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自然科學 大學

為什麼不是E

Q搜尋 07.pdf Chapter 7: Atomic Structure and Periodicity 1. When ignited, a uranium compound burns with a green flame. The wavelength of the light given off by this flame is greater than that of A) red light B) infrared light C) radio waves D) ultraviolet light E) gamma rays ANS: D PTS: 1 DIF: Easy REF: 7.1 KEY: Chemistry | general chemistry | atomic theory light | electromagnetic radiation MSC: Conceptual 2. Which form of electromagnetic radiation has the longest wavelengths? A) gamma rays

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自然科學 大學

求解法 謝謝 (普通物理)

1. Consider a particle moving with the acceleration vs. time graph as in Fig. 1. a, and to are constants with unit in m/s2 and s. Assume the particle is at rest and at origin (L) at t = 0. (a) Find the velocity v(t) for each interval (i.e. 0<t< to, to <t< 2to, 2t, <t (b) Find the displacement x(t) of the particle for each interval. (c) What are the velocity and displacement of the particle at t = 3t0? Fig. 1 an 2ao w ao to to 8:03 来搜寻 co 33°C D

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自然科學 大學

問14題

3. 开 4. 47. 將3庫命之電荷由A點移至B點點,需作功18J,則A與B點間之電位差為多少? 100W燈泡使用20小時,損耗幾度電? 有一抽水馬達輸入功率為500W,若其效率為80%,求其損失為多少? 將4庫命的電荷通過一元件作 200,則元件兩端的電位差為多少? 有一 1500W的電熱水器,連續使用2小時,如果每度電費為2元,則應繳電費多少元? 8. 將10C 電荷,在5秒內由電位10V 處移到70V處,則平均功率為多少? 某導線上之電流為3A,則在10分鐘內流過該導線之電量是多少? 10.一電池以定電壓 1.5V供電 9mA 連續10小時,此 電池所提供之能量為多少? 11. 直徑為5密爾圓形實心導線,其截面積為多少?圓密爾? 2. 電阻值若為120 + 5% 2,則其色碼順序為何? 13. 一個2k2 電阻器和電連接後,有6mA 電流流過,若電池現和6002 電阻器連接,此電 阻器上流過的電流為多少? V14. 有一導線其電阻值為502,現將其拉長(導線不斷裂),使其線徑為原來之一半,其電阻 值為多少? 15. 某電阻值為102 之負載,通有 4A 之電流,則於一分鐘內轉換為熱之能量為多少? 16. 某電機之銅線繞組在30°C時之電阻為100m2,當電機運轉後,溫度上升至80℃,試 求此時電機繞組變為多少? 1-23

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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

e.f.g這三題不知道要如何解釋,請各位大神幫忙解題謝謝

1-8. Consider two inertial reference frames. When an observer in each frame measures the following quantities, which measurements made by the two observers must yield the same re- sults? Explain your reason for each answer. (a) The distance between two events (6) The value of the mass of a proton (c) The speed of light (d) The time interval between two events (e) Newton's first law (f) The order of the elements in the periodic table (g) The value of the electron charge

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自然科學 大學

請問這題該怎麼解

Show Attempt History Current Attempt in Progress X Incorrect The device shown is a part of an automobile seat-back-release mechanism. The part is subjected to the 6.7-N force exerted at A and a 360-N mm restoring moment exerted by a hidden torsional spring. Determine the y-intercept of the line of action of the single equivalent force. Your answer will be positive if the intercept is above and negative if below O. F = 6.7 N 20 mm 27° 46 mm 360 N.mm o Answer: y = i -12.75 mm e Textbook and Media Attempts: 4 of 5 used Submit Answer Save for Later 32°C 小雨

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自然科學 大學

請問這題怎麼解 要用什麼公式?

In 2014 the Philae spacecraft became the first artifact to land on a comet. Unfortunately, Philae bounced off the comet's surface and ultimately landed in a nonideal location. After its first contact, Philae was moving upward at 38 cm/s, and it rose to a maximum height of about 1 km. Estimate the gravitational acceleration of the comet, assuming it's constant (not a very good assumption in this case).

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