2018 NECO PHYSICS PRACTICAL

*PHYSICS PRACTICAL ANSWERS* (2a) In a tabular form: Under tita°: 75, 65, 55, 45, 35 Under MO(cm): 1.1, 2.0, 2.5, 3.4, 3.9 Under NO(cm): 6.2, 6.4, 6.6, 6.8, 7.2 Under H=MO/NO: 0.177, 0.313, 0.379, 0.500, .542 Under Costita: 0.2588, 0.4226, 0.5736, 0.7071, 0.8192 (2axiii) From the graph Slope, S =Δcostita/^ΔH = 0.75-0.45/0.5-0.3 = 0.3/0.2 =1.5 (2axiv) (i) I ensured both the object and the pins were in straight lines so as to avoid error due to parallax. (ii) I made sure there was no air interference (2bi) Snell's law of refraction states that the ratio of the sine of angle of incidence to the sine of the angle of refraction is a constant for a given pair of media. I.e Sini/sinr = Π Where Π is known as refractive index. (2bii) Given refractive index of glass = 1.5 i.e aΠg = 1.5(from air to glass) SinC/sin90 = gΠa SinC/Sinn90 = 1/aΠg SinC/1 = 1/1.5 SinC= 0.6667 C = sin^-1(0.6667) Critical angle for glass C = 42° ==================================================== (3a) (ii) Vo = 2.00v (3av) In a tabular form Under S/N 1, 2, 3, 4, 5 Under R(ohms): 2, 3, 4, 5, 6 Under V(v): 2.10, 2.30, 2.40, 2.50, 2.60 Under R^-1: 0.500, 0.333, 0.250, 0.200, 0.167 Under V^-1(v^-1): 0.476, 0.435, 0.417, 0.400, 0.385 3vii Slope, = Δv^-1/ΔR-1 = 0.5 - 0.355/0.6 - 0 = 0.145/0.6 S = 0.242 Intercept, C = 0.355v^-1 (3aviii) K = S/C K = 0.242/0.355 K = 0.68 (3ix) (i) I ensured tight connections. (ii) I ensured clean terminals. (3bi) (i) Temperature of wire (ii) Cross sectional area of wire (iii) Length of wire (iv) Nature of wire (3bii) Draw the diagram Effective E.m.f = 2v(parallel connection) Effective internal resistance = r * r/r + r = r/2ohms Current, I , 0.8A External resistance R = 2A Using, E = I(R+r) 2 = 0.8(2+r/2) 2.5 = (2+r/2) 2.5 - 2 = r/2 0.5 = r/2 r = 0.5*2 = 1ohms

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