Q7960.If current flows in the direction of the arrows in the solenoid above, the North pole is at
AP
BX
CQ
DY
Correct Answer: A
Using the right-hand grip rule, the North pole is at P.
JAMB (UTME)
Physics
2000
Q7961.A gas would serve as an electrical conductor under
AReduced pressure and reduced potential
BReduced pressure and high current
CIncreased magnetic field
DExposure to visible light
Correct Answer: B
Gases conduct electricity at reduced pressure and high potential difference.
JAMB (UTME)
Physics
2000
Q7962.An electric generator with a power output of $3.0 \mathrm{kW}$ at a voltage of $1.5 \mathrm{kV}$ distributes power along cables of total resistance $20.0 \Omega$. The power loss in the cable is
A$0.1 \mathrm{W}$
B$10.0 \mathrm{W}$
C$40.0 \mathrm{W}$
D$80.0 \mathrm{W}$
Correct Answer: D
$I = \dfrac{P}{V} = \dfrac{3000}{1500} = 2 \mathrm{A}$. Power loss $= I^2R = 2^2 \times 20 = 80 \mathrm{W}$.
JAMB (UTME)
Physics
2000
Q7963.A conductor of length $2 \mathrm{m}$ carries a current of $0.8 \mathrm{A}$ while kept in a magnetic field of magnetic flux density $0.5 \mathrm{T}$. The maximum force acting on it is
Q7964.Which of the following is the correct shape of the velocity-time graph of a spherical steel ball dropped into a viscous fluid in a tall cylinder?
A[Graph A - straight line increasing]
B[Graph B - horizontal line]
C[Graph C - straight line decreasing]
D[Graph D - curve increasing then flattening]
Correct Answer: D
The ball accelerates initially, then attains terminal velocity where the graph becomes horizontal.
JAMB (UTME)
Physics
2001
Q7965.A particle in circular motion performs 30 oscillations in 6 seconds. Its angular velocity is
A$6 \mathrm{rads}^{-1}$
B$5\pi \mathrm{rads}^{-1}$
C$10\pi \mathrm{rads}^{-1}$
D$5 \mathrm{rads}^{-1}$
Correct Answer: C
Frequency $f = \dfrac{30}{6} = 5 \mathrm{Hz}$. $\omega = 2\pi f = 2\pi \times 5 = 10\pi \mathrm{rads}^{-1}$.
JAMB (UTME)
Physics
2001
Q7966.A copper cube weighs $0.25 \mathrm{N}$ in air, $0.17 \mathrm{N}$ when completely immersed in paraffin oil and $0.15 \mathrm{N}$ when completely immersed in water. The ratio of upthrust in oil to upthrust in water is
A$13:10$
B$7:10$
C$3:5$
D$4:5$
Correct Answer: D
Upthrust in oil $= 0.25 - 0.17 = 0.08 \mathrm{N}$. Upthrust in water $= 0.25 - 0.15 = 0.10 \mathrm{N}$. Ratio $= \dfrac{0.08}{0.10} = \dfrac{4}{5}$.
JAMB (UTME)
Physics
2001
Q7967.The hydrostatic blood pressure difference between the head and feet of a boy standing straight is $1.65 \times 10^4 \mathrm{Nm}^{-2}$. Find the height of the boy. [Density of blood $= 1.1 \times 10^3 \mathrm{kgm}^{-3}$, $g = 10 \mathrm{ms}^{-2}$]
Q7968.If the total force acting on a particle is zero, the linear momentum will
ABe constant
BIncrease
CDecrease
DDecrease then increase
Correct Answer: A
If net force is zero, linear momentum is conserved (constant).
JAMB (UTME)
Physics
2001
Q7969.The effect of a particle in a fluid attaining its terminal velocity is that the
ABuoyancy force is more than the weight of the fluid displaced
BBuoyancy force is equal to the viscous retarding force
CAcceleration is maximum
DWeight is equal to the retarding force.
Correct Answer: D
At terminal velocity, weight = upthrust + viscous force, so net force is zero.
JAMB (UTME)
Physics
2001
Q7970.The diagram above shows the force-extension curve of a piece of wire. The energy stored when the wire is stretched from E to F is
A$7.5 \times 10^{-1} \mathrm{J}$
B$7.5 \times 10^{-1} \mathrm{J}$
C$2.5 \times 10^{-1} \mathrm{J}$
D$1.5 \times 10^{-1} \mathrm{J}$
Correct Answer: C
Energy $= \dfrac{1}{2}Fe = \dfrac{1}{2} \times 0.1 \times 0.05 = 0.0025 = 2.5 \times 10^{-3} \mathrm{J}$. The answer key C is incorrect.
JAMB (UTME)
Physics
2001
Q7971.If the distance between two suspended masses $10 \mathrm{kg}$ each is tripled, the gravitational force of attraction between them is reduced by
AOne ninth
BOne quarter
COne third
DOne half
Correct Answer: A
$F \propto \dfrac{1}{r^2}$. Tripling distance reduces force to $\dfrac{1}{9}$.
JAMB (UTME)
Physics
2001
Q7972.A wheel and axle is used to raise a load of $500 \mathrm{N}$ by the application of an effort of $250 \mathrm{N}$. If the radii of the wheel and the axle are $0.4 \mathrm{m}$ and $0.1 \mathrm{m}$ respectively, the efficiency of the machine is
Q7973.The diagram above shows the force (F) acting on an object through a distance (x). The work done on this object is expressed as
A$\dfrac{F}{x}$
B$Fx^2 \mathrm{J}$
C$\dfrac{Fx}{2}$
D$Fx \mathrm{J}$
Correct Answer: C
Work done = area under graph = $\dfrac{1}{2}Fx$.
JAMB (UTME)
Physics
2001
Q7974.A body weighing $80 \mathrm{N}$ stands in an elevator that is about to move. The force exerted by the floor on the body as the elevator moves upwards with an acceleration of $5 \mathrm{ms}^{-2}$ is $[g = 10 \mathrm{ms}^{-2}]$
Q7975.Two forces each of $10 \mathrm{N}$ act on a body, one towards north and the other towards the east. The magnitude and the direction of the resultant force are
A$20 \mathrm{N}, 45^{\circ}\mathrm{W}$
B$10\sqrt{2} \mathrm{N}, 45^{\circ}\mathrm{W}$
C$10\sqrt{2} \mathrm{N}, 45^{\circ}\mathrm{E}$
D$20 \mathrm{N}, 45^{\circ}\mathrm{E}$
Correct Answer: C
$R = \sqrt{10^2 + 10^2} = 10\sqrt{2} \mathrm{N}$. Direction is $45^{\circ}$ East of North.
JAMB (UTME)
Physics
2001
Q7976.A ray of light which strikes a glass slab from air at normal incidence passes through the slab
AUndeviated and displaced at a faster speed
BUndeviated and undisplaced at a lower speed
CDeviated and undisplaced at a lower speed
DDeviated and displaced at a lower speed.
Correct Answer: B
At normal incidence, light passes undeviated and undisplaced, but at a lower speed in glass.
JAMB (UTME)
Physics
2001
Q7977.Which of the following is a characteristic of stationary waves?
AThe distance between two successive nodes is one wavelength.
BThey are formed by two identical waves traveling in opposite directions.
CThe antinode is a point of minimum displacement.
DThey can be transverse or longitudinal.
Correct Answer: B
Stationary waves are formed by two identical waves traveling in opposite directions.
JAMB (UTME)
Physics
2001
Q7978.Which of the following eye defects can be corrected using a cylindrical lens?
APresbyopia
BChromatic aberration
CMyopia
DAstigmatism
Correct Answer: D
Astigmatism is corrected using a cylindrical lens.
JAMB (UTME)
Physics
2001
Q7979.The property that is propagated in a traveling wave is
AAmplitude
BWavelength
CFrequency
DEnergy
Correct Answer: D
Energy is propagated in a traveling wave.
JAMB (UTME)
Physics
2001
Q7980.A concave mirror of radius of curvature $40 \mathrm{cm}$ forms a real image twice as large as the object. The object distance is
Q7981.If tension is maintained on a stretched string of length $0.6 \mathrm{m}$ such that its fundamental frequency of $220 \mathrm{Hz}$ is excited, determine the velocity of the transverse wave in the string.
Q7983.A coin placed below a rectangular glass block of thickness $9 \mathrm{cm}$ and refractive index $1.5$ is viewed vertically above the block. The apparent displacement of the coin is
Q7984.Blowing air over a liquid aids evaporation by
ADecreasing its vapour pressure
BDecreasing its density
CIncreasing its surface area
DIncreasing its temperature
Correct Answer: A
Blowing air removes vapour molecules, decreasing vapour pressure and aiding evaporation.
JAMB (UTME)
Physics
2001
Q7985.The pressure of 3 moles of an ideal gas at a temperature of $27^{\circ}\mathrm{C}$ having a volume of $10^{-3} \mathrm{m}^3$ is $[R = 8.3 \mathrm{Jmol}^{-1}\mathrm{K}^{-1}]$
A$7.47 \times 10^5 \mathrm{Nm}^{-2}$
B$2.49 \times 10^6 \mathrm{Nm}^{-2}$
C$7.47 \times 10^6 \mathrm{Nm}^{-2}$
D$2.49 \times 10^5 \mathrm{Nm}^{-2}$
Correct Answer: A
$P = \dfrac{nRT}{V} = \dfrac{3 \times 8.3 \times 300}{10^{-3}} = 7.47 \times 10^6 \mathrm{Nm}^{-2}$. The answer key A is incorrect; the correct answer is C.
JAMB (UTME)
Physics
2001
Q7986.To produce an enlarged and erect image with a concave mirror, the object must be positioned
ABetween the principal focus and the pole
BBetween the principal focus and the centre of curvature
CBeyond the centre of curvature
DAt the principal focus
Correct Answer: A
A concave mirror produces a virtual, erect, and magnified image when the object is between the pole and the focus.
JAMB (UTME)
Physics
2001
Q7987.The colours seen in soap bubbles are due to
ARefraction
BDiffraction
CInterference
DDispersion
Correct Answer: C
The colours are due to interference of light reflected from the top and bottom surfaces of the soap film.
JAMB (UTME)
Physics
2001
Q7988.The phenomenon that makes sound persist when its source has been removed is known as
AReverberation
BAcoustic vibration
CRarefaction
DEcho
Correct Answer: A
Reverberation is the persistence of sound after the source has stopped.
JAMB (UTME)
Physics
2001
Q7989.Vibrations in a stretched spring cannot be polarized because they are
ALongitudinal waves
BMechanical waves
CStationary waves
DTransverse waves.
Correct Answer: A
Longitudinal waves cannot be polarized.
JAMB (UTME)
Physics
2001
Q7990.I. Temperature
AI, II and IV only
BI and II only
CI, II, III and IV
DII and IV only.
Correct Answer: B
Velocity of sound in air depends on temperature and density of air molecules.
JAMB (UTME)
Physics
2001
Q7991.Water is a poor thermometric liquid because
AWets glass
BHas low vapour pressure
CIs opaque
DIs a poor conductor
Correct Answer: A
Water wets glass, making it difficult to read the meniscus.
JAMB (UTME)
Physics
2001
Q7992.The time rate of loss of heat by a body is proportional to the
ATemperature of its surroundings
BDifference in temperature between the body and its surrounding
CTemperature of the body
DRatio of the temperature of the body to that of its surrounding.
Correct Answer: B
According to Newton's law of cooling, rate of heat loss is proportional to the temperature difference.
JAMB (UTME)
Physics
2001
Q7993.An electric iron is rated $1000 \mathrm{W}$, $230 \mathrm{V}$. What is the resistance of its element?
Q7994.The electric field between the two-point charges is shown in the diagram above. What types of charges are at X and Y?
ABoth X and Y are positive
BX is positive and Y is negative
CX is negative and Y is positive
DBoth X and Y are negative.
Correct Answer: D
The field lines converge towards both X and Y, indicating both are negative.
JAMB (UTME)
Physics
2001
Q7995.The eye controls the amount of light reaching the retina by adjusting the
AIris
BOptic nerve
CCornea
DRetina
Correct Answer: A
The iris controls the pupil size, regulating light entering the eye.
JAMB (UTME)
Physics
2001
Q7996.An electric cell with nominal voltage E has a resistance of $3 \Omega$ connected across it. If the voltage falls to $0.6 \mathrm{V}$, the internal resistance of the cell is
A$2 \Omega$
B$4 \Omega$
C$1 \Omega$
D$3 \Omega$
Correct Answer: A
$V = E - Ir$. $0.6 = E - \dfrac{E}{3 + r} \times r$. This requires more information.
JAMB (UTME)
Physics
2001
Q7997.When connected to a mains $250 \mathrm{V}$, the fuse rating in the plug of an electric device of $1 \mathrm{kW}$ is
A$5 \mathrm{A}$
B$4 \mathrm{A}$
C$3 \mathrm{A}$
D$2 \mathrm{A}$
Correct Answer: A
$I = \dfrac{P}{V} = \dfrac{1000}{250} = 4 \mathrm{A}$. A $5 \mathrm{A}$ fuse is suitable.
JAMB (UTME)
Physics
2001
Q7998.The electromagnetic wave that can produce a heating effect on the environment is
AGamma rays
BX-rays
CUltraviolet rays
DInfrared rays.
Correct Answer: D
Infrared rays produce heating effects.
JAMB (UTME)
Physics
2001
Q7999.The energy stored in a capacitor of capacitance $10 \mu\mathrm{F}$ carrying a charge of $100 \mu\mathrm{C}$ is