What type of bond wob/t.s(t u4kakuld you expect for
(a) the $N_2$ molecule,
(b) the HCl molecule,
(c) Fe atoms in a solid?

Describe how the molecuahy8c y1bng8z/ a l7d0le $ \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 molecul,xned+ 2 yrscj1+30 vcq doe(ge $ \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 n8c i*gbq*9h,q6m0 3h pz4june :iziwcategories. What are they?

  Would you expect the molecule rdm3g9y :r);ia:gia0p1lk r m$ \text{H}_2^+ $ to be stable? If so, where would the single electron spend most of its time?{yes|no}

Explain why the carbon a8; clwex 31iqntom ($ Z=6 $) usually forms four bonds with hydrogen-like atoms.

If conduction electrons are fre6d (rp7dp7h:l (ptsvze to roam about in a metal, why don't they leave the metal enh6srl7 :d(dp( vpptz7 tirely?

Explain why the resistivity of metals increases with temperature whereas the resb 7c9) d lx12lru*xrxlistivity of semiconductors may decrease with increasing temperatbl2l1c9 xdr x*x7 r)luure.

(Fig. Below) shows a "bridge-type" full-wave rectifier. Explain how thke,r/jk 9n8eo e current is rectified and how current flows during e r ,/o9kj8enkeach half cycle.

Compare the resistance of a pn wibmvh )g9tma1.x2p+i(;3wl- od ca djunction diode connected in forward bias to its resistan93b2tax 1hwi;lg ai-pc(.)dvmmw+ d oce when connected in reverse bias.

Explain how a transistor ve sc7ha 7)s7x*bgsz*nn;7zj could be used as a switch.

What is the main difference between n-type and p-type ni*ygstx b6s52 0hl/j semiconductors?

Describe how a pnp transistor can operate as an ampliw:m*p2 m0ln rufier.

In a transistor, the base-emitter junctiov) .c zmu6umx/y (bmz*:gxrj 5n and the base-collector junction are essentially diodes. Are5jg.(6 zm*r yu/) zmxvx:ucmb these junctions reverse-biased or forward-biased in the application shown in (Fig. Below)?

A transistor can amplifpehey cbod5;0ev6l- 3 tev 78hy an electronic signal, meaning it can increase the power opo8ee6v e7lvhhcybd5 e3; t-0f an input signal. Where does it get the energy to increase the power?

A silicon semiconductor is doped with ph2ypsfh 11 xja7osphorus. Will these atoms be donors or acceptors? What type of semicondsj21 1ypfxah7uctor will this be?

  Do diodes and transistors obey Ohm’s lawjn-zq4.sc:yjtr :u a 3? Explain. {yes|no}

  Can a diode be used to amplify a signal? Explain. {yes|6v5g1, rvt*cvwous 7tox,1cd no}

  Estimate the binding energy of a KCl molecule by calculatingfznzh1k4;m2d3 hpx3u+ w gfh+k;o7ux the electrostatic potenti4 3whp ukg+3zu h;7fm hko1dn+z2f; xxal 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 en-.)bmbntkjb tq9e t)7jo/ k+ bergy of KCl is 4.43 eV. From the result of Problem 1, estimate the contribution to the binding energy of the repelling electron clouds at the equilibrium distancetkbjjtkbo-b 9e+.nmt)/) qb7 $ r_0 = 0.28\ \text{nm} $. $PE_{\text{clouds}} =$    $\ \text{eV}$

  Estimate the binding energy oh24 jkr+gv3fs 3 :sh we/jt2z bsf-oc ,y2o7bdf 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 expi :w0*2 mffuqnerimentally 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 :miwnfqf20u *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 the states in t9z(to h-dlxtkrxzrt6 2r4gr6 9yhv1d68v*em he formation of trtz 8*rlv y1ktdx4x9v-r doh 96th(6 z mg62erhe $ \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 quantityi/8jja 62+ wq 8rrvyoh $ \frac{\hbar^2}{2I} $ has units of energy.

  The so-called “characteristic rotational energyuj mxg o7o3j-b*74yrj,” $ \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 chf8 mzn zc+nz9;jz(i +6xr*v jxaracteristic 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 o;ib,) pd vl0rqg nl+5bfx1(wkf 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 mol1-b3nkyyc(*r ppp xm(na 7 uu8ecule given that three successive wavelengths for rotational transitions are 23p*knuc-n x7ur y(83b1 p (ypam.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 7kfq0l(ghg5kt8, m6va4 y,v hy d)gyg$ 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 Cl ions in a NaCl crysta ;comz82+uom 3u/qg wbl is 0.24 nm. What gz2 u8;cbwmu /o+q3mois the spacing between two nearest neighbor Na ions? D =    nm

  Common salt, NaCl, hal5zcswx gl d9c9dpg3q4 ,v44es a density 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 whosei 1jfe;+s4j vt density is $ 1.99\ \text{g/cm}^3 $. $s$ =    nm

Explain on the basis of energy bands why the sodium chloridexiyg3l 7 /(zuj crystal is a good insulator. [Hint: Cong j/u3xy7 z(ilsider the shells of $ \text{Na}^+ $ and $ \text{Cl}^- $ ions.]

  A semiconductor, bombarded with light of slowly increased frequem+ ynx o2gr2;jncy, begins to conductomyr2 n;xj2g+ when the wavelength of light is 640 nm. Estimate the size of the energy gap $ E_g $. $ E_g $ =    eV

  Calculate the longest-wavelength p9hbhsl w: zpl )(5zr/ra,:pg rhoton 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 bandsw6 p:;fe 3ljczzolj1 7 in germanium is 0.72 eV. What range of wavelengths can a photon have to excite an electron from the top of the valence ban7:;z6fcw 13ezjjlpol d 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 ar.a6opv o . *(hq8txjcue $ 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 sexy mrrq a4jhf(;0r*6 tmiconductor is doped with phosphorus so that one silicon atom in m r6;4ftq x*0rrayhj( $ 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 material with an enerhl7, wo /gbx9ngy gapwno,b h/g9l7 x $ E_g = 1.4\ \text{eV} $? $\lambda $ =    $\mu m$

  If an LED emits light of wavelength : s jq j93knl3jho0z.m$ \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 ch(l4c w.tjk ntw1yapp (,o,de 9aracteristics are given in (Fig. Below), is connected innj4 t p1l(cpwe(.dwatky,9,o 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.vv 0yn b(6yc.q 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 asc ibsm- z0md8. 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 very rx,+ 8fbfy;7k5qz)lfwdx5 b 5p laty: poughly the average current in the output resi7 +:bf)pxx5ya5,d b;tzqyk 8pf l5wflstor $ 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 cupr2lc0 tsiv)vo) (1vlrrent only if the forward-bias voltage exceeds about 0.6 V. Make a rough estimate vvc )r2(0)1isvoltplof 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 n-*c apq:+3o4qt up hc8e7fuato be rectified with a full-wave rectifier (Fig. Belfq8a 4a t*- uocc+ p3neqpuh7:ow), 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 forhuef04x/k;f f 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 bindingo;gxqj7e hxce676 +ee energy 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 kinejpo 1i yc2v,zf* 9bh.ntic 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, the separation distance between ions is abo:d l6hka+ f /e(i8zgthut 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 wuv t7go r,96kieakly bound cubic lattice, with each atom connected guro6 7k9vti,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 havehahhn(p70r-la s lbi/72m: n u an activation energy of 1.4 eV. When the molecule is disassociated, 1.6 eV of energy is releasp / hnh : ailh77n-s(0br2uamled. Draw a potential energy curve for this molecule.

  When EM radiation is incident on diamond, it is found that light henmpb-85bx+7 0o9 zdxhz1 z1e,gtm;p j4oyg with wavelengths shorter than 226 nm will cause the diamond to conduct. What is the energy gap between the valenh-mg gzd,zbx8 hpo15b1t j4py ome;0z+nx97ece band and the conduction band for diamond? $E_g$ =    eV

  A TV remote control emits IR light. Ifmwye ,g) *wed8 the detector on the TV set is not to react to visible light, could it make use of silicon as a "window" with its edey*8em,wg) w nergy 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 a1mwa j.2mmf 7pan ;qh. doped silicon 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 dielectric constant w. mmj1.2nm7aphf ;aq$ 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 nmer/ 9 ;*02zny+)v yhbznifn nk. For a solar cell to absorb all this, what energy gap ought the y0vh/fr;e b nnz)zi2n *k+y9n material have? $E_g$ =    eV

  For a certain semiconductor, the longest wavelength radiation that cae0 jme4c*vihu,:l3sjn be absorbed is 1.92 mm. What is the energy gap in thuc 3e4sv,h*i:l0 ej mjis semiconductor? $E_g$ =    $ \times 10^{-4}\ \text{eV}$

  Green and blue LEDs became available many years after red LEDs uec5oaa;tqj/ lu65jf0y j/u2 were first developed. Approximac5fa5tuje; u j2lj0qoy/u 6a/tely 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 voltage mir0-s3ovbv,oj4a 5c(vj e3 mregulator 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?    $\ \text{k}\Omega \leq R_{\text{load}} < \infty$