What type of bond woul8+lise2 b ;i)e4gewfld you expect for
(a) the $N_2$ molecule,
(b) the HCl molecule,
(c) Fe atoms in a solid?

Describe how the moleqvmwgw7;j: i 9cule $ \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 /xrz6 gs5s9zm$ \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 theyge: 01urw/vco ?

  Would you expect the 5b0(9op0 m eid2cispdmolecule $ \text{H}_2^+ $ to be stable? If so, where would the single electron spend most of its time?{yes|no}

Explain why the carbon atu8(1p9nvgnpttp z vzz+ pk4d:;)y hr6om ($ Z=6 $) usually forms four bonds with hydrogen-like atoms.

If conduction electrons are free to rz*df+j jo0pg7 oam about in a metal, why don't they leave the metal entiro*dfjpj+g z0 7ely?

Explain why the resistivity of metals increases with temperature whereas the resf80vwwo-+ 5omg xhg 8(flyaf6 istivity of semiconductors may8gy l-0oa8o fhxgmf(6 wvwf 5+ decrease with increasing temperature.

(Fig. Below) shows a "bridge-type" full-wave rectifier. Explain how the current t;i)1 laatre0g51k d. /3s cnis;qjdpis rectified and how current flows duriglds13i)i ;/paq0.acet ;k 5ns1rjdtng each half cycle.

Compare the resistance of a pn junction diode connected in forward bias to pb3q;mb4q tdrvz64h b6i p/3hits resistance when conm h 6p pr3;bb dz6t4b/qv4q3ihnected in reverse bias.

Explain how a transistor could be u 40g j21i 4 sm)gqup+mlyaxn3vsed as a switch.

What is the main difference between n-type and p-type semiconductvu8d0v rn1n5jp(x(x kors?

Describe how a pnp transistor can operate as nlb: we1/) ddqan amplifier.

In a transistor, the base-emitter junctigxx;:hk rzb7t7*/y b bon and the base-collector junction are essentially diodes. A*h7kbx/ tygr x;: bbz7re these junctions reverse-biased or forward-biased in the application shown in (Fig. Below)?

A transistor can amplify an electronic signal, meaning it can increase the p4ehq4ldtmqk:+.5xu tc9 n3 huower of an input 4t en :txlmq4+3cu 9khd5uh. qsignal. Where does it get the energy to increase the power?

A silicon semiconductor is doped with pho0.,f*v7rf4hv ikg2 l jy(zsvcsphorus. Will these atoms be donors or acceptors? What type of semiconductor will this .*7c,vr2hff 0 gi vk4zvsl( yjbe?

  Do diodes and transiqog( c5iy3c vuux6 i4xw *ij iiy11/5cstors obey Ohm’s law? Explain. {yes|no}

  Can a diode be used to amplify a a50p;4 fcme:pwq (frwl3d 6l gsignal? Explain. {yes|no}

  Estimate the binding energy of a KCl molecule by ca097ach)w balklculating the electrostatic potential energy when t9ah)7la c kbw0he $ \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. ri9es2a *8ojy From the result of Problem 1, estimate the contribution to the binding energy of the repelling electron clouds at the equilibrium distan y9r2 o8ase*jice $ r_0 = 0.28\ \text{nm} $. $PE_{\text{clouds}} =$    $\ \text{eV}$

  Estimate the binding energy pg;fwn5cfm+,qx5sef 0d ( bt+7p3jjkof 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, kg1 y qs18:is2z3my yjand then the binding energy in eV per molecule is ymz8j :12ygs1i 3yqskcalculated 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 the states in the formation 2f2/lgs d9 wo :fdcv+nof t2/c v gf2:o wdd9slf+nhe $ \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 quantityjncd),stl2xs7 s+9mmnp6;u b $ \frac{\hbar^2}{2I} $ has units of energy.

  The so-called “characteristic ;g k id/p3ld,8a5ss vxrotational 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 enev 0l7f e,tc5ccp hnfbuy5e+-:rgy, $ \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 q7t+ 4b+a nfrain 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,6.krgiw6o b fnz8-dl molecule given that three successive wavelengths for rotational transitions are 23.1 mm, 11.6 mm, and 7.71 mm.8,.6 b z-ildw6kfngro $r = $    $\times 10^{-10}\ \text{m}$

  (a) Use the curve of 84xj ad+xrq:u (Fig. Below) to 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” Na and Cl ions in a NaCl crystal is 0.26 ez0hz6 fmkh)4 nm. What is the spacing betheh0zf 6)k6zmween two nearest neighbor Na ions? D =    nm

  Common salt, NaCl, has a densmdk7vf(6vm4f si0l y/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 Ku/ qrf7f;jby3vh,c (61thisy Cl whose density is $ 1.99\ \text{g/cm}^3 $. $s$ =    nm

Explain on the basis of energy bands why the s lk/ fr*b;qd9iodium chloride crystal is a good insulator. [Hint: Consideif9; *bd r/qklr the shells of $ \text{Na}^+ $ and $ \text{Cl}^- $ ions.]

  A semiconductor, bombarded with light of slow9vcqzt() po;yy6ci- pns. +e fly increased frequency, begins to conduct when the wavelength of light is 640 nm. E+t6ov -(.cqycieyp;9fp) sznstimate the size of the energy gap $ E_g $. $ E_g $ =    eV

  Calculate the longest-wavelength photon t +)i0 eiby8n yepjp-k-w23qsvhat 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-z* ,gu/ fkh nzbv y5a/to+h9conduction bands in germanium is 0.72 eV. What range of wavelengths can a photon have to excite an e9nu akcz v5o/t * yhz+h/-bgf,lectron 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 are z.a2fi4 os+) ubrx*ws$ 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 phospho5jo m berp*(9+fovg+f 5x+cui agqq;*rus so that one silicon atom in r of g +ove*5j9qp *xcgu;qfbm+5+ia($ 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 enou:4 xm1m( eeyk/r/y lergy gamey1 /mel:y( 4u /rokxp $ E_g = 1.4\ \text{eV} $? $\lambda $ =    $\mu m$

  If an LED emits light of waveleygkw4h t )e28e +n4 c02cx lmgg0zaep1ngth $ \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 characte53y mpt- o)pl.es 3fly;oaxn)ristics are given in (Fig. Below), is connected in series with a ba)oxfp;a-3s opm y)e lly.n53t ttery 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. Below) is con,kgy gw z3o..snected 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 curregmc2i v4z3rx;3t:1cmsni7f s nt, for $ V > 0 $, for the diode shown in(Fig. Below).

  An ac voltage of 120 V rms is to be rs7y;gf: h*b erectified. Estimate very roughly the average current in the output resistr; he 7ysgbf*:or $ 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 forward-bias voltage v: b5, gm7cdueexceeds about 0.6 V. Make a rough estimate of the avvm7 d:c,gube5erage 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 reumt5 k,z mf efk3of05*ctifier (Fig. Below)fef53tm*k,zkmo0 uf5 , 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 relationc 3 t oqe6+oezryou.: +2.xunbship 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 eru5ms5fr 24r;yna+sinergy 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 o ijhzwz3 18g-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 iqi16h aflk.m flm 1(c7s 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 bound cubic la2ahghd )4v *kbo.)gshttice, with each atom connected t .h)v2d ks)gog4habh*o 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 huic3urhee:a *q:*a9 have an activation energy of 1.4 eV. When the molecule is disassociated, 1.6 eV of energy is released. Draw a potential energy curve for this molecule.*hi *raec3 ::uuheq9a

  When EM radiation is incident on diamond, itu-:snz tz 4od/ is found that light with wavelengths shorter than 226 nm will cause the diamo/zz dt ouns:-4nd to conduct. What is the energy gap between the valence band and the conduction band for diamond? $E_g$ =    eV

  A TV remote control emihoawna:6 /mphh fh/464k i1iqts IR light. If the detector on the TV set is not to react to visible light, could it make use of6ah4 mihh: 1qi p// a6owfnhk4 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 atoz3m2sht (cqm*a zo, z 7+t5ecrm in a doped silicon semiconductor, assume that the "extra" electron moves in a Bohr orbit about thesz+,zq z2cmt5*t ea( c h3mro7 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/yc2ai9 o6,hex4j tlf than 1000 nm. For a solar cell to absorb all this, what energy g6ejhy c xoa,t924fl/iap ought the material have? $E_g$ =    eV

  For a certain semiconductor, the longest wavelength radiation that can be absrrvgiook6klo5n15 gg (g6p+/e9 y :ikorbed is 1.92 mm. What is the energy gap r:/koigo pi(nr15g gk6ko9l6eg v+5yin this semiconductor? $E_g$ =    $ \times 10^{-4}\ \text{eV}$

  Green and blue LEDs becamflx4 shf c qvh1f:sr5,k tg:)y9 7g:lne available many years after red LEDs were first developed. Approximately what energy gaps would you ex :7fgfkh5hg ny,rl )s9:lqf t1xcv4:spect 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,qjdjj .i/.ha (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?    $\ \text{k}\Omega \leq R_{\text{load}} < \infty$