What type of bond would you exg/n8x h1z do5srw8zf9pect for
(a) the $N_2$ molecule,
(b) the HCl molecule,
(c) Fe atoms in a solid?

Describe how the molh3 z,:zzzi ;i6v/uur mecule $ \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 0: 6,bmc4fkh8z3mppa. ajlj c$ \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 qk x1/3nd (itcy2g u;qdivided into four categories. What are they?

  Would you expect the molecule 31 rujiml)n8n9xfqy 4$ \text{H}_2^+ $ to be stable? If so, where would the single electron spend most of its time?{yes|no}

Explain why the carbon ah)hq5fyzs9mjlm:: r2 tom ($ Z=6 $) usually forms four bonds with hydrogen-like atoms.

If conduction electrons are free to roam anvi9 v.1o.mxf bout in a metal, why don't they leave the metal entirely91 fnivm. x.vo?

Explain why the resistivv3+lvr* h snd7ity of metals increases with temperature whereas the resistivity+vd*nv3h rl 7s of semiconductors may decrease with increasing temperature.

(Fig. Below) shows a "bridge-type" ful8lk u+:z km;ff+vuf)rt9 ny8vl-wave rectifier. Explain how the current is rectified and how currenvt+ krfzm8u;+9y)l8 fn:uvf k t flows during each half cycle.

Compare the resistancetmyh2 xpe6vq1;r,k s 6ehq75q x7x (av of a pn junction diode connected in forward bias to its resistance when con,qrxxeqht75a sv71qm ;(h kep2 y6 6vxnected in reverse bias.

Explain how a transistor could be 5q yw.3crr9q6pptnya9km( ,g u5s.qeused as a switch.

What is the main difference between n-type and p-type semiconductors(cgrs2:dc2o a/m69*nyllr tej;, b f x?

Describe how a pnp transistor can operate as an amplifi 6uo,ikf u0dc9er.

In a transistor, the base-emitter junction and the base-collecto5o.p i *sngw8ir junction are essentially diodes. Are tn gp5so. i8wi*hese junctions reverse-biased or forward-biased in the application shown in (Fig. Below)?

A transistor can amplify an electronic signal, meaning it can increase tlvg fs,kp. e,(he power of an input signal. Where does it get the energy tov,.gpf (,s lek increase the power?

A silicon semiconductor is doped with phosphorus. Will these atoms be donors:.uzdlv y- xw ;ly/5sndgdi -qk w,v,7 or acceptors? W 5,7;lwsukyxvqny w idg:/zdv-. -l, dhat type of semiconductor will this be?

  Do diodes and transistors obey Ohm’s law? Explain. {yesh96q qcvp6+j s|no}

  Can a diode be used to am2 wxa:t 9a .xk.ef0wumplify a signal? Explain. {yes|no}

  Estimate the binding energy of a KCl molecule by calculating the electrostatic p99jb -j g hrn45)ft4cr(shzmbotential energy wjsfz-bt(rg )jr 4h9hc5m9b4nhen 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 ej 6m)ps gqk8m2nergy of KCl is 4.43 eV. From the result of Problem 1, estimate the contribution to the binding energy of the repelling elect 6g8 msqpm)j2kron clouds at the equilibrium distance $ r_0 = 0.28\ \text{nm} $. $PE_{\text{clouds}} =$    $\ \text{eV}$

  Estimate the binding energ9 wk:kdd rczzp((13qx m 4p)tqg2ycy-*2qjg jy 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 experimentally in kcal peh39wq i-e4+a5 b 2gq*itiiuxi kr+ lh:r mole, and then the binding ih*lu+kr-4 2 5 ihqie3 :q+g9iitbwaxenergy in eV per molecule is calculated 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 for t7 ao2,osxiz-6p p-dml he states in the formation of thep2pl- adx6soz im,7o - $ \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 quanti4wf* d )tnqa3uji3 n/uty $ \frac{\hbar^2}{2I} $ has units of energy.

  The so-called “characteristic rokchxq c bcgl3z d9gh.x45r7t-(wy 9 4ztational 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 characteristic rotat g3ng15r4 fdfdyvcca4 dhu. 0-ional 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 r 8p9u+mngx,r of H atoms 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 the NaCl molecule;qos )hnblonkj+lu*j 6 .n/s1 given that three successive wavelengths for rotational trl u6; hn son+slo/nk)j*.q1bjansitions are 23.1 mm, 11.6 mm, and 7.71 mm. $r = $    $\times 10^{-10}\ \text{m}$

  (a) Use the curve of (Fig. Below) tt;wj-y hg m qc(a(alc+npkp1b n/2v+4 o estimate 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” N5kav;p5kahip) /px1 ya and Cl ions in a NaCl crystal is 0.24 nm. What is the spacing between two nearest neighbor Npxpap5h kk;5i/ a )1yva ions? D =    nm

  Common salt, NaCl, has a dens(*vrcm-kguj*.b jw t( ity 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 whose denstuh)i oktd0 892j) kycr.cbv +fq8vm:ity is $ 1.99\ \text{g/cm}^3 $. $s$ =    nm

Explain on the basis of energy bands why the sodium chloride cry6u49nd(wt p v d2klis/q82vyestal is a good insulaq2v( 6 d4iudy 9kvnl8w2pe /sttor. [Hint: Consider the shells of $ \text{Na}^+ $ and $ \text{Cl}^- $ ions.]

  A semiconductor, bombarded with light of slowly increasedsfx (a5c4dk y, frequency, begins to conduct when the wavelength of light is 640 nm. Estimate the size od(5akc xs,yf4f the energy gap $ E_g $. $ E_g $ =    eV

  Calculate the longest-wavelength+o4-v s9off1bf lrqp, 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 c /d0jbl f7*drconduction bands in germanium is 0.72 eV. What range of wavelengths can a photon have t d7cd0fb/ *rljo excite an electron from the top of the 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 arewk)z z(2r,ru:v 8yk he $ 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 that one silico5p+i/ o9hkmtso4gw-ma v21akn 4 +5wh ogiapamkm1otv /s2k9-atom 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 from a mat-/m:a,h di nhnerial with an energy gapd-, /nmnhh :ia $ E_g = 1.4\ \text{eV} $? $\lambda $ =    $\mu m$

  If an LED emits lighrzyy, 2j1wq sxy (8gu;q /c:l v-s;nxxt 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 characteristics are given in yi:bzfz 9r2e -(Fig. Below), is connected in series w: ezybr92i-fz ith 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 (Figak9 /wna7, v0qdlflecnv ;v4/. 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 function of current, f ,i ag d/t5nth-66pu(baf s(pjor $ V > 0 $, for the diode shown in(Fig. Below).

  An ac voltage of 120 V rms is to zw658mmmrr j9 be rectified. Estimate very roughly the average current in r8w6m jm95zm rthe 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 only ifj .hqxb xnnvz, ri*.oy+p2u81 the forward-bias voltage exceeds about 0.6 V. Make a rough estimate ooz.* +p.n 1q xu8brivj,hxy2nf 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-wave rectifieca x2+0x:qsj6-r )kty rdb+ pnr (Fig. Below),rpbs+yd+ 6)n x- 0c:kjqa xr2t where $ 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 the relmbz-d,cql g-q xev677ecqc 0* ationship 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 of*.ibhxmzjeglok ;w; 9l,v bvbj; 8 8v0 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 es1i41u hf9y9 g*d 5ssool+ yrfnergy 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 distance between ions is about 0.27 nm b (yu5- q.+p(udvntqsv 5v)zg.
(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 weakly bound cubic lattice, w pbcq+k5t.x/ xith each atom connected to six neighbors, each bond having a binding eptq.+cxkb 5 x/nergy 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 havh)8q4 33 fva*2lis r 4xwzlwvye an activation energy of 1.4 eV. When the molecule is disassociated, 1.6 eV of energy is released. Draw a potential energyf il3v szq xvylawh8w23r 4*)4 curve for this molecule.

  When EM radiation is incident on diamond, it is found that light with wavelengt:uzidu:ww1;s i9s8xouo )lf m86hmj :hs shorter than 22izl)ofjuw:1 u 9hdi;:8w mxom8sus6:6 nm will cause 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 set is not qft+ / rq2-kjor6 d2qbto react26-rq2rqq dobf tj/k+ to visible 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 5 +bw7dm03uwjs-.iam.a p rqzsilicon semiconductor, assume that the "extra" electron moves in a Bohr orbit about the arsenic ion. For this electron in the ground state, take into account the -z a a7qpsr.u05w+.jm idwm 3bdielectric 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 no 6 / e 0jc1m-rm.;mxqgeqv+ l9(mvjtkm. For a solar cell to absorb all this, what energy gap ought m/vqe kj mrg+ej-6m.;t v9 ocq1x(0 lmthe material have? $E_g$ =    eV

  For a certain semiconductor, the longest wavelength r qwv6f 8hp+pp. g,6iyaadiation that can be absorbed is 1.92 mm. What is the energy gap in this semiconwpfha .vq+ y8,i6 g6ppductor? $E_g$ =    $ \times 10^{-4}\ \text{eV}$

  Green and blue LEDs became a)q n*uvtgz ).vvailable many years after red LEDs were first developed. Approximately what energy gaps would you expect t)q. vgtunvz)*o 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 regulatbgi5jc9 aq2v2vn-lnf 7th3 +s or 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?    $\ \text{k}\Omega \leq R_{\text{load}} < \infty$