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Physics
UTME / JAMB 2026
Electricity and Magnetism
Solution
What mass of silver is deposited by electrolysis when a constant current of 0.8 A is applied for 25 minutes [ z = 12 \times 10\(^{−7}\) kg C\(^{−1}\)]?
A
0.14
B
0.86
C
4.3
D
0.22
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Mass of silver deposited: I =0.8 A , t = 25 min t = 25, z = 12 \times 10\(^{−7}\) kg C\(^{−1}\)
t = 25 \times 60 =1500s
m = z I t = (12 \times 10\(^{−7}\)) \times 0.8 \times 1500 = 1.44 \times 10\(^{−3}\) kg
Source: Myschool Past Questions Archive (Record #78266)
Physics
UTME / JAMB 2026
Electricity and Magnetism
Solution
In Lenz’s law of electromagnetic induction
A
A force is exerted on a current-carrying conductor in a magnetic field
B
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
C
The induced current direction is always in opposition to the change causing it
D
The induced charge is constant for a fixed change of flux
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Lenz’s law states that the direction of the induced current is always such that it opposes the change that produces it.
Source: Myschool Past Questions Archive (Record #78260)
Physics
UTME / JAMB 2026
Electricity and Magnetism
Solution
Which of the following is a secondary cell?
A
Accumulator
B
Daniel cell
C
Leclanche cell
D
Simple cell
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
An accumulator (e.g., a lead-acid battery) can be recharged, so it is a secondary cell. Daniel, Leclanché, and simple cells are primary cells (non-rechargeable).
Source: Myschool Past Questions Archive (Record #78282)
Physics
UTME / JAMB 2026
Electricity and Magnetism
Solution
Which of the following is true of the particles emitted in radioactive disintegration?
A
The beta particles are deflected more than the alpha particles in a magnetic field
B
The alpha particles are deflected more than the beta particles in a magnetic field
C
The alpha particles is the helium nucleus \(^3\)H\(_1\)
D
The alpha particles are lighter than the beta particles
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Beta particles (electrons) have a much higher charge-to-mass ratio than alpha particles, so they experience greater deflection in a magnetic field.
Source: Myschool Past Questions Archive (Record #78285)
Physics
UTME / JAMB 2026
Electricity and Magnetism
Solution
A transformer has primary and secondary windings of 200 and 800 turns, respectively. What is the input voltage if the output voltage is 132kV?
A
45,500V
B
33,000V
C
48,000V
D
250V
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
For a transformer: \(\frac{V_s}{V_p} = \frac{N_s}{N_p}\)
Given: N\(_p\) = 200 turns, N\(_s\) = 800 turns, V\(_p\) = ?, V\(_s\) = 132kv = 132000v
V\(_p\) = \(\frac{V_s \times N_s}{N_p}\)
V\(_p\) = \(\frac{132000 \times 200}{800}\) = 33000V
Source: Myschool Past Questions Archive (Record #78289)
Physics
UTME / JAMB 2025
Electricity and Magnetism
Solution
The emf of a cell is the potential difference across its terminals when it is in
A
series connection
B
closed circuit
C
open circuit
D
parallel connection
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Answer: C.
open circuit (EMF is maximum PD with no current drawn.
Source: Myschool Past Questions Archive (Record #74354)
Physics
UTME / JAMB 2025
Electricity and Magnetism
Solution
What mass of silver is deposited during electrolysis when a current of 0.8 A flows for 25 minutes?
A
0.22 g
B
1.86 g
C
0.14 g
D
1.34g
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Answer: D
To calculate the mass of silver deposited during electrolysis, we use the formula:
\(m = \frac{Q \cdot M}{n \cdot F}\)
Where: \( I = 0.8 \, \text{A} \), \( t = 25 \, \text{minutes} = 25 \times 60 = 1500 \, \text{s} \), \( Q = I \cdot t = 0.8 \, \text{A} \cdot 1500 \, \text{s} = 1200 \, \text{C} \)
\( M = 107.87 \, \text{g/mol} \), \( n = 1 \), \( F \approx 96485 \, \text{C/mol} \)
Substituting the values:
\(m = \frac{1200 \, \text{C} \cdot 107.87 \, \text{g/mol}}{1 \cdot 96485 \, \text{C/mol}} = \frac{129444}{96500} \approx 1.34 \, \text{g}\)
Source: Myschool Past Questions Archive (Record #74387)
Physics
UTME / JAMB 2025
Electricity and Magnetism
Solution
At what distance from a 1.2 x 10\(^{-7}\)C point charge will the electric field intensity be equal to 4.8 x 10\(^{-4}\)NC\(^{-1}\) [ Take \(\frac{1}{4\pi ε_0}\) = 9.0 x 10\(^9\)]
A
1.5Km
B
3.0Km
C
2.0Km
D
4.5Km
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
E = \(\frac{\text{Kq}}{r^2}\)
r = \(\sqrt{\frac{\text{Kq}}{\text{E}}}\)
r = \(\sqrt{\frac{9.0 \times 10^9 \times 1.2 \times 10^{-7}}{4.8 \times 10^{-4}}}\)
r = \(\sqrt{2.25 \times 10^6}\) = 1500m = 1.5km
Source: Myschool Past Questions Archive (Record #74549)
Physics
UTME / JAMB 2025
Electricity and Magnetism
Solution
Which of the following is a basic Unit?
A
Joule
B
Volt
C
Ohm
D
Ampere
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
The ampere is a fundamental SI base unit, representing electric current, and is one of the seven base units used in physics
Source: Myschool Past Questions Archive (Record #74560)
Physics
UTME / JAMB 2025
Electricity and Magnetism
Solution
A boat or airplane has a pointed front or head. This is to
A
Reduce the friction of fluid
B
Enables it to stop anytime
C
Increased the friction of fluid
D
Look good
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
A. Reduce the friction of fluid.
The pointed front of a boat or airplane is designed to minimize drag and reduce the frictional resistance as it moves through water or air, enhancing efficiency and improving performance.
Source: Myschool Past Questions Archive (Record #74571)
Physics
UTME / JAMB 2025
Electricity and Magnetism
Solution
Two identical cells, each of emf 1.5V and internal resistance 1\(\Omega\), are connected in parallel to supply current to a 2 \(\Omega\) resistor. What is the total current
A
O.8A
B
1.0A
C
0.4A
D
0.6A
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Equivalent \(\, emf \, E_{eq} = 1.5 \, \text{V} \, (\text{same as single cell})\).
Equivalent \(\, internal \, resistance \, r_{eq} = \frac{1}{2} = 0.5 \, \Omega \, (\text{parallel})\).
Total \(\, resistance \, R_{total} = r_{eq} + 2 = 2.5 \, \Omega\).
Current \(\, I = \frac{E_{eq}}{R_{total}} = \frac{1.5}{2.5} = 0.6 \, \text{A}\).
Source: Myschool Past Questions Archive (Record #74566)
Physics
UTME / JAMB 2024
Electricity and Magnetism
Solution
One of these is not the use of an electroscope
A
testing the type of charge on a charge body
B
measuring ionization current in air
C
detecting the pressure of charge on a charged body
D
producing electric charge in a body
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
An electroscope is a passive device used to detect and measure charges, not to produce or generate electric charge in a body.
Source: Myschool Past Questions Archive (Record #70690)
Physics
UTME / JAMB 2024
Electricity and Magnetism
Diagram
Solution
In the diagram above, the galvanometer is converted to
Attached Figure / Diagram
A
Voltmeter
B
Ammeter
C
Voltameter
D
Hypsometer
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
When a galvanometer is connected to a shunt resistor, it is converted into an ammeter.
By connecting a shunt in parallel with a galvanometer, it can measure larger currents without getting damaged, turning it into an ammeter
Source: Myschool Past Questions Archive (Record #70685)
Physics
WAEC / WASSCE 2024
Electricity and Magnetism
Solution
State three uses of ferromagnetic materials
medium Difficulty
Verified Correct Answer: Option
Physical Principles & Numerical Solution
The uses of ferromagnetic materials are:
(i) Electromagnets
(ii) Magnetic Storage
(iii) Magnetic Sensors
(iv) Magnetic Shielding
(v) Permanent Magnets
(vi) Inductive Components, others are transformers, electric bells, electric generators, etc.
Source: Myschool Past Questions Archive (Record #72088)
Physics
WAEC / WASSCE 2024
Electricity and Magnetism
Diagram
Solution
(a) You are provided with two resistance wires labelled: A and B, standard resistor, R\(_x\) = 1 \(\Omega\), metre bridge, cell of emf,E, Rheostat R\(_h\), galvanometer and apparatus as shown.
Use the circuit diagram above as a guide to perform the experiment.
(i) Connect R\(_x\) in the left-hand gap of the metre bridge, a length L = 100 cm of the wire in the right-hand gap and the other apparatus shown.
(ii) Determine and record the balance point P on the metre bridge wire NQ
(iii) Measure and record L\(_x\) = NP and L\(_y\) = PQ
(iv) Evaluate R\(_1\) = \(\frac{L_y}{L_x}R_x\)
(v) Repeat the procedure for four other values of L = 90cm, 80cm, 70cm, and 60cm. In each case, determine and record the balance point, P and evaluate R\(_1\)
(vi) Repeat the experiment with the second wire B. Obtain the balance point P and evaluate R\(_2\) in each case
(vii) Tabulate the readings
(viii) Plot a graph of R\(_2\) on the vertical axis and R\(_1\) on the horizontal axis
(ix) Determine the slope, s, of the graph
(x) Evaluate K = \(\sqrt{s}\)
(xi) State two precautions taken to ensure accurate results.
b(i) State two advantages of potentiometer over voltmeter for measuring potential difference
(ii) Define internal resistance of a cell.
Attached Figure / Diagram
medium Difficulty
Verified Correct Answer: Option
Physical Principles & Numerical Solution
(vii)
L(cm)
L\(_x\)(cm)
L\(_y\)(cm)
R\(_1\) = (\(\frac{L_y}{L_x})R_x\)\(\Omega\)
L\(_{x2}\)
L\(_{y2}\)
R\(_2\) = \(\frac{L_{y2}}{L_{x2}}R_x\)\(\Omega\)
100.0
5.2
94.8
18.2
21.5
78.5
3.6
90.0
6.0
94.0
15.7
22.5
77.5
3.4
80.0
6.8
93.2
13.7
23.4
76.6
3.3
70.0
7.6
92.4
12.2
24.5
75.5
3.1
60.0
8.4
91.6
10.9
25.6
74.4
2.9
(viii) SEE THE GRAPH ABOVE
(ix) Slope = \(\frac{\Delta R_2}{\Delta R_1}\) = \(\frac{3.5 - 3.3}{17.0 - 14.6}\) = \(\frac{0.2}{2.4}\) = 0.083
(x) K = \(\sqrt{0.083}\) = 0.2881
(xi) I Tight connection/clean terminal was ensured II. Key removed when readings were not being taken.
b(i) I. A potentiometer can be used for measuring the internal resistance of a cell and also to compare the e.m.f. of two cells. II. A potentiometer gives the exact value of potential difference across any two points in a circuit.
(ii) It refers to the opposition to the flow of current offered by the cells and batteries themselves resulting in the generation of heat.
Source: Myschool Past Questions Archive (Record #72108)