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Physics
WAEC / WASSCE 2018
Current Electricity & Electric Circuits
Solution
Which of the following statements about magnetic lines of force is not correct? They
A
pass through even non-magnetic materials
B
run from the north pole to the south pole
C
are in a state of tension and tend to be shorted
D
intersect one another
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Two magnetic lines of force can not intersect each other.
Source: Myschool Past Questions Archive (Record #49864)
Physics
WAEC / WASSCE 2018
Atomic, Quantum, Nuclear Physics & Electronics
In which of the following activities is an induction coil not useful?
A
Investigation of high voltages
B
Study of electric discharge
C
Operation of X-ray tubes
D
A.C. power transmission
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 #49869)
Physics
WAEC / WASSCE 2018
Magnetism, Electromagnetism & AC Circuits
Solution
In a series R-L-C circuit, R = 10\(\Omega\), \(X_{c}\)= 4\(\Omega\) and \(X_{L}\) = 9\(\Omega\). The impedance of the circuit is
A
4.1\(\Omega\)
B
5.0\(\Omega\)
C
10.8\(\Omega\)
D
11.2\(\Omega\)
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
The impedance for a RLC circuit is
\(Z = \sqrt{R^{2} + (X_{L} - X_{C})^{2}}\)
= \(\sqrt{10^{2} + (9 - 4)^{2}}\)
= \(\sqrt{125}\)
= 11.18\(\Omega\) \(\approxeq\) 11.2\(\Omega\)
Source: Myschool Past Questions Archive (Record #49874)
Physics
WAEC / WASSCE 2018
Magnetism, Electromagnetism & AC Circuits
Diagram
Solution
A student uses two compass needles to investigate the magnetic field around a bar magnet. Which of the following diagrams show the correct directions of the needles?
Attached Figure / Diagram
A
A
B
B
C
C
D
D
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
By convention, the field direction is taken to be outward from the North pole and in to the South pole of the magnet. Also, they form closed lines.
Source: Myschool Past Questions Archive (Record #49876)
Physics
WAEC / WASSCE 2018
Atomic, Quantum, Nuclear Physics & Electronics
Solution
Which of the following is emitted in a process of natural radioactivity?
A
\(\alpha\)- particles and \(\beta\)- particles
B
\(\alpha\)- particles and X-rays
C
\(\beta\)- particles and X-rays
D
\(\lambda\)- rays and X-rays
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
In the course of natural radioactivity, alpha, beta and gamma rays are emitted.
Source: Myschool Past Questions Archive (Record #49885)
Physics
WAEC / WASSCE 2018
Atomic, Quantum, Nuclear Physics & Electronics
In which of the following situations is photoelectric effect employed?
I. Automatic devices for switching on light at dusk
II. Automatic doors in departmental stores
III. Automatic devices for switching on air conditioners
IV. Automatic voltage stabilizers
A
I, II and IV only
B
I, III and IV only
C
III and IV only
D
I and II 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 #49887)
Physics
WAEC / WASSCE 2018
Waves, Sound & Vibrations
Solution
Which of the following radiations has the longest wavelength?
A
Gamma ray
B
Radio wave
C
Infrared ray
D
X-ray
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
Radio wave has the longest wavelength and shortest frequency.
Source: Myschool Past Questions Archive (Record #49891)
Physics
WAEC / WASSCE 2018
Current Electricity & Electric Circuits
In which of the following fields is radioisotopes not used?
A
Medicine
B
Oil industry
C
Agriculture
D
Weather forecast
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 #49894)
Physics
WAEC / WASSCE 2018
Current Electricity & Electric Circuits
Solution
A nuclide is represented by \(_{32}^{70}B\). Determine its neutron-proton ratio
A
0.5
B
0.8
C
1.2
D
1.5
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
The element B has a mass number of 70 with atomic number 32. Hence, B has 32 protons and (70-32) = 38 neutrons.
The neutron- proton ratio is 38:32 = \(\frac{38}{32} = 1.1875\)
\(\approxeq 1.2\)
Source: Myschool Past Questions Archive (Record #49900)
Physics
WAEC / WASSCE 2018
Reflection, Refraction & Dispersion of Light
Solution
State three materials used for making optical fibres.
medium Difficulty
Verified Correct Answer: Option
Physical Principles & Numerical Solution
Materials for making optical fibre are Glass, Polycarbonate, Teflon sheath, Silica, quartz, Silicon, Sapphire. Feromagnetic
Source: Myschool Past Questions Archive (Record #52864)
Physics
WAEC / WASSCE 2018
Magnetism, Electromagnetism & AC Circuits
Solution
Name three classes of magnetic materials.
medium Difficulty
Verified Correct Answer: Option
Physical Principles & Numerical Solution
Three classes of magnetic materials are
(i) Diamagnetic
(ii) Paramagnetic
(iii) Feromagnetic
Source: Myschool Past Questions Archive (Record #52865)
Physics
WAEC / WASSCE 2018
Atomic, Quantum, Nuclear Physics & Electronics
Solution
(a) What is an intrinsic semiconductor?
(b) Distinguish between the p-type and n-type semi-conductors.
medium Difficulty
Verified Correct Answer: Option
Physical Principles & Numerical Solution
(a) An intrinsic semiconductor contains equal number of free electrons and holes.
(b)
p— TYPE
n - TYPE
i
The majority carrier of electricity is holes.
The majority carrier of electricity is electron.
ii
Carries a net positive charge
Carries a net negative charge
iii
The impurity is trivalent
The impurity is pentavalent.
Source: Myschool Past Questions Archive (Record #52866)
Physics
WAEC / WASSCE 2018
Gas Laws & Heat Transfer
Solution
a) What does the acronym LASER stand for?
b) What is a laser?
medium Difficulty
Verified Correct Answer: Option
Physical Principles & Numerical Solution
(a) LASER - Light Amplification by Stimulated Emission of Radiation.
(b) A laser is a device that generates an intense beam of coherent monochromatic light.
Source: Myschool Past Questions Archive (Record #52869)
Physics
WAEC / WASSCE 2018
Linear Motion, Projectiles & Kinematics
Diagram
Solution
(a) Define uniform acceleration.
(b) Forces act on a car in motion. List the
(i) horizontal forces and their directions;
(ii) vertical forces and their directions
(c) A car starts from rest and accelerates uniformly for 20s to attain a speed of 25 ms\(^{-1}\). It maintains this speed for 30s before decelerating uniformly to rest. The total time for the journey is 60 seconds.
(i) Sketch a velocity-time graph for the motion.
(ii) Use the graph to determine the (\(\alpha\)) total distance travelled by the car (\(\beta\)) deceleration of the car.
The figure above illustrates a force-extension graph for a stretched spiral spring. Determine the work done on the spring. SEE THE DIAGRAM ABOVE
Attached Figure / Diagram
medium Difficulty
Verified Correct Answer: Option
Physical Principles & Numerical Solution
(a) Uniform acceleration is the constant time rate of increase in velocity.
(b) (i) Horizontal Force;
Forward force - Thrust
backward force - Frictional force
(ii) Vertical Force
Upward force - Normal reaction.
Downward force - Weight of the car.
(c) SEE THE DIAGRAM ABOVE.
(ii) (\(\lambda\)) Total distance
= Area of trapezium OABC
= \(\frac{1}{2}\)[AB + OC] AD
= \(\frac{1}{2}\)[60+30] x 25
=1125m
(\(\beta\)) Deceleration = slope of BC
= \(\frac{BE}{CE} = \frac{25}{10}\)
= 25m/s\(^2\)
(d) Work done = \(\frac{1}{2}\)Fe
= \(\frac{1}{2}\) x 12 x \(\frac{0.5}{100}\)J
= 0.03J
Source: Myschool Past Questions Archive (Record #52870)
Physics
WAEC / WASSCE 2018
Calorimetry, Latent Heat & Change of State
Solution
(a) List two factors each that affect heat loss by:
(i) radiation;
(ii) convection.
(b) State two factors that determine the quantity of heat in a body.
(c) Explain the statement: The vecilic latent heat of vaporization of mercury is 2.72 x 10\(^5\) Jkg\(^{-1}\).
(d)A jug of heat capacity 250 Jkg\(^{-1}\) contains water at 28^\circC. An electric heater of resistance 35\(\Omega\) connected to a 220 V source is used to raise the temperature of the water until it boils at 100^\circC in 4 minutes. After. another 5 minutes, 300 g of water has evaporated. Assuming no heat is lost to the surroundings, calculate the:
(i) mass of water in the jug before heating;
(ii) specific latent heat of vaporization of steam. [Specific heat capacity of water = 4200 kg\(^{-1}\)K\(^{-1}\)]
medium Difficulty
Verified Correct Answer: Option
Physical Principles & Numerical Solution
(a) (i) Radiation:
Surface area, Temperature.
(ii) Convection:
Nature, Density/Viscosity of the fluid, Thermal conductivity of fluid, Specific heat capacity of fluid and Exposed surface area.
(b) Factors that determine the quantity of heat in a body: Heat/thermal capacity and. Temperature
(c) It means that 2.72 x 105J of heat energy is required/ needed to change I kg of mercury at its boiling point to vapour (without temperature change)
(d) (i) heat supplied by heater = ivt = \(\frac{v^2}{R}\)t
heat gained by water = M\(_w\)C\(_w\)(\(\theta_2\) - \(\theta_1\))
where M\(_w\) = mass of water
C\(_w\) = s.h.c of water
\(\theta_2\) = final temp. of water
\(\theta_1\) = initial temp. of water
Heat gained by jug = C\(_j\) (\(\theta_2\) - \(\theta_1\))
\(\frac{v^2t}{R}\) = M\(_w\)C\(_w\) (\(\theta_2\) - \(\theta_1\))
= \(\frac{220^2 \times 4 \times 60}{35}\)
= M\(_w\) x 4200[100 - 28] + 250[100 - 28]
M\(_w\) = 1.038kg
Source: Myschool Past Questions Archive (Record #52871)