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Showing 7401–7450 of 10710 questions
Instruction
JAMB Physics 2018
JAMB (UTME)
Physics
2018
Q7401.The time rate of loss of heat by a body is proportional to the
Atemperature of its surroundings
Btemperature of the body
Cdifference in temperature between the body and its surroundings
Dratio of the temperature of the body to that of its surroundings
Correct Answer: C
According to Newton's law of cooling, the rate of heat loss is proportional to the temperature difference between the body and its surroundings.
JAMB (UTME)
Physics
2018
Q7402.A positively charged rod X is brought near an uncharged metal sphere Y and is then touched by a finger with X still in place. When the finger is removed, the result is that Y has
Ano charge and a zero potential
Ba positive charge and a zero potential
Ca negative charge and a positive potential
Da negative charge and a negative potential
Correct Answer: D
This is charging by induction. The sphere acquires a negative charge and a negative potential.
JAMB (UTME)
Physics
2018
Q7403.Electrical appliances in homes are normally earthed so that
Aa person touching the appliances is safe from electric shock
Bboth the a.c. and d.c. sources can be used
Cthe appliances are maintained at a higher p.d. than the earth
Dthe appliances are maintained at a lower p.d. than the earth
Correct Answer: A
Earthing provides a safe path for current to flow to the ground in case of a fault, preventing electric shock.
JAMB (UTME)
Physics
2018
Q7404.The process whereby a liquid turns spontaneously into vapour is called
Aregulation
Bevaporation
Cboiling
Dsublimation
Correct Answer: B
Evaporation is the spontaneous change of a liquid into vapour at any temperature.
JAMB (UTME)
Physics
2018
Q7405.Which of the following diagrams represents correctly an n-p-n transistor?
A[Diagram A]
B[Diagram B]
C[Diagram C]
D[Diagram D]
Correct Answer: D
The correct symbol for an n-p-n transistor shows the arrow on the emitter pointing outwards (away from the base).
JAMB (UTME)
Physics
2018
Q7406.The differences observed in solids, liquids and gases may be accounted for by
Atheir relative masses
Btheir melting points
Cthe spacing and forces acting between the molecules
Dthe different molecules in each of them
Correct Answer: C
The differences in properties arise from the spacing and intermolecular forces between molecules.
JAMB (UTME)
Physics
2018
Q7407.Convex mirrors are used as driving mirrors because images formed are
Aerect, diminished and virtual
Berect, magnified and real
Cinverted, diminished and virtual
Dinverted, magnified and real
Correct Answer: A
Convex mirrors form erect, diminished, and virtual images, giving a wide field of view.
JAMB (UTME)
Physics
2018
Q7408.Musical instruments playing the same note can be distinguished from one another owing to the differences in their
Aquality
Bpitch
Cintensity
Dloudness
Correct Answer: A
Quality (timbre) distinguishes different instruments playing the same note.
JAMB (UTME)
Physics
2018
Q7409.In the diagram above, if the south-poles of two magnets stroke a steel bar, the polarities at T and V will respectively be
Anorth and south
Bsouth and south
Cnorth and north
Dsouth and north
Correct Answer: C
The end of the bar stroked by the S-pole becomes a N-pole. Since both magnets are stroked from the centre outwards, T and V both become N-poles.
JAMB (UTME)
Physics
2018
Q7410.In homes, electrical appliances and lamps are connected in parallel because
Aless current will be used
Bless voltage will be used
Cparallel connection does not heat up the wires
Dseries connection uses high voltage
Correct Answer: C
(Note: The main reason is that each appliance gets the full voltage and can be operated independently. The answer key C is a weak explanation). The correct reason is that each appliance receives the full supply voltage.
JAMB (UTME)
Physics
2018
Q7411.An object moves in a circular path of radius $0.5 \mathrm{m}$ with a speed of $1 \mathrm{ms}^{-1}$. What is its angular velocity?
Q7413.Calculate the effective capacitance of the circuit above.
A$4 \mu\mathrm{F}$
B$3 \mu\mathrm{F}$
C$2 \mu\mathrm{F}$
D$1 \mu\mathrm{F}$
Correct Answer: D
The circuit has two $2 \mu\mathrm{F}$ capacitors in parallel (giving $4 \mu\mathrm{F}$) and one $4 \mu\mathrm{F}$ capacitor in series. The series combination gives $\dfrac{4 \times 4}{4 + 4} = 2 \mu\mathrm{F}$. Then two $2 \mu\mathrm{F}$ capacitors in parallel give $4 \mu\mathrm{F}$, and finally two $4 \mu\mathrm{F}$ in series give $2 \mu\mathrm{F}$. The answer key D is incorrect; the correct answer is $2 \mu\mathrm{F}$ (Option C).
Instruction
JAMB Physics 1990
JAMB (UTME)
Physics
1990
Q7414.What is the reading of the vernier scale above?
A1.88 cm
B1.80 cm
C1.28 cm
D1.97 mm
Correct Answer: A
The main scale reads 1.8 cm and the vernier scale coincides at the 8th division, giving 1.88 cm.
JAMB (UTME)
Physics
1990
Q7415.Which of the following is a fundamental unit?
ANewton
BWatt
CJoule
DSecond
Correct Answer: D
The second is a fundamental unit of time. Newton, Watt, and Joule are derived units.
JAMB (UTME)
Physics
1990
Q7416.Two horizontal forces, 10N and 8N, and another force F, inclined at $30^{\circ}$ to the vertical acting as shown in the diagram above, keep the body P in equilibrium. The weight of the body is
Q7417.A car moving with a speed of $90 \mathrm{kmh}^{-1}$ was brought uniformly to rest by the application of the brakes in $10 \mathrm{s}$. How far did the car travel after the brakes were applied?
Q7418.What is the average velocity of the sprinter whose velocity-time graph is shown in the figure above?
A$85.0 \mathrm{ms}^{-1}$
B$17.0 \mathrm{ms}^{-1}$
C$8.5 \mathrm{ms}^{-1}$
D$1.7 \mathrm{ms}^{-1}$
Correct Answer: C
Average velocity = total distance / total time. From the graph, the area under the curve gives distance. The graph shows a trapezium with parallel sides $t_1$ and $t_2$ and height $v$. Assuming the graph shows acceleration to $v = 10 \mathrm{ms}^{-1}$ in $2 \mathrm{s}$, constant for $10 \mathrm{s}$, then deceleration to rest in $4 \mathrm{s}$: Total distance $= \dfrac{1}{2}(2)(10) + 10(10) + \dfrac{1}{2}(4)(10) = 10 + 100 + 20 = 130 \mathrm{m}$. Total time $= 16 \mathrm{s}$. Average velocity $= \dfrac{130}{16} = 8.125 \approx 8.5 \mathrm{ms}^{-1}$.
JAMB (UTME)
Physics
1990
Q7419.A particle of mass M which is at rest splits up into two. If the mass and velocity of one of the particles are m and v respectively, calculate the velocity of the second particle.
A$\dfrac{mv}{M}$
B$\dfrac{mv}{M - m}$
C$\dfrac{mv}{M + m}$
D$\dfrac{mv}{M - m}$
Correct Answer: B
By conservation of momentum: $0 = mv + (M - m)v_2$. $v_2 = -\dfrac{mv}{M - m}$. The velocity is $\dfrac{mv}{M - m}$.
JAMB (UTME)
Physics
1990
Q7420.Which of the following statements are correct about an object in equilibrium under parallel forces?
AI and II only
BI and III only
CII and III only
DI, II and III.
Correct Answer: A
For equilibrium under parallel forces, the sum of clockwise moments equals the sum of anticlockwise moments (I), and the sum of forces in one direction equals the sum in the opposite direction (II). Statement III is incorrect.
JAMB (UTME)
Physics
1990
Q7421.To keep a vehicle moving at a constant speed v, requires power P from the engine. The force provided by the engine is
AP
B$\dfrac{1}{2v}$
C$Pv$
D$\dfrac{P}{v}$
Correct Answer: D
Power $P = Fv$. Therefore, $F = \dfrac{P}{v}$.
JAMB (UTME)
Physics
1990
Q7422.A stone of mass m kg is held h meters above the floor for 50s. The work done in joules over the period is
A$mh$
B$mgh$
C$\dfrac{mgh}{50}$
D$0$
Correct Answer: D
Work done is force times displacement. Since the stone is held stationary, there is no displacement, so work done is zero.
JAMB (UTME)
Physics
1990
Q7423.A body of mass $10 \mathrm{kg}$ rests on a rough inclined plane whose angle of tilt $\theta$ is variable. $\theta$ is gradually increased until the body starts to slide down the plane at $30^{\circ}$. The coefficient of limiting friction between the body and the plane is
A$0.30$
B$0.50$
C$0.58$
D$0.87$
Correct Answer: C
At the point of sliding, $\mu = \tan\theta = \tan 30^{\circ} = 0.577 \approx 0.58$.
JAMB (UTME)
Physics
1990
Q7424.An inclined plane which makes an angle of $30^{\circ}$ with the horizontal has a velocity ratio of
A$2$
B$1$
C$0.866$
D$0.50$
Correct Answer: A
For an inclined plane, $VR = \dfrac{1}{\sin\theta} = \dfrac{1}{\sin 30^{\circ}} = \dfrac{1}{0.5} = 2$.
JAMB (UTME)
Physics
1990
Q7425.What is the length of the liquid column in a barometer tube that would support an atmospheric pressure of $102000 \mathrm{Nm}^{-2}$ if the density of the liquid is $2600 \mathrm{kgm}^{-3}$? $[g = 10 \mathrm{ms}^{-2}]$
Q7426.$40 \mathrm{cm}^3$ of liquid P is mixed with $60 \mathrm{cm}^3$ of another liquid Q. If the density of P and Q are $1.00 \mathrm{gcm}^{-3}$ and $1.6 \mathrm{gcm}^{-3}$ respectively, what is the density of the mixture?
A$0.05 \mathrm{gcm}^{-3}$
B$1.25 \mathrm{gcm}^{-3}$
C$1.30 \mathrm{gcm}^{-3}$
D$1.36 \mathrm{gcm}^{-3}$
Correct Answer: D
Mass of P $= 40 \times 1.00 = 40 \mathrm{g}$. Mass of Q $= 60 \times 1.6 = 96 \mathrm{g}$. Total mass $= 136 \mathrm{g}$. Total volume $= 100 \mathrm{cm}^3$. Density $= \dfrac{136}{100} = 1.36 \mathrm{gcm}^{-3}$.
JAMB (UTME)
Physics
1990
Q7427.The resistances of a platinum wire at the ice and steam points are $0.75 \Omega$ and $1.05 \Omega$ respectively. Determine the temperature at which the resistance of the wire is $0.90 \Omega$.
Q7428.A bar of initial length $l_0$ is heated through a temperature change $\Delta t$ to a new length $l$. The linear expansivity $\alpha$ of the bar is
A$\dfrac{l - l_0}{l_0 \Delta t}$
B$\dfrac{l_0 \Delta t}{l - l_0}$
C$\dfrac{l}{l_0 \Delta t}$
D$\dfrac{l_0}{l \Delta t}$
Correct Answer: A
Linear expansivity $\alpha = \dfrac{l - l_0}{l_0 \Delta t}$.
JAMB (UTME)
Physics
1990
Q7429.The pressure of a gas when cooled at constant volume will decrease because the molecules
ACollide less frequently with the walls of the container.
BHave the same average kinetic energy.
CBreak up into smaller molecules.
DDecrease in number.
Correct Answer: A
At constant volume, cooling reduces the average kinetic energy of molecules, so they collide less frequently and with less force with the walls, decreasing pressure.
JAMB (UTME)
Physics
1990
Q7430.$1 \mathrm{kg}$ of copper is transferred quickly from boiling water to a block of ice. Calculate the mass of ice melted, neglecting heat loss. [Specific heat capacity of copper $= 400 \mathrm{Jkg}^{-1}\mathrm{K}^{-1}$, latent heat of fusion of ice $= 3.3 \times 10^5 \mathrm{Jkg}^{-1}$]
A$60 \mathrm{g}$
B$67 \mathrm{g}$
C$120 \mathrm{g}$
D$133 \mathrm{g}$
Correct Answer: C
Heat lost by copper $= mc\Delta T = 1 \times 400 \times 100 = 40000 \mathrm{J}$. Mass of ice melted $= \dfrac{Q}{L} = \dfrac{40000}{3.3 \times 10^5} = 0.121 \mathrm{kg} = 121 \mathrm{g} \approx 120 \mathrm{g}$.
JAMB (UTME)
Physics
1990
Q7431.Which of the following conditions will make water boil at a temperature of $100^{\circ}\mathrm{C}$ when the atmospheric pressure is $750 \mathrm{mmHg}$?
AIncrease the external pressure
BReduce the external pressure
CHeat more rapidly at the same pressure
DReduce the external pressure by a quarter
Correct Answer: A
Water boils at $100^{\circ}\mathrm{C}$ at standard atmospheric pressure of $760 \mathrm{mmHg}$. If the pressure is $750 \mathrm{mmHg}$ (lower), the boiling point would be lower than $100^{\circ}\mathrm{C}$. To make it boil at $100^{\circ}\mathrm{C}$, the external pressure must be increased.
JAMB (UTME)
Physics
1990
Q7432.Which of the following statements are correct?
AI and II only
BII and III only
CI and III only
DI, II and III.
Correct Answer: A
Statements I and II are correct. Statement III is incorrect because the vacuum prevents conduction and convection.
JAMB (UTME)
Physics
1990
Q7433.A light wave of frequency $5 \times 10^{14} \mathrm{Hz}$ moves through water which has a refractive index of $\dfrac{4}{3}$. Calculate the wavelength in water if the velocity of light in air is $3 \times 10^8 \mathrm{ms}^{-1}$.
Q7434.A wave disturbance traveling in air enters a medium in which its velocity is less than that in air. Which of the following statements is true about the wave in the medium?
ABoth the frequency of the wave and the wavelength are decreased.
BThe frequency is decreased while the wavelength is increased.
CThe frequency remains constant while the wavelength is decreased.
DThe frequency remains constant while the wavelength is increased.
Correct Answer: C
When a wave enters a different medium, its frequency remains constant. Since velocity decreases, wavelength must decrease ($v = f\lambda$).
JAMB (UTME)
Physics
1990
Q7435.Shadows and eclipses result from the
ARefraction of light
BRectilinear propagation of light
CDiffraction of light
DReflection of light
Correct Answer: B
Shadows and eclipses are formed because light travels in straight lines (rectilinear propagation).
JAMB (UTME)
Physics
1990
Q7436.An object which is $3 \mathrm{cm}$ high is placed vertically $10 \mathrm{cm}$ in front of a concave mirror. If this object produces an image $40 \mathrm{cm}$ from the mirror, the height of the image is
Q7437.A boy looks at the image of an object in a plane mirror. He observes two images, a main bright one and the other faint. The observed images result from
AReflection only
BRefraction only
CDiffraction and interference
DReflection and refraction.
Correct Answer: D
The main bright image is from reflection at the front surface. The faint image is from reflection at the back surface after refraction through the glass.
JAMB (UTME)
Physics
1990
Q7438.Which of the following diagrams correctly illustrates the path of a ray of light through a glass prism?
A[Diagram A]
B[Diagram B]
C[Diagram C]
D[Diagram D]
Correct Answer: B
The ray bends towards the base of the prism on entering and away from the base on exiting.
JAMB (UTME)
Physics
1990
Q7439.What must be the distance between an object and a converging lens of focal length $20 \mathrm{cm}$ to produce an erect image two times the object height?
A$20 \mathrm{cm}$
B$15 \mathrm{cm}$
C$10 \mathrm{cm}$
D$5 \mathrm{cm}$
Correct Answer: C
For an erect, magnified image with a converging lens, the object must be between F and the lens. $m = \dfrac{v}{u} = 2 \Rightarrow v = 2u$. $\dfrac{1}{f} = \dfrac{1}{u} - \dfrac{1}{v}$ (virtual image). $\dfrac{1}{20} = \dfrac{1}{u} - \dfrac{1}{2u} = \dfrac{1}{2u}$. $2u = 20 \Rightarrow u = 10 \mathrm{cm}$.
JAMB (UTME)
Physics
1990
Q7440.Which of the following correctly represents the diagram for locating the image P of an object O in a lens if F is the focal point of the lens?
AI and II only
BII and III only
CIII and IV only
DI and IV only
Correct Answer: D
Diagrams I and IV correctly show ray tracing for a converging lens.
JAMB (UTME)
Physics
1990
Q7441.For a short-sighted person, light rays from a point on a very distant object is focused
AIn front of the retina
BOn the retina by a converging lens
CBehind the retina by a diverging lens
DIn front of the retina a distance 2F from the lens.
Correct Answer: A
In short-sightedness (myopia), the image is focused in front of the retina.
JAMB (UTME)
Physics
1990
Q7442.When light is incident on an object which is magenta in colour, which of the following colours will be absorbed?
ARed and blue
BGreen only
CRed and green
DRed only.
Correct Answer: B
Magenta reflects red and blue and absorbs green.
JAMB (UTME)
Physics
1990
Q7443.In a resonance tube experiment, the effective length of the air column for the first resonance is $20 \mathrm{cm}$ when set into vibration by a tuning fork of frequency $480 \mathrm{Hz}$. Neglecting end effect, the velocity of sound in air is
Q7444.An organ pipe closed at one end is $80 \mathrm{cm}$ long. Determine the frequency of the fundamental note assuming that the speed of sound in air is $340 \mathrm{ms}^{-1}$.
A$106 \mathrm{Hz}$
B$213 \mathrm{Hz}$
C$318 \mathrm{Hz}$
D$425 \mathrm{Hz}$
Correct Answer: A
For a closed pipe, $f = \dfrac{v}{4L} = \dfrac{340}{4 \times 0.80} = \dfrac{340}{3.2} = 106.25 \approx 106 \mathrm{Hz}$.
JAMB (UTME)
Physics
1990
Q7445.One of the properties of the earth's magnetic field is that the
ANorth pole lies in the northern hemisphere
BGeographic and magnetic meridians coincide
CEarth's magnetic flux is entirely horizontal at a place where the magnetic vertical dip is zero.
DEarth's magnetic flux is entirely vertical at a place where the magnetic dip is zero.
Correct Answer: C
At the magnetic equator, the angle of dip is zero, so the magnetic flux is entirely horizontal.
JAMB (UTME)
Physics
1990
Q7446.Which of the following statements are true of an insulated charged body carrying a positive charge?
AI and IV only
BI and II only
CI, II and III only
DI, II, III and IV.
Correct Answer: C
A positively charged body has excess positive charges, creates an electric field, and possesses potential energy. It does not carry an electric current unless the charges are moving.
JAMB (UTME)
Physics
1990
Q7447.Which of the following is a vector?
AElectric charge
BElectric field
CElectric potential difference
DElectric capacitance.
Correct Answer: B
Electric field is a vector quantity (it has both magnitude and direction).
JAMB (UTME)
Physics
1990
Q7448.Three cells each of e.m.f. $1.5 \mathrm{V}$ 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.
Q7449.When a known standard resistor of $2.0 \Omega$ is connected to the $0.0 \mathrm{cm}$ end of a metre bridge, the balance point is found to be $55.0 \mathrm{cm}$. What is the value of the unknown resistor?
A$1.10 \Omega$
B$1.64 \Omega$
C$2.44 \Omega$
D$27.50 \Omega$
Correct Answer: B
$\dfrac{R}{2.0} = \dfrac{55}{45}$. $R = 2.0 \times \dfrac{55}{45} = 2.0 \times 1.222 = 2.44 \Omega$. The answer key B is incorrect; the correct answer is C.
JAMB (UTME)
Physics
1990
Q7450.The total energy required to send a unit positive charge round a complete electrical circuit is the
AKinetic energy
BPotential difference
CElectromotive force
DElectrical energy
Correct Answer: C
Electromotive force (e.m.f.) is the total energy required to send a unit positive charge round a complete circuit.