Explain why birds can sit on power lines safely, whereas lxd0n9,.xgw s1rvw+aar p uiajg8:9 8veaning a metal ladder up against a power line to fetch ,vp +rsxj9:xrag 0daa1g 8v9.inwu8w a stuck kite is extremely dangerous.

Discuss the advantages and disadvantages of Christmas tree lights connected i /zkh;dt*c7m zn parallel versus those connected in h*kd/7 tcz;mz series.

If all you have is a 120-V line, would it be possible to liy e6yt6l xyx71ght several 6-V lamps without b1t y6yxle7yx6 urning them out? How?

Two lightbulbs of resistane06v20k,fm de wt/ 6)f hqnjbece $R_1$ 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 par6:cur ledjrts0za unm+9- v70allej6s0 0zu9venct:r ad ml+-7 url? How do you know?

With two identical lightbulbs and two identical batteries, how wjfy- z6hvns* f-17 ejsould you arrange the bulbs and batteries in a circuit to get the maximum possible total power out? (Assume the batteries have njejz y-s6 fvh*-7n1sfegligible internal resistance.)

If two identical resistors are connected in s5ngg:g 8x ym7l15vjaveries to a battery, does the battery have to supply more power or less power than when only 7 j5xy8vmg a lg:5n1vgone of the resistors is connected? Explain.

You have a single 60-W bulb on in your room. How does the ovequezq, n p9s; ;jqd8f:u f1hv(rall resistance of your room’s electric circu;,q8dff 1p9q:;e zhusjqv( nu it change when you turn on an additional 100-W bulb?

When applying Kirchhoff’s loop rule (such as in Fig. Belob2lxfqf9rc wzw 83kapb.5 v910dhi9 ew), does the sign (or direction) of a battery’s emf depend on the direction of current through the battery? What about the tlp35rv09b ze8f w9qb a92dfw i1c .kxherminal voltage?

  Given the circuit shown in Fig. 19–36, us4e3ebs-,x qh r. pdvr deos2*e3f62eae the words “increases,” “decreases,” or “stays the same” to completepd2eee*ea32. h34bqofsrds ,6vrx-e 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 whatl-k .4l6kxffzs j0h kxs2.w.v use are they connected in parallel? Does it matter if the batteries are n-4 l 6 wx2f.fjsh.kx kvlsk.z0early identical or not in either case?

Can the terminal voltage of a battery ever exm(aknp/j)k/v fr9z1(qh v m7vceed its emf? Explain.

Explain in detail how you c7 j(;sqfnpz.de55 m tss*hz6n ould measure the internal resistance of a battery.

Compare and discuss the formulas for reb)kuit + pq0 y6xb3a7ksistors and for capacitors when connected kp k+uqa y3xib7t0b) 6in series and in parallel.

Suppose that three identical capacito5(ehw hs1v0 mjrs are connected to a battery. Will they store more energy if cojs5vh(eh mw01nnected in series or in parallel?

Why is it more dangerous to turn on an electric appliance when yo j0yb48o++j )r pcdngdu are standing outside in bare feet than when you are inside wearincd0bd+)gj4 p +ryo8jng shoes with thick soles?

(Fig. Below) is a diagram of a capacitoz8m7i7hd hd+or (or condenser) microphone. The changing air pressure in a sound wave causes one plate of the capacitor C to move back an dih7zh+m7d o8d forth. 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 shown in (Fig. B8k nwu-yr*n1z 24hu6k. t k2p xou4cvcelow) can be used to operate the same lightbulb from opposite sides of a room.wku4hvy u6c 4* - 2nxcz.2kt1rupno8k

In an RC circuit, current flows from th l2csds56g0y.p,jdxs(7pr8wv ogi/b e battery until the capacitor is completely charged. Is the total energy supplied by the battery equal to the total energy stored by the capacitor? If isb s,yg80w.dp65(jolxsp7grv2c d/not, where does the extra energy go?

What is the main difference between an analog voltmet(7z e2suzm (cter and an analog ammeter?

What would happen if you mistakenly used an ammeter where y6x .4ep-ldxo-je x7bv ou needed to use a voxbdp-6 x.-exv jl7eo4ltmeter?

Explain why an ideal amme/elg-3svkf a (ter would have zero resistance and an ideal voltmeter infkevfa3-/(l g sinite resistance.

A voltmeter connected across a resist*y*t2smtntj0t/ xilj4u0 fv 1or always reads less than the actual voltage across the resistor when the meter is not presetumfxj*lt20tijt 0 vy4 1*ns/nt. Explain.

A small battery-operated flashlignm,h;,xgj(fgh t0xg + ys/ y1tq-le6 u c4p9xlht requires a single 1.5-V battery. The bulb is barely glowing, but when you take the battjgq+p usc /-yge;h40m9xn6t lxlt1,, y(x hg fery out and check it with a voltmeter, it registers 1.5 V. How would you explain this?

  Calculate the terminalwfs7xk.gsum m *c(y(7m3wwl + voltage for 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 internalxg:d -5ok2 bgz 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 ld ;m0l6:dqbp as: 5zw$680-\Omega$, 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 r:6 exhw2n qdl(phj8-$6.0-V$ 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 u rmde ep6pz:+2lcez ii( -)q2of $12.0\,V$ 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 se9i0ccy/li2zsqnd d; 9ries 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 inx*v vvj,a3jf 4 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 $    $\Omega$   

  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 cirdi7:f7 shhs-ncuit 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 (l y6wr:2mkd)tcgri ( 4Fig. Below). Answer qualitatively: (drclt )i w:m6rk2g4y
(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 j6 tfq:4t6t8) giuzo5xo-kt/euw/p leb lm8- to the battery in (Fig. Below)? Each resistanceu)ekozubmf ipg6- 8xtl8tqto/: / l4 we 56-tj has $R\,=\,2.8K\Omega$.   k$\Omega$(retain one decimal places)

  Three equal resistors (R) are conwjj)/dqm sf7 nkt m-9:w:k:tk nected to a battery as shown in (Fig. Below). Qualitatively, what happensd/ k9wkn m :tjkmw::qf)s-j7t 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 tl 3h,g ff7rpv:u( do2j4rt2qzhat the sum of all the voltage changes aroun4r3uldg : tf,272hf(pzjo rvq d the circuit is zero.
I $\approx$    A(retain two decimal places)
$\sum$    V

  Determine the terminal voltage of4nw m2s6 y-brh each battery in (Fig. Below). 18V battery    V 12V battery    V

  (a) What is the potential difference between points a and d in (Fitpgy1h x (u qrv2ue242g. Below a) (same circuit as Fig. Below h 2p(gv t x12ur42uqyeb, ), $V_{ad}$    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 4h8315bhaog0j c3*elc ckhx l the potential difference between points a and b. Each resistorkh*xh31 j348c eg5locahlb0c has $R\,=\,75\Omega$ and each battery is 1.5 V.    V

  Determine the magnitudes and dcps70eq7g 83af9z hmzirections 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 assuming that each battev u5.nbt1 ;o(fzu yjer+m 2e9nry 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 andv),-enl kr xgh03v 7d/ ;iozfq directions of the currents in each resistor shown in (Fig. Below). The batteries have emfs )hvrl,kz-xgq07of dve;/i 3n 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 internal0eee: * xrk.gf5mdev 0 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 .p4tu f+d npd8Fig. 19–49.
$2\Omega$    A
$6\Omega$    A
$8\Omega$    A
$10\Omega$    A
$12\Omega$    A

  (a) Determine the curr+re+pbje2bwu+vij or. + dx 8-)ys1 ggents $I_1$,$I_2$, 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 curre x wb issa6i ;))hrqgoi5*b8.qnt $I_1$ 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 Va-z paz )d kbi-5-f,ec, are connected as shown in (Fig. B-p a, -d-af)izkzb5 ecelow). 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 kto+jve ffo 3 9*rt)2zcapacitance 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), ca-hk0qv/-q+l hu1s 9ian:y;i3a doq bqlculate the voltage across eachsu ;qoqqhha-k1qd+i0 la 3 /9ynv b-:i capacitor.
$V_{2.00}$    V
$V_{3.00}$    V
$V_{4.00}$    V

  The capacitance of a do(g)ybz+mwd h ,7kg-portion of a circuit is to be reduced from 4800 pF to 2900 pF7hg+ o() -wmdz g,ybdk.
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 constructed usoinzv w kbm097ow0 4(o)qp :w-n gzr;wing 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 ciraz4:yzr qv 8do5a)av; 0s4ly ucuit shown in (Fig. Below).

  In (Fig. Below), if wly5-zdc;2 qqv 8llnst:);u e$C_1=C_2=2C_3=22.6\mu F$, 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), suppose47cx ufidyx8)v8/0c suwn ;v u $C_1=C_2=2C_3=16.0\mu F$, 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), let ml5o z*pg8v5m ap:* 2t 8; ftaj2mkpfd$V\,=\,78V$ 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 inxv)pn elvces-05 :mj s //gru3 (Fig. Below). lcx e0v/5s:mspv n3rj -gu/)e
(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-j xd;h69ozmkz/m 6pd.ui 44jfbar q-53b j +uipF capacitor hooked across a battery. It is desired to store three times as much energy in a combination of two capacitors by adding a single capacitorid 5p.h;bzjfib d+rj 4x3- 9/jqommzak6 u46 u 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 capacita 1fc h bdvsv9qnr,,68once, and as a series 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 hfqvs 1b8ndcv,6 o9 ,rplates, what is the unknown capacitance?    pF

  Electrocardiographs are often connected as sht /cyu;j/eps*yes;z;own in (Fig. Below). The leads are said to be capacitively coupled. A time constant of 3.0 s is typical and allows rapid changes in potential to be recorded accurat;; s;sutzj e*pe/cy/ yely. 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), tw8 o20n n*yf w9smvsu3he total 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 Fig. Below a (same as Fig. nl n3-cqxm03sbj zgt )u32yl,9 k8suq 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 in (Fi*n5j13e n cgrg bug2hgw7h0xf 73:xnu g. Below). Then a potential difference x rhc2ub n n3nfx735 :jg*u0hwgeg1g 7of 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 thr q9lgxdv1 b zb.gpoen:h 5;1s)t 2(qhe 250-V scale if the meter sensitivity isn)9:vqpb l5oz(qh g 2ted;xh .r11b gs $30,000\,\Omega/V$?    $ \times10^{6 }\;\Omega$

  An ammeter has a sensitivity of 52xu2 m e1bk+yi*s(w clh grz*$20,000\,\Omega/V$? What current in the galvanometer produces full-scale deflection?    $\mu A$

  A galvanometer has an internal resi5cf ew. aryr;:v+ez z2stance 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 seys, m1ggxa.2r lr(*qx nsitivity 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 om 48.:- kciz(e,hixuiy-ig :egg+pbq8dvc 0df 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 negligic h6ug+lkjw-.mp 7 ku0ble 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 int9qy1egh . t py9tbr6)cernal 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 vjp-* ryu oi4v1f6z(myoltmeter of Example 19–15 have to be in error by less fjy(p -y6z1 4o*ivmruthan 3%? $\approx$    k$\Omega$

  When the resistor R in (Fig 9p9cihn5kjtu0c.n p2. 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 potentq .fn71zw3sqvial difference between two points on the human body. Thenvqqw s1zf.37 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 Wv zt j1)j/5v ehjrr.(amrb9 i8, 100 W, or 150 W, at 120 V. Such a bulb contains two filaments that arm. br1) vve 5rjh/8ijt9(zjcan be connected to the 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 run some app8mft9 slowra m 9gi-04aratus that is 95 m from an electric outlet. Each of the wires connecting your 0 i8wastr-9l4fgo9m mapparatus 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, particulan*v-qvt,ne w,rly to patients who are connected to electrodes, such as wve* v,tqn,- nan 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 expend to chava;0 sh sho*s8 qcd3s4rge 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 opetb604nwntd ta)0g 0kpg e(6cmrate 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 resistancihb0hs z ;1xda5psk( bn: -ie/e 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” ushv h,k40w1swv ed to make measurements of resistance. The unknown resistance to be wswv0hkv1 h4,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 place 1e(q-4b dj5uq2cgcp cd as the unknown resistance in a Wheatstone bridge (see Problem 71;Fig. Below). Arms 1 and 2 have resista 5pe2c(qcqgj4cd b- 1unce 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 capacitance which can be obtained by connec h9qvj9d kq7)sjr9) mhting four identical capacitors, ea9 dmqv79qjj9sh)h k)rch having a capacitance C?

  The variable capacitan7ogl79 ,avgk ice of an old radio tuner consists of four plates connectedla7 vggi, o9k7 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 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 4oh iv35 q6 nxczkb)5b.1 eclo+0.8 V when 7.40 A is drawn from it and 47.3 V when 2.20 A is drawn. What are the emf and internal resistance of the battery? +5beqcoi 1bxk6)v3o.h 5c lz n
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 t 3,lm1 aq- .:mwacxchrhe $4.0-k\Omega$ 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 capaci1tdp k):ox4 p+a :fajutance $C_0$. 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), determim7+mx0rdhm yp-l 25nwne
(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 mA2sk .;s pmw(px 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 120 V to an exs2x;sp.k( pw mternal 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, butf9ywr l6zguvo 1b )4n, 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. B ;g2qsobi0 py*elow a) uses a neon-filled tube as in (Fig. Below b). q*ps igy b20;oThis neon 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 the hx:xuqc, ir15l9d 1in$20-\Omega$ 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. Beloija,ts+qbu2yk p;v ock27 7w 1w), the $33-\Omega$ resistor dissipates 0.50 W. What is the battery voltage? $\approx$    V(retain one decimal places)

  (a) What is the equivalent q k 3(;fji6y +jqttg1m-4qvroresistance 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 shown in (Fig. Below a) to mevv;1 ltts7t g3pj2ej6 asure a resistance R. If V is the voltmeter reading, and I is the ammeter reading, the vg 7 evstt32vpj l;6j1talue 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 Vwmxsh1gi xn)xr8 e9*j.0q5qy is operated by a 9.0-V battery. To light the bulb at its rated voltage and power, a resistor R is connected in serie1qjyweqgxsin0h *x5.8)r x m 9s as shown in (Fig. Below). What value should the resistor have?    $\Omega$