Final Exam of Physics - Answer Key

Final exam of physics( 1. A steady current af 3.9A passing through a bulb for 44 min. How many electrons this will represnt? q = It n = We = 39x44x60 = 10296 C = 10296 1.6x10-19 22 6.435x10 electron 2. A battery contains many cells each & 2 V. A 12V. lead a cid battery Gusists of for all battary 12V for one cell 2V so for battay all cells connected in series ET = ne n== 12 2 6 cells 3. A battery with an electromotive force (emp) & 12V and internal resistance of 12 connected to an external resistor of 52 when the circuit switched on the voltage a cross the battery is... I ===2 A R+r EV+Ir = V = Ir = 12 (2×1) 10 Volt 4. Two bullbs marked 100W, 220V and 60 W, 220V are joined in parallel to 220V suply, Power consumed in circui V 220 0.4545 A 60 = 0.2727 A } IT I, +12=0727 IP = 100 =I2= 220 PTIT V = 0.7272 x 220 = 160 W 5. A three cells each of 2V Connected in parallel, the voltage of the pattery is Same (v) 6. A three cells each 2V connected in series, the voltage of battery is The sum Vi V + V = 2+2+2=6V 7. Two resistance R., R₂ when connected in series their equivelant is to 2 and when connected in prallel their equivelant 2.42 the resistances are... R+R = 10 → R. R2 R+R = 2.4 R= 42 R2-62 R. R 10 2.4 (10) (24) R. R2 24 8. The unit of resistivity can expressed as.. P=R 04/9 JS m = J.Smc 9. when a current (I) flows through a resistance(R) par time (4) the electrical energy spent is given by..... => E= Pt work (energy spent) = I'R t 10. Three equal resistance whe combined in series are equivelant to (902). Their equivelant resistance when combined in prallel will be ... ⇒⇒R₁ = R₂ = R3 = = 30~0 = 0.1 1 30 1 30 30 T RT == 102 ٥٠١ 11. Awire of 2 mm diamder resistivity oxio resistance is 142, It's longth is .... xlo 2.m and its 14x314 x1xk 8x107 12. A wire of length I, and resistance of R. = 10 52 the wire is further drawn so that it's new length 12 = 31, and eross section A, = 3A₂, the new R= A, R= A A L A = R 3 R R = 9 => R 9 R. = 9x10 = 90 13. A heating element of a hot plate on electric cooking draws 11.1 A from 220V mains. How many kwh of energy will be consumed in Ihr and 40 min!? t60+40 = 1oo min EP.t = IV t E = 14.652 x10 J kwh = 14.652x10 3.6 x 105 11.1 x 220 x 100 x60 4.07 kwh 14. In the following circuit R. = 22, R-32, R3=60 if Voltage V=8V, then the total Current(I) is... RRRRR= 3x6 = 22 R2+R 3+6 RT R. +Rx = 2+2=4-2 = I V R = 8 = 2A 4 1271 15. In the Circuit on the right R. 102, R₁ = 15 2. R3 = 202, R4 = 252 and V = 12V. The voltage drop a cross the resistor (R4) is R3 IV R+Ra = 12 =0.2667 A 45 V₁ = I2 R4 = 0.2667X25 V4 = 6.667 volt R3+ 24 450 250 16. In the circuit on the right R₁ = 222, R2 = 1852 R3=362 The Current passes through R3 = 0.3A. The current passes through R₂ is...... V = Iy R3 = 0-3×36 V= 10.8 Volt Ix RitR Ix V 10.8 = = Ri+R 22+18 Iy Rs Ix = 0.27 A 17. An object can be seen as result of (reflaction) 18. As the angle of incidence is increased for aray incident on a reflecting surface, the angle between the incident and reflected rays ultimately approaches what value? = 180° 19. A ray of light makes 44° with a mirror. what is the angle between the incident ray and the reflected ray? =92° 44 20. Two perpendicular mirrors, a light ray incident at 35 on horizontal mirror is reflected back on vertical mirror at angle........ = 55° 21. The refracted index of water is 1.33 what is the speed of light in water? V = = = 3x10 = 2.2556x10 m/s n 1-33 22. Aray of light in air is incident on an air to glass boundary at an angle of 39° with the normal. If the index of refraction of glass IS 1.63, what is the angle of refracted ray withen glass with respect to normal? n, dine, nesίηθε sine = n, sine Sine2 = (4) sin(39) 1-63 1 2 = sin 0.386 = 0.386 22.71 23. If the critical angle for internal replaction inside ceratin • transparment material is 43, what is the index of refraction of the material? (Air is outside the material) Sinec nz Sin 43 = 1 1 Sin 43 = = 1.466 24. A light suffers 7 total internal reflaction in obtical fibers, there fore its emerging intensity I relative to initial one I. is :- I = 7 (0.95) Io = (0.95) I. = 0-69831. 25. which of the following best describes of image formed by a plane mirror? Virtual - upright and same size as object 26. At what distance an object must be placed in front of concave (converging) mirror, it's focal length 15 cm to obtain a magnified real image 2 times the object size M=-2 M=-9 P +2 → P 2) (9-2p) 2P P+2P 3X15 x 2D 3p 22.5cm P P+q 27. An object placed 28 am in front of convex (diverging) mirror that has focal length of 15cm. The location of the image is at P-f ... f = - 15cm 28x(-15)= -9.77 cm... 28+15 do = 28 cm 28. An object is placed 16cm in front of a thin convex (Converging) lens of focal length 12 cm. The location of image? q= Pf P- 16 x 12 16-12 = 48 cm Fest 29. A concave (diverging) lens of fool length - 10cm. At what position in front of the lens an object must be placed to obtain a reduce image of one quarter of the body? M = +4 9=-=-0.25p P = = -10 -0-33 -0.33 = 30cm -0.25 P 0.75 P P 9+P = = -0.33p 30. The magnifications power of eyepiece and object leus in microscope are 3,4 respectivaley. The total magnification power is M = M, M2 = 3x4 - 12 31. The object distance is given by :- X32. A star radiate electromagnetic radiation its dominant wavelength is 491.5ym. what its temprature? max T = 2.9x10 T. 2.9x10 2.9x103 = = 9 491.5×10 5900.3 k