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Physics
WAEC / WASSCE 1993
Current Electricity & Electric Circuits
Diagram
ln the diagram below, the galvanometer indicates a null-deflection. What is the potential difference between P and Q?
Attached Figure / Diagram
A
0.0 V
B
1.5 V
C
2.0 V
D
3.0V
E
4.0 V.
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 #25039)
Physics
WAEC / WASSCE 1993
Current Electricity & Electric Circuits
When a potential difference, V is applied across the ends of a resistor of resistance, R a Current, l passes through the resistor. The heat generated in the resistor in time, t is given by the expression
A
V2lt
B
I2t/R
C
l2Rt
D
lR2tR
E
V2Rt
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #25040)
Physics
WAEC / WASSCE 1993
Work, Energy, Power & Simple Machines
Electric motor primarily converts
A
electrical energy into chemical energy
B
electrical energy into heat energy
C
kinetic energy into potential energy
D
electrical energy into mechanical energy
E
mechanical energy into light energy
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 #25041)
Physics
WAEC / WASSCE 1993
Calorimetry, Latent Heat & Change of State
Solution
What amount of current would pass through a 10 \Omega coil if it takes 21s for the coil to just melt a lump of ice of mass 10g at 0oC if there are no heat losses? (Latent heat of fusion of ice = 336 Jg\(^{-1}\)).
A
16.00A
B
4.00 A
C
0.50A
D
0.25A
E
0.06 A
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
I\(^2\)Rt = mI;
I = \(\sqrt{\frac{mI}{Rt}}\)
= \(\sqrt{\frac{10 \times 336}{10 \times 21}}\)
= \(\sqrt{16}\)
= 4.0A
Source: Myschool Past Questions Archive (Record #25042)
Physics
WAEC / WASSCE 1993
Calorimetry, Latent Heat & Change of State
Solution
How long does it take a 750 W heater operating at full rating to raise the temperature of 1 kg of water from 40oC to 70oC? (Take the specific heat capacity of water as 4200 J kg-1 K-1 and neglect heat losses).
A
84s
B
112s
C
168s
D
280s
E
616s
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
div class="eq-c">pt = mcθΔ; t = mcθΔ/p = 1 x 4200 x (70 - 40)/750 = 168s
Source: Myschool Past Questions Archive (Record #25043)
Physics
WAEC / WASSCE 1993
Atomic, Quantum, Nuclear Physics & Electronics
24 Na → 24 mg4 + X + energy 11 2
The equation above represents a nuclear decay of sodium isotope. What is X?
A
Alpha particle
B
Beta particle
C
Gamma ray
D
X-ray
E
Neutron
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #25044)
Physics
WAEC / WASSCE 1993
Atomic, Quantum, Nuclear Physics & Electronics
lf Einstein’s photoelectric equation is represented by hf - W = Φ where h is Planck’s constant, f the frequency of incident radiation and W the work function of the material, what does the symbol Φ up stand for?
A
Energy of the photons
B
Maximum Kinetic energy of the ejected electrons
C
Threshold frequency of the photons
D
Stopping potential of the electrons
E
Velocity of the electrons
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #25045)
Physics
WAEC / WASSCE 1993
Atomic, Quantum, Nuclear Physics & Electronics
The phenomenon of radioactivity was first discovered by
A
Marie Curve
B
Sir J.J Thomson
C
Henn Becquerel
D
Niels Bohr
E
Enrico Fermi
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #25046)
Physics
WAEC / WASSCE 1993
Atomic, Quantum, Nuclear Physics & Electronics
Solution
A radioactive substance has a half-life of 20 hours. What fraction of the original radioactive nuclide will remain after 80 hours?
A
1/32
B
\(\frac{1}{16}\)
C
\(\frac{1}{8}\)
D
\(\frac{1}{4}\)
E
\(\frac{1}{2}\)
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
Fraction remaining = (\(\frac{1}{2}\))\(^{\frac{t}{T_{\frac{1}{2}}}}\)
BUT \(\frac{t}{T_{\frac{1}{2}}}\) = \(\frac{80}{20}\) = 4
Fraction remaining = (\(\frac{1}{2})^4\) = \(\frac{1}{16}\)
Source: Myschool Past Questions Archive (Record #25047)
Physics
WAEC / WASSCE 1993
Elasticity, Density, Pressure & Fluids
According to the kinetic theory of gases the collision
of the molecules of a gas with the wall of the container
is mainly responsible for the l. temperature of the
gas ll. viscosity of the gas Ill. pressure of the gas
Which of the statements above is/are correct?
A
I only
B
II only
C
III only
D
II and III only
E
I, II and III.
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #25049)
Physics
WAEC / WASSCE 1993
Current Electricity & Electric Circuits
Eight or - particles and size B - particles are emitted from an atom of 92238U before it achieves stability. What is the nucleon number of the final product in the chain reaction?
A
206
B
234
C
238
D
240
E
252
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 #25050)
Physics
WAEC / WASSCE 1993
Current Electricity & Electric Circuits
When an atom is in the ground state, it is said to be
A
grounded
B
excited
C
stable
D
ionized
E
radiating
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #25051)
Physics
WAEC / WASSCE 1993
Atomic, Quantum, Nuclear Physics & Electronics
Which of the following are emitted from a radioactive substance without altering either the nucleon number or the proton number of the substance?
A
Gamma rays
B
Alpha particles
C
Beta particles
D
Protons
E
Neutrons
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 #25052)
Physics
WAEC / WASSCE 1993
Work, Energy, Power & Simple Machines
Solution
(a)(i) Explain what is meant by a machine (ii) Define the terms: mechanical advantage, velocity ratio and efficiency as applied to a machine. Derive the equation connecting the three terms.
(b) Explain why the efficiency of a machine is usually less than 100%
(c) A screw jack whose pitch is 4.4mm is used to raise a body of mass 8000 kg through a height of 20cm. The length of the tommy bar of the jack is 70cm. If the efficiency of the jack is 80%, calcuate the: (i) velocity ratio of the jack; (ii) mechanical advantage of the jack (iii) effort required in raising the body, (iv) work done by the effort in raising the body \((g = 10ms^{-2}; \pi = \frac{22}{7}\))
A
Gamma rays
B
Alpha particles
C
Beta particles
D
Protons
E
Neutrons
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
(a)(i) A machine is a device used to overcome a load at one end by the application of an effort at another end. Examples of simple machine include the screw jack, can opener, pulley system. (ii) M.A. is the ratio of the load (L) to the Effort (E).
\(M.A = \frac{Load}{Effort}\)
V.R. is the ratio of the distance moved by the effort tc the distarice moved by the load (at the same time).
\(V.R = \frac{\text{distance moved by effort}}{\text{distance moved by load}}\)
Efficiency (E) is the ratio of the useful work done by the machine (work output) to the total work put into the machine (work input).
\(Efficiency = \frac{\text{work done on load}}{\text{work done by effort}} \times 100%\)
\(Efficiency = \frac{M.A}{V.R} \times 100%\);
\(Work = Force \times Distance\)
\(Efficiency = \frac{\text{work output}}{\text{work input}} \)
= \(\frac{Load \times \text{distance moved by load}}{Effort \times \text{distance moved by effort}}\)
= \(M.A \times \frac{1}{V.R} \times 100%\)
(b) The efficiency of a simple machine is not 100% because of the work done in overcoming friction.
(c) length of tommy bar. L = 70cm = 0.7m; Pitch = 4.4mm = 0.0044m.
(i) \(V.R = \frac{2\pi L}{pitch} = \frac{2 \pi \times 0.7}{0.0044}\)
= \(2 \times \frac{22}{7} \times \frac{0.7}{44 \times 10^{-4}}\)
\(V.R = 1000\)
(ii) \(Efficiency = \frac{M.A}{V.R} \times 100%\)
\(\frac{80}{100} = \frac{M.A}{1000} \implies M.A = 800\)
(iii) \(M.A = \frac{Load}{Effort}\)
\(Effort = \frac{8000 \times 10}{800} = 100N\)
(iv) Work done = \(\frac{load \times \text{distance moved by load}}{effort \times \text{distance moved by effort}}\)
= \(\frac{8000 \times 10 \times 0.2}{0.8} = 20,000J\)
Source: Official Exam / Past Question Archive
Physics
UTME / JAMB 1993
Electrostatics & Capacitors
Solution
In the network shown above, determine the potential difference across the 5µF capacitor
A
3V
B
6V
C
12V
D
18V
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
For capacitors in series
C\(_{\text{eq}} = \frac{C_1 C_2}{C_1 + C_2}\)
C\(_{\text{eq}} = \frac{5 \times 15}{5 + 15} = \frac{75}{20}\) = 3.75μF
Charge on the series branch
Q = Ceq \times V =3.75 \times 24 = 90 μC.
Potential difference across the 5 µF capacitor
V\(_{5} = \frac{Q}{C} = \frac{90}{5}\) = 18 V
Source: Official Exam / Past Question Archive