# 2020 waec Physics Practical Questions and answers

Thursday 20th August 2020
Physics 3(Practical) (Alternative A)(1st set) – 9:30 – 12:15pm
Physics 3(Practical) (Alternative A)(2nd set) – 12:45pm – 3:30pm
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1axi)
PRECAUTIONS
(i) I ensured that the metre rule balances horizontally before readings are taken in order to avoid experimental error.
(ii) I ensured that parallax error was avoided when taking the readings on the metre rule by viewing its calibrations vertically.(1bi)
The moment of a force about a point is defined as the effect of force about that point.
Moment of a force = force × perpendicular distance of its line of action from the point.Moment = F × h
The S.I unit is Newton-metre(Nm). It is a vector quantity(1bii)
Draw the diagram

X = 50 – 25 = 25cm
y = 80 – 50 = 30cm
From the principle of moment :
Sum of clockwise moment = sum of anticlockwise moment
60x = M × y
60×25/30 = M×30/30
M = 60×25/30 = 6×25/3 = 2×25
M = 50g

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(3ai)
E = 3.00V

R(ohms) | I(A) | V(v)
1.0 0.40 0.65
2.0 0.35 0.58
4.0 0.28 0.50
6.0 0.22 0.45
8.0 0.18 0.40

(3aix)
(i) I avoided error due to parallax when reading the ammeter and voltmeter.
(ii) I ensured tight connections.

(3bi)
(i) It increases current supplied.
(ii) It makes up for any defect in any of the cells.

(3bii)
(i) Resistivity of the wire or coil.
(ii) Length of the material  