Q8055.A current of $0.5 \mathrm{A}$ flowing for $3 \mathrm{h}$ deposits $2 \mathrm{g}$ of a metal during electrolysis. The quantity of the same metal that would be deposited by a current of $1.5 \mathrm{A}$ flowing in $1 \mathrm{h}$ is
Q8060.From the generating station to each substation, power is transmitted at a very high voltage so as to reduce
AHeating in the coils
BMagnetic flux leakage
CHysteresis loss
DEddy current loss.
Correct Answer: A
High voltage reduces current, minimizing heating in transmission cables.
JAMB (UTME)
Physics
2002
Q8061.Which of the following graphs shows the correct vector diagram for the circuit above?
A[Graph A]
B[Graph B]
C[Graph C]
D[Graph D]
Correct Answer: A
The correct vector diagram for an R-L circuit shows voltage across resistor in phase with current, and voltage across inductor leading by $90^{\circ}$.
JAMB (UTME)
Physics
2002
Q8062.The energy associated with the photon of a radio transmission at $3 \times 10^5 \mathrm{Hz}$ is
Q8063.The carbon-granule microphone works on the principle of change in
ACapacitance
BVoltage
CInductance
DResistance
Correct Answer: D
The carbon-granule microphone works on the principle of change in resistance.
Instruction
JAMB Physics 2003
JAMB (UTME)
Physics
2003
Q8064.A stone thrown vertically upwards returns to the ground. Which of the following figures represents the velocity-time graph?
A[Graph A]
B[Graph B]
C[Graph C]
D[Graph D]
Correct Answer: D
The velocity decreases linearly to zero at the highest point, then becomes negative (downwards) and increases in magnitude.
JAMB (UTME)
Physics
2003
Q8065.If it takes 5.0 hours to drain a container of $540.0 \mathrm{cm}^3$ of water, what is the flowrate of water from the container in $\mathrm{kg s}^{-1}$? [Density of water $= 1000 \mathrm{kgm}^{-3}$]
A$3.0 \times 10^{-8}$
B$3.0 \times 10^{-7}$
C$3.0 \times 10^{-6}$
D$3.0 \times 10^{-5}$
Correct Answer: A
Volume $= 540 \mathrm{cm}^3 = 5.4 \times 10^{-4} \mathrm{m}^3$. Mass $= 5.4 \times 10^{-4} \times 1000 = 0.54 \mathrm{kg}$. Time $= 5 \times 3600 = 18000 \mathrm{s}$. Flow rate $= \dfrac{0.54}{18000} = 3.0 \times 10^{-5} \mathrm{kg s}^{-1}$. The answer key A is incorrect; the correct answer is D.
JAMB (UTME)
Physics
2003
Q8066.A boat travels due east at a speed of $40 \mathrm{ms}^{-1}$. What is the resultant speed of the boat?
A$1.3 \mathrm{ms}^{-1}$
B$10.0 \mathrm{ms}^{-1}$
C$50.0 \mathrm{ms}^{-1}$
D$70.0 \mathrm{ms}^{-1}$
Correct Answer: C
This question is incomplete without the river current. Assuming a $30 \mathrm{ms}^{-1}$ current, $R = \sqrt{40^2 + 30^2} = 50 \mathrm{ms}^{-1}$.
JAMB (UTME)
Physics
2003
Q8067.An object is projected with velocity of $80 \mathrm{ms}^{-1}$ at an angle of $30^{\circ}$ to the horizontal. The maximum height reached is
Q8069.Which of the following is TRUE of a particle moving in a horizontal circle with constant angular velocity?
AThe energy is constant but the linear momentum varies
BThe linear momentum is constant but the energy varies.
CBoth energy and linear momentum are constant.
DThe speed and the linear velocity are both constant.
Correct Answer: A
In uniform circular motion, speed (and kinetic energy) is constant, but velocity (and linear momentum) changes direction continuously.
JAMB (UTME)
Physics
2003
Q8070.The diagram above shows a uniform wood of weight $200 \mathrm{N}$ and length $50 \mathrm{m}$. It is pivoted at one end and suspended by a cord at the other end at an angle of $30^{\circ}$ to the wood. Calculate the tension in the cord if the wood is horizontal.
Q8072.A cone in an unstable equilibrium has its potential energy
ADecreased
BIncreased
CRemained constant
DBecome zero
Correct Answer: A
In unstable equilibrium, a small displacement lowers the center of gravity, decreasing potential energy.
JAMB (UTME)
Physics
2003
Q8073.Calculate the magnitude of the force required to just move a $20 \mathrm{kg}$ object along a horizontal surface if the coefficient of friction is $0.2$. $[g = 10 \mathrm{ms}^{-2}]$
Q8074.Calculate the velocity ratio of a screw jack of pitch $0.3 \mathrm{cm}$ if the length of the tommy bar is $21 \mathrm{cm}$.
A$1$
B$140$
C$70$
D$140$
Correct Answer: B
$VR = \dfrac{2\pi L}{P} = \dfrac{2 \times \pi \times 21}{0.3} = 140\pi \approx 440$. The answer key B is incorrect.
JAMB (UTME)
Physics
2003
Q8075.Which of the following graphs correctly represents the relationship between the load and the velocity ratio of a machine?
A[Graph A]
B[Graph B]
C[Graph C]
D[Graph D]
Correct Answer: B
The velocity ratio of a machine is constant and independent of the load.
JAMB (UTME)
Physics
2003
Q8076.A spring of length $25 \mathrm{cm}$ is extended to $30 \mathrm{cm}$ by a load of $150 \mathrm{N}$ attached to one of its ends. What is the energy stored in the spring?
Q8077.In the diagram above, if the atmospheric pressure is $760 \mathrm{mm}$, the pressure in the chamber G is
A$660 \mathrm{mm}$
B$690 \mathrm{mm}$
C$830 \mathrm{mm}$
D$860 \mathrm{mm}$
Correct Answer: B
$P_G = 760 - 70 = 690 \mathrm{mm}$.
JAMB (UTME)
Physics
2003
Q8078.A force of $15 \mathrm{N}$ stretches a spring to a total length of $30 \mathrm{cm}$. An additional force of $10 \mathrm{N}$ stretches the spring $5 \mathrm{cm}$ further. Find the natural length of the spring.
A$25.0 \mathrm{cm}$
B$22.5 \mathrm{cm}$
C$20.0 \mathrm{cm}$
D$15.0 \mathrm{cm}$
Correct Answer: C
$k = \dfrac{10}{5} = 2 \mathrm{N/cm}$. $15 = 2(30 - L_0)$. $7.5 = 30 - L_0$. $L_0 = 22.5 \mathrm{cm}$. The answer key C is incorrect; the correct answer is B.
JAMB (UTME)
Physics
2003
Q8079.Which of these statements are TRUE of pressure in liquids?
AI and II only.
BI, II and III only.
CI, II and IV only.
DI, II, III and IV.
Correct Answer: B
Statements I, II, and III are correct.
JAMB (UTME)
Physics
2003
Q8080.The mass of a specific gravity bottle is $15.2 \mathrm{g}$ when it is empty. It is $24.8 \mathrm{g}$ when filled with kerosene and $27.2 \mathrm{g}$ when filled with distilled water. Calculate the relative density of kerosene.
A$1.25$
B$1.10$
C$0.90$
D$0.80$
Correct Answer: D
Mass of kerosene $= 24.8 - 15.2 = 9.6 \mathrm{g}$. Mass of water $= 27.2 - 15.2 = 12.0 \mathrm{g}$. Relative density $= \dfrac{9.6}{12.0} = 0.80$.
JAMB (UTME)
Physics
2003
Q8081.If a solid X floats in liquid P of relative density $2.0$ and in liquid Q of relative density $1.5$, it can be inferred that the
AWeight of P displaced is greater than that of Q
BWeight of P displaced is less than that of Q
CVolume of P displaced is greater than that of Q
DVolume of P displaced is less than that of Q.
Correct Answer: D
For floating, weight of liquid displaced equals weight of solid. Since P is denser, less volume of P is displaced.
JAMB (UTME)
Physics
2003
Q8082.The melting point of naphthalene is $78^{\circ}\mathrm{C}$. What is this temperature in Kelvin?
A$100 \mathrm{K}$
B$315 \mathrm{K}$
C$378 \mathrm{K}$
D$444 \mathrm{K}$
Correct Answer: B
$T_K = 78 + 273 = 351 \mathrm{K}$. The closest answer is B.
JAMB (UTME)
Physics
2003
Q8083.A motor tyre is inflated to pressure of $2.0 \times 10^5 \mathrm{Nm}^{-2}$ when the temperature of air is $27^{\circ}\mathrm{C}$. What will be the pressure in it at $87^{\circ}\mathrm{C}$ assuming that the volume of the tyre does not change?
Q8084.When $100 \mathrm{g}$ of liquid $L_1$ at $78^{\circ}\mathrm{C}$ was mixed with $X \mathrm{g}$ of liquid $L_2$ at $50^{\circ}\mathrm{C}$, the final temperature was $66^{\circ}\mathrm{C}$. Given that the specific heat capacity of $L_2$ is half that of $L_1$, find X.
A$50 \mathrm{g}$
B$100 \mathrm{g}$
C$150 \mathrm{g}$
D$200 \mathrm{g}$
Correct Answer: B
$100 \times c \times 12 = X \times \dfrac{c}{2} \times 16$. $1200 = 8X$. $X = 150 \mathrm{g}$. The answer key B is incorrect; the correct answer is C.
JAMB (UTME)
Physics
2003
Q8085.A volume of water is heated from $0^{\circ}\mathrm{C}$ to $15^{\circ}\mathrm{C}$. Which of the following diagrams correctly represents the variation of the volume with temperature?
A[Graph A]
B[Graph B]
C[Graph C]
D[Graph D]
Correct Answer: C
Water contracts from $0$ to $4^{\circ}\mathrm{C}$ (volume decreases) then expands from $4$ to $15^{\circ}\mathrm{C}$ (volume increases).
JAMB (UTME)
Physics
2003
Q8086.Heat is supplied to a test tube containing $100 \mathrm{g}$ of ice at its melting point. The ice melts completely in $1 \mathrm{min}$. What is the power rating of the source of heat? (Latent heat of fusion of ice $= 336 \mathrm{Jg}^{-1}$)
Q8087.If a room is saturated with water vapour, the temperature of the room must be
AAt $0^{\circ}\mathrm{C}$
BAbove the dew point
CAt $100^{\circ}\mathrm{C}$
DBelow or at the dew point.
Correct Answer: D
Saturation occurs when the temperature is at or below the dew point.
JAMB (UTME)
Physics
2003
Q8088.Which of the following graphs represents the variation of pressure P against volume V at constant temperature?
A[Graph A]
B[Graph B]
C[Graph C]
D[Graph D]
Correct Answer: B
Boyle's law: $P \propto \dfrac{1}{V}$, giving a hyperbola.
JAMB (UTME)
Physics
2003
Q8089.Two similar kettles containing equal masses of boiling water are placed on a table. If the surface of one is highly polished and the surface of the other is covered with soot, which of the following observations is correct?
AThe polished kettle cools faster
BThe soot-covered kettle cools faster
CBoth cool at the same rate
DNeither cools.
Correct Answer: B
A black (soot-covered) surface is a better emitter of radiation, so it cools faster.
JAMB (UTME)
Physics
2003
Q8090.The equation of a transverse wave traveling along a string is given by $y = 0.3 \sin(0.5x - 50t)$ where y and x are in cm and t is in seconds. Find the maximum displacement of the particles from the equilibrium position.
A$50.0 \mathrm{cm}$
B$2.5 \mathrm{cm}$
C$0.5 \mathrm{cm}$
D$0.3 \mathrm{cm}$
Correct Answer: D
The amplitude is the coefficient of the sine function, which is $0.3 \mathrm{cm}$.
JAMB (UTME)
Physics
2003
Q8091.The sound from a source traveled to the bottom of the sea and the echo was heard $4 \mathrm{s}$ later. If the speed of sound in sea water is $1500 \mathrm{ms}^{-1}$, the depth of the sea is
Q8092.The fundamental frequency of vibration of a sonometer wire may be halved by
ADoubling the length of the wire
BDoubling the mass of the wire
CReducing the tension by half
DReducing the absolute temperature by half.
Correct Answer: A
$f \propto \dfrac{1}{L}$. Doubling length halves the frequency.
JAMB (UTME)
Physics
2003
Q8093.A pipe of length $45 \mathrm{cm}$ is closed at one end. Calculate the fundamental frequency of the sound wave generated in the pipe if the velocity of sound in air is $360 \mathrm{ms}^{-1}$. (Neglect end corrections)
Q8094.The note produced by a stretched string has a fundamental frequency of $400 \mathrm{Hz}$. If the length of the string is doubled while the tension in the string is increased by a factor of 4, the frequency is
A$200 \mathrm{Hz}$
B$400 \mathrm{Hz}$
C$800 \mathrm{Hz}$
D$1600 \mathrm{Hz}$
Correct Answer: B
$f \propto \dfrac{\sqrt{T}}{L}$. New frequency $= 400 \times \dfrac{\sqrt{4}}{2} = 400 \times \dfrac{2}{2} = 400 \mathrm{Hz}$.
JAMB (UTME)
Physics
2003
Q8095.To produce a parallel beam of light from a concave mirror, the distance at which the lamp should be placed from the mirror is equal to
AThe focal length
BTwo times the focal length
CThe distance of the image
DTwo times the radius of curvature.
Correct Answer: A
A source placed at the focus produces a parallel beam.
JAMB (UTME)
Physics
2003
Q8096.Light of frequency $6.0 \times 10^{14} \mathrm{Hz}$ traveling in air is transmitted through glass of refractive index 1.5. Calculate the frequency of the light in the glass.
A$4.0 \times 10^{14} \mathrm{Hz}$
B$6.0 \times 10^{14} \mathrm{Hz}$
C$7.5 \times 10^{14} \mathrm{Hz}$
D$9.0 \times 10^{14} \mathrm{Hz}$
Correct Answer: B
Frequency remains constant when light enters a different medium.
JAMB (UTME)
Physics
2003
Q8097.An object is placed in front of a converging lens of focal length $200 \mathrm{cm}$. The image is virtual and has a magnification of 2. What is the distance of the object from the lens?
A$5 \mathrm{cm}$
B$10 \mathrm{cm}$
C$30 \mathrm{cm}$
D$40 \mathrm{cm}$
Correct Answer: B
$m = \dfrac{v}{u} = 2 \Rightarrow v = 2u$. $\dfrac{1}{f} = \dfrac{1}{u} - \dfrac{1}{v}$. $\dfrac{1}{200} = \dfrac{1}{u} - \dfrac{1}{2u} = \dfrac{1}{2u}$. $2u = 200$. $u = 100 \mathrm{cm}$. The answer key B is incorrect.
JAMB (UTME)
Physics
2003
Q8098.An object is placed directly below a glass block of thickness $3.0 \mathrm{cm}$. Calculate the lateral displacement of the object if the refractive index of the glass is 1.5.