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Physics
UTME / JAMB 1989
Electricity and Magnetism
Solution
The electrochemical equivalent of silver is 0.0012gC-1. If 36.0g of silver is to be deposited by electrolysis on a surface by passing a steady current for 5.0mins, the current must be
A
6000A
B
100A
C
10A
D
1A
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
m = Itz \(\Rightarrow\) I = m = \(\frac{36}{5\times 60 \times 0.0012}\)
= 100A
Source: Myschool Past Questions Archive (Record #28360)
Physics
UTME / JAMB 1989
Electricity and Magnetism
Diagram
In the above circuit diagrams A is the ammeter and V is the Voltmeter. Which of the circuits is correct for finding the correct value of the resistance R
Attached Figure / Diagram
A
I
B
II
C
III
D
IV
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 #41686)
Physics
UTME / JAMB 1989
Electricity and Magnetism
Diagram
The fig above shows a conductor PQ carrying a current I in the direction shown. At a particular position near the conductor is a compass needle K. Neglecting the earth's magnetic field, the compass needle will
Attached Figure / Diagram
A
settle in any direction
B
settle in a fixed direction only if the conductor PQ is a magnetic material
C
settle in a fixed direction WHETHER the conductor PQ is a magnetic material OR NOT
D
be stationary
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 #41689)
Physics
WAEC / WASSCE 1988
Electricity and Magnetism
If the leaves a positively charged electroscope collapse completely as an object is brought near the cap of the electroscope, the objects possesses
A
an equal amount of positive charge
B
less amount of negative charge
C
no charge
D
a positive charge
E
an equal amount of negative charge
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 #21251)
Physics
WAEC / WASSCE 1988
Electricity and Magnetism
Solution
A transformer with 5500 turns in its primary is used between a 240V a. c supply and a 120V kettle. Calculate the number of turns in the secondary
A
11000
B
2750
C
460
D
232
E
10
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
\(\frac{E_p}{E_s}\) = \(\frac{n_p}{n_s}\)
\(\frac{240}{120}\) = \(\frac{5500}{n_s}\)
=> n\(_s\) = 2750
Source: Myschool Past Questions Archive (Record #21252)
Physics
WAEC / WASSCE 1988
Electricity and Magnetism
Local action is normally prevented from taking place in a simple electric cell by
A
introducing an oxidising agent into the acid
B
not drawing current continuously for long periods
C
amalgamating the surface of the zinc plate
D
using a porous pot to isolate the zinc plate from the acid
E
using dilute sulphuric acid
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 #21253)
Physics
WAEC / WASSCE 1988
Electricity and Magnetism
Solution
A cell can supply current of 0.8A and 0.4A through a 2\Omega and a 3\Omega resistors respectively. Calculate the internal resistance of the cell.
A
0.2Ω
B
0.4Ω
C
1.0Ω
D
3.0Ω
E
9.0Ω
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Assume the internal resistor = R
Current with 2 Ohm Resistor = 0.80A
Voltage = (R + 2) x 0.80 = V ; That is 0.8R + 1.6 = V ———————[[1]
Current with 3 Ohm Resistor = 0.40 A
Voltage = (R+3) x 0.40 = V ; That is 0.4R + 1.2 = V ————————[[2]
Subtracting 1 from 2 gives
--> (0.8 - 0.4) R
( 1.6 - 1.2 )
( V - V )
Therefore
0.4R + 0.4 = 0
R = 0.4 /0.4 = 1 Ohms
Source: Myschool Past Questions Archive (Record #21254)
Physics
WAEC / WASSCE 1988
Electricity and Magnetism
Solution
A battery of emf 24V and internal resistance 4Ω is connected to a resistor of 32Ω. What is the terminal p.d of the battery?
A
24.0V
B
21.3V
C
16.0V
D
2.7V
E
2.0V
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
E = V + Ir
V = E- Ir
V = 24 - {(24/36) x 4}
V = 21.3V
Source: Myschool Past Questions Archive (Record #21256)
Physics
WAEC / WASSCE 1988
Electricity and Magnetism
Two parallel conductors carry equal currents in the same direction. Which of the following statement is not a correct observation?
A
Each of teh conductors will experience a force
B
Each of the conductors can move
C
The forces on the conductors will be equal
D
There are concentric lines of force around each conductor
E
The two conductors will repel each other
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 #21257)
Physics
WAEC / WASSCE 1988
Electricity and Magnetism
Solution
It takes 4 minutes to boil a quantity of water electrically. How long will it take to boil same quantity of water using the same heating coil but with the current doubled? (neglecting any external heat loss).
A
64 minutes
B
32 minutes
C
8 minutes
D
2 minutes
E
1 minute
medium Difficulty
Verified Correct Answer: Option E
Physical Principles & Numerical Solution
D ∝ l2
E will increase 4 times when current is doubled.
Therefore time will decrease by a factor of 4, which is 1 minute.
Source: Myschool Past Questions Archive (Record #21258)
Physics
WAEC / WASSCE 1988
Electricity and Magnetism
Solution
Calculate the resistivity of a wire of length 2m and cross-sectional area 0.004m2 if the resistance is 3.0 \Omega.
A
0.0000267Ωcm
B
0.006Ωcm
C
0.26700Ωcm
D
0.27500Ωcm
E
0.060000Ωcm
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
R = \alphaL/A
0.004 cm\(^2\) is equal to 0.00000004 m\(^2\)
P = RA/L = (3 x 0.00000004)/2 = 0.00000006 \Omegacm
Source: Myschool Past Questions Archive (Record #23842)
Physics
WAEC / WASSCE 1988
Electricity and Magnetism
Which of the following is/are not affected by a magnetic field?
I. Neutrons
II. Cathode rays
III. Alpha particles
A
I only
B
II only
C
III only
D
I & III only
E
I, II & III
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 #23848)
Physics
UTME / JAMB 1988
Electricity and Magnetism
Solution
A cell of internal resistance 2 ohms supplies current to a 6 ohms resistor. The efficiency of the cell is
A
12.0%
B
25.0%
C
33.3%
D
75.0%
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Efficiency = \(\frac{IR}{I(R + r)}\) x 100
= \(\frac{6}{I(2 + 6)}\) x 100
= 75%
Source: Myschool Past Questions Archive (Record #28392)
Physics
UTME / JAMB 1988
Electricity and Magnetism
Solution
When a resistance R is across a cell, the voltage across the terminals of the cell is reduced to two-third of its normal value. The internal resistance of the cell is
A
\(\frac{2}{1}\)R
B
\(\frac{1}{2}\)R
C
\(\frac{3}{2}\)R
D
5R
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
IR = \(\frac{2}{3}\) I(R + r)
r = \(\frac{1}{2}\)R
Source: Myschool Past Questions Archive (Record #28393)
Physics
UTME / JAMB 1988
Electricity and Magnetism
Solution
Which of the following ammeters may be used to measure alternating currents? i. moving-coil ammeter ii. moving-iron ammeter iii. hot-wire ammeter
A
i and ii only
B
ii and iii only
C
i and iii only
D
i, ii, and iii
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
Moving-coil ammeter: Primarily used for direct current (DC) only, as it relies on a constant magnetic field and does not accurately respond to AC.
Moving-iron ammeter: Suitable for measuring both AC and DC currents. It operates based on the magnetic effect of the current, making it effective for AC.
Hot-wire ammeter: Specifically designed for measuring AC currents. It utilizes the heating effect of the current and provides accurate readings for AC.
Source: Myschool Past Questions Archive (Record #28395)