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Physics
UTME / JAMB 1990
Waves, Sound & Vibrations
Solution
A sonometer wire of length 100cm under a tension of 10N, has a frequency of 250Hz. Keeping the length of the wire constant, the tension is adjusted to produce a new frequency of 350Hz. The new tension is
A
5.1N
B
7.1N
C
14.0N
D
19.6N
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
\(\frac{F_1}{F_2}\) = \(\sqrt\frac{T_1}{T_2}\)
\(\frac{250}{350}\) = \(\sqrt\frac{10}{T_2}\)
T2 = 19.6N
Source: Myschool Past Questions Archive (Record #28267)
Physics
UTME / JAMB 1990
Magnetism, Electromagnetism & AC Circuits
One of the properties of the earth's magnetic field is that the
A
north pole lies in the northern hemisphere
B
geographic and magnetic meridians coincide
C
earth's magnetic flux is entirely horizontal at a place where the magnetic dip is zero
D
earth's magnetic flux is entirely vertical at a place where the magnetic dip is zero
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 #28270)
Physics
UTME / JAMB 1990
Work, Energy, Power & Simple Machines
Solution
Which of the following statements are true of an insulated charged body carrying positive charge? i. it contains excess positive charges. ii. it creates an electric field. iii. it possesses potential energy. iv. it carries electric current.
A
i and iv only
B
i and ii only
C
i, ii, iii only
D
i, ii, iii and iv
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
The correct answer is C. i, ii, iii only, as the insulated charged body carries excess positive charges, creates an electric field, and possesses potential energy, but does not carry electric current(An insulated charged body carrying a positive charge does not carry electric current because it is not part of a circuit that allows the flow of charge.)
Source: Myschool Past Questions Archive (Record #28274)
Physics
UTME / JAMB 1990
Electrostatics & Capacitors
Which of the following is a vector?
A
Electric charge
B
Electric field
C
Electrical potential difference
D
Electrical capacitance
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 #28275)
Physics
UTME / JAMB 1990
Current Electricity & Electric Circuits
Solution
Three cells each of e.m.f. 1.5v and an internal resistance of 1.0\(\Omega\) are connected in parallel across a load resistance of 2.67\(\Omega\). Calculate the current in the load?
A
0.26A
B
0.41A
C
0.50A
D
0.79A
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
E = 1.5v
rT = \(\frac{1 \times 1\times 1}{(1\times1)+ (1\times1) +(1\times1)}\)
E.m. f = I(R + r) = 0.33\(\Omega\)
1.5 = I(2.67 + 0.33)
I = 0.5A
Source: Myschool Past Questions Archive (Record #28278)
Physics
UTME / JAMB 1990
Current Electricity & Electric Circuits
Solution
When a known standard resistor of 2\(\Omega\) is connected to the 0.0cm end of a meter bridge, the balance point is found to be at 55.0cm. What is the value of the unknown resistor?
A
1.10\(\Omega\)
B
1.64\(\Omega\)
C
2.44\(\Omega\)
D
27.50\(\Omega\)
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
\(\frac{R_1}{R_2}\) = \(\frac{L_1}{R_2}\)
\(\frac{2}{R_2}\) = \(\frac{55}{45}\)
R = 1.64\(\Omega\)
Source: Myschool Past Questions Archive (Record #28279)
Physics
UTME / JAMB 1990
Current Electricity & Electric Circuits
Solution
The total energy required to send a unit positive charge round a complete electrical circuit is the
A
kinetic energy
B
potential difference
C
electromotive force
D
electrical energy
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Electromotive Force (EMF) refers to the total energy supplied by a source (like a battery) to move a unit positive charge around a complete circuit. It is measured in volts and indicates how much energy per unit charge is available to drive the current through the circuit.
Source: Myschool Past Questions Archive (Record #28281)
Physics
UTME / JAMB 1990
Current Electricity & Electric Circuits
Which of the following is an essential physical property of the wires used for making fuses?
A
low density
B
high thermal conductivity
C
low electrical resistivity
D
low melting point
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 #28285)
Physics
UTME / JAMB 1990
Current Electricity & Electric Circuits
Solution
Which of the following is most suitable for protecting the circuit of 2000W electric iron connected to a 250V mains?
A
13A
B
8A
C
5A
D
3A
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
P = IV \(\Rightarrow\) I = \(\frac{2000}{250}\)
= 8A
The fuse rating should be higher than the calculated current to avoid nuisance blowing, but still protect the circuit. Therefore, the most suitable fuse rating from the options provided would be: 13A
Source: Myschool Past Questions Archive (Record #28287)
Physics
UTME / JAMB 1990
Current Electricity & Electric Circuits
Electrical power is transmitted at a high voltage rather than low voltage because the amount of energy loss is reduced due to
A
heat dissipation
B
production of eddy currents
C
excessive current discharge
D
excessive voltage distance
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 #28291)
Physics
UTME / JAMB 1990
Current Electricity & Electric Circuits
Solution
A lamp is rated 240V, 60W. The resistance of the filament is
A
960\(\Omega\)
B
16\(\Omega\)
C
15\(\Omega\)
D
4\(\Omega\)
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
P = \(\frac{V_2}{R}\) \(\Rightarrow\) R = \(\frac{V_2}{p}\)
= \(\frac{240\times 240}{60}\)
= 960\(\Omega\)
Source: Myschool Past Questions Archive (Record #28295)
Physics
UTME / JAMB 1990
Current Electricity & Electric Circuits
A 0 - 10mA galvanometer with a coil resistance of 30\(\Omega\) can be converted to a 0 - 10A ammeter by using
A
0.03\(\Omega\) series resistor
B
0.03\(\Omega\) shunt resistor
C
9.99\(\Omega\) shunt resistor
D
9.99\(\Omega\) series resistor
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 #28297)
Physics
UTME / JAMB 1990
Current Electricity & Electric Circuits
Solution
The number of neutrons contained in the nucleus \(^{238}_{92}U\) is
A
92
B
146
C
238
D
330
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
238 - 92 = 146
Source: Myschool Past Questions Archive (Record #28298)
Physics
UTME / JAMB 1990
Magnetism, Electromagnetism & AC Circuits
What precaution should a manufacturer take to ensure that energy loss in a transformer is minimized?
A
the winding of the transformer should be made of high resistance wire
B
the core should be made of thin sheets of metal
C
no magnetic material should be used to make the core
D
the flux linking the primary with the secondary coils should be minimum
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 #28299)
Physics
UTME / JAMB 1990
Atomic, Quantum, Nuclear Physics & Electronics
Solution
A substance has a half of 3mins. after 6mins. the count rate was observed to be 400. What was its count rate at zero time?
A
200
B
1200
C
1600
D
2400
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Let the count rate at zero time be K
Count rate after 3mins, = \(\frac{K}{2}\)
Count rate after 6mins = \(\frac{K}{4}\)
but count after 6mins = 400 ( given )
Then = \(\frac{K}{4}\) = 400
K = 4 X 400 = 1600
∴ = count rate at zero time = 1600.
Source: Myschool Past Questions Archive (Record #28301)