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Physics
WAEC / WASSCE 2021
Electricity and Magnetism
Solution
The reason for laminating the soft iron core of a transformer is to?
A
reduce eddy current.
B
reduce magnetic flux.
C
increase the magnetic flux.
D
reduce its efficiency.
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Laminated iron core means insulating layers glued compact. Now the cores are laminated to reduce Eddy current.
Source: Myschool Past Questions Archive (Record #61869)
Physics
WAEC / WASSCE 2021
Electricity and Magnetism
Solution
Formation of hydrogen bubbles at the copper plate of a primary cell is called?
A
polarization.
B
back e.m.f.
C
electrolysis.
D
local action.
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Polarization:The hydrogen bubbles which are clinging over the surface of copper electrode anode becomes a thin film of hydrogen over the copper electrode.
This hydrogen film increases the internal resistance and reduces the emf of the cell and hence the cell soon becomes inactive. This effect is known as polarization
Source: Myschool Past Questions Archive (Record #61870)
Physics
WAEC / WASSCE 2021
Waves and Optics
Solution
Opening in the eye through which light passes to the retina is called the?
A
pupil
B
cornea.
C
iris
D
optic nerve.
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
The function of the pupil is clearly that of controlling the amount of light entering the eye, and hence the light reflex.
Source: Myschool Past Questions Archive (Record #61874)
Physics
WAEC / WASSCE 2021
Electricity and Magnetism
Which of the following actions will increase capacitance of a parallel plate capacitor?
I. Decreasing the distance between the plates
II. Increasing the distance between the plates.
III. Increasing the area of the plates overlap.
IV. Avoiding the use of dielectric between the plate
A
I and III only
B
II and III only
C
I and IV
D
. III and IV only
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #61889)
Physics
WAEC / WASSCE 2021
Mechanics and Properties of Matter
The acceleration of a moving object can be determined from the?
A
slope of its distance-time graph.
B
area under its distance-time graph.
C
slope of its velocity-time graph.
D
area under its velocity-time graph
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #61899)
Physics
WAEC / WASSCE 2021
Heat Energy & Temperature
A student wishes to measure the potential difference across a resistor,R. She has a galvanometer,G and some connecting wires.
What else does she need?
A
high value resistor connected in parallel with G
B
. low value resistor connected in parallel with G low value
C
resistor connected in series with G
D
high value resistor connected in series with G.
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #61900)
Physics
WAEC / WASSCE 2021
Mechanics and Properties of Matter
Solution
The handle of a screw jack is 35 cm long and the pitch of the screw is 0.5 cm. What force must be applied at the end of the handle to lift a load of 2000N, if the efficiency of the jack is 30% [\pi = \(\frac{22}{7}\)]?
A
152.0N
B
132.0N
C
15.2N
D
440.0N
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
GIVEN:
Handle length r = 35cm = 0.35cm, pitch of screw = 0.5cm = 0.005cm, load W = 2000N, efficiency = 30%
V.R of screw = \(\frac{2\pi r}{p}\) = \(\frac{2 \times \frac{22}{7} \times 0.35}{0.005}\) = 440
Eff = \(\frac{\text{M.A}}{\text{V.R}}\) x 100
M.A = eff. x V. R = 0.3 x 440 = 132
Effort = \(\frac{L}{M.A}\) = \(\frac{2000}{132}\) ≈ 15.2N
Source: Myschool Past Questions Archive (Record #61901)
Physics
WAEC / WASSCE 2021
Heat Energy & Temperature
Which of the following statements about the molecules of solids and liquids is correct? They both
A
have weak attraction.
B
have wide separations.
C
exhibit random motion.
D
exhibit vibratory motion.
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #61881)
Physics
WAEC / WASSCE 2021
Electricity and Magnetism
Solution
Which of the following units is equivalent to the unit of electric current?
A
C s\({-1}\)
B
W
C
J s\({-1}\)
D
C
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Q = It
I = Q/t
I = C / s
= Cs\(^{-1}\)
Source: Myschool Past Questions Archive (Record #61905)
Physics
WAEC / WASSCE 2021
Waves and Optics
Diagram
Solution
Determine the speed of the wave.
Attached Figure / Diagram
A
64 cm/s
B
32 cm/s
C
24 cm/s
D
72 cm/s
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Speed = Wavelength x Frequency
or
V = f\lambda, where frequency = \(\frac{1}{\text{period}}\), f = \(\frac{1}{\text{T}}\).
The period was given as 0.125sec and wavelength = 9cm
: f = \(\frac{1}{\text{T}}\) = \(\frac{1}{0125}\) = 8.
V = f\lambda = 8 \times 9 = 72m/s
Source: Myschool Past Questions Archive (Record #61950)
Physics
WAEC / WASSCE 2021
Waves and Optics
Solution
Which of the following curved surfaces will produce a real image? I. Concave mirror II. Convex mirror III. Diverging lens IV. Converging lens
A
I and III only
B
I, II and IV only
C
II, III and V only
D
I and IV only
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Concave mirror: A concave mirror can produce a real image when the object is placed outside the focal point. While, Convex mirror: a convex mirror always produces virtual images.
Diverging lens: A diverging lens (concave lens) always produces virtual images. While, Converging lens: a converging lens (convex lens) can produce a real image when the object is placed outside the focal point.
Source: Myschool Past Questions Archive (Record #61959)
Physics
WAEC / WASSCE 2021
Heat Energy & Temperature
Solution
The components of vectors Q and R are (-3.0, 5.5) and (9.2, 4.4) respectively. Determine the components of Q + R.
A
(3.7, 7.4)
B
(6.2, 9.9)
C
(2.5, -4 .8).
D
(14.7, 1.4)
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
Put the vectors in their component forms
Q( -3.0i, 5.5j) and P(9.2i, 4.4j)
Q + P = -3.0i, 5.5j + 9.2i, 4.4j = ( - 3.0 + 9.2)i + ( 5.5 + 4.4)j = ( 6.2i + 9.9j)
therefore Q + P = (6.2 , 9.9).
Source: Myschool Past Questions Archive (Record #61962)
Physics
WAEC / WASSCE 2021
Thermal Physics
Solution
Which of the arrangements of radiations below shows decreasing order of wavelengths?
A
X-rays> radio waves > infrared radiations
B
Radio waves> infrared radiations > X-rays
C
Infrared radiations > radio waves > X-rays
D
X-rays> infrared radiations > radio waves
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
radio waves have a longer wavelength than infrared light, and infrared than x-rays in the electromagnetic spectrum.
Source: Myschool Past Questions Archive (Record #61969)
Physics
WAEC / WASSCE 2021
Electricity and Magnetism
An electric pressing iron is connected to the mains using an insulated wire. wire becomes very hot.
The heat generated in the wire can be minimized by replacing the wire with one of?
A
thinner insulation.
B
greater diameter.
C
smaller diameter.
D
thicker insulation.
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #61974)
Physics
WAEC / WASSCE 2021
Mechanics and Properties of Matter
Solution
A current of 2A passes through a wire of resistance 4\Omega for 3 minutes. Calculate the energy lost.
A
960J
B
1440J
C
2880J
D
48J
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Power = current[I]\(^2\) * Resistance[R] → 2\(^2\) * 4 → 4 * 4 = 16watts
time = 3minutes → 3 * 60 = 180s
Energy = power * time → 16 * 180 = 2880j
Source: Myschool Past Questions Archive (Record #61918)