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Physics
UTME / JAMB 2013
Electricity and Magnetism
Solution
To convert a galvanometer to a voltmeter, a
A
high resistance is connected to it in series
B
high resistance is connected to it in parallel
C
low resistance is connected to it in parallel
D
low resistance is connected to it in series
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
To convert a galvanometer (which measures current) into a voltmeter (which measures voltage), a high resistance is connected in series with the galvanometer. This limits the current flowing through the galvanometer, allowing it to measure higher voltages without exceeding its maximum current rating.
Source: Myschool Past Questions Archive (Record #27366)
Physics
UTME / JAMB 2013
Electricity and Magnetism
Solution
If a current of 2.5A flows through an electrolyte for 3 hours and 1.8g of a substance is deposited, what is the mass of the substance that will be deposited if a current of 4A flows through it for 4.8 hours?
A
2.4g
B
3.2g
C
4.6g
D
4.8g
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
First let's find z
z = \(\frac{M}{It}\)
z = \(\frac{1.8}{2.5 \times (3 \times 60 \times 60)}\)
Therefore, the new M equals
M = zIt
M = \(\frac{1.8 \times 4 \times 4.8 \times 60 \times 60}{2.5 \times 3 \times 60 \times 60}\)
M = 4.6g
Source: Myschool Past Questions Archive (Record #27368)
Physics
WAEC / WASSCE 2013
Electricity and Magnetism
Solution
An electric heater has a resistance of 50\(\Omega\). When it is immersed in water and connected to mains source, it draws a current of 4.0A. Calculate the heat gained by the water if the heater is switched on for 2 minutes, assuming no heat losses to the surroundings
A
4200J
B
1600J
C
24000J
D
96000J
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Q = \(I^2RT\)
= \(4^2\) x 50 x 2 x 60
= 96000J
Source: Myschool Past Questions Archive (Record #35670)
Physics
WAEC / WASSCE 2013
Electricity and Magnetism
When a person holds a negatively charges metal rod and stands bare-footed on the ground, how will the charges leak?
A
negative charges flows to the ground through the person's body
B
positive charges flow from the ground through his body to neutralize the negative charges
C
positive charges in the air neutralizes the negative charges the person is holding
D
negative charges will leak through the air
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 #35686)
Physics
WAEC / WASSCE 2013
Electricity and Magnetism
Solution
The capacitance of parallel plates capacitors varies
A
inversely as the square of the distance between the plates
B
directly as the square of the distance between the plates
C
inversely as the distance between the plates
D
directly as the distance between the plate
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
capacitance C is the ability of the capacitor to store charges. and it depends on the size A, shape, and separation d of the conductors and the material separating them ε
C = \(\frac{εA}{d}\)
C is inversely proportional to d.
Source: Myschool Past Questions Archive (Record #35700)
Physics
WAEC / WASSCE 2013
Electricity and Magnetism
Solution
Which of the following devices does not makes use of eddy current for its action? A/An
A
galvanometer
B
speedometer
C
induction furnace
D
induction coil.
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
an induction coil is used to create high potential differences from sources of low potential differences. it does not make of Eddy's current for its action.
Source: Myschool Past Questions Archive (Record #35703)
Physics
WAEC / WASSCE 2013
Electricity and Magnetism
Solution
A coil of inductance 0.12 H and resistance 4\(\Omega\), is connected across a 240V, 50Hz supply. Calculate the current through it. [\(\pi\) = 3.142]
A
6.3A
B
33.3A
C
37.2A
D
40.0A
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
XL = \(2\pi f L\)
= = 2 x 3.142 x 50 x 0.12
= 37.68\(\Omega\)
Z = \(\sqrt{R^2 + X_L^2} = \sqrt{4^2 + 37.68^2}\)
I = \(\frac{V}{z} = \frac{240}{37.89}\)
= 6.3A
Source: Myschool Past Questions Archive (Record #35714)
Physics
WAEC / WASSCE 2013
Electricity and Magnetism
Diagram
Solution
An electric circuit is connected as illustrated above. Determine the equivalent e.m.f and current flowing through the circuit respectively, neglecting the internal resistance of the cells
Attached Figure / Diagram
A
2V, 1.0A
B
2V, 4.0A
C
6V, 0.3a
D
6V, 3.0a
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Net e.m.f = 2.0v ( parallel connection)
= 2V, R = 2\Omega
I = \(\frac{v}{R} = \frac{2}{2}\)
= 1A
Source: Myschool Past Questions Archive (Record #35733)
Physics
UTME / JAMB 2012
Electricity and Magnetism
A newly charged 12V accumulator can easily start a car whereas eight new dry cells in series with a effective e.m.f. of 12V cannot start the same car because
A
The current capacity is high
B
The current capacity is low
C
it cannot be re-charged
D
it cannot easily be connected to a car
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 #27415)
Physics
UTME / JAMB 2012
Electricity and Magnetism
The fuse in an electric device is always connected to the
A
neutral side of an electric supply
B
earth side of an electric supply
C
live side of an electric supply
D
terminal side of an electric supply
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 #27417)
Physics
UTME / JAMB 2012
Electricity and Magnetism
Solution
The current output from of an a.c. source is given as I = 10 sin to t. The d.c equivalent of the current is
A
5.0A
B
7.1A
C
10.0A
D
14.1A
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
Irms = \(\frac{10}{\sqrt{2}}\)
Source: Myschool Past Questions Archive (Record #27420)
Physics
UTME / JAMB 2012
Electricity and Magnetism
Which of the following CANNOT be deflected by both electric and magnetic fields?
A
Gamma rays
B
Alpha particles
C
Wave particles
D
Beta particles
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 #27423)
Physics
UTME / JAMB 2012
Electricity and Magnetism
Solution
If a reverse-biased voltage is applied across a p-n junction, the depletion layer width is
A
increased
B
decreased
C
constant
D
halved
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
The width of the depletion layer in a p-n junction diode increases in reverse bias as charge carriers are swept into battery terminals, holes from the p-type into the negative terminal, and electrons from the n-type into the positive terminal.
Source: Myschool Past Questions Archive (Record #27426)
Physics
WAEC / WASSCE 2012
Electricity and Magnetism
Solution
An object is dropped from the top of a tower. If it takes 4s for it to reach the ground, calculate the height of the tower.(g = 10 ms-2, ignore air resistance)
A
20m
B
40m
C
80m
D
160m
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
H = \(\frac{1}{2} gt^2\)
\(\frac{1}{2} \times 10 \times 4^2 = 80\)
Source: Myschool Past Questions Archive (Record #35534)
Physics
WAEC / WASSCE 2012
Electricity and Magnetism
The magnetic relay is a device used for
A
timing in sports
B
storing magnetic field
C
readin the magnitude of magnetic flux
D
controlling another circuit carrying larger current
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 #35624)