What type of bond would you expect for h*;g- xj 0rw o+cqg0e9 urk9tz
(a) the $N_2$ molecule,
(b) the HCl molecule,
(c) Fe atoms in a solid?

Describe how the mole-l 47dbut,zx)e ,o jmf zbbvlg29ba9)cule $ \text{CaCl}_2 $ could be formed.

  Does the $ \text{H}_2 $ molecule have a permanent dipole moment? Does $ \text{O}_2 $? Does $ \text{H}_2\text{O} $? Explain.

Although the molecule xqb .50soewo,$ \text{H}_3 $ is not stable, the ion $ \text{H}_3^+ $ is. Explain, using the Pauli exclusion principle.

The energy of a molecule can be divided into four categories. What are ,+6l3f 1igvxmzhprg 1udwn l6c 366-guax ky1they?

  Would you expect the mola mre9)i9qyx8p )krm7ecule $ \text{H}_2^+ $ to be stable? If so, where would the single electron spend most of its time?{yes|no}

Explain why the carbon atop7k o0ohv: y6rly 6u-bm ($ Z=6 $) usually forms four bonds with hydrogen-like atoms.

If conduction electrons are free to roam about in p)5e1wjvl g8d .y:sa: dsvhg,a metal, why don't they leave the a1y e)g s vd,vlwdj: :h8sp.g5metal entirely?

Explain why the resistivity piyc, 4/:wj 9aniyj/aof metals increases with temperature whereas the resij anj /w,: 9ycyia/ip4stivity of semiconductors may decrease with increasing temperature.

(Fig. Below) shows a "bridge-type" full-wave rectifier. Explait3qx z qeru 1u6sds5r*.nm80pn how the current is rectifmsqs.tn6 xqu r8up*e1r5d z30ied and how current flows during each half cycle.

Compare the resistance of a pn junction diode connected in forward bia(i 9ht.xiuc:b)qun mmy 7*4ors to its resistanceuxic 9mq*o4nr() :iu. b7 yhtm when connected in reverse bias.

Explain how a transistor could be used abo: ao zj0xr37yg2au+s a switch.

What is the main difference between n-type and p-type semicb giyenxd 4(br,k3-3*q)qbz xonductors?

Describe how a pnp transistor can operate as an am7q-ac(s1fvaqt8nb 3/q 0cb a b; 2cgawplifier.

In a transistor, the base-emitter junction and the;vyit)96d4y y3 twgnd base-collector junction are essentially diodes. Are these junctions reverse-biased or forw9y);tywytdv g46n i d3ard-biased in the application shown in (Fig. Below)?

A transistor can amplify an electronicx3ne1yacy:,t 2*dfw j signal, meaning it can increase the power of an input signal. Where does it get the enewty*1xf3e j,cyna2 : drgy to increase the power?

A silicon semiconductor is doped with phosphorus. Will g-pp1btgd e3-0,0t jr3 p jvxfthese atoms be donors or acceptors? Whx,rt3-tgbe 01g3jp-jfd p 0v pat type of semiconductor will this be?

  Do diodes and transistors obey Ohm’s law? Explainp7v-yx;:26 n rkgwha:ax tj,4:hgj cg . {yes|no}

  Can a diode be used to amplify a signal? Explain. {yes|no517tg+g isqpv ,xg6up}

  Estimate the bindingn:g+dqd7 l prfx+ sp9)it3wbk;q h65u energy of a KCl molecule by calculating the electrostatic potential ener:;g3 df+p 7su)q+xn9qhitkb w5d p6 lrgy when the $ \text{K}^+ $ and $ \text{Cl}^- $ ions are at their stable separation of 0.28 nm. Assume each has a charge of magnitude $ 1.0e $. Binding energy =    eV

  The measured binding energy of KCl is 4.43 eV. From the result of Problem 1, es/,qsxn6n,qjwd,f68aj r n /fb timate the contribution to the /j f6ds/j, 6q8rn nbqwfaxn, ,binding energy of the repelling electron clouds at the equilibrium distance $ r_0 = 0.28\ \text{nm} $. $PE_{\text{clouds}} =$    $\ \text{eV}$

  Estimate the binding energy oer-twy- uti20f the $ \text{H}_2 $ molecule, assuming the two H nuclei are 0.074 nm apart and the two electrons spend 33% of their time midway between them. Binding energy =    eV

  Binding energies are often measured experimentally in kcal per mole, and then t,l f9tx6 zgb5r)ytg t.he binding energy in eV per molecule is c t zb9rgl)gyx6tf5.t ,alculated from that result. What is the conversion factor in going from kcal per mole to eV per molecule? What is the binding energy of $ \text{KCl} (= 4.43\ \text{eV}) $ in kcal per mole?
We convert the units =    $\text{eV/molecule}$
For KCl we have =    $kcal/mol$

(a) Apply reasoning similar to that in the text s ,tzk4x1jd) ec9u ,jwfor the states in the formation xtk)d1, ,zcujes49 jwof the $ \text{H}_2 $ molecule to show why the molecule $ \text{He}_2 $ is not formed.
(b) Explain why the $ \text{He}_2^+ $ molecular ion could form. (Experiment shows it has a binding energy of 3.1 eV at )

Show that the quantityg3+ jtnpv5a3m; 6v bok $ \frac{\hbar^2}{2I} $ has units of energy.

  The so-called “characteristicw++z, cdxu g3z rotational energy,” $ \frac{\hbar^2}{2I} $ for $ \text{N}_2 $ is $ 2.48 \times 10^{-4}\ \text{eV} $. Calculate the $ \text{N}_2 $ bond length. $r = $    $ \times 10^{-10}\ \text{m}$

  (a) Calculate the characte 7l1z6cpif)j )vj 2zh* lhqpe8ristic rotational energy, $ \frac{\hbar^2}{2I} $ for the $ \text{O}_2 $ molecule whose bond length is 0.121 nm. $\frac{\hbar^2}{2I} =$    $ \times 10^{-4}\ \text{eV}$
(b) What are the energy and wavelength of photons emitted in a $ L=2 $ to $ L=1 $ transition? $\lambda $ =    mm

  The equilibrium separation of H ato/;qx *h+p mrmmk +(dcdms in the $ \text{H}_2 $ molecule is 0.074 nm (Fig. Below). Calculate the energies and wavelengths of photons for the rotational transitions
(a) $ L=1 $ to $ L=0 $, $hf $ $=$    $ \times 10^{-2}\ \text{eV}$$\;\;\;\;$$\lambda $ =    mm
(b) $ L=2 $ to $ L=1 $, $hf $ $=$    $ \times 10^{-2}\ \text{eV}$$\;\;\;\;$$\lambda $ =    mm
(c) $ L=3 $ to $ L=2 $. $hf $ $=$    $ \times 10^{-2}\ \text{eV}$$\;\;\;\;$$\lambda $ =    mm

  Calculate the bond length for f (n,gkthd4:xthe NaCl molecule given that three successive wavelengths for rotational x:nkfdh 4 (t,gtransitions are 23.1 mm, 11.6 mm, and 7.71 mm. $r = $    $\times 10^{-10}\ \text{m}$

  (a) Use the curve of (Fig. Below) to estimate th)iv/f5pq :r)sy wq1js e stiffness constant $ k $ for the $ \text{H}_2 $ molecule. (Recall that $ PE = \frac{1}{2}kx^2 $) k =    N/m
(b) Then estimate the fundamental wavelength for vibrational transitions using the classical formula (Chapter 11), but use only the mass of an H atom (because both H atoms move).$\lambda$ =    $\mu m$

  The spacing between “nearest neegi u)t/-ee g/.*tcvz ighbor” Na and Cl ions in a NaCl crystal is 0.24 nm. What is the spacing between two nearest neig/ euz-gevt iec .)tg*/hbor Na ions? D =    nm

  Common salt, NaCl, has a fj*n6 a6twm1;iwfc 5kdensity of $ 2.165\ \text{g/cm}^3 $. The molecular weight of NaCl is 58.44. Estimate the distance between nearest neighbor Na and Cl ions. [Hint: Each ion can be considered to have one "cube" or "cell" of side $ s $ (our unknown) extending out from it.] $s$ =    nm

  Repeat Problem 13 for KCl who(ph v a)l:cqdso9 -r8wse density is $ 1.99\ \text{g/cm}^3 $. $s$ =    nm

Explain on the basis of energy bands why th7(hx8rl9ld zj8 fgj:he sodium chloride crystal is a good insulator. (8lrdh9fl jz h :xg87j[Hint: Consider the shells of $ \text{Na}^+ $ and $ \text{Cl}^- $ ions.]

  A semiconductor, bombarded with light of slowly increa8u9bukhx- 36 l bz7kua tg-v7e2wd/ii sed frequency, begins to conduct when the wavelength l-h6zv t we u3ab79kkbu 7xuig/id2-8 of light is 640 nm. Estimate the size of the energy gap $ E_g $. $ E_g $ =    eV

  Calculate the longest-waveq3 x;s+agqp* - u*lyndlength photon that can cause an electron in silicon ($ E_g = 1.14\ \text{eV} $) to jump from the valence band to the conduction band. $\lambda $ =    $\mu m$

  The energy gap between valence and conduction bqpu2p: uzh8 tgm ua,y//zou2pp60xy, ands in germanium is 0.72 eV. What range of wavelengths can a photon have to excite an electron from the top of th/u u6,xo2y2 tzazmh pp8 q/,gupuy :0pe valence band into the conduction band? $\lambda \leq$    $ \ \mu\text{m}$

  The energy gap $ E_g $ in germanium is 0.72 eV. When used as a photon detector, roughly how many electrons can be made to jump from the valence to the conduction band by the passage of a 760-keV photon that loses all its energy in this fashion? N =    $ \times 10^6$

We saw that there are 6oze9ap+ ssq+ $ 2N $ possible electron states in the 3s band of Na, where $ N $ is the total number of atoms. How many possible electron states are there in the
(a) 2s band,
(b) 2p band,
(c) 3p band?
(d) State a general formula for the total number of possible states in any given electron band.

  Suppose that a silicon semiconductor is doped with pkstth 80e2c 3bhosphorus so that one silicon atom in 2e sth0 bk3t8c$ 10^6 $ is replaced by a phosphorus atom. Assuming that the "extra" electron in every phosphorus atom is donated to the conduction band, by what factor is the density of conduction electrons increased? The density of silicon is $ 2330\ \text{kg/m}^3 $, and the density of conduction electrons in pure silicon is about $ 10^{16}\ \text{m}^{-3} $ at room temperature. $\frac{N_{doping}}{N_{Si}} = $    $ \times 10^6$

  At what wavelength will a56 xo dz xnwz+-vvrkhb3ta1;, iy o.p/n LED radiate if made from a material with an energy gaovra .i o3;hwx1d+pz5t b/y6nx-v, kzp $ E_g = 1.4\ \text{eV} $? $\lambda $ =    $\mu m$

  If an LED emits lighn) 9hib i86,zorajk0yt of wavelength $ \lambda = 650\ \text{nm} $, what is the energy gap (in eV) between valence and conduction bands? $e_g$ =    eV

  A silicon diode, whose current-voltage charag,+sk4) 9 ,wn gd-edlqg l(xzfcteristics are given in (Fig. Below), is connected in series with a battery anxne +kd sdz-l9,, 4gqggf()lwd a $ 960-\Omega $ resistor. What battery voltage is needed to produce a 12-mA current? $V_{\text{battery}}$=    V

  Suppose that the diod:lj s-4ngroe u7,9zgu d(3xmm e of (Fig. Below) is connected in series to a $ 100-\Omega $ resistor and a 2.0-V battery. What current flows in the circuit? [Hint: Draw a line on (Fig. Below) representing the current in the resistor as a function of the voltage across the diode. The intersection of this line with the characteristic curve will give the answer.]    mA

Sketch the resistance as a functktw8v81qz w-r ion of current, for $ V > 0 $, for the diode shown in(Fig. Below).

  An ac voltage of 120 V rms is to be rectifiukdd,p )/cy0f ed. Estimate very roughly the average current in the outpuc 0,)dpfuy/d kt resistor $ R $ ($ 25\ \text{k}\Omega $) for
(a) a half-wave rectifier(Fig. Below a), $I_{av}$ =    mA
(b) a full-wave rectifier (Fig. Below b) without capacitor.$I_{av}$ =    mA

a

b

  A silicon diode passes significant current only if the fo.x: .ko whdxuex d*g8*rward-bias voltage exceeds about 0.6 V. Make a rough estimate of the average current in the output res:xu *kexdo.hx8d.* g wistor $ R $ of
(a) a half-wave rectifier (Fig. Below a),$I _{av}$ =    mA
(b) a full-wave rectifier (Fig. Below b) without a capacitor. Assume that $ R = 150\ \Omega $ in each case and that the ac voltage is 12.0 V rms in each case. $I _{av}$ =    mA
a
b

  A 120-V rms 60-Hz voltage is to be rectified with 3 bg0c, uvxlf4dx wo74a full-wave rectifier (Fig. Below), where xdfl,c3 w40b 4g7vxo u$ R = 21\ \text{k}\Omega $ and $ C = 25\ \mu\text{F} $.
(a) Make a rough estimate of the average current. $I_{av}$ =    mA(smooth)
(b) What happens if $ C = 0.10\ \mu\text{F} $?$I_{av}$ =    mA (rippled)

From !num!2%, write an equation for t (-- 6d fd-pc,y8t(y6tmsxg(gq y ohm2) yelaihe relationship between the base current $ I_B $, the collector current $ I_C $, and the emitter current $ I_E $ (not labeled in the figure).

  Estimate the binding energz b7mnyoepn hrc.0sc,g5;5 p*y of the $ \text{H}_2 $ molecule by calculating the difference in kinetic energy of the electrons between when they are in separate atoms and when they are in the molecule, using the uncertainty principle. Take $ \Delta x $ for the electrons in the separated atoms to be the radius of the first Bohr orbit, 0.053 nm, and for the molecule take $ \Delta x $ to be the separation of the nuclei, 0.074 nm. [Hint: Let $ p \approx \Delta p \approx \hbar/\Delta x $]    eV

  The average translational kinetic enero/e +vpen-pts p(ft+qn gp+ 5k3- cl:zgy of an atom or molecule is about $ KE = \frac{3}{2}kT $ (Eq. 13-8), where $ k = 1.38 \times 10^{-23}\ \text{J/K} $ is Boltzmann's constant. At what temperature $ T $ will $ KE $ be on the order of the bond energy (and hence the bond likely to be broken by thermal motion) for
(a) a covalent bond of binding energy 4.5 eV (say $ \text{H}_2 $), $T =$    $ \times 10^4\ \text{K}$
(b) a "weak" hydrogen bond of binding energy 0.15 eV? $T = $    $ \times 10^3\ \text{K}$

  In the ionic salt KF, the separation d*i/p nsf k3l8nistance between ions is about 0.27 nm.
(a) Estimate the electrostatic potential energy between the ions assuming them to be point charges (magnitude $ 1e $). PE =    eV
(b) It is known that F releases 4.07 eV of energy when it "grabs" an electron, and 4.34 eV is required to ionize K. Find the binding energy of KF relative to free K and F atoms, neglecting the energy of repulsion. Binding energy =   eV

  Consider a monoatomic solid withvvci ipb9:z*wj8): )dwz m ks: a weakly bound cubic lattice, with each atom connected to six neighbors, each bond having a binding enecdv i)pj:: 9mz:8vswiwkz) * brgy of $ 3.9 \times 10^{-3}\ \text{eV} $. When this solid melts, its latent heat of fusion goes directly into breaking the bonds between the atoms. Estimate the latent heat of fusion for this solid, in $ \text{J/kg} $. [Hint: Show that in a simple cubic lattice (Fig. Below), there are three times as many bonds as there are atoms, when the number of atoms is large.]$L_{\text{fusion}} =$    $\times 10^4\ \text{J/kg}$

  For $ \text{O}_2 $ with a bond length of 0.121 nm, what is the moment of inertia about the center of mass? I =    $\times 10^{-46}\ \text{kg·m}^2$

A diatomic molecule is found to have an:-y/z*omzt ,b wnw .mjpj+4ot activation energy of 1.4 eV. When the molecule is disassociated, 1.6 eV o o*- mb+m .z:j 4,pttoywnjwz/f energy is released. Draw a potential energy curve for this molecule.

  When EM radiation isrsz.ojx 5kj sidm/ +9hl1n1 a: incident on diamond, it is found that light with wavelengths shorter than 226 nm will cause the diamond to conduct. What is the e rs j/j5+h1xzasl mi. on19:dknergy gap between the valence band and the conduction band for diamond? $E_g$ =    eV

  A TV remote control emits IR light. I6y v+des55q 9- br/mo foj+qomf the detector on the TV set is not to react to visv f/+95q+m boqro5my6sdoej -ible light, could it make use of silicon as a "window" with its energy gap $ E_g = 1.14\ \text{eV} $? $\lambda $ =    $\mu m$
What is the shortest-wavelength light that can strike silicon without causing electrons to jump from the valence band to the conduction band?

  For an arsenic donor atom in a doped silicon semiconductor, assume th ,v4 8pbq v6s0pq7am ucsz1ltdrc6i ./at the "extra" electron moves in a Bohr orbit about the arsenic ion. For this electron in the ground state, take into account td /p ls41q6 ,z.qv876apib tvmscr u0che dielectric constant $ K = 12 $ of the Si lattice (which represents the weakening of the Coulomb force due to all the other atoms or ions in the lattice), and estimate
(a) the binding energy, E =    eV
(b) the orbit radius for this extra electron. r =    nm

  Most of the Sun's radiation has wavelengths shorter than 1000 n fuez3jpku ;v1 7*luv1hstd(1m. For a solar cell to absorb all this, wd;u 1 ku 3(p7s1fvtzvj*lhu1ehat energy gap ought the material have? $E_g$ =    eV

  For a certain semiconductor, the longest wavelength radiatio;ww o;0 t7r0gpoms8;exbk+ atn that can be absorbed is 1.92 mm. What is the energbs0xgw;0 p m;o ;r +tok78wetay gap in this semiconductor? $E_g$ =    $ \times 10^{-4}\ \text{eV}$

  Green and blue LEDs became av agml*dq8 ff6+ailable many years after red LEDs were first developed. Approxima mgdl*+a 6f8fqtely what energy gaps would you expect to find in green (525 nm) and in blue (465 nm) LEDs?
the green $E_g$ =    eV
the blue $E_g$ =    eV

  A zener diode voltagmq +i af 153d3rv4y(bj96adp 9vtzbzk e regulator is shown in (Fig. Below). Suppose that $ R = 1.80\ \text{k}\Omega $ and that the diode breaks down at a reverse voltage of 130 V. (The current increases rapidly at this point, as shown on the far left of Fig. 29-28 at a voltage of $ -12\ \text{V} $ on that diagram.) The diode is rated at a maximum current of 120 mA.
(a) If $ R_{\text{load}} = 15.0\ \text{k}\Omega $, over what range of supply voltages will the circuit maintain the output voltage at 130 V?   $\ \text{V} \leq V \leq $    $\ \text{V}$
(b) If the supply voltage is 200 V, over what range of load resistance will the voltage be regulated?    $\ \text{k}\Omega \leq R_{\text{load}} < \infty$