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自然科學 大學

求解答案是否正確

Multiple-choice questions: (70 points) write the letter of statement that is not true: 1. A.B.U The Drude Model: (a) It is a classical approach using concepts from the kinetic theory of gases. (b) A relaxation-time approximation is used where the probability of collision is l/t. (c) No forces act on the electrons in between collisions. (d) It predicts accurately the electronic heat capacity of metals. 2. The Sommerfeld Model: (a) The crystal potential is replaced by an average Coulomb potential. (b) The separation of states is so close that a continuum model can be applied. (c) The electrons are highly localized due to a strong crystal potential. (Q) The energy of the highest occupied state at 0 K is the Fermi energy. 3. Density of states in k-space, N(k): (a) N(k) is determined by the boundary value conditions. (b) For lattices in any dimensions, N(k) is constant in k-space. (C) N(k) depends on the direction and magnitude of k. (d) It is directly proportional to the volume of the crystal. E影響, c 4. The Fermi surface of a metal: (a) is responsible for many of the transport properties of the metal, (b) depends on the nature of the chemical bonds, (c) is always a sphere, (d) can involve mixing of electron orbitals. ✓ 5. The conductivity of a material () increases with the mobility of its carriers, (b) increases with the density of carriers, (C) it is inversely proportional to the energy gap. cogu changes with temperature. 6. BID Plasmons: (a) They are an important characteristic of the Sommerfeld electron gas model. (b) Plasmons occur spontaneously in metals. (c) They are related to charge density oscillations. (d) The Plasmon energy is typically of the order of 10 eV. The Fermi energy Ef in intrinsic semiconductors 8) is usually close to y E, at OK (b) it ACiD. can increase or decrease with temperature depending on the ratio of hole and electron effective masses, (c) it represents the point at which the probability of occupation is 12, even though there may not been any states with that energy, (d) its value relative to the electronic bands must remain unaffected in the presence of defects or interfaces.

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自然科學 大學

請問第七題怎麼解

60 s, turn 90 20 km/h for 2.0 min, turn 90° to the point, (a) how far are you from your starting point, and what direction relative to your initial direction of travel are you? V During volcanic eruptions, chunks of solid rock can be blasted out of the volcano; these projectiles are called volcanic bombs. Figure 4-22 shows a cross section of Mt. Fuji, in Japan. (a) At what initial speed would a bomb have to be ejected, at angle 0o = 60.0° to the horizontal, from the vent at A in order to fall at the foot of the volcano at B, at vertical distance h = 2.60 km and horizontal distance d = 9.40 km? Ignore, for the moment, the effects of air on the bomb's travel. (b) What would be the time of flight? (c) Would the effect of the air increase or decrease your answer in (a)?onatlar slow orl w moito Movisio Olovo vibolov te tootsodio dos olvistatani se moltotib nur no vodo as vd botu 29 vd baidot otsi Nomstl moll bottom 12 A plane flies 5 then 1100 km sout) trip, what are the displacement, the velocity, and (e) is 13 An astronau of 4.5 m. (a) Wha eration has a ma minute are requ period of the m 14 A basebal mum height al after reaching that is 86.0 m (a) What may ball? (b) How the ball strike blitt 00 Troede Vibolov sister sam 12 d B 15 The ran also on the place to plac broad jump (where g= by how mu instead in 1 Figure 4-22 Problem 7. 8 Oasis A is 90 km due west of oasis B. A desert camel leaves A and takes 55 h to walk 75 km at 37° north of due east. Next it takes 45 h to walk 65 km due south. Then it rests for 5.0 h. What are the (G) magnitu Cia

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自然科學 大學

求全部詳解,在線等,急QQ(可以部分就好QQ

Pt 謹., 【G@放|中葉生說1 2018-test2-ch26-30 - 訪取0專用 入 圖 器 當數: so=8.85x1072F/m 一、選擇題:每題5分。 1一平行板電容器,若其每板面積為 100 cm?、兩板相距2mm。用 80V 的電池充滿電後,電容上的電荷量為: 0885nc; (8) 177nc;(c)354nc;(0) 708nc (51416nc。 2 南顆電容 G =10uF、G0=20 jiF 串聯後再連接一烽 12 V 的電池。求兩顆踢容總共儲存的能星。 多360p; 480nJ (0) 600nJ; (0) 720 1; (E) 840nJ。 3 一2hF 的平行板電容器,將其連接至 200V 的電池,充滿電後, 不移開。再將介電常數 <=10 的電 介質填滿十板間的空間,則此時電容儲存的艇量為多少?(多005J;(8) 01J;(c) 02J;(D) 04J; 四08 J 4 如右回,電容 帶電 0-8hC,電容 3C不帶電。將開辣閱上,經很久達平衡(此時電流為零)。若C=1hF,則從開始到最終 平衡時,電月R總共消耗的能星為 (8mJ; (8) 12mJ3 (0 16m (0) 20m0; 24nJ。 5 一 吃放電線路 :A=104Q,C=200 hF,電容的初電荷為10 mc。/=0 時,開始放電,則/=2s時,電流為 (人 184mAy 個368mA;(c) 539mA;(D)717mA; (E 904mA2 6一電荷 ?,其骨時速度# = 玉m/s,位於均勻磁場中2-(F+ 縣 245T,則其受力了= (CC2二片絡 (2C244片3 (02C2二中遇 (0)22中片朮(5202中4此嫩 7 一電子(=91x103 kg 7= 1.6x10? 0)以 1.2X10? m/s 的遠率進入一均勻磁場區域內作圓周運動磁場方向與速度方向垂 直, 若磁場大小為 01T,則其財期為 (A 12x1009s7 (8)36x100s; (tc)62x1006s;(0)76x1030s (四97x1009s。 8右圖中立方體的邊長為 40 cm, 電流 /= 10 A, 均勻磁場 52=02T, 則 09 段受到的磁力為: 人(95(症生N (80s(二全N3 (095二生N) (Do9sFN3(ED-95N3 二、計算題 1. Foureapactors are connectedas shownimnFig 1 Take Go 4pnF,人6 @2nF, =2nFande=14V Fmnd (the equivalentcapacitance;(b) the charge on Gi (c) the potentaldifferenceacross @(12仿 2 Forthe Acchargng crcutofFig 24akeA=100kg,c= 2nF,ande=20V heswitchisclosedat/=0.Fnd (a) tme constant tb) he maximum charge and curent (c) the charge on ihe capacftorat/=015(d) hecurentat/015(@ thepowerimthebatteryat/=01s。(20幼 3 Find (a) the currents 4、&and 6; (b) the potental difference between ponts 2and cinFig 3.(15 約 4 圖四的電路,將開關關上,經很久以後,(a)電流 +、/Z各為何 ? (b)電容上的電荷量為何 ? (c) 今將開關打開 ,則經多久後電容 的電荷量為10uC。(12 爺 5 如圖五,兩根通電流的長直導線:4=3Aand&=5A。若 7= 20 cm,求 人點磁場及與吃。(10 分)

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