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問題的種類

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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英文 高中

錯誤的地方有點不理解,現在是在高一先修的部分,求解錯誤的地方 謝謝🙏

garage 18. There was something wrong with my car; therefore, I sent it to the and got it O ( (B) to check A (A) examined 26. All the passengers should keep their seatbelts during the flight. (A) fastened (B) fastening (C) fasten (D) been fastened )27. Michael went to work in a hurry and left the door ( - (B) open Don (C) to repaired (D) be fixed 19. He failed to make himself in French; none of the audience spoke English. (A) understand begao (B) to understand (C) to be understood (D) understood 20. Airplanes make it possible for us ♡ A ( (A) to open (C) opened (D) openly 28. Michael felt that little girl his hand. (A) pull (B) is pulling (C) pulled (D) to pull 229. Don't leave the water (A) run (B) to run (C) running (D) ran )30. Choose the correct sentence. (A) I found her stared out the window. (B) He was heard to sing a beautiful song, (C) I got him finish his homework. (D) Don't keep me wait too long. O ( long distances in a relatively short time.bosted on SA (A) traveling (8) (B) to travel (A) (C) travel show (1) (D) for traveling 121. What's making the lake? 520 x 20 bar (A) pollutes (B) to pollutem ad (C) be polluted (D) polluted) )22. On my way home, I found a frog by a car on the road. (A) to run overkow 35 (B) running over (C) ran over (D) run over iq393 )23. You had better that bad tooth pulled out. sos (A) have protes W2 (B) letgols yngstown (C) made (D) move ( 1924. I saw a thief your store a few minuses ago. TOTO (A) breaks into (B) broke into it to (C) break into (D) to break into ( in the house and told him not to do that again. (B) smokedowe (D) is smoking 上。 & )25. My mom saw my dad (A) to smoke (C) smoking 10

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英文 高中

為什麼25不能選B

When a person sneezes, 崗e droplets can Spread diseases. Now ress 8 that blants have asomewhat 多 problem. Plant diseases can also spread througeh ater d 全 Water drops 世at jump offF leaves 一 aplant's version ofa sneeZes Scientists already knew earlier that wind and splashes of rainw ater can move bacteri and other germs from leaf to leaf (edge Other possible transmission routes. Tesearechers at Virginia Tech observed water drops on the leaves of wheat plants that were lnfected witt leaf must They found that the sick plants could “sneeze”and _為 timy water drops filled witl Jeafrust germs, Spreading the disease to heighboring plants. The researchers noticed that small drops of water on the wheat leaves Would move t6 combine and form a ]arger drop. As 也ey were moving, the energy of the droplets in motion Would be released. This energy allowed the water 2 into the air which looked just like SneezZlng! However, not all plants can sneeze. The ability is 2 to those With leaves that are hydrophobic, or repel water 一 a special feature that forees the liquid to move away when the eaf is exposed to 半 太 外1 (A) similar (B) miserable 蔬 旋 (A) As aresult of (B) In asearch for Cl realistic (D) temporary ( (CO With aview to (D) To the extent 0+ 信 (2 shoot out 選hold On (C) come across 售 give up 【 多 (A) jump (B) to jump (C@ jumping D) jumped 私 為 (A) curious (By relative (C) unique Di primitive 【

尚未解決 回答數: 1