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Physics
UTME / JAMB 2000
Electricity and Magnetism
Solution
A cell of internal resistance 1Ω supplies current to an external resistor of 3Ω. The efficiency of the cell is
A
25%
B
33%
C
50%
D
75%
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Efficiency = Output/input x 100/1
Efficiency = 3/(3+1) x 100/1
= 3/4 x 100/1 = 75%
Source: Myschool Past Questions Archive (Record #1501)
Physics
UTME / JAMB 2000
Electricity and Magnetism
Diagram
Solution
The diagram above shows two capacitors P and Q of capacitance 5\muF and 10\muF. Find the charges stored in P and Q respectively
Attached Figure / Diagram
A
2μC and 4μC
B
4μC and 2μC
C
100μC and 200μC
D
200μC and 100μC
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Since capacitance C = Q/V, => Q = CV
∴ Qp = 5 x 10\(^{-6}\) x 20
= 100 x 10\(^{-6}\) or 100\muC
Qp = 10 x 10\(^{-6}\) x 20
= 200 x 10\(^{-6}\) or 200\muC
Correct option 100\muC and 200\muC
Source: Myschool Past Questions Archive (Record #11721)
Physics
UTME / JAMB 2000
Electricity and Magnetism
Diagram
Solution
In the diagram above, the values of V1 and V2 are respectively
Attached Figure / Diagram
A
1V and 1/3V
B
1/3V and 1V
C
1/3V and 2/3V
D
1V and 2/3V
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Effective resistance in the circuit
= 3 + 2 + 1 = 6\Omega
Current through the I = \(\frac{E}{(R+r)}\)
∴ I = \(\frac{2}{6}\)
=> V1 = I x R1 = \(\frac{2}{6}\times\frac{3}{1}\) = 1V
= V2 = I x R2 = \(\frac{2}{6}\times\frac{2}{1}\) = \(\frac{2}{3}\)V
∴ we have 1V and \(\frac{2}{3}\)V
Source: Myschool Past Questions Archive (Record #11737)
Physics
UTME / JAMB 2000
Electricity and Magnetism
Diagram
Solution
The correct position for a fuse in the diagram above is
Attached Figure / Diagram
A
between P and Q
B
Q
C
S
D
P
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
In the provided circuit diagram, the correct position for a fuse is between the "Line" connection and the component labeled "P".
The purpose of a fuse is to protect the circuit and the connected device from excessive current flow that could potentially cause damage. By placing the fuse at position P, it will be in series with the "live" or "hot" wire, allowing it to interrupt the circuit if the current exceeds the fuse's rated capacity.
Source: Myschool Past Questions Archive (Record #11739)
Physics
UTME / JAMB 2000
Electricity and Magnetism
Diagram
Solution
In the a.c circuit above, the current value is
Attached Figure / Diagram
A
0.58 A
B
3.00 A
C
4.00 A
D
6.67 A
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Impedance Z = \(\sqrt{R^2 + X^2}\)
= \(\sqrt{(30)^2 + (40)^2}\)
∴ Z = \(\sqrt{2500}\) = 50\(\Omega\)
But current I = \(\frac{V}{Z}\) = \(\frac{200}{50}\) = 4.00 A
Source: Myschool Past Questions Archive (Record #11745)
Physics
WAEC / WASSCE 2000
Electricity and Magnetism
Solution
A device used to prevent wearing away of the make and-brake contacts of an induction coil is called a\an
A
fuse
B
electroscope
C
resistor
D
capacitor
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
A capacitor can be used in circuits with induction coils to smooth out voltage spikes and reduce arcing at the contacts. It helps absorb sudden changes in voltage, thereby minimizing wear and prolonging the life of the contacts.
Source: Myschool Past Questions Archive (Record #33840)
Physics
WAEC / WASSCE 2000
Electricity and Magnetism
Solution
calculate the inductance of an inductor whose reactance is one ohm at 50 Hz.
A
2.00 x 10-2H
B
6.36 x 10-2H
C
3.18 x 10-3H
D
4.55 x 10-2H
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
The inductive reactance (X\(_L\)) of an inductor is given by the formula:
Given: X\(_L\) = 1\(\Omega\), f = 50Hz
X\(_L\) = 2\pifL
L = \(\frac{1}{2\pif}\) = \(\frac{1}{2\pi \times50}\) = \(\frac{1}{100\pi}\) = 3.183 x 10\(^{-3}\)H
Source: Myschool Past Questions Archive (Record #33844)
Physics
WAEC / WASSCE 2000
Electricity and Magnetism
Diagram
Solution
In the diagram above, the current passing through the 6\(\Omega\) resistor is 1.5A. Calculate the current in the 3\(\Omega\) resistor
Attached Figure / Diagram
A
1.20A
B
0.90A
C
0.75A
D
0.60A
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
\(\frac{1}{\text{R}}\) = \(\frac{1}{2}\) + \(\frac{1}{3}\) = \(\frac{5}{6}\)
R = \(\frac{6}{5}\) = 1.2\(\Omega\); So p.d through the 3\(\Omega\) and 2\(\Omega\) resistors in parallel = 1.5 x 1.2 =1.8V
So the current through the 3\(\Omega\) resistor(I) = \(\frac{\text{V}}{\text{R}}\) = \(\frac{1.8}{3}\) = 0.6A (recall V = IR)
Source: Myschool Past Questions Archive (Record #33836)
Physics
WAEC / WASSCE 2000
Electricity and Magnetism
Solution
The region around a magnet in which the magnetic influence is experienced is called
A
magnetic flux
B
magnetic field
C
magnetic meridian
D
magnetic declination
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
"magnetic field" is the term that describes the region where magnetic effects are felt.
Source: Myschool Past Questions Archive (Record #33839)
Physics
NECO SSCE 2000
Electricity and Magnetism
If a positively charged glass-rod is used to charge an electroscope X by contact and an electroscope Y by induction, then
A
X and Y will be negatively charge
B
X and Y will be positively charged
C
X will be negatively charged and Y positively charged
D
X will be positively charged and Y negatively charged
E
X will be positively charged and Y will remain uncharged
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 #42737)
Physics
NECO SSCE 2000
Electricity and Magnetism
An electric iron rated 250 V has a coil of resistance 125Ω. What is the cost of using it for I hour at 10k per kWh?
A
1.25k
B
2.50k
C
5.00k
D
10.00k
E
20.00k
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 #42752)
Physics
NECO SSCE 2000
Electricity and Magnetism
Solution
Calculate the peak voltage of a mains supply of r.ms. value 220V.
A
121 V
B
156 V
C
225 V
D
240 V
E
311 V
medium Difficulty
Verified Correct Answer: Option E
Physical Principles & Numerical Solution
To calculate the peak voltage (\(V_p\)) from the root mean square (RMS) voltage (\(V_{rms}\)), we use the formula:
\(V_p = V_{rms} \times \sqrt{2}\)
Given:
\(V_{rms} = 220 \, \text{V}\)
Calculate the Peak Voltage
\(V_p = 220 \, \text{V} \times \sqrt{2} \approx 220 \, \text{V} \times 1.4142 \approx 311.1 \, \text{V}\)
The peak voltage is approximately:
311 V
Source: Myschool Past Questions Archive (Record #42771)
Physics
NECO SSCE 2000
Electricity and Magnetism
Two 2.0Ω resistors can be combined circuit to give an overall resistance of
A
0.5Ω only
B
1.0 Ω only
C
either 0,5Ω or 1.0 Ω
D
either 1.0Ω or 4.0 Ω
E
either 0.5Ω, 1.0Ω or 4.0Ω
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 #42775)
Physics
NECO SSCE 2000
Electricity and Magnetism
Which of the following is/areNOT affected by a magnetic field?
I. Alpha particle
II. Cathode rays
III. Neutrons
A
I only
B
II only
C
III only
D
I and II only
E
I,II & 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 #42800)
Physics
NECO SSCE 2000
Electricity and Magnetism
An electric bell operated within an evacuated bell jar enables us to infer correctly that
A
light waves require a medium for transmission
B
sound waves do not require a medium for transmission
C
light waves do not require a medium for transmission but sound waves do
D
light waves travel much faster than sound waves
E
light waves and sound waves travel at the same speed
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 #42809)