Explain why birds can sit on power lines safel65 gwcodwa +8mftl5 5iy, whereas leaning a metal ladder up against a power line to fetch a stuck kitewgd65 w8+o 5 5liatcmf is extremely dangerous.

Discuss the advantages and disadvantages of Christmas tree li3g/2s;xp0a bw/p, mf5,awd6m *ygmac y,aqo xghts connected in parallel versus those connectey;o wamxgsqwx p cmf*, 0m,/6 b,y/d3pg25aaad in series.

If all you have is a 120-V line, would it be possible to light several 6-V vn4,( m:mk/ ailq fmj+ +bup)klamps without burning ,(mv:++ mqn/f aib m)uljk4pkthem out? How?

Two lightbulbs of resistancex:) b/c .) tvv:pk7zp8q: beqcrpk7mt $R_1$ 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 series or pad01 ,ui4fx lvhrallel? How do you x i,lf041dvhu know?

With two identical lightbulbs and two icqnv,- ;+u/nl7u v ihkqt7r/edentical batteries, how would you arrange the b/7 qi+nuu /q;vn-h,ev l7k ctrulbs and batteries in a circuit to get the maximum possible total power out? (Assume the batteries have negligible internal resistance.)

If two identical resistors are conneif19ggzs+m; h-od9)vxh j k t)cted in series to a battery, does the battery have to supply more power or less power than when only on1kisdj h;zvx)9 tfh9 -+mo g)ge of the resistors is connected? Explain.

You have a single 60-W bulb on in your room. Hy:4vlr) xn7jylei y6(n l :4e;ic/txe ow does the overall resistance of your room’s electric circuit change when you turn on al/4te nixvc ;yyn7i4 re(l):yel6j:x n additional 100-W bulb?

When applying Kirchhoff’s v*tklt:p od8v4++5n2grji6 fxl r d;sloop rule (such as in Fig. Below), does the sign (or direction) of a battery’s emf depend on the direction of cvr 2;i5 84gfdo j tt*l+6:npxr+s kvdlurrent through the battery? What about the terminal voltage?

  Given the circuit shown in Fig. 19–36, bml kjg49j ()-nea8 doh1j: wlt,6a8z l/rxzkuse the words “increases,” “decreases,” or ro8dmzjklz/ab(g lw:hn-xk 1l 4)8et,6j 9ja “stays 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 are they co0dmcwra gx2 k(i 4mk5-nnected in parallel? Does it matter if the batteries are nea45g -wxkd km(i2 r0mcarly identical or not in either case?

Can the terminal volj ciq j2k5d.5vtage of a battery ever exceed its emf? Explain.

Explain in detail how you coulj,wnhv67c goj p9i)g-d measure the internal resistance of a battery.

Compare and discuss the formul+d/j;h3t:uk:gzjdy, ( izj ohl go1 p*as for resistors and for capacitors when connected in series and in ( z3digth,z j; opukj1yh/:jld+og*:parallel.

Suppose that three identical capacitors are connectedb3gt0 pr, rh7ewz8z, d to a battery. Will they store more enegwz08,,7pzr3dht b errgy if connected in series or in parallel?

Why is it more dangerous to turnl b+r69-exa oi-hs5,pjilz 0p on an electric appliance when you are standing outside in bare feet than whs ieb+zoihl0jx ppa95- 6r,l-en you are inside wearing shoes with thick soles?

(Fig. Below) is a diagram o2w1ayhff3fk77;ez p r f a capacitor (or condenser) microphone. The changing air pressure in a sound wave causes one plate of the capacitor C to move back and h k3z;y f72p waef17frforth. Explain how a current of the same frequency as the sound wave is produced.

Design a circuit in which two different switches of the type sp0 ycz4kgqd2ubuir5 :vuf1) 9hown in (Fig. Below) can be used to operate the same lightbulb from opposite sidescd012byzk9):u uv u5prf q4g i of a room.

In an RC circuit, current flows from the battery until 3n 9urlh*zz9zthe capacitor is completely charged. Is the total energy supplied by the battery equal to the total enern99luz* rzhz3 gy stored by the capacitor? If not, where does the extra energy go?

What is the main difference between an analog voltt /xu n5:b5gowmeter and an analog ammeter?

What would happen if you mlg q vz,ty.7/2o* mgugistakenly used an ammeter where you needed to use a voltgzmu / gqvy2*t go,l.7meter?

Explain why an ideal ammeter would have zero resistance and an ideal po6w1obh91 b 9ohly 2tvoltmeter infinite resis62o l1wpoho9tbhby91 tance.

A voltmeter connected ;i gffle+m36b7mn y0ldt:e o1 across a resistor always reads less than the actual voltage across the resistor when the mete:mbe 1l ofy6dfn0e;t+i m l3g7r is not present. Explain.

A small battery-operated flashlight requires a single 1.5-V bgz x/g4e*)y qaattery. The bulb is barely glowing, but when yozgy/4a qxe )*gu take the battery out and check it with a voltmeter, it registers 1.5 V. How would you explain this?

  Calculate the terminal voltage 91lb vvm gfv.u b98f9;z0b ahjfor 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 resistan h5vl1m j;de:xce 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 havel ;42z*yz rt vz65rgpgnp;( iox75mvc a $680-\Omega$, 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 hav zl(b,rlg 6ociu fm t-.rq5y; i4a7)ewe 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 of ;kp )ml ehdw 04t kj+/buom;-b$12.0\,V$ 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 cowy3j0gsd 9 q.bb(v(lgw- bifsub; t*5nnected 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 in p;; ym:;v2ulx hbgfp;aarallel 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 $    $\Omega$   

  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 electricu 5+crnhafs 24 circuit 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 resistors shown in (Fig. Below). Answer quax)d b 3g9u,xijlitatively: d) x9g uj3,bix
(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. B,ic-t;s(.r pta:n cjv ooc-+eelow)+c:ot(tor ci ;c ,v-s .-epajn? Each resistance has $R\,=\,2.8K\Omega$.   k$\Omega$(retain one decimal places)

  Three equal resistors (R) are codx.pgu 3i)+: ypvea 5gs1ngz(nnected to a battery as shown in (Fig. Below). Qualitatively, what happens to eg5+(3z d) iyg xng.puas1p:v
(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 su ot)hzttyjgxk6n 961jb6 n8. zyfnw/0m of all the voltage changes zth ojwnt 16gnj y6./kyt0z fb) 96xn8around the circuit is zero.
I $\approx$    A(retain two decimal places)
$\sum$    V

  Determine the terminal voltage of each batterzz o0s5 3sv95e0btdmt y in (Fig. Below). 18V battery    V 12V battery    V

  (a) What is the potential difference betweo/m8+2 ba 0h*2 m8muznf mzghden points a and d in (Fig. Below a) (same circuit as Fig. Below g* z 80b/2 m+dm8umzoaf2hhmnb, ), $V_{ad}$    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 pr1o36 j3z rv*pm 4cnsvoints a and nm3c6o1pv jrz4* 3v srb. Each resistor has $R\,=\,75\Omega$ and each battery is 1.5 V.    V

  Determine the magnitudes and directions of the cu bte4z8 kq4l pk+gbu)2rrents 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 battery h;,siw3+f7wyyl 6f xdk 93lgy eas 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 8oii* )prn*amvdt w/(cbu ;e/yf b5m7 and directions of the currents in each resistor shown in (Fig. Below). The batte/w5;i*8)n *cae bopbmm ( fvu7/ ytidrries 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 battery has internal ws1lq.1q oh,+d3e )ls dgafm6resistance $r\,=\,1.0\Omega$.
$I_1$ $\approx$    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 ea.xwewp p3uv8 fa(p +-nch resistor of Fig. 19–49.
$2\Omega$    A
$6\Omega$    A
$8\Omega$    A
$10\Omega$    A
$12\Omega$    A

  (a) Determine the currents6l8j) jgfie aab 0xz(c;k86ui 4-hd aj $I_1$,$I_2$, 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 curren37sypbj ;ki 7ct $I_1$ 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*+wo-hmxu eo(yo ;c88 odq u3t of 2.00 V and 3.00 V, are connected as shown in (Fig. Bel- 8cuxoho3* (oqdwtmo 8e u;y+ow). If each 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 capacitance zg(q(hl5f,t ap j4j*1o8rw li3200 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 wholi5l abw6g tu*+e network of (Fig. Below), calculate the voltage across e+u*t6 l 5iwbagach capacitor.
$V_{2.00}$    V
$V_{3.00}$    V
$V_{4.00}$    V

  The capacitance of a portion of a circuit is to be reducpy* vm vv0id.ap,w-t*ed from 4800 pF to 2900 pF v dpwym,v*ia.0t- p*v.
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 accident/ 0ufshm31s vyally constructed 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 shown in (Fig. Below).(o1*z1e6 htltf g ri5kw73cv m

  In (Fig. Below), if zirfgycus atr76,hr 8;5q3 j*$C_1=C_2=2C_3=22.6\mu F$, 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), suppfm x5 (y-6g8dkc) vpjcose $C_1=C_2=2C_3=16.0\mu F$, 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), letsvnfpqly 11:u 7o nvee(r0e :- $V\,=\,78V$ 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 connecqfr45m u;ydp* lj xf8g1:;fnp ted as shown in (Fig. Below).n4py5 pu;d:8fm;qflr1 fjx g*
(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 singl77+zmv kr4 qbd+s *hrqgx/cpxwfh2rj: y)4. g e 250-pF capacitor hooked across a battery. It is desired to store three times as muchrg /rp4gbdh kfjy2 m7cq4xw+*xr7 )h+q.v zs: energy in a combination of two capacitors by adding a 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 series with fc7i(yv m+fc)4/v ptlan unknown capacitance, and as a series combination they fcv4 f(ic+7yl m/tp)vare 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 are often connecteut17q/4 k4rs j(*kl u wczn:xi-n+qrud as shown in (Fig. Below). The leads are said to be capacitive 4/n7-qusrqtc*wkz4lu k+ iu1nr xj:(ly coupled. A time constant of 3.0 s is typical 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 totkl/yfvg m tza94w,z-* al resistance 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 Figeqe45.,cgijtfqlnv/ x1sm .0p/byh). Below a (same 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 i 7(lzcz h*8kiln (Fig. Below). Then a potentiai hl ck*8z7l(zl 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 on the 250-V s+ j; e7lc4hyi n fmux6,g5;svscale if the meter sensitivity v4x5us,hf6e;j+ gi nmcl7;ysis $30,000\,\Omega/V$?    $ \times10^{6 }\;\Omega$

  An ammeter has a sensitivity o/yz8pwgkcro.f -e y;9f $20,000\,\Omega/V$? What current in the galvanometer produces full-scale deflection?    $\mu A$

  A galvanometer has an inter pb p9nnndd57tv)s.5h nal resistance 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 senp:vpy8k. q3bcln n/j6sitivity 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 .ajq+5di)s bw.v ,rlimA full scale. It consists 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 negligiblilhz4bk 5*8x;4eq a t(npduq 6e 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 resistancm khgaq*zi355e 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 vb sz3h8c7vw2 koltmeter of Example 19–15 have to be in error bbzh2ckswv837 y less than 3%? $\approx$    k$\Omega$

  When the resistor R in (Figmrh)wzzu .4m- kcg3/kwq5c(+g e mb,o. 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.a 7(b 7hxkks42(stanbzq02 ld25-V potential difference between two points on the human body. The resistance 2zqx2 slh0n tk7((4kb7d saba 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 Wmru m+;t 0bj jtexzt0;y o.3q8, or 150 W, at 120 V. Such a bulb contains two filaments that can be connected to the 120 V indq0 jer+b3o;t8 mt jtxzym;0u.ividually 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 run some apparatus that is 95 qq2 ;o(dm5qgkhg; 9 uibb ,a6vm from an electric outlet. Each of the wires connecting your apparatus to the 120-V source has a rebq d( mb5qg6 v;uqg29ik;ah,osistance 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, partx2cv x4.81r ), 3kjnaklv ihgqicularly to patients who are connected 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 mahx ni3g4akkjx21v8, .qcl )vrde 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 z-1fjn lfmy96mk52nn+ y4qln 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 designedim.v.t(s v/up.g r oh, to operate at 72 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 resistancmy1fk9 -uu0 q3sg-4nkyb*9a juws t4pe 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 circuit” usuzmf6 rt0-.qv xr+j:h ed to make measurements of resistance. Tfqh-:+jmrz ux. 6 t0vrhe 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 diam*ew5v * z czg488m3o hzhcjs/*ybq i/ceter is placed as the unknown resistancmo54gjh3iyh* w8cvzz/z cc bq8s/e** e in a Wheatstone bridge (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 effectnyzq67ma- bz3qbt tijq 3v:88ive capacitance which can be obtained by connecting four identical capacitors, eaqq m -qt8z3n3b78tya i vbj:z6ch having a capacitance C?

  The variable capacitance of an o-b l m(j4bopx+ld 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 mb x4+b jpo-(lneighbor by 1.5 mm of air. One set of plates can move so that the area of overlap of 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 7.40 A is dry -*hti(g3zdw :;csg3kie ( awawn from it and 47.3 V when 2.20 A is drawn. What ar-cgwy(g i*(3 ;hw k:3iztsd eae 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 thesvh* ;auoz;ais- 0r v5 $4.0-k\Omega$ 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 capacit*ualw, 0 c9bzd6xd,l6i (zjf6 k qhbg/or has 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 shown in(Fig. Below), determinckht9kf4l8nl09gch0 60.goxt n)mj z e
(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 mlg-eyjr;uo, x3ch 6j0A at 0.80 V when exposed to full sunlight. A solar panel that delivers close to 1.0 A of -0j x3co,ger;6 yhjulcurrent 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.gsk j- ka+/i(d:cu kx,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) uses a neon-filled tg odp:h ;qj8z-aar7,7-ngn ymube as in (Fig. Below b). This neon lamp has a threshodaogp7:h --, m7 nq8rj;gayznld 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 tzy 574 v3a tbgrip46fhhe $20-\Omega$ 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.05v/v bzedei*4f:hajm+;a bk 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 circuk /v7f70.+braikbis3f 2z fdx3abs b /it 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 shown i,6h :duc rcw6dmik )7k 3grbw4n (Fig. Below a) to measure a resistance R. If V is the voltmeter reading, and I is the ammeter reading, the value of R will not quite be dwbh:mw)3kg 66d cu7rk, icr4$V/I$ (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 8- y gebmlng-p a2eerrd cb -6/3d)d7hoperated by a 9.0-V battery. To light the bulb at its rated voltage and power, a resistor R is connected in series as shown in (Fig. Below). What valuel-rd/yg 7bdpec3gmahbd--8 ) n er6e 2 should the resistor have?    $\Omega$