_1$ =    $ \times10^{-6 }\;C$
(c) Repeat parts (a) and (b) assuming the two capacitors are in parallel.
$V_1$ =    V
$V_2$ =    V
$Q_1$ =    $ \times10^{-6 }\;C$
$Q_2$ =    $ \times10^{-6 }\;C$

Three conducting plates, each of area A, are connected as show+xyno 7)s pop(n in (Fig. Below).+7pp(sxo ny o)
(a) Are the two capacitors formed connected in series or in parallel?
(b) Determine C as a function of $d_1$,$d_2$, and A. Assume $d_1+d_2$ is much less than the dimensions of the plates.

  A circuit contains a single 250-pF capacitor hooked acrosgth wh4j 3+nqu(xnq)*h3/mvrs a battery. It is desired to store three times as much energy in a combination of two capacitors by adding a single capac nuh3 qw/(q h4r*gvhx3)jtnm +itor to this one.
How would you hook it up? ----待选择----parallelseries 
what would its value be?    pF

  A 185-pF capacitor is connected in series with an unknown capacitance, and asa 63 j3jin 3veg8dn/ ;j tqfa.5pmcp;b a series combination they are connected to a battery with an emf of 25.0 V. If the 185-pF capacitor sto5mjnn3ga/;j afvc d8b 6p eq;pi33. jtres 125 pC of charge on its plates, what is the unknown capacitance?    pF

  Electrocardiographs are often connected as shown in (Fig. Below). Ti;c 9o,llw2w whe leads are said to be capacitively coupled. A time constant of 3.0 s is typicalw2lco;l9 ,wiw and allows rapid changes in potential to be recorded accurately. If $C\,=\,3.0\mu F$, what value must R have? [Hint: consider each leg as a separate circuit.]    $ \times10^{6 }\;\Omega$

  In Fig. Below a (same as Fig. Below b), the total resistance iles,on(f d)f l1;l n)hs $15.0k\Omega$, and the battery’s emf is 24.0 V. If the time constant is measured to be $35.0\mu s$, calculate
(a) the total capacitance of the circuit    $ \times10^{-9 }\;F$
(b) the time it takes for the voltage across the resistor to reach 16.0 V after the switch is closed.    $ \times10^{-5 }\;s$

a
b

  The RC circuit of Fig. Below a (2qn ;+uqp0gkh+b gff0x 3.hhwsame as Fig. Below b) has $R\,=\,6.7k\Omega$ and $C\,=\,3.0\,\mu F$. The capacitor is at voltage $V_0$ at $t=0$. when the switch is closed. How long does it take the capacitor to discharge to 1.0% of its initial voltage?    $ \times10^{ -2}\;s$
a
b

  Two resistors and two uncharged capacitors are arranged as shown inp uy( um22lym7 (Fig. Below). Then a potential difference of 24 V is applied across the combinatu 2 2yp7mmu(ylion as shown.
(a) What is the potential at point a with switch S open? (Let $V=0$ at the negative terminal of the source.)    V
(b) What is the potential at point b with the switch open?    V
(c) When the switch is closed, what is the final potential of point b?    V
(d) How much charge flows through the switch S after it is closed?    $\mu F$

  What is the resistance of a voltmeter onowtokturb7m9 e);e3 n v44lf :o/*fc v the 250-V scale if the meter sensitivitr c vum ft:f4*7ew/t9oob4; knev3 ol)y is $30,000\,\Omega/V$?    $ \times10^{6 }\;\Omega$

  An ammeter has a sensitiv w4zbldg/. mm gr5b *r:xyv(7jity of $20,000\,\Omega/V$? What current in the galvanometer produces full-scale deflection?    $\mu A$

  A galvanometer has an internal resistanccxj p*o,;q3c )f+aiujib0*uo e of $30\Omega$ and deflects full scale for a $50-\mu A$ current. Describe how to use this galvanometer to make
(a) an ammeter to read currents up to 30 A,    $ \times10^{-5 }\;\Omega$
(b) a voltmeter to give a full-scale deflection of 250 V.    $ \times10^{6 }\;\Omega$

  A galvanometer has a sensitivity omagmf9(+4 nwf0s3 ;gd th ani0f $35k\Omega/V$ and internal resistance $20.0\Omega$. How could you make this into
(a) an ammeter that reads 2.0 A full scale,
   $ \times10^{-4 }\;\Omega$ in
 ----待选择----parallelseries 
(b) a voltmeter reading 1.00 V full scale?
   k$\Omega$
 ----待选择----parallelseries 

  A milliammeter reads 10 mA full scale. It consis mrfk5g(wz2a/ts of a $0.20-\Omega$ resistor in parallel with a $33-\Omega$ galvanometer. How can you change this ammeter to a voltmeter giving a full-scale reading of 10 V without taking the ammeter apart? What will be the sensitivity ($\Omega/V$) of your voltmeter?
$R_{ser}$ $\approx$    $\Omega$(Round to the nearest integer)
The sensitivity is    $\Omega/V$

  A 45-V battery of negligib v9j.5v .t bt(qr hmz +v9sghp9uv,ez;le internal resistance is connected to a $R_1$=$38-k\Omega$ and a $R_2$=$27-k\Omega$ resistor in series. What reading will a voltmeter, of internal resistance $95k\Omega$ give when used to measure the voltage across each resistor? What is the percent inaccuracy due to meter resistance for each case?
$V_1$$\approx$    V (retain one decimal places) % error    % too  ----待选择----uplow 
$V_2$$\approx$    V (Round to the nearest integer) % error    % too  ----待选择----uplow 

  An ammeter whose internal resistancejf ( ++aj. j(wv6yxewf is $63\Omega$ reads 5.25 mA when connected in a circuit containing a battery and two resistors in series whose values are $750\Omega$ and $480\Omega$. What is the actual current when the ammeter is absent?    $ \times10^{ -3}\;A$

  A battery with $E\,=\,12.0V$ and internal resistance $r\,=\,1.0\Omega$ is connected to two $9.0-k\Omega$ resistors in series. An ammeter of internal resistance $0.50\Omega$ measures the current, and at the same time a voltmeter with internal resistance $15k\Omega$ measures the voltage across one of the $9.0-k\Omega$ resistors in the circuit. What do the ammeter and voltmeter read?
$I_{source}$   $ \times10^{ -4}\;A$
$V_{meter}$    V

  Two $9.4-k\Omega$ resistors are placed in series and connected to a battery. A voltmeter of sensitivity $1000\Omega/V$ is on the 3.0-V scale and reads 2.0 V when placed across either resistor. What is the emf of the battery? (Ignore its internal resistance.) $\approx$    V（Round to the nearest integer）

  What internal resistance should the voltmeter of Example 19–15 haves:rl sk8 u,- dqcwrlg -n-*rz- to be in error by*g r c- -ns:l8d-rkl wzsqr-,u less than 3%? $\approx$    k$\Omega$

  When the resistor R ini v+j x9f:3yt.hxv *fb (Fig. Below) is $35\Omega$, the high-resistance voltmeter reads 9.7 V. When R is replaced by a $9.0-k\Omega$ resistor, the voltmeter reading drops to 8.1 V. What are the emf and internal resistance of the battery?
r $\approx$    $\Omega$(retain one decimal places)
$\varepsilon$ $\approx$   V(retain one decimal places)

  Suppose that you wish to apply a 0.25-V potential diffrtbq9i ;btf6l0 ,*qf/w 7. vrmrbjt9y)vya ;nerence between two points on the human body. The resi9vitlr bv/q9rbw )6a;y f7ntm , qy0t.* rbf;jstance is about $2000\Omega$, and you only have a 9.0-V battery. How can you connect up one or more resistors to produce the desired voltage?    k$\Omega$

  A three-way lightbulb can produce 50 W, 100 W, or 150 W, at 120 V. Such*a,swf) q14d4 ad ezzg a bulb contains two filaments that can be connected to the 120 V individually ow q*a z44)d,afg z1dser in parallel.
(a) Describe how the connections to the two filaments are made to give each of the three wattages.
50 W output use  ----待选择---- higher-resistance filament lower-resistance filamentfilaments in parallel 
100 W output use  ----待选择---- higher-resistance filament lower-resistance filamentfilaments in parallel 
150 W output use  ----待选择---- higher-resistance filament lower-resistance filamentfilaments in parallel 
(b) What must be the resistance of each filament?
$R_{50W}$    $\Omega$
$R_{100W}$    $\Omega$

  Suppose you want to run some apparatus that is 95 m from an elect p+8(dk/-8nepgn awemric outlet. Each of the wires connecting your apparatpn8 m/nwg8e+a (k pe-dus to the 120-V source has a resistance per unit length of $0.0065\Omega/m$. If your apparatus draws 3.0 A, what will be the voltage drop across the connecting wires and what voltage will be applied to your apparatus?
$V_{wires}$    V
the voltage applied to the apparatus is $\approx$    V(Round to the nearest integer)

  Electricity can be a hazard in hospitals, particularly to patients who are conpk,fs (3omj, vnected to electrodes, such as an ECG. For example, suppose that the motor of a motorized bed shorts out to the bed frame, and the bed frame’s connection to a ground has broken (or was not there in the first place). If a nurse touches the bed and the patient at the same time, she becomes a conductor and a complete circuit can be made through the patient to ground through the ECG apparatus. This is shown schematically in Fig. 19–60. Calculate the current through the patieo,k mfsv, 3jp(nt. $\approx$    $ \times10^{-3 }\;A$(retain three decimal places)

  How much energy must a 45ronvg1e7x+gl (ze 3kpm1ubnb 1+o a60 -V battery expend to charge a $0.40-\mu F$ and a $0.60-\mu F$ capacitor fully when they are placed
(a) in parallel,    $ \times10^{-3 }\;J$
(b) in series?    $ \times10^{-4 }\;J$
(c) How much charge flowed from the battery in each case?
$Q_a$ =    $\mu C$
$Q_b$ $\approx$    $\mu C$(Round to the nearest integer)

  A heart pacemaker is designed to operate at 72b)o wv 67z3xy(rr. ;c6xa mopv beats/min using a $7.5-\mu F$ capacitor in a simple RC circuit. What value of resistance should be used if the pacemaker is to fire (capacitor discharge) when the voltage reaches 63% of maximum?    $ \times10^{-5 }\;\Omega$

  Suppose that a person’s body resistancp nui8-wacy krfg) (gj-4z7 2pe is $950\Omega$
(a) What current passes through the body when the person accidentally is connected to 110 V?   A
(b) If there is an alternative path to ground whose resistance is $45\Omega$, what current passes through the person?   A
(c) If the voltage source can produce at most 1.5 A, how much current passes through the person in case (b)? $\approx$    mA(retain three decimal places)

  A Wheatstone bridge is o+ c y.ef3(agqr r)1pqt+)u kya type of “bridge circuit” used to make measurements of resistance. The unknown res )+o.t q+ p u(q)1yerfcagr3kyistance to be measured, $R_x$, is placed in the circuit with accurately known resistances $R_1$ ,$R_2$, and $R_3$(Fig. Below). One of these, $R_3$, is a variable resistor which is adjusted so that when the switch is closed momentarily, the ammeter Ann Meter shows zero current flow.
(a) Determine $R_x$ in terms of $R_1$ ,$R_2$, and $R_3$.
(b) If a Wheatstone bridge is “balanced” when $R_1\,=\,630\Omega$,$R_2\,=\,972\Omega$, and $R_3\,=\,42.6\Omega$, what is the value of the unknown resistance?    $\Omega$

  An unknown length of platinum wire 0.920 mm in diamets 2l;nilsdt,;la6qg zw 4;ulc/;h .lmer is placed as the unknown resistance in a Wheatstone bridn/g,ll; ldsatlz.u iqc;2 ;l4 wms;6 hge (see Problem 71;Fig. Below). Arms 1 and 2 have resistance of $38.0\Omega$ and $46.0\Omega$ respectively. Balance is achieved when $R_3$ is $3.48\Omega$ How long is the platinum wire?    m

What are the values of effective capacitgq, z6 c.0gsvzgy)b,23u pjz aance which can be obtained by connecting four identicasg6)ga3zzgv ,q0zyp,2 u.cj bl capacitors, each having a capacitance C?

  The variable capacitance of tra;(9)8uv k 6 kqdugqan old radio tuner consists of four plates connected together placed alternately between four other plates, also connected together (Fig. Below). Each plate is separated from its neighbor by 1.5 mm of air. One set of plates can move so that the area of overlap of6g )uaq9v(quktr 8 ;dk each plate varies from $2.0cm^2$ to $9.5cm^2$
(a) Are these seven capacitors connected in series or in parallel?  ----待选择----parallelseries 
(b) Determine the range of capacitance values. from    pF to    pF

  A battery produces 40.8 V when*vsd6hz c x ;1r.lsuq8n,0cil 7.40 A is drawn from it and 47.3 V when 2.20 A is drawn. What are the emf and internal resistanlsn8l xs0; .qcudvhzc*1,i 6rce of the battery?
r =    $\Omega$
$\varepsilon$ =    V

  How many $\frac{1}{2}-W$ resistors, each of the same resistance, must be used to produce an equivalent $2.2-k\Omega$, $3.5-W$ resistor?    $\Omega$ resistors, each rated at ½ W, in  ----待选择----seriesparallel 
What is the resistance of each, and how must they be connected? Do not exceed $P\,=\,\frac{1}{2}W$ in each resistor.    k$\Omega$ resistors, each rated at ½ W, in  ----待选择----seriesparallel 

  The current through the 3 t)gbg;/y9:qeib0 c+yj 5gnx6 vq snw$4.0-k\Omega$ resistor in (Fig. Below) is 3.50 mA. What is the terminal voltage $V_{ba}$ of the “unknown” battery? (There are two answers. Why?) [Hint: use conservation of energy or Kirchhoff’s rules.]
right $V_{ab}$    V
left $V_{ab}$    V

An air-filled parallel-plate capacitor has capacitance k76 gmmko (4uo$C_0$. If two identically sized dielectric slabs of dielectric constants $K_1$ and $K_2$ are inserted as shown in Fig. 19–64, what is the new capacitance? [Hint: treat this as two capacitors in combination.]

  For the circuit shown in(Fig. Bel arb9i1t,04 p(ya9ndp6 ddw ;;lachnmow), determine
(a) the current through the 14-V battery $I_1$ =    $ \times10^{-5 }\;A$ ----待选择----downupward 
(b) the potential difference between points a and b, $V_a-V_b$ =    V

  A solar cell, 3.0 cm square, has an output of 350 mA at 0.80 V whenlj r; ,:xuz: o8k5kd/ygz4efb exposed to full sunlight. A solar panel that delivers close to 1.0 A:u:ko je4zdkzb / gx5yrf;,8l of current at an emf of 120 V to an external load is needed.
How many cells will you need to create the panel?    cells
How big a panel will you need, and how should you connect the cells to one another?    $m^2$
How can you optimize the output of your solar panel?    banks of    cells in series per bank, with the banks in  ----待选择----parallelseries  always have the panel ----待选择---- pointedturned  directly at the sun。

  A power supply has a fixed output voltage of 12.0 V, but you nee8u8 nikxaury-z7 k*z )d $V_T\,=\,3.0V$ for an experiment.
(a) Using the voltage divider shown in (Fig. Below), what should $R_2$ be if $R_1$ is $10.0\Omega$? $\approx$    $\Omega$(retain one decimal places)
(b) What will the terminal voltage $V_T$ be if you connect a load to the 3.0-V terminal, assuming the load has a resistance of $7.0\Omega$? $\approx$    V(retain one decimal places)

  The circuit shown in (Fig. Below a) uses a neon-filled tube as in (gd 0ym9 qrdba *2n:pr;Fig. Below b). This neon lm *rdn29g;brq 0:aypdamp has a threshold voltage $V_0$ for conduction, because no current flows until the neon gas in the tube is ionized by a sufficiently strong electric field. Once the threshold voltage is exceeded, the lamp has negligible resistance. The capacitor stores electrical energy, which can be released to flash the lamp. Assume that $C=0.150\mathrm{~}\mu\mathrm{F},R=2.35\times10\mathrm{~}^6\Omega,V_0=90.0\mathrm{~V}$ and Ann meter=105 V
(a) Assuming that the circuit is hooked up to the emf at time $t\,=\,0$, at what time will the light first flash?    s
(b) If the value of R is increased, will the time you found in part (a) increase or decrease?  ----待选择---- increase decrease 
(c) The flashing of the lamp is very brief. Why?
(d) Explain what happens after the lamp flashes for the first time.

a
b

  The current through the zs j3(.xojx*z 88 b(noa c;9 kpswmwq4$20-\Omega$ resistor in (Fig. Below) does not change whether the two switches $S_1$ and $S_2$ are both open or both closed. Use this clue to determine the value of the unknown resistance R.    $\Omega$

  In the circuit shown in (Fig. B *r y,ey7:srn0lhvor 9 )ms4ncelow), the $33-\Omega$ resistor dissipates 0.50 W. What is the battery voltage? $\approx$    V(retain one decimal places)

  (a) What is the equivaleipdxd cy zq/; 30oo05ent resistance of the circuit shown in (Fig. Below)? $R_{eq}$ $\approx$    $\Omega$(retain one decimal places)
(b) What is the current in the $18-\Omega$ resistor?    A
(c) What is the current in the $12-\Omega$ resistor?    A
(d) What is the power dissipation in the $4.5-\Omega$ resistor?   W

(a) A voltmeter and an ammeter can be connected as sno kb(f7(k+ uuao-0 jmhown in (Fig. Below a) to measure a resistance R. If V is the voltmeter read(moun kk a0juf+bo(7- ing, and I is the ammeter reading, the value of R will not quite be $V/I$ (as in Ohm’s law) because some of the current actually goes through the voltmeter. Show that the actual value of R is given by
$\frac{1}{R}=\frac{I}{V}-\frac{1}{R_\mathrm{V}}$,
where $R_V$ is the voltmeter resistance. Note that $R\approx V/I\quad\mathrm{if}\quad R_\mathrm{V}\gg R$ .
(b) A voltmeter and an ammeter can also be connected as shown in (Fig. Below b) to measure a resistance R. Show in this case that
$R=\frac{V}{I}-R_\mathrm{A},$
where V and I are the voltmeter and ammeter readings and $R_A$ is the resistance of the ammeter. Note that $R_\mathrm{A}\quad\mathrm{if}\quad R\approx V/I\quad\mathrm{if}\quad
R_\mathrm{A}\ll R.$

  A flash lightbulb rated at 2.5 W and 3.0 V is operated by abvu9ra:g 45f nho gmkb n43;+r 9.0-V battery. To light the bulb at its rated voltage and power, a resistor R is connectbh bgguor3k 5:;4na+9mnfvr4 ed in series as shown in (Fig. Below). What value should the resistor have?    $\Omega$