WAEC - Physics (2021)

1
Which of the following quantities is not an example of force?
Răspuns
(A)
Mass
2
The reason for laminating the soft iron core of a transformer is to?
Răspuns
(A)
reduce eddy current.
3
Formation of hydrogen bubbles at the copper plate of a primary cell is called?
Răspuns
(A)
polarization.
4
Which of the following factors does not affect the rate of evaporation of a liquid?
Răspuns
(B)
volume
5
Opening in the eye through which light passes to the retina is called the?
Răspuns
(A)
pupil
6
A heat sensitive resistor made of a semiconductor is called?
Răspuns
(C)
thermistor
7
Electric motor primarily converts?
Răspuns
(C)
electrical energy to mechanical energy
8
Which of the following statements about the molecules of solids and liquids is correct? They both
Răspuns
(D)
exhibit vibratory motion.
9
The distance between a node and its adjacent antinode of a transverse wave is equal to?
Răspuns
(D)
quarter of the wavelength.
10

Which of the sketched graphs above illustrates the correct variation of the gravitational force, Fg between two objects and the distance, d, between the centre
Răspuns
(B)
B
11
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

Răspuns
(A)
I and III only
12
A metallic sphere is heated from 27°C to 200°C Without change of state. Which of the following changes would have resulted from the heating?

Răspuns
(C)
Its volume increases and its density decrease
13
The acceleration of a moving object can be determined from the?
Răspuns
(C)
slope of its velocity-time graph.
14
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?

Răspuns
(D)
high value resistor connected in series with G.
15
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% [π = $\frac{22}{7}$]?
Răspuns
(C)
15.2N
16
The inductive reactance in a circuit of frequency 100Hz is 1ohms. Calculate the inductance of the inductor[π = 3.14]

Răspuns
(B)
1.59 x 10$_{-3}$H
17

The diagram above illustrates the velocity-time graph of a body. Calculate the distance covered by the body during the motion
Răspuns
(C)
72m
18
An atom that emits an a-particle?

Răspuns
(A)
may become a different element.
19
Which of the following units is equivalent to the unit of electric current?
Răspuns
(A)
C s${-1}$
20
A ball is swung in a horizontal circle of centre O with a constant speed. What is the direction of its acceleration?
Răspuns
(C)
Toward centre O
21
Which of the following statements is an effect of compressing gas molecules at constant temperature?
Răspuns
(C)
The molecules make more impact per second on the walls of the container.
22

The diagram above is an illustration of an a.c. circuit.Calculate the reactance of the capacitor.

Răspuns
(C)
200Ω
23
A current of 2A passes through a wire of resistance 4Ω for 3 minutes. Calculate the energy lost.
Răspuns
(C)
2880J
24
Which of the following statements about the universal gravitational constant, G, is true?
Răspuns
(B)
It has dimension M-¹L³T-².
25

The sketched graph above represents a progressive wave moving from the left to the right. The period of the wave is 0.125s.

Determine the values of the amplitude and wavelength, respectively, of the wave.

Răspuns
(B)
8 cm; 9 cm
26

Determine the speed of the wave.

Răspuns
(D)
72 cm/s
27
Which of the following curved surfaces will produce a real image? I. Concave mirror II. Convex mirror III. Diverging lens IV. Converging lens
Răspuns
(D)
I and IV only
28
The components of vectors Q and R are (-3.0, 5.5) and (9.2, 4.4) respectively. Determine the components of Q + R.
Răspuns
(B)
(6.2, 9.9)
29
Which of the arrangements of radiations below shows decreasing order of wavelengths?
Răspuns
(B)
Radio waves> infrared radiations > X-rays
30
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?

Răspuns
(B)
greater diameter.
31

In the diagram above, a bulb is lit by drawing 2.0A from 440V a.c. source. Calculate the cost of keeping the bulb on for two days at $0.40 per kilowatt-hour .

Răspuns
(A)
$16.90
32
A wire of cross-sectional area 2π * 10$^-{8}$ m$2$ and resistivity 1.1 x 10$^-{8}$ Ω m, has a resistance of 21Ω.

Calculate the length of the wire. [π=22/7]
Răspuns
(C)
120 m
33
Which of the following statements best describes the particles in a solid at room temperature? They are
Răspuns
(B)
close together and vibrating.
34
A man weighing 200 N runs up a staircase in 5s. If the height of the staircase is 9 m, calculate the power of the man.
Răspuns
(B)
360 W
35
A rotating disc contains a set of holes in a circle. An air jet is directed onto the holes and a note of frequency 480 Hz is produced. If the number of holes is 20, calculate the speed of rotation of the disc.
Răspuns
(C)
24 rev/s
36
A force of 10 N, acting continuously, increases the kinetic energy of an object from 20.J to 60 J. Find the distance moved by the object.
Răspuns
(C)
4m
37
An electric circuit consists of a resistor. a battery and a key. If the voltage of the battery is increased, there Would be an increase in the?
Răspuns
(C)
current and temperature only.
38
A radioactive material has a half-life of 1.0 hour If 200.0 g of it was present at 6 a.m. on a certain day, how many grams will have decayed by 9 a.m. on the same day?

Răspuns
(A)
175.0 g
39
The following statements about a loudspeaker are correct except?
Răspuns
(D)
the magnetic force on the speech coil is uni-directional.
40
An ice cube has mass of 20 g at 5°C. Calculate the energy required to raise its temperature to 0°C. [Specific heat capacity of ice = 2.1 J/g°c]

Răspuns
(D)
210 J
41
A stone is thrown horizontally with initial velocity 15m/s from a tower 20 m high. How long does it take to reach the ground? [g= 10m/s$^2$

Răspuns
(A)
2s
42
Which of the following statements is not a characteristic of a plane progressive wave?
Răspuns
(B)
Neighboring points along the profile possess different amplitudes
43
The electrons in a cathode-ray tube are produced by?
Răspuns
(A)
heating a metal filament.
44
Which of the following statements about distance and displacement is not correct?
Răspuns
(D)
Distance is a vector quantity.
45
A note produced by an instrument is distinguished from a similar note produced by another instrument by the?
Răspuns
(C)
overtones.