2023 JAMB PHYSICS LIKELY QUESTIONS AND ANSWERS

2023 JAMB PHYSICS LIKELY QUESTIONS

1
The relative densities of zinc, brass, copper, gold and silver are respectively 7.1, 8.5, 8.9, 19.3, 10.5. A metal ornament which weighs 0.425kg and can displace 50 x 10-6m3m of water is made of

A.
zinc

B.
brass✅

C.
copper

D.
gold

E.
silver

Explanation
R.D = density of objectdensity of water

= \frac{\frac{0.425}{50 10^-6}{1000}

= 8.5

2
When a ray of light passes from water to glass, it is

A.
bent away from the normal

B.
bent towards the normal✅

C.
totally internally reflected

D.
absorbed by the glass

E.
broken into a pure spectrum

3
Which of the following statements is CORRECT?

A.
charges generated on glass rubbed with silk are called negative

B.
charges in various media can be carried by protons detached from their atom

C.
the magnitude of any charge is a multiple of the charge of an electron✅

D.
the intensity of an electric field is a scalar quantity

E.
if 500 joules of work are required to move a 2-coulomb charge between two points, the potential difference between the two point is 100V

4
The force responsible for holding the moon in its orbit around the earth against the gravitational pull of the earth is

A.
centrifugal

B.
rotational

C.
reaction

D.
centripetal✅

E.
tractional

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5
The total length of a spring when a mass of 20g is hung from its end is 14cm, while its total length is 16cm when a mass of 30g is hung from the same end. Calculate the unstretched length of the spring assuming Hooke’s law is obeyed.

A.
9.33cm

B.
10.00cm✅

C.
10.66cm

D.
12.00cm

E.
15.00cm

Explanation
Let unstretched length = L

e1 = 14 – L and e2 = 16 – L

Using, m1e1 = m2e2

2014−L = 3016−L

L = 10cm

6
Which of the following is a correct explanation of the inertia of a body?

A.
ability to overcome the earth’s gravity

B.
reluctance to stop moving

C.
readiness to start moving

D.
reluctance to start moving and its readiness to stop moving once it has begun to move

E.
reluctance to start moving its reluctance to stop moving once it has begun to move✅

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7
A galvanometer of resistance 5.0Ω has full-scale deflection for a current of 100mA. How would its range be extended to 1.0A? By placing a resistance of

A.
59Ω in parallel✅

B.
95Ω in series

C.
45Ω in parallel

D.
45Ω in series

E.
95Ω in parallel

Explanation
Given Data:
Ig = 100ma = 0.1A
Rg=5
where Is = I – Ig → 1 – 0.1

Is = 0.9

IgRg = IsRs

0.1 * 5 = 0.9 * Rs
Rs = 0.1∗50.9
Rs = 59

8
The speed of sound in air at sea-level is 340ms-1 while that of light is 300 000kms-1. How far (to the nearest meter) from the center of a thunderstorm is an observer who hears a thunder 2s after a lightening flash?

A.
170ms-1

B.
340ms-1

C.
600ms-1

D.
680ms-1✅

Explanation
Distance = 340 x 2 = 680ms-1

9
The photocell works on the principle of the

A.
voltaic cell

B.
emision of electrons by incident radiation✅

C.
emision of protons by incident electrons

D.
photographic plate

10

A spring of force constant 1500Nm-1 is acted upon by a constant force of 75N. Calculate the potential energy stored in the string

A.
1.9J✅

B.
2.8J

C.
3.45J

D.
0.43J

Explanation
P.E = 12Fe

= 12FK

= 12 x 75×751500

= 1.9J

11
The spiral spring of a spring balance is 25.0cm long when 5N hangs on it and 30cm long, when the weight is 10N. What is the length of the spring if the weight is 3N assuming Hooke’s law is obeyed?

A.
15.0cm

B.
17.0cm

C.
20.0cm

D.
23.0cm✅

Explanation
let the length be Lcm

5−325−L = 10−530−25

L = 23cm

12
The speed of light in air is 3 x 108ms-1. What is the speed in glass with a refractive index of 1.50?

A.
1.5 x 108ms-1

B.
3.0 x 108ms-1

C.
2.0 x 108ms-1✅

D.
6.0 x 108ms-1

Explanation
1.5 = 3×108v

v = 2.0 x 108ms-1

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13
Which of the following waves can propagate through a vacuum?

A.
High velocity sound waves

B.
Ultrasonic waves

C.
Acoustic waves

D.
Infra-red waves✅

14

A solid of weight 0.600N is totally immersed in oil and water respectively. If the upthrust of oil is 0.210N and the relative density of oil is 0.875. Find the upthrust in water.

A.
0.600N

B.
0.360N

C.
0.240N✅

D.
0.180N

Explanation
Rd = upthrust in oilupthrust in H2O

thus; 0.875 = 0.21upthrust in H2O

upthrust in H2O = 0.24N

15
A lead bullet of mass 0.05kg is fired with a velocity of 200ms−1 into a lead block of mass 0.95kg. Given that the lead block can move freely, the final kinetic energy after impact is

A.
50 J✅

B.
100 J

C.
150 J

D.
200 J

Explanation
From principle of conservation of linear momentum,
(0.05 x 200) + (0.95 x 0) = (0.05 + 0.95) x V (since collision is inelastic).

10 + 0 = V

Thus V = 10m/s.

Recall Kinetic Energy = 12mv2
∴ K.E = 1/2 (0.05 + 0.95) x 102
K.E = 1/2 (1 x 100) = 50 J.

16

The inside portion of part of a hollow metal sphere of diameter 20cm is polished. The portion will therefore form a

A.
concave mirror of focal length 5cm✅

B.
concave mirror of focal length 10cm

C.
convex mirror of focal length 5cm

D.
convex mirror of focal length 20cm

17
I. Its velocity is constant
II. No work is done on the body
III. It has constant acceleration directed away from the centre
IV. The centripetal force is directed towards the centre

Which combination of the above is true of a body moving with constant speed in a circular track?

A.
II and IV✅

B.
I and IV

C.
II and III

D.
I and III

18
The radiator of a motor car is cooled by

A.
radiation

B.
conduction

C.
convection✅

D.
radiation and conduction

Explanation
The function of the radiator of a motor car is to “collect” heat from the circulating water and radiate some out, but it is itself cooled by the fan adjacent to it. whose function is primarily based on convection

19
A transistor is used in the amplification of signals because it

A.
controls the flow of current✅

B.
consumes a lot of power

C.
allows doping

D.
contains electron and hole carriers

20
An electron of charge 1.6 x 10-19C is accelerated between two metal plates. If the kinetics energy of the electron is 4.8 x 10-17J, the potential difference between the plate is

A.
30V

B.
40V

C.
300V✅

D.
400V

Explanation
In general, if a charged particle is accelerated between two metal plates/a region by potential difference V volts, the work done on the charge, given by the product of the charge and the potential difference, is equal to the kinetic energy of the charge
Thus eV = K.E
1.6 x 10-19 x V = 4.8 x 10-17
∴ V = 4.8 x 10-17
1.6 x 10-19

= 300V

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21
A ray of light makes an angle of 35o with a plane mirror. What is the angle of reflection?

A.
35o

B.
55o✅

C.
70o

D.
65o

Explanation

35o =35o = 70o
180 – 70 = 110
110/2 = 55o

22
Transverse waves can be distinguished from longitudinal waves using the characteristic of

A.
diffraction

B.
refraction

C.
polarization✅

D.
reflection

23
A person can focus objects when they lie beyond 75 cm from his eyes. The focal length of the lens required to reduce his least distance of distinct vision to 25 cm is?

A.
37.50 cm✅

B.
75.00 cm

C.
18.75

D.
25.00 cm

Explanation
The least distance of distinct vision required = 25 cm.
∴ for the person to see an object clearly at 25 cm from the eye, the image must be formed at 75 cm on the same side of lens, at his near point.
∴ U = 25 cm; V = -75 cm (image should be virtual)
thus (1)/f = (1)/v +(1)/u
= (1)/75 + (1)/25
=(-1 + 3)/75 = (2)/75
∴f = (75)/2 = 37.50

24
A shooter wants to fire a bullet in such a way that its horizontal range is equal to three times its maximum height. At the what angle should he fire the bullet to achieve this?

A.
68o

B.
53o✅

C.
30o

D.
45o

Explanation
Horizontal range = 3 x maxi. height
=> (U2Sin2θ) / g = (3 x U2sin2θ) / 2g
∴sin2θ = 3sin2θ
2

=> 2sinθcosθ = 3sin2θ
2

∴ 4sinθcosθ = 3sin2θ
=> 4cosθ = 3sinθ
∴ sinθ/cosθ = 4/3; => tanθ = 4/3 = 1.3333
θ = tan-1 (1.3333)
= 53o

25

A machine has a velocity ratio of 4. if it requires 800 N to overcome a load of 1600 N,what is the efficiency of the machine?

A.
60%

B.
50%✅

C.
40%

D.
2%

Explanation
Efficiency = (M.A)/V.R X (100)/1
But M.A = (Load)/Effort = (1600)/800 = 2
Efficiency = (2)/4 x (100)/1 = 50%

26
The d.c generator has essentially the same components as the a.c generator except the presence of?

A.
slip-ring

B.
carbon brushes

C.
split ring✅

D.
armature

Explanation
To correct and A.C generator with a D.C generator the slip ring is replaced with split-ring communicator

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27
If a light wave has a wavelength of 500nm in air what is the frequency of the wave?
[c = 3 x 108 ms-1]

A.
3.0 x 1014 Hz

B.
6.0 x 1014 Hz✅

C.
6.0 x 1012 Hz

D.
2.5 x 1014 Hz

Explanation
f = c/λ

∴ f = c = 3 x 108
λ 500 x 10-9

=6.0 x 1014 Hz

28
If a wire 30 cm long is extended to 30.5 cm by a force of 300 N. find the strain energy of wire

A.
0.75 J✅

B.
7.50 J

C.
75.00 J

D.
750.00 J

Explanation
Energy stored in a stretched wire (strain energy)
= average force x extension
= (1)/2 Fe
= (1)/2 x 300 N (30.5 – 30.0) x 10-2 m
= (300)/2 x 0.5 x 10-2 = 0.75J

29
One special advantage of alcohol over mercury as a thermometric liquid is its?

A.
low density

B.
low freezing point✅

C.
high specific

D.
low boiling point

Explanation
The low freezing point of alcohol, -115°c enable low temperatures to be measured. mercury freezes at 39°c, and cannot be used in countries like Russia where winter temperatures of -40°c are common

30
A bob of weight 0.1 N hangs from a massless string of length 50 cm. A variable horizontal force which increase from zero is applied to pull the bob until the string makes an angle of 60o with the vertical. The work done is?

A.
0.500 J

B.
0.250 J

C.
0.050 J

D.
0.025 J✅

Explanation

Length of the string
L = y + x = 0.5m
∴ x = L – y
= distance moved in the direction of force (which is the weight) when the body is released But cos 60o = y/0.5
∴ y = 0.5cos60 = 0.5 x 1/2 = 0.25
∴ x = l – y = 0.5 – 0.25 = 0.25m
Work done = force x distance moved in the direction of force.
= 0.1 x 0.25 = 0.025J

31
In Faradays law of electrolysis, a graph of the mass deposited against the quantity of electricity is plotted. The slope of the graph gives?

A.
the energy released

B.
the electrochemical equivalent✅

C.
the current flowing

D.
the charge released

Explanation
In Faradays law of electrolysis
M = It = Q
Where M is the mass of substance deposit . Q is the quantity of charge. A graph of m against Q is a straight line passing through the origin with slope equal to the electrochemical equivalent.Z

32
If it takes an object 3s to fall freely to the ground from a certain height, what is the distance covered by the object?

A.
90 m

B.
30 m

C.
45 m✅

D.
60 m

Explanation
S = (1)/2gt2
S = (1)/2 x (10)/1 x 32 =5 x 9 = 45 m

33
A perfect emitter or absorber of radiant energy is a

A.
conductor

B.
black body✅

C.
white body

D.
red body

Explanation
Dull, black surface are good emitters or absorbers of energy

34
Steam burn is more severe than that of boiling water because

A.
steam burn is independent of relative humidity

B.
steam possesses greater heat energy per unit mass✅

C.
water boils at a higher temperature

D.
steam burn is dependent on relative humidity

Explanation
The specific latent heat of vaporization of steam is 2.1 x 106JKg-1
while the energy required to raise the temperature of a unit mass of water from 0°c to 100°c = C x Dt = 4200 x 100 = 420000 = 4.2 x 105 JKg-1
∴ steam possesses greater heat energy per unit mass

35
The pair of physical quantities that are scalar only are ?

A.
volume and area✅

B.
moment and momentum

C.
length and displacement

D.
Impulse and time

Explanation
This is because volume and the area have only magnitude but no direction

36

The bond between silicon and germanium is

A.
dative

B.
covalent bond✅

C.
trivalent

D.
ionic

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37
A car accelerates uniformly from rest at 3ms-2. its velocity after traveling a distance of 24m is

A.
12ms-1✅

B.
144ms-1

C.
72ms-1

D.
36ms-1

Explanation
V2 = U2 x 2ax
V2 = 0 x 2(3)(24)
V2 = 144
V = 144−−−√
V = 12ms-1

38
Boyle’s law may be Written as

A.
P1V1= P2V2✅

B.
V1 = V2 ÷ T1T2

C.
P1T1 = P2T2

D.
P1V1 ÷ T1 = P1V1 ÷ T2

Explanation
Boyle‘s law stats that the volume of a given mass of a gas, at a constant temperature is inversely proportional to us pressure.

Mathematically

V ∝ l/p, v = k/p (where k is constant)

K = VP

Let k = k1

Then, if k = k, V and P = V1P1

V1P1 = V2P2

39
An object is placed 15cm in front of a plane mirror. If the mirror is moved further 5cm away from the object and the image is

A.
80cm

B.
40cm✅

C.
50cm

D.
70cm

40
Vapour is said to be saturated on top of an enclosed liquid if _________

A.
The rate of condensation is greater than that of vapourization

B.
The rate of condensation is equal to that of vapourization✅

C.
There is neither condensation nor vaporization of the liquid

D.
The rate of condensation is less that that of vaporization

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