200 exam questions 2020-2021, Exams of Phylogenetics

Download 200 exam questions 2020-2021 and more Exams Phylogenetics in PDF only on Docsity! PHYS 104 Form A Taibah University - Yanbu Branch Faculty of Sciences and Arts at Yanbu Department of Physics Physics (2): Midterm Exam Monday 02nd May 2011 AD, 28th Jumada al-awwal 1432 AH 16:00 a.m to 18:00 a.m Duration of Exam: Two Hours Answer ALL questions in the answer sheet Electronic calculators may be used, provided that they cannot store text USE OF MOBILE PHONES IS STRICTLY PROHIBITED, EVEN AS CALCULATORS A list of relevant constants and equations is provided Each multiple-choice question is marked out of 1 The total mark for this exam is 20 YOU MAY FIND THE FOLLOWING USEFUL ~F = qQ 4πǫ0 d̂ |~d |2 F = k qQ d2 , ~E = Q 4πǫ0 d̂ |~d |2 E = k Q d2 , ~F = q ~E, p = qd, from − to + ~τ = ~p× ~E = pE sin φ n̂ U = −~p. ~E = −pE cosφ ΦE = ∫ ~E.d ~A ΦE = qenc ǫ0 Vab = Va − Vb = − ∫ a b ~E.d~r Vab = Ed (uniform field) Er = − dV dr C = Q V 1 Cs = ∑ 1 Ci , Series Cp = ∑ Ci, Parallel I = dQ dt V = IR Rs = ∑ Ri, Series 1 Rp = ∑ 1 Ri , Parallel P = IV ∑ I = 0 in a junction ∑ V = 0 in a loop I = I0 exp(−t/τ), charging τ = RC PHYSICAL CONSTANTS AND CONVERSION FACTORS SYMBOL DESCRIPTION NUMERICAL VALUE n nano 10−9 µ micro 10−6 m milli 10−3 e electric charge 1.602×10−19 C ǫ0 permittivity of free space 8.854× 10−12 C2N−1m−2 k 1 4πǫ0 8.988 ×109 N.m2/C2 1 12. A wire carries a steady current of I = 2 A. The charge that passes through a cross section of the wire in t = 2 s is: (a) Q = 6.4× 10−19 C (b) Q = 1 C (c) Q = 4 C (d) Q = 2 C 13. For the network of resistors shown in figure 1, what is the equivalent resistance? 1Ω 1Ω1Ω 1Ω a b Figure 1: Question 13 (a) 4 Ω (b) 2 Ω (c) 0.5 Ω (d) 1 Ω 14. In figure 2, the switch S is initially open. The am-metre reads 2.0 A. When the switch S is closed the current in the am-metre becomes: b b 20Ω 60Ω S 15Ω A 70 V Figure 2: Questions 14 - 16 (a) 0 (b) 1 A 4 (c) 2 A (d) 2.33 A 15. In figure 2 (with the switch S closed), what is the current in the 60Ω resistor? [Hint: You may first calculate the potential difference across the resistors 60Ω and 20Ω] (a) 0.58 A (b) 1.75 A (c) 2.33 A (d) 2100 A 16. In figure 2 (with the switch S closed), what is the electric power consumption of the circuit? (a) 150 W (b) 163 W (c) 120 W (d) 75 W 17. In the circuit shown in figure 3, the capacitor is initially uncharged. At time t = 0, the switch S is closed. If τ denotes the circuit time constant, the approximate current through the 3 Ω resistor when t = τ/10 is: b b 6Ω 6µ F 3Ω10 V S Figure 3: Question 17 (a) 1.0 A (b) 0.38 A (c) 0.50 A (d) 0.75 A Questions 18 - 20: A spherical capacitor is made of a spherical conductor of radius a and charge +Q, surrounded by a thin spherical shell of radius b and charge −Q (a < b) (see figure 4). The two spheres are concentric. The electric field is zero everywhere except in the region between the conductors. 18. What is the magnitude of the electric field E(r) within the region a < r < b? where r is the distance from the centre of the spheres. 5 a b + + + + − −− − − −− − + ++ + Figure 4: Questions 18 - 20 (a) 0 (b) Q 4πǫ0 1 r (c) Q 4πǫ0 1 r2 (d) Q 4πǫ0 1 r3 19. What is the electric potential difference across the capacitor: Vab = − ∫ a b E(r)dr? You may assume that ∫ 1 r2 dr = − 1 r . (a) 0 (b) Q 4πǫ0 ( 1 a3 − 1 b3 ) (c) Q 4πǫ0 ( 1 a2 − 1 b2 ) (d) Q 4πǫ0 ( 1 a − 1 b ) 20. What is the capacitance of the capacitor C = Q/Vab (a) 4πǫ0ab/(b− a) (b) 4πǫ0(b− a)/ab (c) 0 (d) 1 4πǫ0 b−a ab END OF EXAM 6