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Physics
UTME / JAMB 1997
Electricity and Magnetism
Solution
Two bodies X and Y are projected on the same horizontal plane, with the same initial speed but at angles 30 and 60 respectively to the horizontal. Neglecting air resistance, the ratio of the range of X to that of Y is
A
1:1
B
1:2
C
√3:1
D
√3
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Range = \(\frac{U^2sin2{\theta}}{g}\)
\(\frac{R_x}{R_y}\) = \(\frac{U^2_xsin60}{U^2_ysin120}\)
sin60o = sin120o
\(\frac{R_x}{R_y}\) = \(\frac{1}{1}\)
hence, = 1:1
Source: Myschool Past Questions Archive (Record #27681)
Physics
UTME / JAMB 1997
Electricity and Magnetism
Solution
An electric water pump rate 1.5 kW, lifts 200kg of water through a vertical height of 6 meters in 10 seconds. What is the efficiency of the pump? [g = 10ms-2, neglecting air resistance]
A
90.0%
B
85.0%
C
80.0%
D
65.0%
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Efficiency = output x 100
= \(\frac{\frac{200 {\times} 10 {\times} {6}}{10}}{1500}\) x \(\frac{100}{1}\)
= 80%
Source: Myschool Past Questions Archive (Record #27686)
Physics
UTME / JAMB 1997
Electricity and Magnetism
Solution
Three electric cells each of e.m.f 1.5V and internal resistance of 1.0\(\Omega\) are connected in parallel across an external resistance of \(\frac{2}{3}\)\(\Omega\). Calculate the value of the current in the resistor
A
0.5 A
B
0.9A
C
1.5A
D
4.5A
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
E.m.f = 1.5
r = \(\frac{1 \times\ 1 \times 1}{(1 \times\ 1) + (1 \times\ 1) + (1 \times\ 1)}\)
r = \(\frac{1}{3}\)\(\Omega\)
I = \(\frac{E.m.f}{r + R}\)
I = \(\frac{1.5}{\frac{1}{3}\ + \frac{2}{3}}\)
I = 1.5A
Source: Myschool Past Questions Archive (Record #27717)
Physics
UTME / JAMB 1997
Electricity and Magnetism
A galvanometer of internal resistance 50\(\Omega\) has a full scale deflection for a current of 5mA. What is the resistance required to covert it to a voltmeter with full scale deflection of 10V?
A
1750\(\Omega\)
B
1950\(\Omega\)
C
2000\(\Omega\)
D
2500\(\Omega\)
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 #27723)
Physics
UTME / JAMB 1997
Electricity and Magnetism
Solution
Two 50\(\mu\)F parallel plate capacitors are connected in series. The combined capacitor is then connected across a 100-V battery. The charge on each plate of the capacitor is
A
5.00 x 10-5C
B
2.50 x 10-3C
C
1.25 x 10-3C
D
1.00 x 10-2C
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
For series, C = \(\frac{50 \times\ 50}{50 + 50}\)
C= 25\(\mu\)F
Q = CV
Q = 25 x 100 x 10-3
Q = 2.5 x 10-3C
Source: Myschool Past Questions Archive (Record #27732)
Physics
UTME / JAMB 1997
Electricity and Magnetism
In a purely inductive circuit, the current
A
lags behind the voltage in phase by 90o
B
leads the voltage in phase by 90o
C
is in the same phase with the voltage
D
leads the voltage by 180o
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 #27736)
Physics
WAEC / WASSCE 1996
Electricity and Magnetism
The heating element in an electric kettle is usually located near the bottom of the kettle because
A
water is a good conductor of heat
B
heat can be more quickly radiated to all parts of the water
C
no heat can be lost to the surroundings
D
the convectional currents which are set up can carry heat to all parts of the water
E
the molecules of the heating element can carry heat to all parts of the water.
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 #25216)
Physics
WAEC / WASSCE 1996
Electricity and Magnetism
Which of the following is not a component of a d.c. electric motor?
A
Commutator
B
Field magnets
C
Slip rings
D
Armature
E
Carbon brushes
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 #25241)
Physics
WAEC / WASSCE 1996
Electricity and Magnetism
Diagram
The diagram above illustrates the conversion of a galvanometer of resistance 29 to an ammeter. The galvanometer gives a full-scale deflection for a current of 10mA. Calculate the value of R.
Attached Figure / Diagram
A
2.0 x 103 Ω
B
2.0 x 102 Ω
C
2.0 x 10-1 Ω
D
2.0 x 10-2 Ω
E
2.0 x 10-3 Ω
medium Difficulty
Verified Correct Answer: Option E
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option E.
Source: Myschool Past Questions Archive (Record #25242)
Physics
WAEC / WASSCE 1996
Electricity and Magnetism
Solution
A wire of length 100cm and cross-sectional area of 2.0 x 10-3cm2 has a resistance of 0.10 \Omega. Calculate its electrical conductivity.
A
5.0 x 107Ω-1cm-1
B
5.0 x 106Ω-1cm-1
C
2.0 x 106Ω-1cm-1
D
5.0 x 105Ω-1cm-1
E
2.0 x 106Ω-1cm-1
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Given: Length of the wire, \( L = 100 \, \text{cm} = 1.0 \, \text{m} \), Cross-sectional area, \( A = 2.0 \times 10^{-3} \, \text{cm}^2 = 2.0 \times 10^{-7} \, \text{m}^2 \)
Resistance, \( R = 0.10 \, \Omega \)
The formula for resistivity \( \rho \) is given by:
\(\rho = R \cdot \frac{A}{L}\)
Substituting the values:
\(\rho = 0.10 \, \Omega \cdot \frac{2.0 \times 10^{-7} \, \text{m}^2}{1.0 \, \text{m}} = 2.0 \times 10^{-8} \, \Omega \cdot \text{m}\)
Now, we can find the conductivity \( \sigma \):
\(\sigma = \frac{1}{\rho} = \frac{1}{2.0 \times 10^{-8} \, \Omega \cdot \text{m}} = 5.0 \times 10^{7} \, \Omega^{-1} \cdot \text{m}^{-1}\)
To convert to \( \text{cm}^{-1} \):
\(\sigma = 5.0 \times 10^{7} \, \Omega^{-1} \cdot \text{m}^{-1} \times \left( \frac{1}{100 \, \text{cm}} \right) = 5.0 \times 10^{5} \, \Omega^{-1} \cdot \text{cm}^{-1}\)
Thus, the electrical conductivity is:
\(\sigma = 5.0 \times 10^{5} \, \Omega^{-1} \cdot \text{cm}^{-1}\).
Source: Myschool Past Questions Archive (Record #25243)
Physics
WAEC / WASSCE 1996
Electricity and Magnetism
Lenz's law of electromagnetic induction states that
A
e.m.f. is induced in a circuit whenever there is a change in the magnetic flux linked with the circuit.
B
the induced current in a conductor is in such a direction as to oppose the change producing it
C
the magnitude of the induced e.m.f. in a circuit is proportional to the rate of change of the number of lines of force linking the circuit
D
a force is exerted on a current-carrying conductor in a magnetic Held
E
the induced charge is constant for a fixed change of flux.
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 #25244)
Physics
WAEC / WASSCE 1996
Electricity and Magnetism
A cell of e.m.f. 1.5V is connected in series with a resistor of resistance 39. A high-resistance voltmeter connected across the cell registers only 0.9V. Calculate the internal resistance of the cell
A
1.85Ω
B
2.0Ω
C
2.4Ω
D
4.5Ω
E
5.0Ω
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 #25245)
Physics
WAEC / WASSCE 1996
Electricity and Magnetism
Soft iron is used in making the armature of an electric bell because it
A
retains its magnetism for a longtime
B
Loses its magnetism readily
C
Produces permanent magnets
D
is not easily magnetised
E
decreases the magnetic effect of a direct current
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 #25246)
Physics
WAEC / WASSCE 1996
Electricity and Magnetism
Diagram
The diagram above illustrates an isolated metal sphere carrying charge W in a medium whose permittivity is so. The magnitude of the electric field intensity at P can be expressed as
Attached Figure / Diagram
A
Q2/(4πεor2)
B
Q/(4πεor2)
C
Q/(4πεor)
D
Q2/(4πεor2)
E
Q/(4πεor) 2
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 #25247)
Physics
WAEC / WASSCE 1996
Electricity and Magnetism
Diagram
The electric potential at point P in the diagram above can be expressed as
Attached Figure / Diagram
A
Q2/(4πεor2)
B
Q/(4πεor2)
C
Q/(4πεor)
D
Q2/(4πεor2)
E
Q/(4πεor) 2
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 #25248)