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Physics
UTME / JAMB 1991
Electricity and Magnetism
A moving coil galvanometer of 300\(\Omega\) resistance gives full scale deflection for 1.0mA. The resistance R, of the shunt that is required to convert the galvanometer into a 3.0A ammeter is
A
899.70\(\Omega\)
B
10.00\(\Omega\)
C
0.10\(\Omega\)
D
0.01\(\Omega\)
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 #28198)
Physics
UTME / JAMB 1991
Electricity and Magnetism
Which of the following obeys Ohm's Law?
A
Glass
B
Diode
C
All electrolytes
D
All metals
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 #28199)
Physics
UTME / JAMB 1991
Electricity and Magnetism
To convert an alternating current dynamo into a direct current dynamo, the
A
number of turns in the coil is increased
B
strength of the field magnet is increased
C
slip rings are replaced with a split ring commutator
D
coil is wound on a soft iron armature
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 #28201)
Physics
UTME / JAMB 1991
Electricity and Magnetism
If a current carrying coil is mounted on a metal frame, the back e.m.f. induced in the coil causes
A
inductance
B
eddy currents
C
elecro-magnetism
D
dipole moment
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 #28202)
Physics
UTME / JAMB 1991
Electricity and Magnetism
Solution
The electrochemical equivalent of platinum is 5.0 x 10-7kgC-1 to plate-out 1.0kg of platinum, a current of 100A must be passed through an appropriate vessel for
A
5.6 hours
B
56 hours
C
1.4 x 104 hours
D
2.0 x 104 hours
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
m = Itz
1 = 100 x 5 x 10-7 x t
t = 20,000sec
= 5.6hrs
Source: Myschool Past Questions Archive (Record #28203)
Physics
UTME / JAMB 1991
Electricity and Magnetism
When an atom loses or gains a charge, it becomes
A
an electron
B
an ion
C
a neutron
D
a proton
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 #28206)
Physics
UTME / JAMB 1991
Electricity and Magnetism
Which of the following phenomena is called photoelectric effect?
A
high energy electrons impinge on a metalic anode which then emits photons
B
a high energy photon emits photons as it slowed down
C
a metal absorbs quanta of light and then emits electrons
D
Two electrons are created from a quantum of light
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 #28210)
Physics
WAEC / WASSCE 1991
Electricity and Magnetism
Diagram
In which of the points labelled A, B, C, D and E on the conductor shown would electric charge tend to concentrate most?
Attached Figure / Diagram
A
A
B
B
C
C
D
D
E
E
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 #33431)
Physics
WAEC / WASSCE 1991
Electricity and Magnetism
Solution
A house is supplied with a 240V a.c mains. To operate a door bell rated at 8v, a transformer is used if the number of turns in the primary coil of the transformer is 900. calculate the number of turns in the secondary coil of the transformer
A
30
B
240
C
248
D
450
E
1248
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
\(\frac{E_p}{E_s} = \frac{n_p}{n_s}\)
ns = 30
Source: Myschool Past Questions Archive (Record #33438)
Physics
WAEC / WASSCE 1991
Electricity and Magnetism
Diagram
The diagram above shows a current carrying wire between the poles of a magnet. In which direction would the wire tend to move?
Attached Figure / Diagram
A
into the paper
B
out of the paper
C
towargs the north pole of the magnet
D
towards the south pole of the magnet
E
towards the top of the pages
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 #33440)
Physics
UTME / JAMB 1991
Electricity and Magnetism
Diagram
Solution
The internal resistance of each of the cells E\(^1\) and E\(^2\), shown in the figure above, is 2 Ohms. Calculate the total current in the circuit
Attached Figure / Diagram
A
0.80A
B
0.50A
C
0.40A
D
0.004A
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
The total internal resistance is \( r = 1 \, \Omega \) and the total resistance in the circuit is given by:
\(R = 4 + 1 = 5 \, \Omega\)
Using Ohm's law, we have:
\(V = I(R + r)\)
Substituting the values:
\(2 = I \cdot 5\)
Solving for \( I \):
\(I = \frac{2}{5} = 0.4 \, \text{A}\)
Source: Myschool Past Questions Archive (Record #41698)
Physics
UTME / JAMB 1991
Electricity and Magnetism
Diagram
Solution
In the above circuit, The fuse wire melts when
Attached Figure / Diagram
A
K is Opened
B
K is closed
C
the 14 ohm resistor is doubled with k closed
D
the 6 ohm resistor is doubled with k closed
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
K is closed: This is when the current exceeds the 2 A rating of the fuse, causing it to melt.
Source: Myschool Past Questions Archive (Record #41700)
Physics
WAEC / WASSCE 1990
Electricity and Magnetism
Diagram
Solution
Calculate the current in the 3Ω resistor shown in
the diagram above.
Attached Figure / Diagram
A
3.0A
B
4.0A
C
4.3A
D
12.0A
E
39.0A
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
Total Resistance R = 1/R = 1/R1 + 1/R2 + 1/R3
R = 12/13Ω
V = IR = (12/13) x 13 = 12v
1 across 3Ω = V/R = 12/3 = 4A
Source: Myschool Past Questions Archive (Record #24118)
Physics
WAEC / WASSCE 1990
Electricity and Magnetism
Solution
Calculate the resistance of the filament of a lamp rates 240 V, 40 W
A
240Ω
B
360Ω
C
720Ω
D
1440Ω
E
2880Ω
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
R = V2/P = 2402/40 = 1440Ω
Source: Myschool Past Questions Archive (Record #24152)
Physics
WAEC / WASSCE 1990
Electricity and Magnetism
Solution
A cell of e.m.f. 1.5 V and internal resistance of 2.59 is connected in series with an ammeter of resistance 0.59 and a resistor of resistance 7.09. Calculate the current in the circuit.
A
0.15 A
B
0.20 A
C
0.60A
D
3.00A
E
6.67 A.
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
I = E/R + r = 1.5/2.5 + 0.5 + 7 = 0.15
Source: Myschool Past Questions Archive (Record #24154)