2018 WAEC GCE PHYSICS PRACTICAL ANSWER NOW AVAILABLE.

(1)
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

1aix )
(i) I avoided parallax error in reading clock / weight balance
ii) I ensue repeated readings are taken to avoid random error

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=
(2a)
Tabulate
S/n | Ag/cm | 8C1/cm | tiata | U= Bc/Ac | cost Rita |

Under S/n: 1, 2, 3, 4, 5

Under Ag/cm: 7.10, 7.90, 8.10, 8.70, 9.35

Under 8C1/cm: 2.10, 3.60, 4.25, 5.30, 6.40

Under tita: 70, 46, 35, 25, 19

Under U = Bc/Ac: 0.29, 0.45, 0.52, 0.60, 0.65

Under cos tita: 0.34, 0.69, 0.80, 0.90, 0.94

(2av)
(I) I would avoid error due to parallax
(II) I would ensure right Postion of the ruler while taking the reading

(bii)
H2 = 2cm, Do = 6cm
H2 = 6cm
H2 = 4.1cm
M = Hi/Ho = 4.1/2
= 2.05
M = Di/Do = 2.05 = Di/6
Di = 6 x 2.05 = 12.16
= 12.3cm

(2bii)
Principal axis is an imaginary line passing through the center of the lens in which the principal force of the lens passes through.

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(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

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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

(3av)
Slope = Change in R^-1/V^-1/Change in V^-1
=2.5-0.25/0.6-0.38
=2.25/0.22
= 10.23

(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

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