What type of bond would you expect fo4dp;mk utv(2bn pj/zpb 1q:q (r
(a) the $N_2$ molecule,
(b) the HCl molecule,
(c) Fe atoms in a solid?

Describe how the moleculed 8vatfd8 :mohrv(x)h f8gl 0/gb(y u5 $ \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 moleculeqsr k3 h(s9sv m4hi7h7 $ \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 cat: 7ksc)ezz(qqegories. What are they?

  Would you expect the moleculnfklg9b(mu m nym-,/-e $ \text{H}_2^+ $ to be stable? If so, where would the single electron spend most of its time?{yes|no}

Explain why the carb p9e7zk) h3ewcon atom ($ Z=6 $) usually forms four bonds with hydrogen-like atoms.

If conduction electrons are free to roam about0y/dyl y9w d.w in a metal, why don't they leave the metal entid 0yy/w d9ywl.rely?

Explain why the resistivity of metals increases wkt c9d,rsq) i xdxvn (k-/n,z4ith temperature whereas the resistivity of semiconducto q(xn 9 ,i,k-cnr )v4zkd/dsxtrs may decrease with increasing temperature.

(Fig. Below) shows a "bridge-type" full-wave rectifier. Explain how the curren221 y98o(jt biefk92rloahurdkeh1l3 eq 64 qt is rectified and how a2oi42bf1182edl63h9(rk lh u te9jky qrqeocurrent flows during each half cycle.

Compare the resistance of a pn junction diode connectnpm-8rm j;fvt3o v()jed in forward bias to its resistance when connected in revef-pj vr8(vo jn3; mmt)rse bias.

Explain how a transisto0ui: zw7tdkrtk m5/r: p0 uib6r could be used as a switch.

What is the main difference between n-type an 5+ xfz6i5sha7)wias pd p-type semiconductors?

Describe how a pnp transistor can operate as an a i vx5/kjskxwz;+ux8m3f:d /pmplifier.

In a transistor, the base-emitter junction/qd+ x) qg;rl1k0 q ouxg8uxx8 and the base-collector junction are essentially diodes. Are the lx8;8 )dxgxok0gu+ qxu q1q/rse junctions reverse-biased or forward-biased in the application shown in (Fig. Below)?

A transistor can amplify an electronic signal, meaning it can increasplpj52. +ux,f,kd1g q)g xkmb-tyr )je the power of an input signgxgd,mfrp -)k xkb l tq 25+.ujpjy1),al. Where does it get the energy to increase the power?

A silicon semiconductor is doped with phosphorus. Will these atoms ber4brbhdu3d nt a ed/ xy38jcj314y 1u- donors or acceptors? What type of semiconductor jybbre8t4ydc3 rhnu113- /34jd u xdawill this be?

  Do diodes and transistors obey Ohm’s law? Explt;r 0e6f8)munq zch;dain. {yes|no}

  Can a diode be used to amplify a signal? Exat9h+31ig nrwplain. {yes|no}

  Estimate the binding energy of a 7ux0 zzod3o86aujic;. 2bsbpKCl molecule by calculating the electrostatic potential energy when tdbzb o.a73u2u0s c8p x6i;jozhe $ \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 iz*py8wxat-ysy wt4 u jt,5l3+o:g q-ds 4.43 eV. From the result of Problem 1, estimate the contribution to the binding energy of the repelling electrx 3ud*- tyw-z4t8oqyw5tgp+:l ,s y ajon clouds at the equilibrium distance $ r_0 = 0.28\ \text{nm} $. $PE_{\text{clouds}} =$    $\ \text{eV}$

  Estimate the binding pn.*xfk fyp71energy of 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 expmjeeg8dkf /;n63p.;ftnrmi) erimentally in kcal per mole, and then the binding energy in eV per molecule is calculated from that result. What is the conversion factor in going fj/8m meg ;3nirnpe. )tdfk; 6from 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 fjvi/p,0ibbuy+c z)+lse j* 7p )nctm3 or the states in the formation ofjtzps7y+) nbl, +/cjemv i 0ib c)u3*p 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 quantiss;md:3w b*hb. w -x9hp dca)nty $ \frac{\hbar^2}{2I} $ has units of energy.

  The so-called “characteristic rotational ens 89 qvfo a:u)m,df3olergy,” $ \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 characteristic rotational enerhuy w3b;zz20 i i,jkp( gux )z2xyc81zgy, $ \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 atoms in the 2flq,i *j gedh8,pmo 1$ \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 the NaCl molecule given39 q 8ajino3f:vrl pvl 4fcd8;ii(ry/ that three successive wavelengths for rotational transit/(4 39drcorf:8 iq;n ja8p3i lvyvfilions 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 estima u/(cyqk0 6ssyte the 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 neighbor” Na an mq0h7vb430evs/.zz jgy 9w0p s* reoud Cl ions in a NaCl crystal is 0.24 nm. What is thehvwueb.*jzg0ypo3s90 ser7 mvq04 z/ spacing between two nearest neighbor Na ions? D =    nm

  Common salt, NaCl, has a density omba4 fr9 :r oe*()vzmvf $ 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 w4 3vc n(uzsl(s2 jv0dKCl whose density is $ 1.99\ \text{g/cm}^3 $. $s$ =    nm

Explain on the basis of energy band(qjzbgap (,jf zf7y,;s why the sodium chloride crystal is a good insulator. [Hint: Consider the g ,qj(pz bf(7ajf ;zy,shells of $ \text{Na}^+ $ and $ \text{Cl}^- $ ions.]

  A semiconductor, bombarded with light of slowly increased 57 s5:kojjrh+bu;o d)+i(q u*km blrw frequency, begins to conduct when the wavelength of light is 640 nm. Estimate the size of theb7w mos dr)+; u(iro5lkkj bh*:q+j5u energy gap $ E_g $. $ E_g $ =    eV

  Calculate the longest-wavelength photon that can cause an electrimls o: xk;u2w3 jqz/.on 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 bands in germanium ishl(c9a/) fy pnof;4 bk 0.72 eV. What range of wavelengths can a photon have to excite an electron from the top of the valence band into the conduction b4n ;ach k)ffp9oy/(l 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 areb 3) ro5mofqjf/o vw60 $ 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 phosphorus so t egz17 wwb(okwk,) ii,hat one silicon atom ke,wwiw1b7(,k o )igz in $ 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 an LED radiate if made froyk k fj g*d;;lp s8qay6e/yo,*ax02 frm a material with an energy gap;xl8aqffkprg*oye/s d ,a k;yj02*y 6 $ E_g = 1.4\ \text{eV} $? $\lambda $ =    $\mu m$

  If an LED emits light of epr0gy /wt /jq78rl0dwavelength $ \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 chamqd(oy4q3bv x51yrn- racteristics are given in (Fig. Below), is connected yb-45y3( odn1rxqmqv in series with a battery and a $ 960-\Omega $ resistor. What battery voltage is needed to produce a 12-mA current? $V_{\text{battery}}$=    V

  Suppose that the diode of (Fig.q:lqzd- l sz0w8)wal* +e,juu 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 a3 2ia x,61tk izahex)q function of current, for $ V > 0 $, for the diode shown in(Fig. Below).

  An ac voltage of 120 V rms is to be rectified. Estimate s8bgc6i2pk 2.7ic 8it+qwixr very roughly the average current in t8cqicwx2rg 6i+8b7.tik2i ps he output 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 o ,xbz;xezv41 fnly if the forward-bias voltage exceeds aboutvx4x, ;bzzef1 0.6 V. Make a rough estimate of the average current in the output resistor $ 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 a full-.v7vta*q. t tvwave rectifier (Fig. Below), wha tv*.tv7.qtv ere $ 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 faiwfj. 9lg x8*e0+l dbor the 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 energy ozr:1zf- 1 gdlrf 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 translat r4i(kx+sxe e2mp:b8 mional kinetic energy 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, xb lw 8g72vbahm7 076xarsosrr1 ke )( cs4p*xthe separation distance 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 with a we8wb)zc fj 1wg:kzde4:akly bound cubic lattice, with each atom connected to six neighbors, each bonczew 4 :fbz1gdkj8:) wd having a binding energy 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 activation energy of 1.4 eV. When to x-,8ryg8fw fhe molecule is disassociated,8wo rfx8,-fg y 1.6 eV of energy is released. Draw a potential energy curve for this molecule.

  When EM radiation is incident on diamond, it is fo:zln wls2 ;io;und that light with wavelengths shorter than 226 nm will cn; 2l;wsloiz: ause the diamond to conduct. What is the energy gap between the valence band and the conduction band for diamond? $E_g$ =    eV

  A TV remote control emits IR light. If the detector on the TV s6qj4/5m vpbn fcq h./1m )yakaet is not to react to visible ligq .64 /f5ja mavknp/b1qmch)yht, 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 that the "ext 1 gux(rxn44ij/mc yw8ra" electron moves in a Bohr orbit about the arsenic ion. For this electron in the ground state, take into account the jcny uwxrg(8/ i14xm4dielectric 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 1b qxm-+;c/a r5 flzpy+)owhw1000 nm. For a solar cell to absorb all this, what energy gap ought the material y +bw -q+xrwm;) c ph/15zoalfhave? $E_g$ =    eV

  For a certain semiconductor, the longest 0ps5lrp*h)h ii/za 4gwavelength radiation that can be absorbed is 1.92 mm. Wh /ar4s5hp il)zp0ig*hat is the energy gap in this semiconductor? $E_g$ =    $ \times 10^{-4}\ \text{eV}$

  Green and blue LEDs became available many years after red LEDs werea)(9qtbrfu 6t first developed. Approximately what energy gaps would you)r fqtu9tb (a6 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 voltage regulator is shown in-65oh(mi5 aawfpt l.z (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?    $\ \text{k}\Omega \leq R_{\text{load}} < \infty$