2020/2021 WAEC/NECO Answers: 2021 NECO PHYSICS ANSWERS



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Tuesday 25th June
5033/5032 Paper III & II: Objective & Essay Commerce 2hrs 40mins 10:00am 12:40pm



COMMERCE OBJ
1-10: ACAEDABDBC
11-20: EBEDEDCDBC
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31-40: BADBEEEBCD
41-50: EAEECDECED
51-60: CBEBADEBBB

This is actually the 2019 NECO PHYSICS ANSWERSAnswers as questions sent to our subscribers on WHATSAPP, if you are looking for 2021 WAEC/NECO Answers midnight before the exam, try contacting us.





PHYSICS THEORY ANSWERS
PART I
Answer SIX Questions From This Part (No 1 and any other FIVE)

(1a)
(Pick Any TWO)
(i) Solar Electric Power Generation
(ii) Solar Cooking
(iii) Solar Thermal Power Production
(iv) Solar-distillation

(1b)
Natural sattelite is a celestial body in space that orbits a larger body, such as Moon Which moves around the Earth.
Artificial satellite is a machine of human creation that is sent to the space or the orbit of the Earth for the collection of data, communication and other ends

(1c)
The applicable relationship is Ns/Np = Vs/Vp meaning the ratio of secondary voltage to primary voltage is equal to the ratio of secondary turns to primary turns
Ns = 200turns , Vs = 300V , Np = ? , Vp= 60V
Ns/Np=Vs/Vp
Np=Ns(Vp/Vs)
Np= 200 × (60/300)
Np = 200 × 0.2
Np= 40 turns

================================================


(2a)
Force is an agent that changes or tends to change the state of rest or of uniform motion in a straight line of a body

(2b)
Contact force is a force which is in contact with the body to which they are applied while Field force is a force whose sources do not require contact with the body to which the are applied

=================================================


(3a)
Maximum range (R) is defined as when the angle of the projection (Φ) is equal to 45° ie R = U²sin90/g and Φ=45°
R= U²sin90/g and sin90=1
Rmax=U²/g

(3b)
(i) Stable Equilibrium - A cone resting on its base
(ii) Unstable Equilibrium - A cone resting on its apex or vertex

======================================================

(4a)
It means that the glycerine which is in solid state will require a heat of 13°c to change to liquid state

(4b)
(i) The S.I unit of mass is in kilogram (kg) while that of weight is in Newton (N)
(ii) Mass is the quantity of matter in a body while weight is the earth's pull on a body
(iii) Mass is a scaler quantity while weight is a vector quantity

=======================================================

(5)
The lower fixed point is determined by placing the thermometer upright in pure melting ice contained in a glass funnel as shown below:

PLEASE DRAW THE DIAGRAM HERE, THEN CONTINUE BELOW.

When the mercury level remains steady, a mark is made on the stem of the thermomenter at this level which represents the lower fixed point

========================================================

(6)
Constructive interference is formed when the wave amplitudes reinforce each other, building a wave of even greater amplitude. Destructive interference is formed when the wave amplitudes oppose each other, resulting in waves of reduced amplitude.

========================================================

(7)
DRAWING

=========================================================


(8a)
Faraday's law states that the induced e.m.f. in a conducting circuit is directly proportional to the rate of change of magnetic flux linkage, Φ, with the circuit.

(8b)
(i) Induction motors
(ii) Electric generators

==========================================================

(9a)
Electric field acts on charges (Q) while Gravitational field acts on masses (m)

(9b)
Emf =12v
r =0.45Ω
R =5.0Ω
I =?
I =Emf/R+r
I =12/5+0.45=12/5.45
I =2.20A
=====================================================


(11)
ADVANTAGE:
_(Pick Only ONE)_
(i) It is used in generating heat energy required to generate electricity
(ii) It can be operated non-stop with the same nuclear capacity


DISADVANTAGES:
(Pick Only TWO)
(i) The plant set up is capital intensive
(ii) Principal raw material (uranuim) is not easily available.
(iii) Careless exposure to raw material affects the cell tissues due to radiation effect.
=====================================



PART II
Answer Any FOUR Questions From This Part

(12a)
Centripetal force and centrifugal force

(12b)
DRAWING

(12ci)
Archimede's principle states that when a body is totally or partially immersed in a fluid, it experience an upthrust which is equal to the weight of the fluid displaced.

(12cii)
eo = 4×10⁴ kg/m³
Mo = 0.4kg
Vo = ?
eL = 1.2×10² kg/m³
Where,
eo = Density of object
Mo = mass of object
Vo = volume of object
eo = Mo/Vo
Vo = Mo/eo = 0.4/4×10⁴
Vo = 0.00001m³
Mo in the liquid = eL × Vo
= 1.2×10² × Vo × 3/4
= (1.2×10² × 0.00001×3)/4
= 0.0009kg
= 9×10-⁴ kg
Reading of the spring = 9×10-⁴ ×10 = 9×10-³ N

========================================================

(13a)
Examples of Renewable energy are :
(i) solar energy
(ii) Wind energy

(13b)
Radius of the wheel = B
Radius of the axle = O
V. R= Distance moved by effort/ Distance moved by load
Effort moves through a distance is equal to the circumference of the wheel 2Ï€B and at the same time interval the load moves through the axle 2Ï€D
V.R=2Ï€B/2Ï€D =B/D

(13ci)
It breaks because ice is less dense than water and water expands when it is frozen

(13cii)
Evaporation takes place at all temperature while boiling takes place at a particular temperature (100°c)

(13d)
m1=200kg
u1 = 16.7m/s
V2 = 0.5m/s
m2 = 200kg
m1u1 + m2V2 = (m1+m2)V
200×16.7 + 200×0.5 = (200+200)V
V = 3340+100/400 = 3440/400
V=8.6m/s

=======================================================


(14ai)
A wave is a disturbance which travels through a medium transferring energy from one point to another without causing any permanent displacement of the medium

(14aii)
Tabulate
-Light wave:
(i) It is an electromagnetic wave
(ii) It can be polarized

-Sound wave:
(i) It is a mechanical wave
(ii) It can can not be polarized

(14b)
Long sight ( hypermetropia ) can be corrected with converging lens

(14c)
F= 440Hz
L1= 18.8cm
L2= 57.8cm

(14ci)
At resonance L+c= λ/4
Where C is the end correction. Assuming the end correction C is negligible,then
L1= λ/4
4L1=
4 × 18.8 = λ
4×18.8/100=0.752m

(14cii)
First position L1=λ
Second position L2 =λ
Hence, L2-L1 = λ/4
V= fλ or f=V/λ
V = 2f(L2-L1)
V= 2×440( 0.5733 - 0.188)
V= 880(0.385)
V=338.8m/s

(14ciii)
Overtime = 5λ/4
5×0.752/4
= 3.76/4
= 0.94m or 94cm

=======================================================


(15a)
Electric field intensity is the measure of intensity or strength of electrical force per unit charge at any given point in the electric field. It is denoted by the letter E and its Unit is Newton per Coulomb (N/C). Where
F is force (N)
Q is Change (C)

(15bi)
A lead accumulator in charged by passing direct current (d.c) through it in the opposite direction to that which its supplies. The positive terminal of the d.c is connected to the positive terminal of the lead accumulator and the negative terminal of the d.c is connected to the negative terminal of the accumulator.

(15bii)
Electrolyte in battery os a solution of SO⁴ and H²O and over time can be lost by slight spills and evaporation and using distilled water it is free from additional minerals that can be find in tap water and these minerals can significantly decrease in life of batteries

(15ci)
Faraday's law of electrolysis states that the chemical deposition due to the flow of current through an electrolyte is directly proportional to the quantity of electricity (coulombs) passed through it. i.e. mass of chemical deposition.

(15cii)
Area = 50cm² => 5*10-³ M²
I = 7A
t = 45*60(s)
T = thickness
M = z i t
m = 3.3 *10^-7 *7845*60
=>6.237 * 10-³ kg
P=m/v
8.9 * 10³kg/m³ = 6.237 * 10-³/V
V = 6.237 * 10-³/8.9 * 10³
=> 7.008*10 -> m³
Thickness = volume/area
7.008*10^-7/5*10-³
=> 1.40*10-⁴m

========================================================


(16ai)
Binding energy is the minimum energy or work required to separate the nucleons of an atom

(16aii)
(i)it is used in medicine as a radiotherapy
(ii)it is used in industry to study the defects in metals and welded joints

(16bi)
The intensity of x- ray can be increased in x- ray tube by increasing the voltage which results to an increase intensity of an electron

(16bii)
(i) Both are electromagnetic waves
(ii) Both are high energy photography

(16ci)
W=2.25*10^-19J
λ=3.0*10^-7m
fo=?
W= hfo
2.25*10^-19 = 6.6 *10^-34fo
fo= 2.25*10 ^-19/6.6*10^-34
= 2.25/6.6 *10^-19 +34
=0.341*10^15Hz
=3.41*10^14Hz

(16cii)
Max energy liberated = E=hc/λ - W
= (6.6×10^-34 × 3×10^8/3.0×10^-7) - 2.28×10^-19
(6.6×10^-19) - (2.25×10^-19)
= 4.35×10^-19 J

==================================================



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