Explain why birds can sit on power lines sab 6(+ .fprycjk,ukat /5hap4x fely, whereas leaning a metal ladder up against a power line to fetch a stuck kite isp+ uax.c( 4f6krhy5b/ t,a kpj extremely dangerous.

Discuss the advantages and disadvantages of Christmas tree lights connect py7tmr52qp .ved in parallel versus those connected 2y5rpt7 mvq.pin series.

If all you have is a 12zph2x uoj-9u ej91o/dw ecsm:f 6- rz40-V line, would it be possible to light several 6-V lamps without bur4f/6umez 9ro- usw9xocjd:12-hzj pening them out? How?

Two lightbulbs of resists)l6tl5ndy 5lzo 4.pf 3ff ,taance $R_1$ 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 con. l1,zhbdd0a6tj4 iwu nected in series or parallel? How do yo,w zdj1 i.u 0dta6hl4bu know?

With two identical lightbulbs and two identical batteries, how would ;x g )usd2ee-b4jql6c5 qe)xb you arrange the bulbs and batteries in a ci5; xcbj6qlq2 4 d-e s)ugxe)bercuit to get the maximum possible total power out? (Assume the batteries have negligible internal resistance.)

If two identical resistors are connected in series to a battery, dua)jqdwi54bqd h u ,y*d2xx+ 5oes the battery have to supply more power or less power than when only oib+h5dwu) q4yxxu5 ,2* d jaqdne of the resistors is connected? Explain.

You have a single 60-W bulb on in yyr37yj ifq(-hzrad: +to9 h uy/ ly-0kour room. How does the overall resistance of your room’s elec+9laty0 qu7fr y-kr-(z: 3yyj/hi hdotric circuit change when you turn on an additional 100-W bulb?

When applying Kirchhoff’s loop rule (such as in Fig. Below), does the sigtc 4;ea/rq(k( ;b5tkezr bsp0n (or direction) of a batte ctz /k0e4t(brkre s5q; bap(;ry’s emf depend on the direction of current through the battery? What about the terminal voltage?

  Given the circuit shown in Fig. 19–36, use the words “increases,”m gyz* .jh;-bhw:jr,u “decreases,” or “stay*yrhg mjw.h,u;j -b:zs the same” 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 use anb q3pt+qs5. (tyx0 x d;dxnh9re they connected in parallel? Does it matter if the batteries are nearly identical or not in either nxt;x. 0 s+93(n5hxbt qdypq dcase?

Can the terminal voltage of a battery ever exceed its emf? Explainlr6(qr:+tk gv .

Explain in detail how you could measure the internal resistance of ugj7nv2fqd .i u7vac3l4 8q/6z+uj rd a battery.

Compare and discuss the formulas for resistors and for capacit4m.p tjfx7 th5ors when connected in series and in p. mtj5fx47thparallel.

Suppose that three identical capacitors are connected to a battery. Will theol36np238zanle m ej-y store more energy if connected in series or in paral8nejl-e 3onzpam3 2l6lel?

Why is it more dangerous 1t8x8coqz- hk mt7qg3 to turn on an electric appliance when you are standing outside in bare feet than when you are inside wearing sho8-c7tkzm xgt3ho8 1qqes with thick soles?

(Fig. Below) is a diagram of a capacitor (59af 4 w,wzjwhor condenser) microphone. The changing air pressure in a sound wave causes one plate of the capacitor C to move back and forth. Explain how a current of the same fzf95aww j,w4h requency as the sound wave is produced.

Design a circuit in which two different switches of th*.4 n -ufripege type shown in (Fig. Below) can be used to operate the same lightbulb from opposite sides of a i .ugn4-f e*prroom.

In an RC circuit, current flows from the battery until the capacitor 8 i-av-.(pl*x6imsv-ba k*hh w8 tlfughh c00is completely charged. Is the total energy supplied by the battery equal to the total energy stored by the capacitor? If not, where does the extra enkhv*hla6(gml wtcs*--ub88p.h xvhfa i i0-0 ergy go?

What is the main difference between an analog voltmeter and an analog amm qpnop91rjjg e3/9ctu0sb5 ;geter?

What would happen if you mistakenly used an ammeter wherw ( io-;jf0qqwmtzid o / 39-;l6jdtxfe you needed to use a voltmete0i--ltojm d zw;wx/t(qf;f i3 d 9jq6or?

Explain why an ideal ammeter would have zero r yawmm4h0 /lb;esistance and an ideal voltmeter infinite resista bm/mly4;0hw ance.

A voltmeter connected across a resistor a vj .upf9n6)b czq2wu*lways reads less than the actual voltage across the resistor when w6jfv 2)bup*. q9cuzn the meter is not present. Explain.

A small battery-operated flashlight ,r-jk*fgb w kl(*l jj9w:.cqrrequires a single 1.5-V battery. The bulb is barely glowijq jb *cww r-l9flk( rk*:,.jgng, but when you take the battery out and check it with a voltmeter, it registers 1.5 V. How would you explain this?

  Calculate the terminal voltage for 0 6c29ewup2wq7shg ms a battery with an internal resistance 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 al.4d /j5kw)kr iwx9jresistance 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 g5t,fr :pyt k4a $680-\Omega$, 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 a-edr4 8oe;uglbrpoy::z a,4 z $6.0-V$ 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 of3xiy :/mm:60lehp5efnlg9icu8v/d u $12.0\,V$ 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 connected in series acrhm) :o61ri*+pvpztegu0sn 6 pseo1 s *80rhn loss 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 in parallel t,zmtp w17 ry; jvfdj;;o 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 circuit reveals that a y+ud 6q1ymxp7x(g 5q ,e)u gco$480-\Omega$ 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 resiy e1-js5.qq rc wuplszol(gn/04m6h11 t/atg stors shown in (Fig. Below). Answer qualitatively: 6/ a r/(1j-tss0gcmnz11 plwo4geu5tlqh.yq
(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 battery in (Fig. ad fuz6bz 87j*7jobf2;en- un Below)? Each resistance h7n6bu- ;ufj 8z2*jn fe aozdb7as $R\,=\,2.8K\Omega$.   k$\Omega$(retain one decimal places)

  Three equal resistors )+z 2jy y-frhq(R) are connected to a battery as shown in (Fig. Below). Qualitatqf y+y2z)rj-hively, 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 circuit of (Fig. Below) and show that the sum of avh r+aks)3*r sll t r3*) vrkhs+sahe voltage changes around the circuit is zero.
I $\approx$    A(retain two decimal places)
$\sum$ =    V

  Determine the terminal voltage of each battery in (z0q8w( h e 2yg4v;ypslFig. Below). 18V battery =    V 12V battery =    V

  (a) What is the potential difference between points a and d in (Fi1gce9q szmsy8 o g79*sg. Below a) (same circuit as Fig. Below eg*csy9g1978sqz ms ob, ), $V_{ad}$    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), find the potential difference between *6rn/e hrp ze6p+wqv: zp6 )lnpoints a and b /ee:+w66pnlh6znzr p) *rpqv. Each resistor has $R\,=\,75\Omega$ and each battery is 1.5 V.    V

  Determine the magnitudes and directions od0 ee/dh)r)lsi8y.a waab 0o; f 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 assuming that each hxymdk 7k 2u::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 magnitudes and directyknigu7x+i ;:p5 b:ytqacol -.d8w l;ions of the currents in each resistor shown in (Fig.; -ydb lu;i8tnl+cpqo iawxk: 75 .:gy Below). The batteries 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 each batp/d7da 1)5 p5rrhqk,5t noin bq63 vsmtery 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 :a1 ska038yvc0 gwzrc8mh63yf*.hfxr k jkr)each resistor of (Fig. Below).
$2\Omega$    A
$6\Omega$    A
$8\Omega$    A
$10\Omega$    A
$12\Omega$    A

  (a) Determine the currents ,bxf(guk zqr/9 -wb ins3ks0 d.d 68qh$I_1$,$I_2$, 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 by:7 nrhhr)-47;9 ix qvni cyv$I_1$ 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 2.00bgt;2r : 5szrkcq+7y o V and 3.00 V, are connected as shown in (Fig. Below). If eac+t o q5szyg;:2rrkbc7h internal resistance 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 capacitors, of ;ip24)snung( 0x 7ck8u shempcapacitance 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 across the whole network of (Fig. Below), calculate the voyu/:cul k hc:-ju )-sajq07dciqp:2nltageq0u:) pcuuhndc- c-:s/ 7lk yj:q2jai across each capacitor.
$V_{2.00}$ =    V
$V_{3.00}$ =    V
$V_{4.00}$ =    V

  The capacitance of a portion of a ci;0z ccglj8 h:-)xhdtmrcuit is to be reduced from 4800 pF to 2900 pc)8zjd :h0mh-;c t glxF.
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 conste- sev2fad-- xyz;pk7ructed 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 capacitance of the circuit showby qk ,4irr9k59xr:emh ww8 p7n in (Fig. Below).

  In (Fig. Below), if /; h:rs6tud up.x0kfc$C_1=C_2=2C_3=22.6\mu F$, 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), suppozn,q;rjj8x 9e se $C_1=C_2=2C_3=16.0\mu F$, 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), leto:dl br((qe 7r $V\,=\,78V$ 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 shown in (Fig. Below).3 hk y/usvq0tkjd-: v(:d u3y(0q /j-vk vhkst
(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 hcub xb,cn9j/s ;m yufqag 5/.,ooked across a battery. It is desired to store three times as much energy in a combination of two capacitors by adding jcb , fuanyu,5gqxb9/c.; /msa single capacitor 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 serii7sxjk *vvz..es with an unknown capacitance, and as a serixz7jivk sv*..es combination they are connected to a battery with an emf of 25.0 V. If the 185-pF capacitor stores 125 pC of charge on its plates, what is the unknown capacitance?    pF

  Electrocardiographs aresy*b-h/r6 qol 0msh2 (wyt wq* often connected as shown in (Fig. Below). The leads are said to be capacitively coupled. A time constant of 3.0 s is typical and allows rapid chan(q hswly60r sm/*y *2hotwb-qges 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 r 16e:nl/ioft 4wuy5kx esistance is $15.0k\Omega$, 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 (sam ;za +nobt snnq8dq.bp(;/eet3h1jhfbg 6. d(e 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 i2sf(is:d:lhs hbf0p, ce0e9 tn (Fig. Below)2( 9ff:itp0lcseb d 0 eh,shs:. Then a potential difference of 24 V is applied across the combination 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 o v/w zc)ooyo84c ,zd*sdalgg..ea 6s;n the 250-V scale if the meter sensitivitg*oyva es6)l8zc. /,acgdo d4;z .w osy is $30,000\,\Omega/V$?    $ \times10^{6 }\;\Omega$

  An ammeter has a sensiti i9k. g xq:o-ly.fvbx6vity of $20,000\,\Omega/V$? What current in the galvanometer produces full-scale deflection?    $\mu A$

  A galvanometer has an internal resistance a;k)9 29d+y32yzxrm ezcj nx0)rgibrof $30\Omega$ 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 sensqgs/rkp/9 ;qa2tv wa-itivity of $35k\Omega/V$ 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 consists ,q +hoil c2z5nnrxtsce**l1( 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 negligible internal resistance is connecxz6 5uz7l5ii;r,1ma*(t 3:ctk)uy auuknzgw ted 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 internaocz al (.k vg3.p-i4lhl resistance 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 Excp 7 3myvv79bxample 19–15 have to be in error x p9bc v77v3myby less than 3%? $\approx$    k$\Omega$

  When the resistor R in (Figv.7zo4g pf:ji3xoweepx44 r :. 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 aprkua5(lz+ st :ply a 0.25-V potential difference between two points o5(sal+: krut zn the human body. The resistance 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 150h3 t*j 2fg sczf0nzs;nl))+n z W, at 120 V. Such a bulb contains two filaments that can be connected to thesjzz) nh0nl) stff*; g3zc2n+ 120 V individually or 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 r4bz2eir.7mun2k gw5mun some apparatus that is 95 m from an electric outlet. Each of the wires connecting your apparatus to the 120-V source has a resistance per unit lenn 5big ru2 .7mmzew24kgth 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 hazappexs(t2q4 1 )or9; xplp*y lord in hospitals, particularly to patients who are connected to elec*xo4 pp)yl e o;1s9xplrpt2 q(trodes, 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 patient. $\approx$    $ \times10^{-3 }\;A$(retain three decimal places)

  How much energy must a 45-V battery ex2xqsx+e w/0owd 8x ;mok dfd66pend 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 72 beats/mig w7: gk;2:vqchm3s6fiup1r ln 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 resistan8lqc ;t: 5/hf c5xyjikce 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 a type of “bridge circu+c ko2,i baznnh ;oi8hcl7 1(cit” used to make measurements of resistance. The b8oil(knh21 nc;+ i ha7c czo,unknown resistance 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 diameter is /6hcp9-gzx ji;e- fm hplaced as the unknown resistance in a Wheatstone bridge (see Problem 71; 69-ecx/ pmhhij- zfg;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 cap 1qvk3 fuof1n/ ejy7l4acitance which can be obtained by connecting four identical capacitors, each having a capaciel1j u3 vfnyf7k/o1q4tance C?

  The variable capacitance of an old rad 1deb (.cf)agneb/fq (io 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 of each bf n)b gf 1(qaecd.(e/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 7.40 A is drawn from it and 47.3 V6j.wpay/ yugt)ot-g, when 2.20 A is drawn. Wh-p,tya6 ugt/gw .)jo yat are the emf and internal resistance 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 .( e8+cqa 6maxpjf vt7$4.0-k\Omega$ 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 3lh woh f zr9s/1x;iy- h(-fdohas capacitance $C_0$. 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 show-:5 1,cn32k pedbn8f(*)en py jcfaaw prm. jan in(Fig. Below), 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 ajwxfa 2)ly *9wh)sbgc) gm+l-n output of 350 mA at 0.80 V when exposed to full sunlight. A solar panel that delivers close to 1.0 A of current at an emf of f29y*s- w+algbg)c jx)lw h)m 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 op6bt d( 0v4vmxf 12.0 V, but you need $V_T\,=\,3.0V$ 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) usqa,u. 9db; auf-a 6)sylj3 xebes a neon-filled tube as in (Fig. Below b). This bujbe-.,3ax q) s fyl;ud9 aa6neon lamp 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 l)5 xu3/;iagkeqx r:d-ec:hx the $20-\Omega$ 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 (F,,ss8 :c4pdof jg ,p; uevz*tzig. Below), the $33-\Omega$ resistor dissipates 0.50 W. What is the battery voltage? $\approx$    V(retain one decimal places)

  (a) What is the equivalent resistance of the circuit showcwx 23enwzrd23h (o. wn 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 ammeteud4b iz9 . )sbvtaqn+*r can be connected as shown in (Fig. Below a) to measure a resistance R. If V is the volt 9.d+az4tvn sqbui*b) meter reading, 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 isgr neib-k .,w, operated by a 9.0-V battery. To light the bulb at its rated voltb .g -i,we,rknage and power, a resistor R is connected in series as shown in (Fig. Below). What value should the resistor have?    $\Omega$