# ## ONLINE CANDIDATES : 38  ### Confirmation Page # 2019/2020 WAEC GCE PHYSICS OBJ AND ESSAY EXPO | PHYSICS QUESTIONS AND ANSWERS VERIFIED ### PHYSICS-OBj 1-10: BCCDBDCDDB 11-20: ABDBACABDA 21-30: CBDDADCBBD 31-40: DBCACACBCB 41-50: CDADBDDDBA

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PHYSICS-Theory.
(4i)
Conduction of heat : This is the process by which heat is passed along a metal object from one particle at higher temperature to another lower temperature without the heated particle appearing to move

(4ii)
Convection : This is the process by which heat energy is transferred in a fluid by actual movement of the heated particle

(4iii)
Radiation : This is the process by which heat is transferred from it’s source to the body absorbing it without heating the intervening medium

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(3)
F=KA/V
Fr=KAV
K=Fr/Av
Where F=ma
=MLT-²
r=M, V=LT-¹
and A=m²
K=MLT-²*M/M²*LT-¹
K = LT-² ×L-¹T-¹
K = T-¹

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(12a)
Thermoelectric are electrons emitted at a high temperature such as one produced in a thermionic valves. They are negatively charged

(12bi)
Low voltage battery : Used to heat the heater or heating element

(12bii)
target metal : Used to collect the emitted electrons

(12ci)
α – particle has a Helium nuclei He while a β-particle has high energy electrons

(12cii)
α-particle has a charge at +2e while β-particle has a charge of -e

(12di)
The radioactive decay law states that the probability per time that a nucleus will decay is constant, independent of time.

(12dii)
(i) Damage to skin.
(ii) Causes cancer.

(12ei)
Given 238 U –> m X + 2α
92 n
= 238 U –> m X + 2 4He
92 n 2
m+(2×4) = 238
m + 8 = 238
m = 238 – 8 = 230
Also
N + (2×2) = 92
N + 4 = 92
N = 92 – 4
n = 88

(12eii)
230
X
88

No of neutrons = 230 – 88 = 142
Neutron – Proton ratio = 142/88 = 1.61

(12eiii)
It is unstable.

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(12 continuation)

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(11a)
An electric field is a region where an electric force is experienced by a charged body.

(11b)
In a tabular form
Under gravitational potential
(i) Scalar quantity
(ii) Unit is Joule per coulomb

Under gravitational field strength
(i) Vector quantity.
(ii) Unit is Newton per coulomb.

(11ci)
Equivalent capacitance = 5uf//(2uf + 2uf)
= 5uf // 4uf
= 5×4/5+4 uf
= 20/9 uf
= 2.22uf

(11cii)
Total energy stored = 1/2cv²
= 1/2×20/9×10^-6×12×12
=160×10^-6
= 0.00016Joules.

(11di)
Given: Im = 20×10^-3A; V = 25sin100πl
Capacitive reactance Xl = Vm/Im = 25/26×10^-3 = 1250ohms

(11dii)
1/2πfc = Xl
Where f = 50Hz
1/2×22/7×50c = 1250
314.286c × 1250 = 1
392857 c = 1
C = 1/392857 = 2.545×10^-6F
= 2.545uf

(11e)
A phasor diagram is a graphical way of representing the magnitude and directional relationship between two or more alternating quantities.

(11 complete)

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(5)
(i)by colour
(ii)by nature of substance
(iii) by conductivity
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(2a)
H=ut+½gt²
Where H=80m, t=?
80=0(t) + ½(10)(t²)
80=0 + 5t²
80=5t²
80/5=t²
16=t²
t=√16
t=4s

(2b)
Range = U²/g
20²/10
=400/10
=40m

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(6a)
ferromagnetic materials are those substances which exhibit strong magnetism in the same direction of the field, when a magnetic field is applied to it.

(6b)
(i)Iron
(ii)nickel
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(8ai)
Pressure is defined as the force acting per unit area on a surface.

(8aii)
Density of liquid.
Depth of point from liquid surface.

(8aiii)
Total pressure = P + pgh
= 75.5cmHg + 1000×10×15
= 75.5cmHg + 150000
= 0.755mHg + 150000
= 150000.755

(8b)
In a tabular form between mass and weight

Under mass
(i) The same everywhere on the earth.
(ii) Scalar quantity.

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Under weight
(i) Greater at the poles than at the equator ie it varies.
(ii) Vector quantity.

(8Ci)
(i) Both moving in opposite direction.
(ii) Both moving in the same direction but with one faster than the other.

(8cii)
Given Ma = 0.2kg; Mb = 0.5kg
Va = 5m/s, Vb = 3m/s
Using MaVa + MbVb = V(Ma+Mb)
0.2×(-5) + 0.5×3 = v(0.2 + 0.5)
-1 + 1.5 = 0.7v
0.7v = 0.5
V = 0.5/0.7
Common velocity = 0.71m/s Join Our Telegram Channel | Whatsapp Our Admins: Click Any Name Mr.Paul or Mr.Henry

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Posted by on 10th September 2019.

Categories: Waec Gce