2018 Waec Gce Physics Practical Answers

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(1a)
Tabulate:
xi(cm)|yi(cm)|zi(cm)|W1(Nx10^-2)|W2(Nx10^-2)|u=(w1-w2)(Nx10^-2)|v=(w1-w3)(Nx10-2)
=>1.80|1.50|1.70|3.6|3.00|3.40|0.60|0.20
=>3.80|3.00|3.00|7.6|6.00|6.00|1.60|1.60
=>5.50|4.40|5.00|11.10|8.00|10.00|2.20|1.00
=>7.30|5.90|6.60|14.60|11.80|13.00|2.80|1.40
=>9.20|7.30|8.30|18.40|14.60|16.60|3.80|1.80
=>11.10|8.30|10.00|22.20|16.60|20.00|5.60|2.20
(1b)
Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity usually means relative density with respect to water.
(1bii)
Given volume of solid immersed
Vsi =1/2*30cm³
=15cm³
Density of liquid (water)ew= 1g/cm³
Acceleration due to gravity, g = 10m/s²
Upthrust, U= eVsi g
U= 1000*(15*10^-6)*10
U=15*10-²
U=0.15N
Weight of solid =mg
=EsVs g
given: Es=2.4g/cm³ (2400kg/m³)
Vs=30cm (30*10^-6 m³)
g=10m/s²
Weight, w=30*10^-6*2400*10
=72*10-²
=0.72N
Reading on spring balance =W-U
=0.72-0.15
=0.57N
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(2)
In a tabular form
Under S/N
1, 2, 3, 4, 5

Under ACi/cm
7.20, 7.80, 8.10, 8.70, 9.30

Under BCi/cm
2.10, 3.70, 4.30, 5.30, 6.30

Under titai(Φ)
68.0, 48.0, 38.0, 28.0, 20.0

Under U = BC/AC
0.2917, 0.4744, 0.5309, 0.6092, 0.6774

Under cos tita(Φ)
0.3746, 0.6691, 0.7880, 0.8829, 0.9397

(2av)
(i) I would avoid error due to parallax.
(ii) I would ensure right position of ruler while taking readings.

(2bi)
Principal axis is an imaginary line passing through the center of the lens in which the principal force of the lens passes through.
(3a)
R ohms
R1 = 1ohms R3 = 3ohms
R2 = 2ohms R4 = 4ohms
R5 = 5ohms
V1 = 1.90v
V2 = 2.15v
V3 = 2.3v
V4 = 2.40v
V5 = 2.5v

In a tabular form
Under S/N
1, 2, 3, 4, 5

Under R(ohms )
1.00, 2.00, 3.00, 4.00, 5.00

Under V(v)
1.90, 2.15, 2.30, 2.40, 2.50

Under R^-1(ohms^-1)
1.000, 5.000, 0.333, 0.250, 0.200

Under V^-1(V^-1)
0.5263, 0.465, 0.4347, 0.4167, 0.400

Under R^-1/V^-1
1.900, 1.07, 0.768, 0.5999, 0.500

(3avi)
(i) Ensure tight connections.
(ii) Avoid error due to parallax when reading the voltmeter

(3b)
(i) Length of wire
(ii) Nature of wire

(3bii)
Total resistance,
R = 3 + (3×3)/(3+3)
R = 4.5 ohms
Current, I = V/R
I = 6/4.5
I = 1.33 A