oot ) we Knowledge Innovation Excellence BUNDA/CITY CAMPUS BASIC SCIENCES DEPARTMENT 2018/19 ACADEMIC YEAR PHYSICS I - PHY 121 END OF SEMESTER ‘| WO EXAMINATION Instructions: ~gh 1, Write your name, student ID number and programme on the answer book. 2. This paper contains 4 questions and 4 pages. 3. Answer all questions in the answer book. 4. Formulae are given in the appendix on the last page.QUESTION 1 .e modes of heat transfer Gmarks) a. State dn nal conductivity of 0.25 Wimi*C. If the b. A concrete wall of'sides 3m by 2 bas «th wall ig 0.3 m thick and hay outside and inside temperatures of 25°C and 15°C determine the rate at which heat is transferred through the wall from (6 marks) respectively, ouside. .. A circular pan is removed from fire after reaching a temperature of 125°C: and is placed wounding air has a heat transfer coefficient AD on bare ground interact wit it.The of 0W/m7/°C and receives heat at the rate of 2000 W from the pan, Calculate the x ~ temperature of the air given that area of the pan is 2 m*. (6 marks) & \ d. Calculate the energy radiated in one minute by a black body of surface area 0.2 m” maintained at 400 K. (Boltzmann constant = 5.67x 10" Wm"K“J. (S marks) QUESTION 2 a. Define thermodynamics (2 marks) b. State the following: - i, Zeroth law of thermodynamics (2 marks) ii, First law of thermodynamics. (2 marks) eA gas expands from 175 @ to 225 £ at constant pressure of 4 atm. [f one atmosphere is 1.0 x 10° Nm”, calculate the work done by the gas during ‘expan (4 marks) 4. The source temperature of a Camot engine is 127 °C. IL takes 500 cal of heat from the source and rejects 400 cal to the sink during each cycle. What is the temperature of the sink? (4 matks) e. A farmer designed a freezer to produce ice for the storage of perishable farm produce. The designed freezer is a reverse Camot engine and extracts 42 kJ as heat at -15°C during each cycle. If the freezer has a coefficient of performance of 5.7 and operates in a store room whose temperatures 303°C, calculate the amount of heat energy per cycle delivered to the room. (omatsyovestions 4. “A tyre of afar tractor is filled to a gauge pressure of 400 kPa at 20°C. After driving 200 km the temperature within the tyre rises to 80°C. Determine the new pressure in the tyre at 80°C. (6 marks) b. A thermometer of mass 0.0550 kg and of specific heat 0.837 ki/kg.K reads 15.0°C. It is then completely immersed in 0.300 kg of water, and it comes to the same final temperature as that of water. If the thermometer now reads 44.4°C, what was the ‘temperature of the water before insertion of the tiermometer? (7 marks) Calculate the value of the resistor R required to be used in an immersion heater to raise the temperature of 1.5 kg of water from 10°C to 0°C in 10 minutes while operating at nov. (7 marks) QUESTION 4 a. Explain any two similarities between an electric feld and a magnetic field. (4 marks) ». Using Figure 1, calculate the magnitude of: i, current i) passing through R (2 marks) i Voltage, Vs Gmahs) Figure 1: Electrie eireuit #12 aC and Qy = +15 uC are placed at the vertices of a triangle as «. Two charges Q shown in Figure 2, Caleulate electric field intensity at point A. (9 marks) yy Figure 2: Electric charges END OF QUESTION PAPER. a ia aaaAPPENDIX A TABLE OF FORMULAE SIN ] FORMULA 1. T,-Tr =Al | a 7 2 [a= Ah, — 0) a tl 3 P= oeAT* ts O of 4. Qn =W+, § 5 a Th gy Gan rs S ca 5 Qu TH ww Ei 2318 & coP tr A go S 5 RI- 7 Q=mcaT 8 [ke = 9x10°N.m?C? 9. KeX41X G2 Fo ee 10 = heq Fo@ Knowledge Innovation Excellence BUNDA/CITY CAMPUS & ODL PROGRAMME. BASIC SCIENCES DEPARTMENT. 2019/20 ACADEMIC YEAR PHYSICS Il - PHY 121 END OF SEMESTER TWO EXAMINATION DATE: 11% June, 2021 TIME: 3Hrs (09:00 - 12:00) — I ts (09:00 = 12:00) Instructions: 1, Write your name, student ID number and programme on the answer book. 2. This paper contains 4 questions and 4 pages. 3. Answer all questions in the answer book. 4. Formulae are given in the appendix on the last pageQUESTION 1 a, State the Torricelli’s theorem, (2 marks) b. Determine the head of a siream of water moving at 20 mis. G marks) . Heat amounting o 845 J is added to 2 0.200 kg aluminum block at 312 K. If'specifie heat of aluminium block is 903 Jikg/K, calculate the final temperature of aluminium block. (5 marks) 4. The wall of an industrial furnace is constructed from 0.15 m thick fire-clay brick having a thermal conductivity of 1.7 WirVK. Measurements made during steady-state ‘operation reveal temperatures of 1400 K and 1150 K at the inner and ovter surfaces, respectively. Determine the rate of heat loss through a wall that is 0.5 m by 1.2 m on aside (5 marks) Calculate the Coefficient of Performance (COP) of a reftigerator whose source and sink temperatures are 27°C and -3°C respectively (5 marks) | Ak C QUESTION 2 a. Define the following terns as used in thermodynamics (S marks) ai, Process be Vailhe ¢ Bf 2 iv. Entropy Th o\sus ve HeatEnging 4) v b. Ana eylindr for a seuba diver contains 180 moles oF ai at 15 °C. The eylinder has a volume of 0.012 m? Calculate the volume ofthe gos when tis released a 100 kPa and 25°C. (R= 8.31 Jik/mal. (S marks) ‘A.gas expands from 200 m? to 250 mata constant pressure of 6 atmospheres afer seceiving00 J of heat. IF 1 atmosphere is 1.01 x 10* Pa, determine the change i intemal energy ofthe system (5 maths) 4. A Camot engine designed by a Fist year engineering student at LUANAR delivers 746 3 of work when iis operating between 27 °C and 227 °C, Calculate the amount thea supplied 19 the engine (S marks) Ame vy ape UK, \QUESTION 3 a Briefly explain the major difference between cect force andelectre fel intensity (2 marks) b, Three negative charges; Q, 4uC, Qa + 2UC and Qs = = 3pC are placed at the vertices of an equilateral triangle as in Figure 1. Caleulate the magnitude of the resultant electrostatic force on Qe due to the other two charges. (10 marks) vet Figure |: Electric charges . A farmer designed a circuit for a chicken kraal as shown in Figure 2, Calculate the magnitude of voltage across the 80 resistor. (S marks) 4. Determine the magnitude of the force required to move an electron in a 12 * 10°T ‘magnetic field at 2 mvs. (q= 1.6 * 10°C), (3 marks) QUESTION 4. r ee ‘a. Briefly explain why light is considered asa ‘ s i Wave 2s rks) ii, Particle (2 marks) b. A wave of ight of wavelength 600 nm is traveling in fre space. Calculate the: i. Frequency ofthe wave (4:marks) fi, Velocity of the wave in a block of diamond whose n= 2.4 (4 marks) iii, Wavelength of light in a block of diamond. (4marks) 3¢.A light ray moves from 4 block of eubic zirconia into a piece of crown glass. Ifthe ray makes an angle of 20° in crown glass, determine the angle of refraction in cubic zirconia given that indecies of refraction for cubic zirconia and crown glass are 2.2 and 1.52 respectively. (4 marks) , END OF QUESTION PAPER, a Ge Or —o A TABLE OF FORMULAE : feracie rea FORMULA 7 A to 1, 2 9 = Ak Se tC. = ith ao NG e LK o®& i “ 4 he N \ oe a Af Er