What type of bond wouv6)gzdv.t9+fdz g u r5c7 ;ro,v;bu+ywnch 3 yld you expect for
(a) the $N_2$ molecule,
(b) the HCl molecule,
(c) Fe atoms in a solid?

Describe how the molecule,bj;k;jt wo7gpf- l8x $ \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 zs1 q6 ih,v(xv)8hhhip*js,m$ \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 ivf;8kps 562exz)m m kento four categories. What are they?

  Would you expect the molecule4ww do5 2z;n i;4j bc8zz8mgxe $ \text{H}_2^+ $ to be stable? If so, where would the single electron spend most of its time?{yes|no}

Explain why the carbovao;1.-:ic vw (kmn4w - nftmln atom ($ Z=6 $) usually forms four bonds with hydrogen-like atoms.

If conduction electrons are free to roam abo /(emnap .y*;oih wc-ghs-4wx ut in a metal, why don't they leave the metal ent -/me wy*ic.wp(sg- ohhan4 ;xirely?

Explain why the resistivi.5+ t si9fcky /od6czity of metals increases with temperature whereas the resistivity of set5+syc9ofi zi /d6c.kmiconductors may decrease with increasing temperature.

(Fig. Below) shows a "bridge-type" full-wave rectifier. Explain how the curr vtv9a/p4)grsent i)/gvr st4av 9ps rectified and how current flows during each half cycle.

Compare the resistance of a pn junction diode connecaqe8,qo+34i7tefj uee 7/bl gted in forward bias to its resistance when connected in reverselb8 e tqe7/i 7gu3afo 4eqe,j+ bias.

Explain how a transistor could be used aul+ cu,/jkbtt)b0 z*1 whvdxk2n88hls a switch.

What is the main difference between n-type and p-type semiconds le+266q ke .a wn.4m mgcbq17ycq,vkuctors?

Describe how a pnp transistor can opera1j 4-xr1zg e5ut2efba te as an amplifier.

In a transistor, the base-emitter junctiornw.;wsix 79 e-/ ds)gz4z c kcvuxnbw/68qm/ n and the base-collector junction are essentially diodes. Are these junctions reverse-biased or forward-biased in )s bw/nn ;c k/z7rx-/imqse9wu8gcd 46vwz.x the application shown in (Fig. Below)?

A transistor can amplify an electronic signal, meaning it can incrnwtb25n,j)ml*xy y; yease the power of an input signaly,xm jyw)t5 *2lb;ny n. Where does it get the energy to increase the power?

A silicon semiconductor is doped with phosphorus. Will these atoms be donors orwmjlnehb;b )tr.to:7( ,kvq ( qk)1fa acceptors? What type of semiconductor will thiloq .tkerw7nab1ktqbj( :(;), )vhf ms be?

  Do diodes and transistors obef(-awmnn(v ugi01asyy6bt 3fs1 (j (cy Ohm’s law? Explain. {yes|no}

  Can a diode be used to ampli+ -5wxbf n4nv53bmdyy fy a signal? Explain. {yes|no}

  Estimate the binding energy of a KCl molecule by calculatin8wje8awcc0e+ g the electrostatic potentiece8c0 j +a8wwal energy 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 of4: z ,i(x by6najgfme, cr;+e1w)aq cz Problem 1, estimate the contribution to the binding energy of the repelling eleqjaenr:m(x g z,+ayf)bi ;z46c,ec w1ctron clouds at the equilibrium distance $ r_0 = 0.28\ \text{nm} $. $PE_{\text{clouds}} =$    $\ \text{eV}$

  Estimate the bindingqzt;.bhf lxncm i+3 31 energy 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 lddq 3(5stan2experimentally in kcal per mole, and then the binding energy in eV per mole(ntqa 5d 32sdlcule 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 thm 2zd4t-noweef1w: 1je states in the formation of the m 1f21weowjed :nt-z4$ \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 quantity . w)e sa0robx7y cid-kii8d5;$ \frac{\hbar^2}{2I} $ has units of energy.

  The so-called “characteris8 mzq vo/k5ix.h cv*64nqlo7mtic 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 characteristic rotational energy, jrtd6u(gg9ik4i69 d v$ \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 atan0wexyb8s-*.r0mc 8ci5-c t* xsv:lph a 8yhoms 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 zk,i2*r eyet7sgto: amv 157rfor the NaCl molecule given that three successive wavelen5e ko1y ,vsg*r7m :ra 2zeti7tgths for rotational transitions 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 the stiffness constant :g.qjlg b* n+w$ 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 and vx 6tn98m+hx6xg z(ve Cl ions in a NaCl crystal is 0.24 nm. g e+(ztm x8xh6vn 9x6vWhat is the spacing between two nearest neighbor Na ions? D =    nm

  Common salt, NaCl, has a density of2m* rg +hc3oolj amd-8 $ 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 d,r:2e 1g 3vklxzmu1xj ensity is $ 1.99\ \text{g/cm}^3 $. $s$ =    nm

Explain on the basis of energy bands why thkl 5 ob g,ciezcw04*vavch 6.)e sodium chloride crystal is a good insulator. [Hini* vh aoc4l5 w6b,z)g.vcc0 ket: Consider the shells of $ \text{Na}^+ $ and $ \text{Cl}^- $ ions.]

  A semiconductor, bombarded with light of slowly increasesggk5 ci z p5hm:;(b*jc6rb:wd frequency, begins to conduct when the wavelength of light is 640 nm. Estima:(*gh;cjp:c5 wsg5im b brzk 6te the size of the energy gap $ E_g $. $ E_g $ =    eV

  Calculate the longest-wavelength photon thath*l eu l1md3mbb68mtgla991n 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 band( 1e((o49 mj ok hool1ubh. 7sergshw/s in germanium is 0.72 eV. What range of wavelengths can a photon have 1s.eh (roswe ko/(mlh (j oh9u4g17boto 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 arg)-wk lp8.b-whb r0we e $ 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 thi k 1hc(ae;nweh.nr1kd:iqf24 do 86uat one silicon at:cid8hkow a.6r neendf4khui2( q1;1 om 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 LE/7 bk 8bqx*vtd 9gkpyo/nn);iD radiate if made from a material with an energy gapy*)kbt n7o ; idvn8gbkxp//q9 $ E_g = 1.4\ \text{eV} $? $\lambda $ =    $\mu m$

  If an LED emits light of wavelent/55nvty9 /:khy: a jf (xppysgth $ \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 c -z:o2aig jl0m05wbn sharacteristics are given in (Fig. Below), is connected in series with a battery a-2josbiw05n lg m:0 aznd 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. Belowqcn0m xi2, u;1yk agb5) 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 resistance3m a2t-cvea/p as a 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 vkpaz oc2xe),1 ery roughly the average current in the output resistopcae )x12 ozk,r $ 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 sigxx +hqc,:3pr5 :ybc oinificant current only if the forward-bias voltage exceeds about 0.6 V. Make a rough estimate of the average current in the output resistor :5, x:xcocby+hr3p iq$ 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 recti,0125fp *-nkrlmmk. ghajidd fied with a full-wave rectifier (Fig. Below) afh52,jp k*n -d1l0 mid.kmrg, 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 relationship between the 3qdhd*q rl ck3 ry8mdh+30.rlbase current $ I_B $, the collector current $ I_C $, and the emitter current $ I_E $ (not labeled in the figure).

  Estimate the binding enek7dfvdf+ g *f9rgy 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 energy of an atom or molecule is a+ 811cw /-ghdrx6vx gti1qrfubout $ 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; 2hvx+/.fecwprrlr9 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 weakly boundx) 7egwi y z4glee9s65 cubic lattice, with each atom connectei4 eg9lyw sgeez 6)75xd to six neighbors, each bond 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.ppwwb8.7lf2*63 yyoy; bhr bw When the molecule i; o b*6w8.hpwb rbpl y2fy7y3ws disassociated, 1.6 eV of energy is released. Draw a potential energy curve for this molecule.

  When EM radiation is incident on diamond, it is found that w)59ap.6tr:vlcy1 ; oo 8rklikkn ; hnlight with wavelengths shorter than 226 nm will cause the diamond to conduct. What is the energy gap k8:rlkc96h k.wv 5 ty;ao1r; npi)lno between the valence band and the conduction band for diamond? $E_g$ =    eV

  A TV remote control :4. 8*mzz ;gtn znwmghemits IR light. If the detector on the TV set is not to react to visible light, could it make use of silicon as a "window" with its hz mn8 m:tg4zz.n;* gwenergy 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, aihj 40;binu;r8 nk2cassume that the "extra" electron moves in a Bohr orbit aboun 4jih ;akb8r 0;u2icnt the arsenic ion. For this electron in the ground state, take into account the 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 nm. For 9 3ag.4)kaa3sts zfe/nj .tr wa solar cell to absorb all this, what energy gap ougtats. )9 f eargz/3n43 ajwks.ht the material have? $E_g$ =    eV

  For a certain semiconductor, the longes-(dfre1u yu ;bu.8s nmt wavelength radiation that can be absorbed is 1.92 mm. What is the energy gap-s m.nudyub (fr8 ;u1e in this semiconductor? $E_g$ =    $ \times 10^{-4}\ \text{eV}$

  Green and blue LEDs became available many years after red LEDs were firstj4i yr h96xkv std09)w-c1o ds developed. Approximately what energy gaps would you expect to find in green (525 nm) and in blue s6 hw yo4 s1)-i9dcxrdkj0vt9(465 nm) LEDs?
the green $E_g$ =    eV
the blue $E_g$ =    eV

  A zener diode voltage regulaskg 6, da,iav4tor 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?    $\ \text{k}\Omega \leq R_{\text{load}} < \infty$